release: 0.0.10

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

.gitea/workflows/release.yml

@@ -13,22 +13,26 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - name: Set up go
+
+      - name: Setup go
         uses: https://github.com/actions/setup-go@v5
         with:
-          go-version: '>=1.20.1'
+          go-version: '>=1.23.0'
+
       - name: Get dependencies
         run: >-
-          sudo apt-get update &&
-          sudo apt-get install -y
+          apt-get update &&
+          apt-get install -y
           gcc
           pkg-config
           libacl1-dev
         if: ${{ runner.os == 'Linux' }}
+
       - name: Build for Linux
         run: >-
           sh -c "go build -v -ldflags '-s -w -X main.Version=${{ github.ref_name }}' -o bin/fortify &&
           sha256sum --tag -b bin/fortify > bin/fortify.sha256"
+
       - name: Release
         id: use-go-action
         uses: https://gitea.com/actions/release-action@main

.gitea/workflows/test.yml

@@ -0,0 +1,37 @@
+name: test
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup go
+        uses: https://github.com/actions/setup-go@v5
+        with:
+          go-version: '>=1.23.0'
+
+      - name: Get dependencies
+        run: >-
+          apt-get update &&
+          apt-get install -y
+          gcc
+          pkg-config
+          libacl1-dev
+        if: ${{ runner.os == 'Linux' }}
+
+      - name: Run tests
+        run: >-
+          go test ./...
+
+      - name: Build for Linux
+        run: >-
+          sh -c "go build -v -ldflags '-s -w -X main.Version=${{ github.ref_name }}' -o bin/fortify &&
+          sha256sum --tag -b bin/fortify > bin/fortify.sha256"

README.md

@@ -1,9 +1,9 @@
 Fortify
 =======
 
-[![Go Reference](https://pkg.go.dev/badge/git.ophivana.moe/cat/fortify.svg)](https://pkg.go.dev/git.ophivana.moe/cat/fortify)
+[![Go Reference](https://pkg.go.dev/badge/git.ophivana.moe/security/fortify.svg)](https://pkg.go.dev/git.ophivana.moe/security/fortify)
 
-Lets you run graphical applications as another user ~~in an Android-like sandbox environment~~ (WIP) with a nice NixOS
+Lets you run graphical applications as another user in a confined environment with a nice NixOS
 module to configure target users and provide launchers and desktop files for your privileged user.
 
 Why would you want this?
@@ -12,7 +12,7 @@ Why would you want this?
 
 - It protects applications from each other.
 
-- It provides UID isolation on top of ~~the standard application sandbox~~ (WIP).
+- It provides UID isolation on top of the standard application sandbox.
 
 There are a few different things to set up for this to work:
 
@@ -26,7 +26,7 @@ There are a few different things to set up for this to work:
 If you have a flakes-enabled nix environment, you can try out the tool by running:
 
 ```shell
-nix run git+https://git.ophivana.moe/cat/fortify -- -h
+nix run git+https://git.ophivana.moe/security/fortify -- -h
 ```
 
 ## Module usage
@@ -41,7 +41,7 @@ To use the module, import it into your configuration with
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
 
     fortify = {
-      url = "git+https://git.ophivana.moe/cat/fortify";
+      url = "git+https://git.ophivana.moe/security/fortify";
 
       # Optional but recommended to limit the size of your system closure.
       inputs.nixpkgs.follows = "nixpkgs";

acl/export.go

@@ -25,7 +25,25 @@ const (
 	Other        = C.ACL_OTHER
 )
 
-type Perm C.acl_perm_t
+type (
+	Perm  C.acl_perm_t
+	Perms []Perm
+)
+
+func (ps Perms) String() string {
+	var s = []byte("---")
+	for _, p := range ps {
+		switch p {
+		case Read:
+			s[0] = 'r'
+		case Write:
+			s[1] = 'w'
+		case Execute:
+			s[2] = 'x'
+		}
+	}
+	return string(s)
+}
 
 func UpdatePerm(path string, uid int, perms ...Perm) error {
 	// read acl from file

cmd/fsu/main.go

@@ -0,0 +1,140 @@
+package main
+
+import (
+	"bufio"
+	"log"
+	"os"
+	"path"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+const (
+	fsuConfFile = "/etc/fsurc"
+	envShim     = "FORTIFY_SHIM"
+	envAID      = "FORTIFY_APP_ID"
+
+	fpPoison = "INVALIDINVALIDINVALIDINVALIDINVALID"
+)
+
+// FortifyPath is the path to fortify, set at compile time.
+var FortifyPath = fpPoison
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("fsu: ")
+	log.SetOutput(os.Stderr)
+
+	if os.Geteuid() != 0 {
+		log.Fatal("this program must be owned by uid 0 and have the setuid bit set")
+	}
+
+	puid := os.Getuid()
+	if puid == 0 {
+		log.Fatal("this program must not be started by root")
+	}
+
+	// validate compiled in fortify path
+	if FortifyPath == fpPoison || !path.IsAbs(FortifyPath) {
+		log.Fatal("invalid fortify path, this copy of fsu is not compiled correctly")
+	}
+
+	pexe := path.Join("/proc", strconv.Itoa(os.Getppid()), "exe")
+	if p, err := os.Readlink(pexe); err != nil {
+		log.Fatalf("cannot read parent executable path: %v", err)
+	} else if strings.HasSuffix(p, " (deleted)") {
+		log.Fatal("fortify executable has been deleted")
+	} else if p != FortifyPath {
+		log.Fatal("this program must be started by fortify")
+	}
+
+	// uid = 1000000 +
+	//   fid * 10000 +
+	//           aid
+	uid := 1000000
+
+	// authenticate before accepting user input
+	if fid, ok := parseConfig(fsuConfFile, puid); !ok {
+		log.Fatalf("uid %d is not in the fsurc file", puid)
+	} else {
+		uid += fid * 10000
+	}
+
+	// pass through setup path to shim
+	var shimSetupPath string
+	if s, ok := os.LookupEnv(envShim); !ok {
+		log.Fatal("FORTIFY_SHIM not set")
+	} else if !path.IsAbs(s) {
+		log.Fatal("FORTIFY_SHIM is not absolute")
+	} else {
+		shimSetupPath = s
+	}
+
+	// allowed aid range 0 to 9999
+	if as, ok := os.LookupEnv(envAID); !ok {
+		log.Fatal("FORTIFY_APP_ID not set")
+	} else if aid, err := strconv.Atoi(as); err != nil || aid < 0 || aid > 9999 {
+		log.Fatal("invalid aid")
+	} else {
+		uid += aid
+	}
+
+	if err := syscall.Setresgid(uid, uid, uid); err != nil {
+		log.Fatalf("cannot set gid: %v", err)
+	}
+	if err := syscall.Setresuid(uid, uid, uid); err != nil {
+		log.Fatalf("cannot set uid: %v", err)
+	}
+	if err := syscall.Exec(FortifyPath, []string{"fortify", "shim"}, []string{envShim + "=" + shimSetupPath}); err != nil {
+		log.Fatalf("cannot start shim: %v", err)
+	}
+
+	panic("unreachable")
+}
+
+func parseConfig(p string, puid int) (fid int, ok bool) {
+	// refuse to run if fsurc is not protected correctly
+	if s, err := os.Stat(p); err != nil {
+		log.Fatal(err)
+	} else if s.Mode().Perm() != 0400 {
+		log.Fatal("bad fsurc perm")
+	} else if st := s.Sys().(*syscall.Stat_t); st.Uid != 0 || st.Gid != 0 {
+		log.Fatal("fsurc must be owned by uid 0")
+	}
+
+	if r, err := os.Open(p); err != nil {
+		log.Fatal(err)
+		return -1, false
+	} else {
+		s := bufio.NewScanner(r)
+		var line int
+		for s.Scan() {
+			line++
+
+			// <puid> <fid>
+			lf := strings.SplitN(s.Text(), " ", 2)
+			if len(lf) != 2 {
+				log.Fatalf("invalid entry on line %d", line)
+			}
+
+			var puid0 int
+			if puid0, err = strconv.Atoi(lf[0]); err != nil || puid0 < 1 {
+				log.Fatalf("invalid parent uid on line %d", line)
+			}
+
+			ok = puid0 == puid
+			if ok {
+				// allowed fid range 0 to 99
+				if fid, err = strconv.Atoi(lf[1]); err != nil || fid < 0 || fid > 99 {
+					log.Fatalf("invalid fortify uid on line %d", line)
+				}
+				return
+			}
+		}
+		if err = s.Err(); err != nil {
+			log.Fatalf("cannot read fsurc: %v", err)
+		}
+		return -1, false
+	}
+}

config.go

@@ -4,12 +4,11 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
-	"os"
 
-	"git.ophivana.moe/cat/fortify/dbus"
-	"git.ophivana.moe/cat/fortify/internal"
-	"git.ophivana.moe/cat/fortify/internal/app"
-	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/internal/app"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 var (
@@ -24,7 +23,7 @@ var (
 	dbusVerbose       bool
 
 	userName    string
-	enablements [state.EnableLength]bool
+	enablements [system.ELen]bool
 
 	launchMethodText string
 )
@@ -42,15 +41,15 @@ func init() {
 	flag.BoolVar(&dbusVerbose, "dbus-log", false, "Force logging in the D-Bus proxy")
 
 	flag.StringVar(&userName, "u", "chronos", "Passwd name of user to run as")
-	flag.BoolVar(&enablements[state.EnableWayland], "wayland", false, "Share Wayland socket")
-	flag.BoolVar(&enablements[state.EnableX], "X", false, "Share X11 socket and allow connection")
-	flag.BoolVar(&enablements[state.EnableDBus], "dbus", false, "Proxy D-Bus connection")
-	flag.BoolVar(&enablements[state.EnablePulse], "pulse", false, "Share PulseAudio socket and cookie")
+	flag.BoolVar(&enablements[system.EWayland], "wayland", false, "Share Wayland socket")
+	flag.BoolVar(&enablements[system.EX11], "X", false, "Share X11 socket and allow connection")
+	flag.BoolVar(&enablements[system.EDBus], "dbus", false, "Proxy D-Bus connection")
+	flag.BoolVar(&enablements[system.EPulse], "pulse", false, "Share PulseAudio socket and cookie")
 }
 
 func init() {
 	methodHelpString := "Method of launching the child process, can be one of \"sudo\""
-	if internal.SdBootedV {
+	if os.SdBooted() {
 		methodHelpString += ", \"systemd\""
 	}
 
@@ -60,12 +59,12 @@ func init() {
 func tryTemplate() {
 	if printTemplate {
 		if s, err := json.MarshalIndent(app.Template(), "", "  "); err != nil {
-			fatalf("cannot generate template: %v", err)
+			fmsg.Fatalf("cannot generate template: %v", err)
 			panic("unreachable")
 		} else {
 			fmt.Println(string(s))
 		}
-		os.Exit(0)
+		fmsg.Exit(0)
 	}
 }
 
@@ -77,10 +76,10 @@ func loadConfig() *app.Config {
 		// config from file
 		c := new(app.Config)
 		if f, err := os.Open(confPath); err != nil {
-			fatalf("cannot access config file '%s': %s\n", confPath, err)
+			fmsg.Fatalf("cannot access config file %q: %s", confPath, err)
 			panic("unreachable")
 		} else if err = json.NewDecoder(f).Decode(&c); err != nil {
-			fatalf("cannot parse config file '%s': %s\n", confPath, err)
+			fmsg.Fatalf("cannot parse config file %q: %s", confPath, err)
 			panic("unreachable")
 		} else {
 			return c
@@ -98,19 +97,19 @@ func configFromFlags() (config *app.Config) {
 	}
 
 	// enablements from flags
-	for i := state.Enablement(0); i < state.EnableLength; i++ {
+	for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
 		if enablements[i] {
 			config.Confinement.Enablements.Set(i)
 		}
 	}
 
 	// parse D-Bus config file from flags if applicable
-	if enablements[state.EnableDBus] {
+	if enablements[system.EDBus] {
 		if dbusConfigSession == "builtin" {
 			config.Confinement.SessionBus = dbus.NewConfig(dbusID, true, mpris)
 		} else {
 			if c, err := dbus.NewConfigFromFile(dbusConfigSession); err != nil {
-				fatalf("cannot load session bus proxy config from %q: %s\n", dbusConfigSession, err)
+				fmsg.Fatalf("cannot load session bus proxy config from %q: %s", dbusConfigSession, err)
 			} else {
 				config.Confinement.SessionBus = c
 			}
@@ -119,7 +118,7 @@ func configFromFlags() (config *app.Config) {
 		// system bus proxy is optional
 		if dbusConfigSystem != "nil" {
 			if c, err := dbus.NewConfigFromFile(dbusConfigSystem); err != nil {
-				fatalf("cannot load system bus proxy config from %q: %s\n", dbusConfigSystem, err)
+				fmsg.Fatalf("cannot load system bus proxy config from %q: %s", dbusConfigSystem, err)
 			} else {
 				config.Confinement.SystemBus = c
 			}

dbus/config_test.go

@@ -9,7 +9,7 @@ import (
 	"strings"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/dbus"
+	"git.ophivana.moe/security/fortify/dbus"
 )
 
 func TestConfig_Args(t *testing.T) {

dbus/dbus_test.go

@@ -5,8 +5,8 @@ import (
 	"strings"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/dbus"
-	"git.ophivana.moe/cat/fortify/helper"
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/helper"
 )
 
 func TestNew(t *testing.T) {

dbus/proxy.go

@@ -6,8 +6,8 @@ import (
 	"io"
 	"sync"
 
-	"git.ophivana.moe/cat/fortify/helper"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
 )
 
 // ProxyName is the file name or path to the proxy program.
@@ -28,6 +28,21 @@ type Proxy struct {
 	lock sync.RWMutex
 }
 
+func (p *Proxy) Session() [2]string {
+	return p.session
+}
+
+func (p *Proxy) System() [2]string {
+	return p.system
+}
+
+func (p *Proxy) Sealed() bool {
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+
+	return p.seal != nil
+}
+
 var (
 	ErrConfig = errors.New("no configuration to seal")
 )

dbus/run.go

@@ -9,9 +9,9 @@ import (
 	"strconv"
 	"strings"
 
-	"git.ophivana.moe/cat/fortify/helper"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
-	"git.ophivana.moe/cat/fortify/ldd"
+	"git.ophivana.moe/security/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/ldd"
 )
 
 // Start launches the D-Bus proxy and sets up the Wait method.
@@ -79,11 +79,9 @@ func (p *Proxy) Start(ready chan error, output io.Writer, sandbox bool) error {
 				}
 			}
 		}
-		bindTargetDedup := make([][2]string, 0, len(bindTarget))
 		for k := range bindTarget {
-			bindTargetDedup = append(bindTargetDedup, [2]string{k, k})
+			bc.Bind(k, k, false, true)
 		}
-		bc.Bind = append(bc.Bind, bindTargetDedup...)
 
 		roBindTarget := make(map[string]struct{}, 2+1+len(proxyDeps))
 
@@ -103,11 +101,9 @@ func (p *Proxy) Start(ready chan error, output io.Writer, sandbox bool) error {
 			}
 		}
 
-		roBindTargetDedup := make([][2]string, 0, len(roBindTarget))
 		for k := range roBindTarget {
-			roBindTargetDedup = append(roBindTargetDedup, [2]string{k, k})
+			bc.Bind(k, k)
 		}
-		bc.ROBind = append(bc.ROBind, roBindTargetDedup...)
 
 		h = helper.MustNewBwrap(bc, p.seal, toolPath, argF)
 		cmd = h.Unwrap()

dbus/samples_test.go

@@ -3,7 +3,7 @@ package dbus_test
 import (
 	"sync"
 
-	"git.ophivana.moe/cat/fortify/dbus"
+	"git.ophivana.moe/security/fortify/dbus"
 )
 
 var samples = []dbusTestCase{

dbus/stub_test.go

@@ -3,7 +3,7 @@ package dbus_test
 import (
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper"
 )
 
 func TestHelperChildStub(t *testing.T) {

error.go

@@ -2,22 +2,21 @@ package main
 
 import (
 	"errors"
-	"fmt"
-	"os"
 
-	"git.ophivana.moe/cat/fortify/internal/app"
+	"git.ophivana.moe/security/fortify/internal/app"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
 func logWaitError(err error) {
-	var e *app.BaseError
-	if !app.AsBaseError(err, &e) {
-		fmt.Println("fortify: wait failed:", err)
+	var e *fmsg.BaseError
+	if !fmsg.AsBaseError(err, &e) {
+		fmsg.Println("wait failed:", err)
 	} else {
 		// Wait only returns either *app.ProcessError or *app.StateStoreError wrapped in a *app.BaseError
 		var se *app.StateStoreError
 		if !errors.As(err, &se) {
 			// does not need special handling
-			fmt.Print("fortify: " + e.Message())
+			fmsg.Print(e.Message())
 		} else {
 			// inner error are either unwrapped store errors
 			// or joined errors returned by *appSealTx revert
@@ -25,19 +24,19 @@ func logWaitError(err error) {
 			var ej app.RevertCompoundError
 			if !errors.As(se.InnerErr, &ej) {
 				// does not require special handling
-				fmt.Print("fortify: " + e.Message())
+				fmsg.Print(e.Message())
 			} else {
 				errs := ej.Unwrap()
 
 				// every error here is wrapped in *app.BaseError
 				for _, ei := range errs {
-					var eb *app.BaseError
+					var eb *fmsg.BaseError
 					if !errors.As(ei, &eb) {
 						// unreachable
-						fmt.Println("fortify: invalid error type returned by revert:", ei)
+						fmsg.Println("invalid error type returned by revert:", ei)
 					} else {
 						// print inner *app.BaseError message
-						fmt.Print("fortify: " + eb.Message())
+						fmsg.Print(eb.Message())
 					}
 				}
 			}
@@ -46,16 +45,11 @@ func logWaitError(err error) {
 }
 
 func logBaseError(err error, message string) {
-	var e *app.BaseError
+	var e *fmsg.BaseError
 
-	if app.AsBaseError(err, &e) {
-		fmt.Print("fortify: " + e.Message())
+	if fmsg.AsBaseError(err, &e) {
+		fmsg.Print(e.Message())
 	} else {
-		fmt.Println(message, err)
+		fmsg.Println(message, err)
 	}
 }
-
-func fatalf(format string, a ...any) {
-	fmt.Printf("fortify: "+format, a...)
-	os.Exit(1)
-}

flake.nix

@@ -34,6 +34,10 @@
 
       devShells = forAllSystems (system: {
         default = nixpkgsFor.${system}.mkShell {
+          buildInputs = with nixpkgsFor.${system}; self.packages.${system}.fortify.buildInputs;
+        };
+
+        withPackage = nixpkgsFor.${system}.mkShell {
           buildInputs =
             with nixpkgsFor.${system};
             self.packages.${system}.fortify.buildInputs ++ [ self.packages.${system}.fortify ];

go.mod

@@ -1,3 +1,3 @@
-module git.ophivana.moe/cat/fortify
+module git.ophivana.moe/security/fortify
 
 go 1.22

helper/args_test.go

@@ -6,7 +6,7 @@ import (
 	"strings"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper"
 )
 
 func Test_argsFD_String(t *testing.T) {

helper/bwrap.go

@@ -7,7 +7,7 @@ import (
 	"strconv"
 	"sync"
 
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
 )
 
 // BubblewrapName is the file name or path to bubblewrap.

helper/bwrap/arg.go

@@ -0,0 +1,77 @@
+package bwrap
+
+import "encoding/gob"
+
+type Builder interface {
+	Len() int
+	Append(args *[]string)
+}
+
+type FSBuilder interface {
+	Path() string
+	Builder
+}
+
+func init() {
+	gob.Register(new(pairF))
+	gob.Register(new(stringF))
+}
+
+type pairF [3]string
+
+func (p *pairF) Path() string {
+	return p[2]
+}
+
+func (p *pairF) Len() int {
+	return len(p) // compiler replaces this with 3
+}
+
+func (p *pairF) Append(args *[]string) {
+	*args = append(*args, p[0], p[1], p[2])
+}
+
+type stringF [2]string
+
+func (s stringF) Path() string {
+	return s[1]
+}
+
+func (s stringF) Len() int {
+	return len(s) // compiler replaces this with 2
+}
+
+func (s stringF) Append(args *[]string) {
+	*args = append(*args, s[0], s[1])
+}
+
+// Args returns a slice of bwrap args corresponding to c.
+func (c *Config) Args() (args []string) {
+	builders := []Builder{
+		c.boolArgs(),
+		c.intArgs(),
+		c.stringArgs(),
+		c.pairArgs(),
+	}
+
+	// copy FSBuilder slice to builder slice
+	fb := make([]Builder, len(c.Filesystem)+1)
+	for i, f := range c.Filesystem {
+		fb[i] = f
+	}
+	fb[len(fb)-1] = c.Chmod
+	builders = append(builders, fb...)
+
+	// accumulate arg count
+	argc := 0
+	for _, b := range builders {
+		argc += b.Len()
+	}
+
+	args = make([]string, 0, argc)
+	for _, b := range builders {
+		b.Append(&args)
+	}
+
+	return
+}

helper/bwrap/arg.static.awkward.go

@@ -0,0 +1,13 @@
+package bwrap
+
+const (
+	Tmpfs = iota
+	Dir
+	Symlink
+)
+
+var awkwardArgs = [...]string{
+	Tmpfs:   "--tmpfs",
+	Dir:     "--dir",
+	Symlink: "--symlink",
+}

helper/bwrap/arg.static.bool.go

@@ -0,0 +1,81 @@
+package bwrap
+
+const (
+	UnshareAll = iota
+	UnshareUser
+	UnshareIPC
+	UnsharePID
+	UnshareNet
+	UnshareUTS
+	UnshareCGroup
+	ShareNet
+
+	UserNS
+	Clearenv
+
+	NewSession
+	DieWithParent
+	AsInit
+)
+
+var boolArgs = [...][]string{
+	UnshareAll:    {"--unshare-all", "--unshare-user"},
+	UnshareUser:   {"--unshare-user"},
+	UnshareIPC:    {"--unshare-ipc"},
+	UnsharePID:    {"--unshare-pid"},
+	UnshareNet:    {"--unshare-net"},
+	UnshareUTS:    {"--unshare-uts"},
+	UnshareCGroup: {"--unshare-cgroup"},
+	ShareNet:      {"--share-net"},
+
+	UserNS:   {"--disable-userns", "--assert-userns-disabled"},
+	Clearenv: {"--clearenv"},
+
+	NewSession:    {"--new-session"},
+	DieWithParent: {"--die-with-parent"},
+	AsInit:        {"--as-pid-1"},
+}
+
+func (c *Config) boolArgs() Builder {
+	b := boolArg{
+		UserNS:   !c.UserNS,
+		Clearenv: c.Clearenv,
+
+		NewSession:    c.NewSession,
+		DieWithParent: c.DieWithParent,
+		AsInit:        c.AsInit,
+	}
+
+	if c.Unshare == nil {
+		b[UnshareAll] = true
+		b[ShareNet] = c.Net
+	} else {
+		b[UnshareUser] = c.Unshare.User
+		b[UnshareIPC] = c.Unshare.IPC
+		b[UnsharePID] = c.Unshare.PID
+		b[UnshareNet] = c.Unshare.Net
+		b[UnshareUTS] = c.Unshare.UTS
+		b[UnshareCGroup] = c.Unshare.CGroup
+	}
+
+	return &b
+}
+
+type boolArg [len(boolArgs)]bool
+
+func (b *boolArg) Len() (l int) {
+	for i, v := range b {
+		if v {
+			l += len(boolArgs[i])
+		}
+	}
+	return
+}
+
+func (b *boolArg) Append(args *[]string) {
+	for i, v := range b {
+		if v {
+			*args = append(*args, boolArgs[i]...)
+		}
+	}
+}

helper/bwrap/arg.static.int.go

@@ -0,0 +1,47 @@
+package bwrap
+
+import "strconv"
+
+const (
+	UID = iota
+	GID
+	Perms
+	Size
+)
+
+var intArgs = [...]string{
+	UID:   "--uid",
+	GID:   "--gid",
+	Perms: "--perms",
+	Size:  "--size",
+}
+
+func (c *Config) intArgs() Builder {
+	// Arg types:
+	//   Perms
+	// are handled by the sequential builder
+
+	return &intArg{
+		UID: c.UID,
+		GID: c.GID,
+	}
+}
+
+type intArg [len(intArgs)]*int
+
+func (n *intArg) Len() (l int) {
+	for _, v := range n {
+		if v != nil {
+			l += 2
+		}
+	}
+	return
+}
+
+func (n *intArg) Append(args *[]string) {
+	for i, v := range n {
+		if v != nil {
+			*args = append(*args, intArgs[i], strconv.Itoa(*v))
+		}
+	}
+}

helper/bwrap/arg.static.pair.go

@@ -0,0 +1,73 @@
+package bwrap
+
+import (
+	"slices"
+)
+
+const (
+	SetEnv = iota
+
+	Bind
+	BindTry
+	DevBind
+	DevBindTry
+	ROBind
+	ROBindTry
+
+	Chmod
+)
+
+var pairArgs = [...]string{
+	SetEnv: "--setenv",
+
+	Bind:       "--bind",
+	BindTry:    "--bind-try",
+	DevBind:    "--dev-bind",
+	DevBindTry: "--dev-bind-try",
+	ROBind:     "--ro-bind",
+	ROBindTry:  "--ro-bind-try",
+
+	Chmod: "--chmod",
+}
+
+func (c *Config) pairArgs() Builder {
+	var n pairArg
+	n[SetEnv] = make([][2]string, len(c.SetEnv))
+	keys := make([]string, 0, len(c.SetEnv))
+	for k := range c.SetEnv {
+		keys = append(keys, k)
+	}
+	slices.Sort(keys)
+	for i, k := range keys {
+		n[SetEnv][i] = [2]string{k, c.SetEnv[k]}
+	}
+
+	// Arg types:
+	//   Bind
+	//   BindTry
+	//   DevBind
+	//   DevBindTry
+	//   ROBind
+	//   ROBindTry
+	//   Chmod
+	// are handled by the sequential builder
+
+	return &n
+}
+
+type pairArg [len(pairArgs)][][2]string
+
+func (p *pairArg) Len() (l int) {
+	for _, v := range p {
+		l += len(v) * 3
+	}
+	return
+}
+
+func (p *pairArg) Append(args *[]string) {
+	for i, arg := range p {
+		for _, v := range arg {
+			*args = append(*args, pairArgs[i], v[0], v[1])
+		}
+	}
+}

helper/bwrap/arg.static.string.go

@@ -0,0 +1,65 @@
+package bwrap
+
+const (
+	Hostname = iota
+	Chdir
+	UnsetEnv
+	LockFile
+
+	RemountRO
+	Procfs
+	DevTmpfs
+	Mqueue
+)
+
+var stringArgs = [...]string{
+	Hostname: "--hostname",
+	Chdir:    "--chdir",
+	UnsetEnv: "--unsetenv",
+	LockFile: "--lock-file",
+
+	RemountRO: "--remount-ro",
+	Procfs:    "--proc",
+	DevTmpfs:  "--dev",
+	Mqueue:    "--mqueue",
+}
+
+func (c *Config) stringArgs() Builder {
+	n := stringArg{
+		UnsetEnv: c.UnsetEnv,
+		LockFile: c.LockFile,
+	}
+
+	if c.Hostname != "" {
+		n[Hostname] = []string{c.Hostname}
+	}
+	if c.Chdir != "" {
+		n[Chdir] = []string{c.Chdir}
+	}
+
+	// Arg types:
+	// 	 RemountRO
+	//   Procfs
+	//   DevTmpfs
+	//   Mqueue
+	// are handled by the sequential builder
+
+	return &n
+}
+
+type stringArg [len(stringArgs)][]string
+
+func (s *stringArg) Len() (l int) {
+	for _, arg := range s {
+		l += len(arg) * 2
+	}
+	return
+}
+
+func (s *stringArg) Append(args *[]string) {
+	for i, arg := range s {
+		for _, v := range arg {
+			*args = append(*args, stringArgs[i], v)
+		}
+	}
+}

helper/bwrap/config.bool.go

@@ -1,64 +0,0 @@
-package bwrap
-
-const (
-	UnshareAll = iota
-	UnshareUser
-	UnshareIPC
-	UnsharePID
-	UnshareNet
-	UnshareUTS
-	UnshareCGroup
-	ShareNet
-
-	UserNS
-	Clearenv
-
-	NewSession
-	DieWithParent
-	AsInit
-
-	boolC
-)
-
-var boolArgs = func() (b [boolC][]string) {
-	b[UnshareAll] = []string{"--unshare-all", "--unshare-user"}
-	b[UnshareUser] = []string{"--unshare-user"}
-	b[UnshareIPC] = []string{"--unshare-ipc"}
-	b[UnsharePID] = []string{"--unshare-pid"}
-	b[UnshareNet] = []string{"--unshare-net"}
-	b[UnshareUTS] = []string{"--unshare-uts"}
-	b[UnshareCGroup] = []string{"--unshare-cgroup"}
-	b[ShareNet] = []string{"--share-net"}
-
-	b[UserNS] = []string{"--disable-userns", "--assert-userns-disabled"}
-	b[Clearenv] = []string{"--clearenv"}
-
-	b[NewSession] = []string{"--new-session"}
-	b[DieWithParent] = []string{"--die-with-parent"}
-	b[AsInit] = []string{"--as-pid-1"}
-
-	return
-}()
-
-func (c *Config) boolArgs() (b [boolC]bool) {
-	if c.Unshare == nil {
-		b[UnshareAll] = true
-		b[ShareNet] = c.Net
-	} else {
-		b[UnshareUser] = c.Unshare.User
-		b[UnshareIPC] = c.Unshare.IPC
-		b[UnsharePID] = c.Unshare.PID
-		b[UnshareNet] = c.Unshare.Net
-		b[UnshareUTS] = c.Unshare.UTS
-		b[UnshareCGroup] = c.Unshare.CGroup
-	}
-
-	b[UserNS] = !c.UserNS
-	b[Clearenv] = c.Clearenv
-
-	b[NewSession] = c.NewSession
-	b[DieWithParent] = c.DieWithParent
-	b[AsInit] = c.AsInit
-
-	return
-}

helper/bwrap/config.go

@@ -1,77 +1,14 @@
 package bwrap
 
 import (
+	"encoding/gob"
 	"os"
 	"strconv"
 )
 
-func (c *Config) Args() (args []string) {
-	b := c.boolArgs()
-	n := c.intArgs()
-	g := c.interfaceArgs()
-	s := c.stringArgs()
-	p := c.pairArgs()
-
-	argc := 0
-	for i, arg := range b {
-		if arg {
-			argc += len(boolArgs[i])
-		}
-	}
-	for _, arg := range n {
-		if arg != nil {
-			argc += 2
-		}
-	}
-	for _, arg := range g {
-		argc += len(arg) * 3
-	}
-	for _, arg := range s {
-		argc += len(arg) * 2
-	}
-	for _, arg := range p {
-		argc += len(arg) * 3
-	}
-
-	args = make([]string, 0, argc)
-	for i, arg := range b {
-		if arg {
-			args = append(args, boolArgs[i]...)
-		}
-	}
-	for i, arg := range n {
-		if arg != nil {
-			args = append(args, intArgs[i], strconv.Itoa(*arg))
-		}
-	}
-	for i, arg := range g {
-		for _, v := range arg {
-			if v.Later() {
-				continue
-			}
-			args = append(args, v.Value(interfaceArgs[i])...)
-		}
-	}
-	for i, arg := range s {
-		for _, v := range arg {
-			args = append(args, stringArgs[i], v)
-		}
-	}
-	for i, arg := range p {
-		for _, v := range arg {
-			args = append(args, pairArgs[i], v[0], v[1])
-		}
-	}
-	for i, arg := range g {
-		for _, v := range arg {
-			if !v.Later() {
-				continue
-			}
-			args = append(args, v.Value(interfaceArgs[i])...)
-		}
-	}
-
-	return
+func init() {
+	gob.Register(new(PermConfig[SymlinkConfig]))
+	gob.Register(new(PermConfig[*TmpfsConfig]))
 }
 
 type Config struct {
@@ -114,53 +51,12 @@ type Config struct {
 	// (--lock-file DEST)
 	LockFile []string `json:"lock_file,omitempty"`
 
-	// bind mount host path on sandbox
-	// (--bind SRC DEST)
-	Bind [][2]string `json:"bind,omitempty"`
-	// equal to Bind but ignores non-existent host path
-	// (--bind-try SRC DEST)
-	BindTry [][2]string `json:"bind_try,omitempty"`
-
-	// bind mount host path on sandbox, allowing device access
-	// (--dev-bind SRC DEST)
-	DevBind [][2]string `json:"dev_bind,omitempty"`
-	// equal to DevBind but ignores non-existent host path
-	// (--dev-bind-try SRC DEST)
-	DevBindTry [][2]string `json:"dev_bind_try,omitempty"`
-
-	// bind mount host path readonly on sandbox
-	// (--ro-bind SRC DEST)
-	ROBind [][2]string `json:"ro_bind,omitempty"`
-	// equal to ROBind but ignores non-existent host path
-	// (--ro-bind-try SRC DEST)
-	ROBindTry [][2]string `json:"ro_bind_try,omitempty"`
-
-	// remount path as readonly; does not recursively remount
-	// (--remount-ro DEST)
-	RemountRO []string `json:"remount_ro,omitempty"`
-
-	// mount new procfs in sandbox
-	// (--proc DEST)
-	Procfs []string `json:"proc,omitempty"`
-	// mount new dev in sandbox
-	// (--dev DEST)
-	DevTmpfs []string `json:"dev,omitempty"`
-	// mount new tmpfs in sandbox
-	// (--tmpfs DEST)
-	Tmpfs []PermConfig[TmpfsConfig] `json:"tmpfs,omitempty"`
-	// mount new mqueue in sandbox
-	// (--mqueue DEST)
-	Mqueue []string `json:"mqueue,omitempty"`
-	// create dir in sandbox
-	// (--dir DEST)
-	Dir []PermConfig[string] `json:"dir,omitempty"`
-	// create symlink within sandbox
-	// (--symlink SRC DEST)
-	Symlink []PermConfig[[2]string] `json:"symlink,omitempty"`
+	// ordered filesystem args
+	Filesystem []FSBuilder
 
 	// change permissions (must already exist)
 	// (--chmod OCTAL PATH)
-	Chmod map[string]os.FileMode `json:"chmod,omitempty"`
+	Chmod ChmodConfig `json:"chmod,omitempty"`
 
 	// create a new terminal session
 	// (--new-session)
@@ -217,6 +113,34 @@ type UnshareConfig struct {
 	CGroup bool `json:"cgroup"`
 }
 
+type PermConfig[T FSBuilder] struct {
+	// set permissions of next argument
+	// (--perms OCTAL)
+	Mode *os.FileMode `json:"mode,omitempty"`
+	// path to get the new permission
+	// (--bind-data, --file, etc.)
+	Inner T `json:"path"`
+}
+
+func (p *PermConfig[T]) Path() string {
+	return p.Inner.Path()
+}
+
+func (p *PermConfig[T]) Len() int {
+	if p.Mode != nil {
+		return p.Inner.Len() + 2
+	} else {
+		return p.Inner.Len()
+	}
+}
+
+func (p *PermConfig[T]) Append(args *[]string) {
+	if p.Mode != nil {
+		*args = append(*args, intArgs[Perms], strconv.FormatInt(int64(*p.Mode), 8))
+	}
+	p.Inner.Append(args)
+}
+
 type TmpfsConfig struct {
 	// set size of tmpfs
 	// (--size BYTES)
@@ -226,62 +150,47 @@ type TmpfsConfig struct {
 	Dir string `json:"dir"`
 }
 
-type argOf interface {
-	Value(arg string) (args []string)
-	Later() bool
+func (t *TmpfsConfig) Path() string {
+	return t.Dir
 }
 
-func copyToArgOfSlice[T [2]string | string | TmpfsConfig](src []PermConfig[T]) (dst []argOf) {
-	dst = make([]argOf, len(src))
-	for i, arg := range src {
-		dst[i] = arg
-	}
-	return
-}
-
-type PermConfig[T [2]string | string | TmpfsConfig] struct {
-	// append this at the end of the argument stream
-	Last bool
-
-	// set permissions of next argument
-	// (--perms OCTAL)
-	Mode *os.FileMode `json:"mode,omitempty"`
-	// path to get the new permission
-	// (--bind-data, --file, etc.)
-	Path T
-}
-
-func (p PermConfig[T]) Later() bool {
-	return p.Last
-}
-
-func (p PermConfig[T]) Value(arg string) (args []string) {
-	// max possible size
-	if p.Mode != nil {
-		args = make([]string, 0, 6)
-		args = append(args, "--perms", strconv.Itoa(int(*p.Mode)))
+func (t *TmpfsConfig) Len() int {
+	if t.Size > 0 {
+		return 4
 	} else {
-		args = make([]string, 0, 4)
-	}
-
-	switch v := any(p.Path).(type) {
-	case string:
-		args = append(args, arg, v)
-		return
-	case [2]string:
-		args = append(args, arg, v[0], v[1])
-		return
-	case TmpfsConfig:
-		if arg != "--tmpfs" {
-			panic("unreachable")
-		}
-
-		if v.Size > 0 {
-			args = append(args, "--size", strconv.Itoa(v.Size))
-		}
-		args = append(args, arg, v.Dir)
-		return
-	default:
-		panic("unreachable")
+		return 2
+	}
+}
+
+func (t *TmpfsConfig) Append(args *[]string) {
+	if t.Size > 0 {
+		*args = append(*args, intArgs[Size], strconv.Itoa(t.Size))
+	}
+	*args = append(*args, awkwardArgs[Tmpfs], t.Dir)
+}
+
+type SymlinkConfig [2]string
+
+func (s SymlinkConfig) Path() string {
+	return s[1]
+}
+
+func (s SymlinkConfig) Len() int {
+	return 3
+}
+
+func (s SymlinkConfig) Append(args *[]string) {
+	*args = append(*args, awkwardArgs[Symlink], s[0], s[1])
+}
+
+type ChmodConfig map[string]os.FileMode
+
+func (c ChmodConfig) Len() int {
+	return len(c)
+}
+
+func (c ChmodConfig) Append(args *[]string) {
+	for path, mode := range c {
+		*args = append(*args, pairArgs[Chmod], strconv.FormatInt(int64(mode), 8), path)
 	}
 }

helper/bwrap/config.int.go

@@ -1,22 +0,0 @@
-package bwrap
-
-const (
-	UID = iota
-	GID
-
-	intC
-)
-
-var intArgs = func() (n [intC]string) {
-	n[UID] = "--uid"
-	n[GID] = "--gid"
-
-	return
-}()
-
-func (c *Config) intArgs() (n [intC]*int) {
-	n[UID] = c.UID
-	n[GID] = c.GID
-
-	return
-}

helper/bwrap/config.interface.go

@@ -1,25 +0,0 @@
-package bwrap
-
-const (
-	Tmpfs = iota
-	Dir
-	Symlink
-
-	interfaceC
-)
-
-var interfaceArgs = func() (g [interfaceC]string) {
-	g[Tmpfs] = "--tmpfs"
-	g[Dir] = "--dir"
-	g[Symlink] = "--symlink"
-
-	return
-}()
-
-func (c *Config) interfaceArgs() (g [interfaceC][]argOf) {
-	g[Tmpfs] = copyToArgOfSlice(c.Tmpfs)
-	g[Dir] = copyToArgOfSlice(c.Dir)
-	g[Symlink] = copyToArgOfSlice(c.Symlink)
-
-	return
-}

helper/bwrap/config.pair.go

@@ -1,54 +0,0 @@
-package bwrap
-
-import "strconv"
-
-const (
-	SetEnv = iota
-
-	Bind
-	BindTry
-	DevBind
-	DevBindTry
-	ROBind
-	ROBindTry
-
-	Chmod
-
-	pairC
-)
-
-var pairArgs = func() (n [pairC]string) {
-	n[SetEnv] = "--setenv"
-
-	n[Bind] = "--bind"
-	n[BindTry] = "--bind-try"
-	n[DevBind] = "--dev-bind"
-	n[DevBindTry] = "--dev-bind-try"
-	n[ROBind] = "--ro-bind"
-	n[ROBindTry] = "--ro-bind-try"
-
-	n[Chmod] = "--chmod"
-
-	return
-}()
-
-func (c *Config) pairArgs() (n [pairC][][2]string) {
-	n[SetEnv] = make([][2]string, 0, len(c.SetEnv))
-	for k, v := range c.SetEnv {
-		n[SetEnv] = append(n[SetEnv], [2]string{k, v})
-	}
-
-	n[Bind] = c.Bind
-	n[BindTry] = c.BindTry
-	n[DevBind] = c.DevBind
-	n[DevBindTry] = c.DevBindTry
-	n[ROBind] = c.ROBind
-	n[ROBindTry] = c.ROBindTry
-
-	n[Chmod] = make([][2]string, 0, len(c.Chmod))
-	for path, octal := range c.Chmod {
-		n[Chmod] = append(n[Chmod], [2]string{strconv.Itoa(int(octal)), path})
-	}
-
-	return
-}

helper/bwrap/config.set.go

@@ -0,0 +1,138 @@
+package bwrap
+
+import "os"
+
+/*
+Bind binds mount src on host to dest in sandbox.
+
+Bind(src, dest) bind mount host path readonly on sandbox
+(--ro-bind SRC DEST).
+Bind(src, dest, true) equal to ROBind but ignores non-existent host path
+(--ro-bind-try SRC DEST).
+
+Bind(src, dest, false, true) bind mount host path on sandbox.
+(--bind SRC DEST).
+Bind(src, dest, true, true) equal to Bind but ignores non-existent host path
+(--bind-try SRC DEST).
+
+Bind(src, dest, false, true, true) bind mount host path on sandbox, allowing device access
+(--dev-bind SRC DEST).
+Bind(src, dest, true, true, true) equal to DevBind but ignores non-existent host path
+(--dev-bind-try SRC DEST).
+*/
+func (c *Config) Bind(src, dest string, opts ...bool) *Config {
+	var (
+		try   bool
+		write bool
+		dev   bool
+	)
+
+	if len(opts) > 0 {
+		try = opts[0]
+	}
+	if len(opts) > 1 {
+		write = opts[1]
+	}
+	if len(opts) > 2 {
+		dev = opts[2]
+	}
+
+	if dev {
+		if try {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[DevBindTry], src, dest})
+		} else {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[DevBind], src, dest})
+		}
+		return c
+	} else if write {
+		if try {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[BindTry], src, dest})
+		} else {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[Bind], src, dest})
+		}
+		return c
+	} else {
+		if try {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[ROBindTry], src, dest})
+		} else {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[ROBind], src, dest})
+		}
+		return c
+	}
+}
+
+// RemountRO remount path as readonly; does not recursively remount
+// (--remount-ro DEST)
+func (c *Config) RemountRO(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[RemountRO], dest})
+	return c
+}
+
+// Procfs mount new procfs in sandbox
+// (--proc DEST)
+func (c *Config) Procfs(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[Procfs], dest})
+	return c
+}
+
+// DevTmpfs mount new dev in sandbox
+// (--dev DEST)
+func (c *Config) DevTmpfs(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[DevTmpfs], dest})
+	return c
+}
+
+// Tmpfs mount new tmpfs in sandbox
+// (--tmpfs DEST)
+func (c *Config) Tmpfs(dest string, size int, perm ...os.FileMode) *Config {
+	tmpfs := &PermConfig[*TmpfsConfig]{Inner: &TmpfsConfig{Dir: dest}}
+	if size >= 0 {
+		tmpfs.Inner.Size = size
+	}
+	if len(perm) == 1 {
+		tmpfs.Mode = &perm[0]
+	}
+	c.Filesystem = append(c.Filesystem, tmpfs)
+	return c
+}
+
+// Mqueue mount new mqueue in sandbox
+// (--mqueue DEST)
+func (c *Config) Mqueue(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[Mqueue], dest})
+	return c
+}
+
+// Dir create dir in sandbox
+// (--dir DEST)
+func (c *Config) Dir(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[Dir], dest})
+	return c
+}
+
+// Symlink create symlink within sandbox
+// (--symlink SRC DEST)
+func (c *Config) Symlink(src, dest string, perm ...os.FileMode) *Config {
+	symlink := &PermConfig[SymlinkConfig]{Inner: SymlinkConfig{src, dest}}
+	if len(perm) == 1 {
+		symlink.Mode = &perm[0]
+	}
+	c.Filesystem = append(c.Filesystem, symlink)
+	return c
+}
+
+// SetUID sets custom uid in the sandbox, requires new user namespace (--uid UID).
+func (c *Config) SetUID(uid int) *Config {
+	if uid >= 0 {
+		c.UID = &uid
+	}
+	return c
+}
+
+// SetGID sets custom gid in the sandbox, requires new user namespace (--gid GID).
+func (c *Config) SetGID(gid int) *Config {
+	if gid >= 0 {
+		c.GID = &gid
+	}
+	return c
+}

helper/bwrap/config.string.go

@@ -1,44 +0,0 @@
-package bwrap
-
-const (
-	Hostname = iota
-	Chdir
-	UnsetEnv
-	LockFile
-	RemountRO
-	Procfs
-	DevTmpfs
-	Mqueue
-
-	stringC
-)
-
-var stringArgs = func() (n [stringC]string) {
-	n[Hostname] = "--hostname"
-	n[Chdir] = "--chdir"
-	n[UnsetEnv] = "--unsetenv"
-	n[LockFile] = "--lock-file"
-	n[RemountRO] = "--remount-ro"
-	n[Procfs] = "--proc"
-	n[DevTmpfs] = "--dev"
-	n[Mqueue] = "--mqueue"
-
-	return
-}()
-
-func (c *Config) stringArgs() (n [stringC][]string) {
-	if c.Hostname != "" {
-		n[Hostname] = []string{c.Hostname}
-	}
-	if c.Chdir != "" {
-		n[Chdir] = []string{c.Chdir}
-	}
-	n[UnsetEnv] = c.UnsetEnv
-	n[LockFile] = c.LockFile
-	n[RemountRO] = c.RemountRO
-	n[Procfs] = c.Procfs
-	n[DevTmpfs] = c.DevTmpfs
-	n[Mqueue] = c.Mqueue
-
-	return
-}

helper/bwrap/config_test.go

@@ -13,47 +13,38 @@ func TestConfig_Args(t *testing.T) {
 	}{
 		{
 			name: "xdg-dbus-proxy constraint sample",
-			conf: &Config{
-				Unshare:  nil,
-				UserNS:   false,
-				Clearenv: true,
-				Symlink: []PermConfig[[2]string]{
-					{Path: [2]string{"usr/bin", "/bin"}},
-					{Path: [2]string{"var/home", "/home"}},
-					{Path: [2]string{"usr/lib", "/lib"}},
-					{Path: [2]string{"usr/lib64", "/lib64"}},
-					{Path: [2]string{"run/media", "/media"}},
-					{Path: [2]string{"var/mnt", "/mnt"}},
-					{Path: [2]string{"var/opt", "/opt"}},
-					{Path: [2]string{"sysroot/ostree", "/ostree"}},
-					{Path: [2]string{"var/roothome", "/root"}},
-					{Path: [2]string{"usr/sbin", "/sbin"}},
-					{Path: [2]string{"var/srv", "/srv"}},
-				},
-				Bind: [][2]string{
-					{"/run", "/run"},
-					{"/tmp", "/tmp"},
-					{"/var", "/var"},
-					{"/run/user/1971/.dbus-proxy/", "/run/user/1971/.dbus-proxy/"},
-				},
-				ROBind: [][2]string{
-					{"/boot", "/boot"},
-					{"/dev", "/dev"},
-					{"/proc", "/proc"},
-					{"/sys", "/sys"},
-					{"/sysroot", "/sysroot"},
-					{"/usr", "/usr"},
-					{"/etc", "/etc"},
-				},
+			conf: (&Config{
+				Unshare:       nil,
+				UserNS:        false,
+				Clearenv:      true,
 				DieWithParent: true,
-			},
+			}).
+				Symlink("usr/bin", "/bin").
+				Symlink("var/home", "/home").
+				Symlink("usr/lib", "/lib").
+				Symlink("usr/lib64", "/lib64").
+				Symlink("run/media", "/media").
+				Symlink("var/mnt", "/mnt").
+				Symlink("var/opt", "/opt").
+				Symlink("sysroot/ostree", "/ostree").
+				Symlink("var/roothome", "/root").
+				Symlink("usr/sbin", "/sbin").
+				Symlink("var/srv", "/srv").
+				Bind("/run", "/run", false, true).
+				Bind("/tmp", "/tmp", false, true).
+				Bind("/var", "/var", false, true).
+				Bind("/run/user/1971/.dbus-proxy/", "/run/user/1971/.dbus-proxy/", false, true).
+				Bind("/boot", "/boot").
+				Bind("/dev", "/dev").
+				Bind("/proc", "/proc").
+				Bind("/sys", "/sys").
+				Bind("/sysroot", "/sysroot").
+				Bind("/usr", "/usr").
+				Bind("/etc", "/etc"),
 			want: []string{
-				"--unshare-all",
-				"--unshare-user",
-				"--disable-userns",
-				"--assert-userns-disabled",
-				"--clearenv",
-				"--die-with-parent",
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				"--clearenv", "--die-with-parent",
 				"--symlink", "usr/bin", "/bin",
 				"--symlink", "var/home", "/home",
 				"--symlink", "usr/lib", "/lib",
@@ -78,6 +69,148 @@ func TestConfig_Args(t *testing.T) {
 				"--ro-bind", "/etc", "/etc",
 			},
 		},
+		{
+			name: "fortify permissive default nixos",
+			conf: (&Config{
+				Unshare:  nil,
+				Net:      true,
+				UserNS:   true,
+				Clearenv: true,
+				SetEnv: map[string]string{
+					"HOME":              "/home/chronos",
+					"TERM":              "xterm-256color",
+					"FORTIFY_INIT":      "3",
+					"XDG_RUNTIME_DIR":   "/run/user/150",
+					"XDG_SESSION_CLASS": "user",
+					"XDG_SESSION_TYPE":  "tty",
+					"SHELL":             "/run/current-system/sw/bin/zsh",
+					"USER":              "chronos",
+				},
+				DieWithParent: true,
+				AsInit:        true,
+			}).SetUID(65534).SetGID(65534).
+				Procfs("/proc").DevTmpfs("/dev").Mqueue("/dev/mqueue").
+				Bind("/bin", "/bin", false, true).
+				Bind("/boot", "/boot", false, true).
+				Bind("/etc", "/etc", false, true).
+				Bind("/home", "/home", false, true).
+				Bind("/lib", "/lib", false, true).
+				Bind("/lib64", "/lib64", false, true).
+				Bind("/nix", "/nix", false, true).
+				Bind("/root", "/root", false, true).
+				Bind("/srv", "/srv", false, true).
+				Bind("/sys", "/sys", false, true).
+				Bind("/usr", "/usr", false, true).
+				Bind("/var", "/var", false, true).
+				Bind("/run/NetworkManager", "/run/NetworkManager", false, true).
+				Bind("/run/agetty.reload", "/run/agetty.reload", false, true).
+				Bind("/run/binfmt", "/run/binfmt", false, true).
+				Bind("/run/booted-system", "/run/booted-system", false, true).
+				Bind("/run/credentials", "/run/credentials", false, true).
+				Bind("/run/cryptsetup", "/run/cryptsetup", false, true).
+				Bind("/run/current-system", "/run/current-system", false, true).
+				Bind("/run/host", "/run/host", false, true).
+				Bind("/run/keys", "/run/keys", false, true).
+				Bind("/run/libvirt", "/run/libvirt", false, true).
+				Bind("/run/libvirtd.pid", "/run/libvirtd.pid", false, true).
+				Bind("/run/lock", "/run/lock", false, true).
+				Bind("/run/log", "/run/log", false, true).
+				Bind("/run/lvm", "/run/lvm", false, true).
+				Bind("/run/mount", "/run/mount", false, true).
+				Bind("/run/nginx", "/run/nginx", false, true).
+				Bind("/run/nscd", "/run/nscd", false, true).
+				Bind("/run/opengl-driver", "/run/opengl-driver", false, true).
+				Bind("/run/pppd", "/run/pppd", false, true).
+				Bind("/run/resolvconf", "/run/resolvconf", false, true).
+				Bind("/run/sddm", "/run/sddm", false, true).
+				Bind("/run/syncoid", "/run/syncoid", false, true).
+				Bind("/run/systemd", "/run/systemd", false, true).
+				Bind("/run/tmpfiles.d", "/run/tmpfiles.d", false, true).
+				Bind("/run/udev", "/run/udev", false, true).
+				Bind("/run/udisks2", "/run/udisks2", false, true).
+				Bind("/run/utmp", "/run/utmp", false, true).
+				Bind("/run/virtlogd.pid", "/run/virtlogd.pid", false, true).
+				Bind("/run/wrappers", "/run/wrappers", false, true).
+				Bind("/run/zed.pid", "/run/zed.pid", false, true).
+				Bind("/run/zed.state", "/run/zed.state", false, true).
+				Bind("/tmp/fortify.1971/tmpdir/150", "/tmp", false, true).
+				Tmpfs("/tmp/fortify.1971", 1048576).
+				Tmpfs("/run/user", 1048576).
+				Tmpfs("/run/user/150", 8388608).
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd").
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group").
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/etc/passwd").
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/etc/group").
+				Tmpfs("/var/run/nscd", 8192),
+			want: []string{
+				"--unshare-all", "--unshare-user", "--share-net",
+				"--clearenv", "--die-with-parent", "--as-pid-1",
+				"--uid", "65534",
+				"--gid", "65534",
+				"--setenv", "FORTIFY_INIT", "3",
+				"--setenv", "HOME", "/home/chronos",
+				"--setenv", "SHELL", "/run/current-system/sw/bin/zsh",
+				"--setenv", "TERM", "xterm-256color",
+				"--setenv", "USER", "chronos",
+				"--setenv", "XDG_RUNTIME_DIR", "/run/user/150",
+				"--setenv", "XDG_SESSION_CLASS", "user",
+				"--setenv", "XDG_SESSION_TYPE", "tty",
+				"--proc", "/proc", "--dev", "/dev",
+				"--mqueue", "/dev/mqueue",
+				"--bind", "/bin", "/bin",
+				"--bind", "/boot", "/boot",
+				"--bind", "/etc", "/etc",
+				"--bind", "/home", "/home",
+				"--bind", "/lib", "/lib",
+				"--bind", "/lib64", "/lib64",
+				"--bind", "/nix", "/nix",
+				"--bind", "/root", "/root",
+				"--bind", "/srv", "/srv",
+				"--bind", "/sys", "/sys",
+				"--bind", "/usr", "/usr",
+				"--bind", "/var", "/var",
+				"--bind", "/run/NetworkManager", "/run/NetworkManager",
+				"--bind", "/run/agetty.reload", "/run/agetty.reload",
+				"--bind", "/run/binfmt", "/run/binfmt",
+				"--bind", "/run/booted-system", "/run/booted-system",
+				"--bind", "/run/credentials", "/run/credentials",
+				"--bind", "/run/cryptsetup", "/run/cryptsetup",
+				"--bind", "/run/current-system", "/run/current-system",
+				"--bind", "/run/host", "/run/host",
+				"--bind", "/run/keys", "/run/keys",
+				"--bind", "/run/libvirt", "/run/libvirt",
+				"--bind", "/run/libvirtd.pid", "/run/libvirtd.pid",
+				"--bind", "/run/lock", "/run/lock",
+				"--bind", "/run/log", "/run/log",
+				"--bind", "/run/lvm", "/run/lvm",
+				"--bind", "/run/mount", "/run/mount",
+				"--bind", "/run/nginx", "/run/nginx",
+				"--bind", "/run/nscd", "/run/nscd",
+				"--bind", "/run/opengl-driver", "/run/opengl-driver",
+				"--bind", "/run/pppd", "/run/pppd",
+				"--bind", "/run/resolvconf", "/run/resolvconf",
+				"--bind", "/run/sddm", "/run/sddm",
+				"--bind", "/run/syncoid", "/run/syncoid",
+				"--bind", "/run/systemd", "/run/systemd",
+				"--bind", "/run/tmpfiles.d", "/run/tmpfiles.d",
+				"--bind", "/run/udev", "/run/udev",
+				"--bind", "/run/udisks2", "/run/udisks2",
+				"--bind", "/run/utmp", "/run/utmp",
+				"--bind", "/run/virtlogd.pid", "/run/virtlogd.pid",
+				"--bind", "/run/wrappers", "/run/wrappers",
+				"--bind", "/run/zed.pid", "/run/zed.pid",
+				"--bind", "/run/zed.state", "/run/zed.state",
+				"--bind", "/tmp/fortify.1971/tmpdir/150", "/tmp",
+				"--size", "1048576", "--tmpfs", "/tmp/fortify.1971",
+				"--size", "1048576", "--tmpfs", "/run/user",
+				"--size", "8388608", "--tmpfs", "/run/user/150",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/etc/passwd",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/etc/group",
+				"--size", "8192", "--tmpfs", "/var/run/nscd",
+			},
+		},
 	}
 
 	for _, tc := range testCases {

helper/bwrap_test.go

@@ -7,8 +7,8 @@ import (
 	"strings"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/helper"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
 )
 
 func TestBwrap(t *testing.T) {

helper/direct_test.go

@@ -5,7 +5,7 @@ import (
 	"os"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper"
 )
 
 func TestDirect(t *testing.T) {

helper/helper_test.go

@@ -6,7 +6,7 @@ import (
 	"testing"
 	"time"
 
-	"git.ophivana.moe/cat/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper"
 )
 
 var (

helper/stub.go

@@ -10,7 +10,8 @@ import (
 	"syscall"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
 // InternalChildStub is an internal function but exported because it is cross-package;
@@ -33,7 +34,7 @@ func InternalChildStub() {
 		genericStub(argsFD, statFD)
 	}
 
-	os.Exit(0)
+	fmsg.Exit(0)
 }
 
 // InternalReplaceExecCommand is an internal function but exported because it is cross-package;

helper/stub_test.go

@@ -3,7 +3,7 @@ package helper_test
 import (
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper"
 )
 
 func TestHelperChildStub(t *testing.T) {

internal/app/app.go

@@ -1,32 +1,45 @@
 package app
 
 import (
-	"net"
-	"os/exec"
 	"sync"
+
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/shim"
 )
 
 type App interface {
-	Seal(config *Config) error
+	// ID returns a copy of App's unique ID.
+	ID() ID
+	// Start sets up the system and starts the App.
 	Start() error
+	// Wait waits for App's process to exit and reverts system setup.
 	Wait() (int, error)
+	// WaitErr returns error returned by the underlying wait syscall.
 	WaitErr() error
+
+	Seal(config *Config) error
 	String() string
 }
 
 type app struct {
+	// application unique identifier
+	id *ID
+	// operating system interface
+	os internal.System
+	// shim process manager
+	shim *shim.Shim
 	// child process related information
 	seal *appSeal
-	// underlying fortified child process
-	cmd *exec.Cmd
-	// wayland connection if wayland mediation is enabled
-	wayland *net.UnixConn
 	// error returned waiting for process
-	wait error
+	waitErr error
 
 	lock sync.RWMutex
 }
 
+func (a *app) ID() ID {
+	return *a.id
+}
+
 func (a *app) String() string {
 	if a == nil {
 		return "(invalid fortified app)"
@@ -35,21 +48,24 @@ func (a *app) String() string {
 	a.lock.RLock()
 	defer a.lock.RUnlock()
 
-	if a.cmd != nil {
-		return a.cmd.String()
+	if a.shim != nil {
+		return a.shim.String()
 	}
 
 	if a.seal != nil {
-		return "(sealed fortified app as uid " + a.seal.sys.Uid + ")"
+		return "(sealed fortified app as uid " + a.seal.sys.user.Uid + ")"
 	}
 
 	return "(unsealed fortified app)"
 }
 
 func (a *app) WaitErr() error {
-	return a.wait
+	return a.waitErr
 }
 
-func New() App {
-	return new(app)
+func New(os internal.System) (App, error) {
+	a := new(app)
+	a.id = new(ID)
+	a.os = os
+	return a, newAppID(a.id)
 }

internal/app/app_nixos_test.go

@@ -0,0 +1,592 @@
+package app_test
+
+import (
+	"fmt"
+	"io/fs"
+	"os/user"
+	"strconv"
+
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/app"
+	"git.ophivana.moe/security/fortify/internal/system"
+)
+
+var testCasesNixos = []sealTestCase{
+	{
+		"nixos permissive defaults no enablements", new(stubNixOS),
+		&app.Config{
+			User:    "chronos",
+			Command: make([]string, 0),
+			Method:  "sudo",
+		},
+		app.ID{
+			0x4a, 0x45, 0x0b, 0x65,
+			0x96, 0xd7, 0xbc, 0x15,
+			0xbd, 0x01, 0x78, 0x0e,
+			0xb9, 0xa6, 0x07, 0xac,
+		},
+		system.New(150).
+			Ensure("/tmp/fortify.1971", 0701).
+			Ephemeral(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac", 0701).
+			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/150", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/150", acl.Read, acl.Write, acl.Execute).
+			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
+			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+			Ephemeral(system.Process, "/run/user/1971/fortify/4a450b6596d7bc15bd01780eb9a607ac", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/4a450b6596d7bc15bd01780eb9a607ac", acl.Execute).
+			WriteType(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n").
+			WriteType(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/group", "fortify:x:65534:\n"),
+		(&bwrap.Config{
+			Net:      true,
+			UserNS:   true,
+			Clearenv: true,
+			SetEnv: map[string]string{
+				"HOME":              "/home/chronos",
+				"SHELL":             "/run/current-system/sw/bin/zsh",
+				"TERM":              "xterm-256color",
+				"USER":              "chronos",
+				"XDG_RUNTIME_DIR":   "/run/user/150",
+				"XDG_SESSION_CLASS": "user",
+				"XDG_SESSION_TYPE":  "tty"},
+			Chmod:         make(bwrap.ChmodConfig),
+			DieWithParent: true,
+			AsInit:        true,
+		}).SetUID(65534).SetGID(65534).
+			Procfs("/proc").DevTmpfs("/dev").Mqueue("/dev/mqueue").
+			Tmpfs("/dev/fortify", 4096).
+			Bind("/bin", "/bin", false, true).
+			Bind("/boot", "/boot", false, true).
+			Bind("/etc", "/dev/fortify/etc").
+			Bind("/home", "/home", false, true).
+			Bind("/lib", "/lib", false, true).
+			Bind("/lib64", "/lib64", false, true).
+			Bind("/nix", "/nix", false, true).
+			Bind("/root", "/root", false, true).
+			Bind("/srv", "/srv", false, true).
+			Bind("/sys", "/sys", false, true).
+			Bind("/usr", "/usr", false, true).
+			Bind("/var", "/var", false, true).
+			Bind("/run/agetty.reload", "/run/agetty.reload", false, true).
+			Bind("/run/binfmt", "/run/binfmt", false, true).
+			Bind("/run/booted-system", "/run/booted-system", false, true).
+			Bind("/run/credentials", "/run/credentials", false, true).
+			Bind("/run/cryptsetup", "/run/cryptsetup", false, true).
+			Bind("/run/current-system", "/run/current-system", false, true).
+			Bind("/run/host", "/run/host", false, true).
+			Bind("/run/keys", "/run/keys", false, true).
+			Bind("/run/libvirt", "/run/libvirt", false, true).
+			Bind("/run/libvirtd.pid", "/run/libvirtd.pid", false, true).
+			Bind("/run/lock", "/run/lock", false, true).
+			Bind("/run/log", "/run/log", false, true).
+			Bind("/run/lvm", "/run/lvm", false, true).
+			Bind("/run/mount", "/run/mount", false, true).
+			Bind("/run/NetworkManager", "/run/NetworkManager", false, true).
+			Bind("/run/nginx", "/run/nginx", false, true).
+			Bind("/run/nixos", "/run/nixos", false, true).
+			Bind("/run/nscd", "/run/nscd", false, true).
+			Bind("/run/opengl-driver", "/run/opengl-driver", false, true).
+			Bind("/run/pppd", "/run/pppd", false, true).
+			Bind("/run/resolvconf", "/run/resolvconf", false, true).
+			Bind("/run/sddm", "/run/sddm", false, true).
+			Bind("/run/store", "/run/store", false, true).
+			Bind("/run/syncoid", "/run/syncoid", false, true).
+			Bind("/run/system", "/run/system", false, true).
+			Bind("/run/systemd", "/run/systemd", false, true).
+			Bind("/run/tmpfiles.d", "/run/tmpfiles.d", false, true).
+			Bind("/run/udev", "/run/udev", false, true).
+			Bind("/run/udisks2", "/run/udisks2", false, true).
+			Bind("/run/utmp", "/run/utmp", false, true).
+			Bind("/run/virtlogd.pid", "/run/virtlogd.pid", false, true).
+			Bind("/run/wrappers", "/run/wrappers", false, true).
+			Bind("/run/zed.pid", "/run/zed.pid", false, true).
+			Bind("/run/zed.state", "/run/zed.state", false, true).
+			Symlink("/dev/fortify/etc/alsa", "/etc/alsa").
+			Symlink("/dev/fortify/etc/bashrc", "/etc/bashrc").
+			Symlink("/dev/fortify/etc/binfmt.d", "/etc/binfmt.d").
+			Symlink("/dev/fortify/etc/dbus-1", "/etc/dbus-1").
+			Symlink("/dev/fortify/etc/default", "/etc/default").
+			Symlink("/dev/fortify/etc/ethertypes", "/etc/ethertypes").
+			Symlink("/dev/fortify/etc/fonts", "/etc/fonts").
+			Symlink("/dev/fortify/etc/fstab", "/etc/fstab").
+			Symlink("/dev/fortify/etc/fuse.conf", "/etc/fuse.conf").
+			Symlink("/dev/fortify/etc/host.conf", "/etc/host.conf").
+			Symlink("/dev/fortify/etc/hostid", "/etc/hostid").
+			Symlink("/dev/fortify/etc/hostname", "/etc/hostname").
+			Symlink("/dev/fortify/etc/hostname.CHECKSUM", "/etc/hostname.CHECKSUM").
+			Symlink("/dev/fortify/etc/hosts", "/etc/hosts").
+			Symlink("/dev/fortify/etc/inputrc", "/etc/inputrc").
+			Symlink("/dev/fortify/etc/ipsec.d", "/etc/ipsec.d").
+			Symlink("/dev/fortify/etc/issue", "/etc/issue").
+			Symlink("/dev/fortify/etc/kbd", "/etc/kbd").
+			Symlink("/dev/fortify/etc/libblockdev", "/etc/libblockdev").
+			Symlink("/dev/fortify/etc/locale.conf", "/etc/locale.conf").
+			Symlink("/dev/fortify/etc/localtime", "/etc/localtime").
+			Symlink("/dev/fortify/etc/login.defs", "/etc/login.defs").
+			Symlink("/dev/fortify/etc/lsb-release", "/etc/lsb-release").
+			Symlink("/dev/fortify/etc/lvm", "/etc/lvm").
+			Symlink("/dev/fortify/etc/machine-id", "/etc/machine-id").
+			Symlink("/dev/fortify/etc/man_db.conf", "/etc/man_db.conf").
+			Symlink("/dev/fortify/etc/modprobe.d", "/etc/modprobe.d").
+			Symlink("/dev/fortify/etc/modules-load.d", "/etc/modules-load.d").
+			Symlink("/proc/mounts", "/etc/mtab").
+			Symlink("/dev/fortify/etc/nanorc", "/etc/nanorc").
+			Symlink("/dev/fortify/etc/netgroup", "/etc/netgroup").
+			Symlink("/dev/fortify/etc/NetworkManager", "/etc/NetworkManager").
+			Symlink("/dev/fortify/etc/nix", "/etc/nix").
+			Symlink("/dev/fortify/etc/nixos", "/etc/nixos").
+			Symlink("/dev/fortify/etc/NIXOS", "/etc/NIXOS").
+			Symlink("/dev/fortify/etc/nscd.conf", "/etc/nscd.conf").
+			Symlink("/dev/fortify/etc/nsswitch.conf", "/etc/nsswitch.conf").
+			Symlink("/dev/fortify/etc/opensnitchd", "/etc/opensnitchd").
+			Symlink("/dev/fortify/etc/os-release", "/etc/os-release").
+			Symlink("/dev/fortify/etc/pam", "/etc/pam").
+			Symlink("/dev/fortify/etc/pam.d", "/etc/pam.d").
+			Symlink("/dev/fortify/etc/pipewire", "/etc/pipewire").
+			Symlink("/dev/fortify/etc/pki", "/etc/pki").
+			Symlink("/dev/fortify/etc/polkit-1", "/etc/polkit-1").
+			Symlink("/dev/fortify/etc/profile", "/etc/profile").
+			Symlink("/dev/fortify/etc/protocols", "/etc/protocols").
+			Symlink("/dev/fortify/etc/qemu", "/etc/qemu").
+			Symlink("/dev/fortify/etc/resolv.conf", "/etc/resolv.conf").
+			Symlink("/dev/fortify/etc/resolvconf.conf", "/etc/resolvconf.conf").
+			Symlink("/dev/fortify/etc/rpc", "/etc/rpc").
+			Symlink("/dev/fortify/etc/samba", "/etc/samba").
+			Symlink("/dev/fortify/etc/sddm.conf", "/etc/sddm.conf").
+			Symlink("/dev/fortify/etc/secureboot", "/etc/secureboot").
+			Symlink("/dev/fortify/etc/services", "/etc/services").
+			Symlink("/dev/fortify/etc/set-environment", "/etc/set-environment").
+			Symlink("/dev/fortify/etc/shadow", "/etc/shadow").
+			Symlink("/dev/fortify/etc/shells", "/etc/shells").
+			Symlink("/dev/fortify/etc/ssh", "/etc/ssh").
+			Symlink("/dev/fortify/etc/ssl", "/etc/ssl").
+			Symlink("/dev/fortify/etc/static", "/etc/static").
+			Symlink("/dev/fortify/etc/subgid", "/etc/subgid").
+			Symlink("/dev/fortify/etc/subuid", "/etc/subuid").
+			Symlink("/dev/fortify/etc/sudoers", "/etc/sudoers").
+			Symlink("/dev/fortify/etc/sysctl.d", "/etc/sysctl.d").
+			Symlink("/dev/fortify/etc/systemd", "/etc/systemd").
+			Symlink("/dev/fortify/etc/terminfo", "/etc/terminfo").
+			Symlink("/dev/fortify/etc/tmpfiles.d", "/etc/tmpfiles.d").
+			Symlink("/dev/fortify/etc/udev", "/etc/udev").
+			Symlink("/dev/fortify/etc/udisks2", "/etc/udisks2").
+			Symlink("/dev/fortify/etc/UPower", "/etc/UPower").
+			Symlink("/dev/fortify/etc/vconsole.conf", "/etc/vconsole.conf").
+			Symlink("/dev/fortify/etc/X11", "/etc/X11").
+			Symlink("/dev/fortify/etc/zfs", "/etc/zfs").
+			Symlink("/dev/fortify/etc/zinputrc", "/etc/zinputrc").
+			Symlink("/dev/fortify/etc/zoneinfo", "/etc/zoneinfo").
+			Symlink("/dev/fortify/etc/zprofile", "/etc/zprofile").
+			Symlink("/dev/fortify/etc/zshenv", "/etc/zshenv").
+			Symlink("/dev/fortify/etc/zshrc", "/etc/zshrc").
+			Bind("/tmp/fortify.1971/tmpdir/150", "/tmp", false, true).
+			Tmpfs("/tmp/fortify.1971", 1048576).
+			Tmpfs("/run/user", 1048576).
+			Tmpfs("/run/user/150", 8388608).
+			Bind("/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/passwd", "/etc/passwd").
+			Bind("/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/group", "/etc/group").
+			Tmpfs("/var/run/nscd", 8192),
+	},
+	{
+		"nixos permissive defaults chromium", new(stubNixOS),
+		&app.Config{
+			ID:      "org.chromium.Chromium",
+			User:    "chronos",
+			Command: []string{"/run/current-system/sw/bin/zsh", "-c", "exec chromium "},
+			Confinement: app.ConfinementConfig{
+				SessionBus: &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.Notifications",
+						"org.freedesktop.FileManager1",
+						"org.freedesktop.ScreenSaver",
+						"org.freedesktop.secrets",
+						"org.kde.kwalletd5",
+						"org.kde.kwalletd6",
+						"org.gnome.SessionManager",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{
+						"org.freedesktop.portal.*": "*",
+					},
+					Broadcast: map[string]string{
+						"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
+					},
+					Filter: true,
+				},
+				SystemBus: &dbus.Config{
+					Talk: []string{
+						"org.bluez",
+						"org.freedesktop.Avahi",
+						"org.freedesktop.UPower",
+					},
+					Filter: true,
+				},
+				Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
+			},
+			Method: "systemd",
+		},
+		app.ID{
+			0xeb, 0xf0, 0x83, 0xd1,
+			0xb1, 0x75, 0x91, 0x17,
+			0x82, 0xd4, 0x13, 0x36,
+			0x9b, 0x64, 0xce, 0x7c,
+		},
+		system.New(150).
+			Ensure("/tmp/fortify.1971", 0701).
+			Ephemeral(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c", 0701).
+			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/150", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/150", acl.Read, acl.Write, acl.Execute).
+			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
+			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+			Ephemeral(system.Process, "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c", acl.Execute).
+			WriteType(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n").
+			WriteType(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/group", "fortify:x:65534:\n").
+			Link("/run/user/1971/wayland-0", "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/wayland").
+			UpdatePermType(system.EWayland, "/run/user/1971/wayland-0", acl.Read, acl.Write, acl.Execute).
+			Link("/run/user/1971/pulse/native", "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/pulse").
+			CopyFile("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie").
+			MustProxyDBus("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", &dbus.Config{
+				Talk: []string{
+					"org.freedesktop.Notifications",
+					"org.freedesktop.FileManager1",
+					"org.freedesktop.ScreenSaver",
+					"org.freedesktop.secrets",
+					"org.kde.kwalletd5",
+					"org.kde.kwalletd6",
+					"org.gnome.SessionManager",
+				},
+				Own: []string{
+					"org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.chromium.*",
+				},
+				Call: map[string]string{
+					"org.freedesktop.portal.*": "*",
+				},
+				Broadcast: map[string]string{
+					"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
+				},
+				Filter: true,
+			}, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", &dbus.Config{
+				Talk: []string{
+					"org.bluez",
+					"org.freedesktop.Avahi",
+					"org.freedesktop.UPower",
+				},
+				Filter: true,
+			}).
+			UpdatePerm("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", acl.Read, acl.Write).
+			UpdatePerm("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", acl.Read, acl.Write),
+		(&bwrap.Config{
+			Net:      true,
+			UserNS:   true,
+			Clearenv: true,
+			SetEnv: map[string]string{
+				"DBUS_SESSION_BUS_ADDRESS": "unix:path=/run/user/150/bus",
+				"DBUS_SYSTEM_BUS_ADDRESS":  "unix:path=/run/dbus/system_bus_socket",
+				"HOME":                     "/home/chronos",
+				"PULSE_COOKIE":             "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie",
+				"PULSE_SERVER":             "unix:/run/user/150/pulse/native",
+				"SHELL":                    "/run/current-system/sw/bin/zsh",
+				"TERM":                     "xterm-256color",
+				"USER":                     "chronos",
+				"WAYLAND_DISPLAY":          "/run/user/150/wayland-0",
+				"XDG_RUNTIME_DIR":          "/run/user/150",
+				"XDG_SESSION_CLASS":        "user",
+				"XDG_SESSION_TYPE":         "tty",
+			},
+			Chmod:         make(bwrap.ChmodConfig),
+			DieWithParent: true,
+			AsInit:        true,
+		}).SetUID(65534).SetGID(65534).
+			Procfs("/proc").DevTmpfs("/dev").Mqueue("/dev/mqueue").
+			Tmpfs("/dev/fortify", 4096).
+			Bind("/bin", "/bin", false, true).
+			Bind("/boot", "/boot", false, true).
+			Bind("/etc", "/dev/fortify/etc").
+			Bind("/home", "/home", false, true).
+			Bind("/lib", "/lib", false, true).
+			Bind("/lib64", "/lib64", false, true).
+			Bind("/nix", "/nix", false, true).
+			Bind("/root", "/root", false, true).
+			Bind("/srv", "/srv", false, true).
+			Bind("/sys", "/sys", false, true).
+			Bind("/usr", "/usr", false, true).
+			Bind("/var", "/var", false, true).
+			Bind("/run/agetty.reload", "/run/agetty.reload", false, true).
+			Bind("/run/binfmt", "/run/binfmt", false, true).
+			Bind("/run/booted-system", "/run/booted-system", false, true).
+			Bind("/run/credentials", "/run/credentials", false, true).
+			Bind("/run/cryptsetup", "/run/cryptsetup", false, true).
+			Bind("/run/current-system", "/run/current-system", false, true).
+			Bind("/run/host", "/run/host", false, true).
+			Bind("/run/keys", "/run/keys", false, true).
+			Bind("/run/libvirt", "/run/libvirt", false, true).
+			Bind("/run/libvirtd.pid", "/run/libvirtd.pid", false, true).
+			Bind("/run/lock", "/run/lock", false, true).
+			Bind("/run/log", "/run/log", false, true).
+			Bind("/run/lvm", "/run/lvm", false, true).
+			Bind("/run/mount", "/run/mount", false, true).
+			Bind("/run/NetworkManager", "/run/NetworkManager", false, true).
+			Bind("/run/nginx", "/run/nginx", false, true).
+			Bind("/run/nixos", "/run/nixos", false, true).
+			Bind("/run/nscd", "/run/nscd", false, true).
+			Bind("/run/opengl-driver", "/run/opengl-driver", false, true).
+			Bind("/run/pppd", "/run/pppd", false, true).
+			Bind("/run/resolvconf", "/run/resolvconf", false, true).
+			Bind("/run/sddm", "/run/sddm", false, true).
+			Bind("/run/store", "/run/store", false, true).
+			Bind("/run/syncoid", "/run/syncoid", false, true).
+			Bind("/run/system", "/run/system", false, true).
+			Bind("/run/systemd", "/run/systemd", false, true).
+			Bind("/run/tmpfiles.d", "/run/tmpfiles.d", false, true).
+			Bind("/run/udev", "/run/udev", false, true).
+			Bind("/run/udisks2", "/run/udisks2", false, true).
+			Bind("/run/utmp", "/run/utmp", false, true).
+			Bind("/run/virtlogd.pid", "/run/virtlogd.pid", false, true).
+			Bind("/run/wrappers", "/run/wrappers", false, true).
+			Bind("/run/zed.pid", "/run/zed.pid", false, true).
+			Bind("/run/zed.state", "/run/zed.state", false, true).
+			Bind("/dev/dri", "/dev/dri", true, true, true).
+			Symlink("/dev/fortify/etc/alsa", "/etc/alsa").
+			Symlink("/dev/fortify/etc/bashrc", "/etc/bashrc").
+			Symlink("/dev/fortify/etc/binfmt.d", "/etc/binfmt.d").
+			Symlink("/dev/fortify/etc/dbus-1", "/etc/dbus-1").
+			Symlink("/dev/fortify/etc/default", "/etc/default").
+			Symlink("/dev/fortify/etc/ethertypes", "/etc/ethertypes").
+			Symlink("/dev/fortify/etc/fonts", "/etc/fonts").
+			Symlink("/dev/fortify/etc/fstab", "/etc/fstab").
+			Symlink("/dev/fortify/etc/fuse.conf", "/etc/fuse.conf").
+			Symlink("/dev/fortify/etc/host.conf", "/etc/host.conf").
+			Symlink("/dev/fortify/etc/hostid", "/etc/hostid").
+			Symlink("/dev/fortify/etc/hostname", "/etc/hostname").
+			Symlink("/dev/fortify/etc/hostname.CHECKSUM", "/etc/hostname.CHECKSUM").
+			Symlink("/dev/fortify/etc/hosts", "/etc/hosts").
+			Symlink("/dev/fortify/etc/inputrc", "/etc/inputrc").
+			Symlink("/dev/fortify/etc/ipsec.d", "/etc/ipsec.d").
+			Symlink("/dev/fortify/etc/issue", "/etc/issue").
+			Symlink("/dev/fortify/etc/kbd", "/etc/kbd").
+			Symlink("/dev/fortify/etc/libblockdev", "/etc/libblockdev").
+			Symlink("/dev/fortify/etc/locale.conf", "/etc/locale.conf").
+			Symlink("/dev/fortify/etc/localtime", "/etc/localtime").
+			Symlink("/dev/fortify/etc/login.defs", "/etc/login.defs").
+			Symlink("/dev/fortify/etc/lsb-release", "/etc/lsb-release").
+			Symlink("/dev/fortify/etc/lvm", "/etc/lvm").
+			Symlink("/dev/fortify/etc/machine-id", "/etc/machine-id").
+			Symlink("/dev/fortify/etc/man_db.conf", "/etc/man_db.conf").
+			Symlink("/dev/fortify/etc/modprobe.d", "/etc/modprobe.d").
+			Symlink("/dev/fortify/etc/modules-load.d", "/etc/modules-load.d").
+			Symlink("/proc/mounts", "/etc/mtab").
+			Symlink("/dev/fortify/etc/nanorc", "/etc/nanorc").
+			Symlink("/dev/fortify/etc/netgroup", "/etc/netgroup").
+			Symlink("/dev/fortify/etc/NetworkManager", "/etc/NetworkManager").
+			Symlink("/dev/fortify/etc/nix", "/etc/nix").
+			Symlink("/dev/fortify/etc/nixos", "/etc/nixos").
+			Symlink("/dev/fortify/etc/NIXOS", "/etc/NIXOS").
+			Symlink("/dev/fortify/etc/nscd.conf", "/etc/nscd.conf").
+			Symlink("/dev/fortify/etc/nsswitch.conf", "/etc/nsswitch.conf").
+			Symlink("/dev/fortify/etc/opensnitchd", "/etc/opensnitchd").
+			Symlink("/dev/fortify/etc/os-release", "/etc/os-release").
+			Symlink("/dev/fortify/etc/pam", "/etc/pam").
+			Symlink("/dev/fortify/etc/pam.d", "/etc/pam.d").
+			Symlink("/dev/fortify/etc/pipewire", "/etc/pipewire").
+			Symlink("/dev/fortify/etc/pki", "/etc/pki").
+			Symlink("/dev/fortify/etc/polkit-1", "/etc/polkit-1").
+			Symlink("/dev/fortify/etc/profile", "/etc/profile").
+			Symlink("/dev/fortify/etc/protocols", "/etc/protocols").
+			Symlink("/dev/fortify/etc/qemu", "/etc/qemu").
+			Symlink("/dev/fortify/etc/resolv.conf", "/etc/resolv.conf").
+			Symlink("/dev/fortify/etc/resolvconf.conf", "/etc/resolvconf.conf").
+			Symlink("/dev/fortify/etc/rpc", "/etc/rpc").
+			Symlink("/dev/fortify/etc/samba", "/etc/samba").
+			Symlink("/dev/fortify/etc/sddm.conf", "/etc/sddm.conf").
+			Symlink("/dev/fortify/etc/secureboot", "/etc/secureboot").
+			Symlink("/dev/fortify/etc/services", "/etc/services").
+			Symlink("/dev/fortify/etc/set-environment", "/etc/set-environment").
+			Symlink("/dev/fortify/etc/shadow", "/etc/shadow").
+			Symlink("/dev/fortify/etc/shells", "/etc/shells").
+			Symlink("/dev/fortify/etc/ssh", "/etc/ssh").
+			Symlink("/dev/fortify/etc/ssl", "/etc/ssl").
+			Symlink("/dev/fortify/etc/static", "/etc/static").
+			Symlink("/dev/fortify/etc/subgid", "/etc/subgid").
+			Symlink("/dev/fortify/etc/subuid", "/etc/subuid").
+			Symlink("/dev/fortify/etc/sudoers", "/etc/sudoers").
+			Symlink("/dev/fortify/etc/sysctl.d", "/etc/sysctl.d").
+			Symlink("/dev/fortify/etc/systemd", "/etc/systemd").
+			Symlink("/dev/fortify/etc/terminfo", "/etc/terminfo").
+			Symlink("/dev/fortify/etc/tmpfiles.d", "/etc/tmpfiles.d").
+			Symlink("/dev/fortify/etc/udev", "/etc/udev").
+			Symlink("/dev/fortify/etc/udisks2", "/etc/udisks2").
+			Symlink("/dev/fortify/etc/UPower", "/etc/UPower").
+			Symlink("/dev/fortify/etc/vconsole.conf", "/etc/vconsole.conf").
+			Symlink("/dev/fortify/etc/X11", "/etc/X11").
+			Symlink("/dev/fortify/etc/zfs", "/etc/zfs").
+			Symlink("/dev/fortify/etc/zinputrc", "/etc/zinputrc").
+			Symlink("/dev/fortify/etc/zoneinfo", "/etc/zoneinfo").
+			Symlink("/dev/fortify/etc/zprofile", "/etc/zprofile").
+			Symlink("/dev/fortify/etc/zshenv", "/etc/zshenv").
+			Symlink("/dev/fortify/etc/zshrc", "/etc/zshrc").
+			Bind("/tmp/fortify.1971/tmpdir/150", "/tmp", false, true).
+			Tmpfs("/tmp/fortify.1971", 1048576).
+			Tmpfs("/run/user", 1048576).
+			Tmpfs("/run/user/150", 8388608).
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/passwd", "/etc/passwd").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/group", "/etc/group").
+			Bind("/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/wayland", "/run/user/150/wayland-0").
+			Bind("/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/pulse", "/run/user/150/pulse/native").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie", "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", "/run/user/150/bus").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", "/run/dbus/system_bus_socket").
+			Tmpfs("/var/run/nscd", 8192),
+	},
+}
+
+// fs methods are not implemented using a real FS
+// to help better understand filesystem access behaviour
+type stubNixOS struct {
+	lookPathErr map[string]error
+	usernameErr map[string]error
+}
+
+func (s *stubNixOS) Geteuid() int {
+	return 1971
+}
+
+func (s *stubNixOS) LookupEnv(key string) (string, bool) {
+	switch key {
+	case "SHELL":
+		return "/run/current-system/sw/bin/zsh", true
+	case "TERM":
+		return "xterm-256color", true
+	case "WAYLAND_DISPLAY":
+		return "wayland-0", true
+	case "PULSE_COOKIE":
+		return "", false
+	case "HOME":
+		return "/home/ophestra", true
+	case "XDG_CONFIG_HOME":
+		return "/home/ophestra/xdg/config", true
+	default:
+		panic(fmt.Sprintf("attempted to access unexpected environment variable %q", key))
+	}
+}
+
+func (s *stubNixOS) TempDir() string {
+	return "/tmp"
+}
+
+func (s *stubNixOS) LookPath(file string) (string, error) {
+	if s.lookPathErr != nil {
+		if err, ok := s.lookPathErr[file]; ok {
+			return "", err
+		}
+	}
+
+	switch file {
+	case "sudo":
+		return "/run/wrappers/bin/sudo", nil
+	case "machinectl":
+		return "/home/ophestra/.nix-profile/bin/machinectl", nil
+	default:
+		panic(fmt.Sprintf("attempted to look up unexpected executable %q", file))
+	}
+}
+
+func (s *stubNixOS) Executable() (string, error) {
+	return "/home/ophestra/.nix-profile/bin/fortify", nil
+}
+
+func (s *stubNixOS) Lookup(username string) (*user.User, error) {
+	if s.usernameErr != nil {
+		if err, ok := s.usernameErr[username]; ok {
+			return nil, err
+		}
+	}
+
+	switch username {
+	case "chronos":
+		return &user.User{
+			Uid:      "150",
+			Gid:      "101",
+			Username: "chronos",
+			HomeDir:  "/home/chronos",
+		}, nil
+	default:
+		return nil, user.UnknownUserError(username)
+	}
+}
+
+func (s *stubNixOS) ReadDir(name string) ([]fs.DirEntry, error) {
+	switch name {
+	case "/":
+		return stubDirEntries("bin", "boot", "dev", "etc", "home", "lib",
+			"lib64", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var")
+	case "/run":
+		return stubDirEntries("agetty.reload", "binfmt", "booted-system",
+			"credentials", "cryptsetup", "current-system", "dbus", "host", "keys",
+			"libvirt", "libvirtd.pid", "lock", "log", "lvm", "mount", "NetworkManager",
+			"nginx", "nixos", "nscd", "opengl-driver", "pppd", "resolvconf", "sddm",
+			"store", "syncoid", "system", "systemd", "tmpfiles.d", "udev", "udisks2",
+			"user", "utmp", "virtlogd.pid", "wrappers", "zed.pid", "zed.state")
+	case "/etc":
+		return stubDirEntries("alsa", "bashrc", "binfmt.d", "dbus-1", "default",
+			"ethertypes", "fonts", "fstab", "fuse.conf", "group", "host.conf", "hostid",
+			"hostname", "hostname.CHECKSUM", "hosts", "inputrc", "ipsec.d", "issue", "kbd",
+			"libblockdev", "locale.conf", "localtime", "login.defs", "lsb-release", "lvm",
+			"machine-id", "man_db.conf", "modprobe.d", "modules-load.d", "mtab", "nanorc",
+			"netgroup", "NetworkManager", "nix", "nixos", "NIXOS", "nscd.conf", "nsswitch.conf",
+			"opensnitchd", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1",
+			"profile", "protocols", "qemu", "resolv.conf", "resolvconf.conf", "rpc", "samba",
+			"sddm.conf", "secureboot", "services", "set-environment", "shadow", "shells", "ssh",
+			"ssl", "static", "subgid", "subuid", "sudoers", "sysctl.d", "systemd", "terminfo",
+			"tmpfiles.d", "udev", "udisks2", "UPower", "vconsole.conf", "X11", "zfs", "zinputrc",
+			"zoneinfo", "zprofile", "zshenv", "zshrc")
+	default:
+		panic(fmt.Sprintf("attempted to read unexpected directory %q", name))
+	}
+}
+
+func (s *stubNixOS) Stat(name string) (fs.FileInfo, error) {
+	switch name {
+	case "/var/run/nscd":
+		return nil, nil
+	case "/run/user/1971/pulse":
+		return nil, nil
+	case "/run/user/1971/pulse/native":
+		return stubFileInfoMode(0666), nil
+	case "/home/ophestra/.pulse-cookie":
+		return stubFileInfoIsDir(true), nil
+	case "/home/ophestra/xdg/config/pulse/cookie":
+		return stubFileInfoIsDir(false), nil
+	default:
+		panic(fmt.Sprintf("attempted to stat unexpected path %q", name))
+	}
+}
+
+func (s *stubNixOS) Open(name string) (fs.File, error) {
+	switch name {
+	default:
+		panic(fmt.Sprintf("attempted to open unexpected file %q", name))
+	}
+}
+
+func (s *stubNixOS) Exit(code int) {
+	panic("called exit on stub with code " + strconv.Itoa(code))
+}
+
+func (s *stubNixOS) Paths() internal.Paths {
+	return internal.Paths{
+		SharePath:   "/tmp/fortify.1971",
+		RuntimePath: "/run/user/1971",
+		RunDirPath:  "/run/user/1971/fortify",
+	}
+}
+
+func (s *stubNixOS) SdBooted() bool {
+	return true
+}

internal/app/app_test.go

@@ -0,0 +1,134 @@
+package app_test
+
+import (
+	"io/fs"
+	"reflect"
+	"testing"
+	"time"
+
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/app"
+	"git.ophivana.moe/security/fortify/internal/system"
+)
+
+type sealTestCase struct {
+	name      string
+	os        internal.System
+	config    *app.Config
+	id        app.ID
+	wantSys   *system.I
+	wantBwrap *bwrap.Config
+}
+
+func TestApp(t *testing.T) {
+	testCases := append(testCasesNixos)
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			a := app.NewWithID(tc.id, tc.os)
+
+			if !t.Run("seal", func(t *testing.T) {
+				if err := a.Seal(tc.config); err != nil {
+					t.Errorf("Seal: error = %v", err)
+				}
+			}) {
+				return
+			}
+
+			gotSys, gotBwrap := app.AppSystemBwrap(a)
+
+			t.Run("compare sys", func(t *testing.T) {
+				if !gotSys.Equal(tc.wantSys) {
+					t.Errorf("Seal: sys = %#v, want %#v",
+						gotSys, tc.wantSys)
+				}
+			})
+
+			t.Run("compare bwrap", func(t *testing.T) {
+				if !reflect.DeepEqual(gotBwrap, tc.wantBwrap) {
+					t.Errorf("seal: bwrap = %#v, want %#v",
+						gotBwrap, tc.wantBwrap)
+				}
+			})
+		})
+	}
+}
+
+func stubDirEntries(names ...string) (e []fs.DirEntry, err error) {
+	e = make([]fs.DirEntry, len(names))
+	for i, name := range names {
+		e[i] = stubDirEntryPath(name)
+	}
+	return
+}
+
+type stubDirEntryPath string
+
+func (p stubDirEntryPath) Name() string {
+	return string(p)
+}
+
+func (p stubDirEntryPath) IsDir() bool {
+	panic("attempted to call IsDir")
+}
+
+func (p stubDirEntryPath) Type() fs.FileMode {
+	panic("attempted to call Type")
+}
+
+func (p stubDirEntryPath) Info() (fs.FileInfo, error) {
+	panic("attempted to call Info")
+}
+
+type stubFileInfoMode fs.FileMode
+
+func (s stubFileInfoMode) Name() string {
+	panic("attempted to call Name")
+}
+
+func (s stubFileInfoMode) Size() int64 {
+	panic("attempted to call Size")
+}
+
+func (s stubFileInfoMode) Mode() fs.FileMode {
+	return fs.FileMode(s)
+}
+
+func (s stubFileInfoMode) ModTime() time.Time {
+	panic("attempted to call ModTime")
+}
+
+func (s stubFileInfoMode) IsDir() bool {
+	panic("attempted to call IsDir")
+}
+
+func (s stubFileInfoMode) Sys() any {
+	panic("attempted to call Sys")
+}
+
+type stubFileInfoIsDir bool
+
+func (s stubFileInfoIsDir) Name() string {
+	panic("attempted to call Name")
+}
+
+func (s stubFileInfoIsDir) Size() int64 {
+	panic("attempted to call Size")
+}
+
+func (s stubFileInfoIsDir) Mode() fs.FileMode {
+	panic("attempted to call Mode")
+}
+
+func (s stubFileInfoIsDir) ModTime() time.Time {
+	panic("attempted to call ModTime")
+}
+
+func (s stubFileInfoIsDir) IsDir() bool {
+	return bool(s)
+}
+
+func (s stubFileInfoIsDir) Sys() any {
+	panic("attempted to call Sys")
+}

internal/app/config.go

@@ -1,9 +1,11 @@
 package app
 
 import (
-	"git.ophivana.moe/cat/fortify/dbus"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
-	"git.ophivana.moe/cat/fortify/internal/state"
+	"os"
+
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 // Config is used to seal an *App
@@ -34,7 +36,7 @@ type ConfinementConfig struct {
 	SessionBus *dbus.Config `json:"session_bus,omitempty"`
 
 	// child capability enablements
-	Enablements state.Enablements `json:"enablements"`
+	Enablements system.Enablements `json:"enablements"`
 }
 
 // SandboxConfig describes resources made available to the sandbox.
@@ -54,8 +56,10 @@ type SandboxConfig struct {
 	Env map[string]string `json:"env"`
 	// sandbox host filesystem access
 	Filesystem []*FilesystemConfig `json:"filesystem"`
-	// tmpfs mount points to mount last
-	Tmpfs []bwrap.TmpfsConfig `json:"tmpfs"`
+	// symlinks created inside the sandbox
+	Link [][2]string `json:"symlink"`
+	// paths to override by mounting tmpfs over them
+	Override []string `json:"override"`
 }
 
 type FilesystemConfig struct {
@@ -71,61 +75,44 @@ type FilesystemConfig struct {
 	Must bool `json:"require,omitempty"`
 }
 
+// Bwrap returns the address of the corresponding bwrap.Config to s.
+// Note that remaining tmpfs entries must be queued by the caller prior to launch.
 func (s *SandboxConfig) Bwrap() *bwrap.Config {
 	if s == nil {
 		return nil
 	}
 
-	nobody := 65534
-	conf := &bwrap.Config{
+	conf := (&bwrap.Config{
 		Net:           s.Net,
 		UserNS:        s.UserNS,
-		UID:           &nobody,
-		GID:           &nobody,
 		Hostname:      s.Hostname,
 		Clearenv:      true,
 		SetEnv:        s.Env,
-		Procfs:        []string{"/proc"},
-		DevTmpfs:      []string{"/dev"},
-		Mqueue:        []string{"/dev/mqueue"},
 		NewSession:    !s.NoNewSession,
 		DieWithParent: true,
 		AsInit:        true,
-	}
+
+		// initialise map
+		Chmod: make(map[string]os.FileMode),
+	}).
+		SetUID(65534).SetGID(65534).
+		Procfs("/proc").DevTmpfs("/dev").Mqueue("/dev/mqueue").
+		Tmpfs("/dev/fortify", 4*1024)
 
 	for _, c := range s.Filesystem {
 		if c == nil {
 			continue
 		}
-		p := [2]string{c.Src, c.Dst}
+		src := c.Src
+		dest := c.Dst
 		if c.Dst == "" {
-			p[1] = c.Src
-		}
-
-		switch {
-		case c.Device:
-			if c.Must {
-				conf.DevBind = append(conf.DevBind, p)
-			} else {
-				conf.DevBindTry = append(conf.DevBindTry, p)
-			}
-		case c.Write:
-			if c.Must {
-				conf.Bind = append(conf.Bind, p)
-			} else {
-				conf.BindTry = append(conf.BindTry, p)
-			}
-		default:
-			if c.Must {
-				conf.ROBind = append(conf.ROBind, p)
-			} else {
-				conf.ROBindTry = append(conf.ROBindTry, p)
-			}
+			dest = c.Src
 		}
+		conf.Bind(src, dest, !c.Must, c.Write, c.Device)
 	}
 
-	for _, tmpfs := range s.Tmpfs {
-		conf.Tmpfs = append(conf.Tmpfs, bwrap.PermConfig[bwrap.TmpfsConfig]{Path: tmpfs, Last: true})
+	for _, l := range s.Link {
+		conf.Symlink(l[0], l[1])
 	}
 
 	return conf
@@ -164,9 +151,8 @@ func Template() *Config {
 					{Src: "/data/user/0", Dst: "/data/data", Write: true, Must: true},
 					{Src: "/var/tmp", Write: true},
 				},
-				Tmpfs: []bwrap.TmpfsConfig{
-					{Size: 8 * 1024, Dir: "/var/run/nscd"},
-				},
+				Link:     [][2]string{{"/dev/fortify/etc", "/etc"}},
+				Override: []string{"/var/run/nscd"},
 			},
 			SystemBus: &dbus.Config{
 				See:       nil,
@@ -188,7 +174,7 @@ func Template() *Config {
 				Log:       false,
 				Filter:    true,
 			},
-			Enablements: state.EnableWayland.Mask() | state.EnableDBus.Mask() | state.EnablePulse.Mask(),
+			Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
 		},
 	}
 }

internal/app/copy.go

@@ -1,33 +0,0 @@
-package app
-
-import (
-	"io"
-	"os"
-)
-
-func copyFile(dst, src string) error {
-	srcD, err := os.Open(src)
-	if err != nil {
-		return err
-	}
-	defer func() {
-		if srcD.Close() != nil {
-			// unreachable
-			panic("src file closed prematurely")
-		}
-	}()
-
-	dstD, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
-	if err != nil {
-		return err
-	}
-	defer func() {
-		if dstD.Close() != nil {
-			// unreachable
-			panic("dst file closed prematurely")
-		}
-	}()
-
-	_, err = io.Copy(dstD, srcD)
-	return err
-}

internal/app/export_test.go

@@ -0,0 +1,19 @@
+package app
+
+import (
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/system"
+)
+
+func NewWithID(id ID, os internal.System) App {
+	a := new(app)
+	a.id = &id
+	a.os = os
+	return a
+}
+
+func AppSystemBwrap(a App) (*system.I, *bwrap.Config) {
+	v := a.(*app)
+	return v.seal.sys.I, v.seal.sys.bwrap
+}

internal/app/id.go

@@ -5,14 +5,13 @@ import (
 	"encoding/hex"
 )
 
-type appID [16]byte
+type ID [16]byte
 
-func (a *appID) String() string {
+func (a *ID) String() string {
 	return hex.EncodeToString(a[:])
 }
 
-func newAppID() (*appID, error) {
-	a := &appID{}
-	_, err := rand.Read(a[:])
-	return a, err
+func newAppID(id *ID) error {
+	_, err := rand.Read(id[:])
+	return err
 }

internal/app/launch.machinectl.go

@@ -1,21 +1,19 @@
 package app
 
 import (
-	"os/exec"
 	"strings"
 
-	"git.ophivana.moe/cat/fortify/internal/state"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
 func (a *app) commandBuilderMachineCtl(shimEnv string) (args []string) {
 	args = make([]string, 0, 9+len(a.seal.sys.bwrap.SetEnv))
 
 	// shell --uid=$USER
-	args = append(args, "shell", "--uid="+a.seal.sys.Username)
+	args = append(args, "shell", "--uid="+a.seal.sys.user.Username)
 
 	// --quiet
-	if !verbose.Get() {
+	if !fmsg.Verbose() {
 		args = append(args, "--quiet")
 	}
 
@@ -32,7 +30,7 @@ func (a *app) commandBuilderMachineCtl(shimEnv string) (args []string) {
 	args = append(args, "--", ".host")
 
 	// /bin/sh -c
-	if sh, err := exec.LookPath("sh"); err != nil {
+	if sh, err := a.os.LookPath("sh"); err != nil {
 		// hardcode /bin/sh path since it exists more often than not
 		args = append(args, "/bin/sh", "-c")
 	} else {
@@ -49,14 +47,6 @@ func (a *app) commandBuilderMachineCtl(shimEnv string) (args []string) {
 	}
 	innerCommand.WriteString("; ")
 
-	// override message bus address if enabled
-	if a.seal.et.Has(state.EnableDBus) {
-		innerCommand.WriteString(dbusSessionBusAddress + "=" + "'" + "unix:path=" + a.seal.sys.dbusAddr[0][1] + "' ")
-		if a.seal.sys.dbusSystem {
-			innerCommand.WriteString(dbusSystemBusAddress + "=" + "'" + "unix:path=" + a.seal.sys.dbusAddr[1][1] + "' ")
-		}
-	}
-
 	// launch fortify as shim
 	innerCommand.WriteString("exec " + a.seal.sys.executable + " shim")
 

internal/app/launch.sudo.go

@@ -1,9 +1,7 @@
 package app
 
 import (
-	"os"
-
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
 const (
@@ -14,11 +12,11 @@ func (a *app) commandBuilderSudo(shimEnv string) (args []string) {
 	args = make([]string, 0, 8)
 
 	// -Hiu $USER
-	args = append(args, "-Hiu", a.seal.sys.Username)
+	args = append(args, "-Hiu", a.seal.sys.user.Username)
 
 	// -A?
-	if _, ok := os.LookupEnv(sudoAskPass); ok {
-		verbose.Printf("%s set, adding askpass flag\n", sudoAskPass)
+	if _, ok := a.os.LookupEnv(sudoAskPass); ok {
+		fmsg.VPrintln(sudoAskPass, "set, adding askpass flag")
 		args = append(args, "-A")
 	}
 

internal/app/seal.go

@@ -2,17 +2,17 @@ package app
 
 import (
 	"errors"
-	"os"
-	"os/exec"
+	"io/fs"
 	"os/user"
 	"path"
 	"strconv"
 
-	"git.ophivana.moe/cat/fortify/dbus"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
-	"git.ophivana.moe/cat/fortify/internal"
-	"git.ophivana.moe/cat/fortify/internal/state"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/shim"
+	"git.ophivana.moe/security/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 const (
@@ -20,6 +20,11 @@ const (
 	LaunchMethodMachineCtl
 )
 
+var method = [...]string{
+	LaunchMethodSudo:       "sudo",
+	LaunchMethodMachineCtl: "systemd",
+}
+
 var (
 	ErrConfig = errors.New("no configuration to seal")
 	ErrUser   = errors.New("unknown user")
@@ -30,11 +35,41 @@ var (
 	ErrMachineCtl = errors.New("machinectl not available")
 )
 
-type (
-	SealConfigError     BaseError
-	LauncherLookupError BaseError
-	SecurityError       BaseError
-)
+// appSeal seals the application with child-related information
+type appSeal struct {
+	// app unique ID string representation
+	id string
+	// wayland mediation, disabled if nil
+	wl *shim.Wayland
+
+	// freedesktop application ID
+	fid string
+	// argv to start process with in the final confined environment
+	command []string
+	// persistent process state store
+	store state.Store
+
+	// uint8 representation of launch method sealed from config
+	launchOption uint8
+	// process-specific share directory path
+	share string
+	// process-specific share directory path local to XDG_RUNTIME_DIR
+	shareLocal string
+
+	// path to launcher program
+	toolPath string
+	// pass-through enablement tracking from config
+	et system.Enablements
+
+	// prevents sharing from happening twice
+	shared bool
+	// seal system-level component
+	sys *appSealSys
+
+	internal.Paths
+
+	// protected by upstream mutex
+}
 
 // Seal seals the app launch context
 func (a *app) Seal(config *Config) error {
@@ -46,77 +81,75 @@ func (a *app) Seal(config *Config) error {
 	}
 
 	if config == nil {
-		return (*SealConfigError)(wrapError(ErrConfig, "attempted to seal app with nil config"))
+		return fmsg.WrapError(ErrConfig,
+			"attempted to seal app with nil config")
 	}
 
 	// create seal
 	seal := new(appSeal)
 
-	// generate application ID
-	if id, err := newAppID(); err != nil {
-		return (*SecurityError)(wrapError(err, "cannot generate application ID:", err))
-	} else {
-		seal.id = id
-	}
-
 	// fetch system constants
-	seal.SystemConstants = internal.GetSC()
+	seal.Paths = a.os.Paths()
 
 	// pass through config values
+	seal.id = a.id.String()
 	seal.fid = config.ID
 	seal.command = config.Command
 
 	// parses launch method text and looks up tool path
 	switch config.Method {
-	case "sudo":
+	case method[LaunchMethodSudo]:
 		seal.launchOption = LaunchMethodSudo
-		if sudoPath, err := exec.LookPath("sudo"); err != nil {
-			return (*LauncherLookupError)(wrapError(ErrSudo, "sudo not found"))
+		if sudoPath, err := a.os.LookPath("sudo"); err != nil {
+			return fmsg.WrapError(ErrSudo,
+				"sudo not found")
 		} else {
 			seal.toolPath = sudoPath
 		}
-	case "systemd":
+	case method[LaunchMethodMachineCtl]:
 		seal.launchOption = LaunchMethodMachineCtl
-		if !internal.SdBootedV {
-			return (*LauncherLookupError)(wrapError(ErrSystemd,
-				"system has not been booted with systemd as init system"))
+		if !a.os.SdBooted() {
+			return fmsg.WrapError(ErrSystemd,
+				"system has not been booted with systemd as init system")
 		}
 
-		if machineCtlPath, err := exec.LookPath("machinectl"); err != nil {
-			return (*LauncherLookupError)(wrapError(ErrMachineCtl, "machinectl not found"))
+		if machineCtlPath, err := a.os.LookPath("machinectl"); err != nil {
+			return fmsg.WrapError(ErrMachineCtl,
+				"machinectl not found")
 		} else {
 			seal.toolPath = machineCtlPath
 		}
 	default:
-		return (*SealConfigError)(wrapError(ErrLaunch, "invalid launch method"))
+		return fmsg.WrapError(ErrLaunch,
+			"invalid launch method")
 	}
 
 	// create seal system component
-	seal.sys = new(appSealTx)
+	seal.sys = new(appSealSys)
 
 	// look up fortify executable path
-	if p, err := os.Executable(); err != nil {
-		return (*LauncherLookupError)(wrapError(err, "cannot look up fortify executable path:", err))
+	if p, err := a.os.Executable(); err != nil {
+		return fmsg.WrapErrorSuffix(err, "cannot look up fortify executable path:")
 	} else {
 		seal.sys.executable = p
 	}
 
 	// look up user from system
-	if u, err := user.Lookup(config.User); err != nil {
+	if u, err := a.os.Lookup(config.User); err != nil {
 		if errors.As(err, new(user.UnknownUserError)) {
-			return (*SealConfigError)(wrapError(ErrUser, "unknown user", config.User))
+			return fmsg.WrapError(ErrUser, "unknown user", config.User)
 		} else {
 			// unreachable
 			panic(err)
 		}
 	} else {
-		seal.sys.User = u
+		seal.sys.user = u
 		seal.sys.runtime = path.Join("/run/user", u.Uid)
 	}
 
 	// map sandbox config to bwrap
 	if config.Confinement.Sandbox == nil {
-		verbose.Println("sandbox configuration not supplied, PROCEED WITH CAUTION")
+		fmsg.VPrintln("sandbox configuration not supplied, PROCEED WITH CAUTION")
 
 		// permissive defaults
 		conf := &SandboxConfig{
@@ -125,26 +158,29 @@ func (a *app) Seal(config *Config) error {
 			NoNewSession: true,
 		}
 		// bind entries in /
-		if d, err := os.ReadDir("/"); err != nil {
+		if d, err := a.os.ReadDir("/"); err != nil {
 			return err
 		} else {
 			b := make([]*FilesystemConfig, 0, len(d))
 			for _, ent := range d {
-				name := ent.Name()
-				switch name {
-				case "proc":
-				case "dev":
-				case "run":
-				case "mnt":
+				p := "/" + ent.Name()
+				switch p {
+				case "/proc":
+				case "/dev":
+				case "/run":
+				case "/tmp":
+				case "/mnt":
+
+				case "/etc":
+					b = append(b, &FilesystemConfig{Src: p, Dst: "/dev/fortify/etc", Write: false, Must: true})
 				default:
-					p := "/" + name
 					b = append(b, &FilesystemConfig{Src: p, Write: true, Must: true})
 				}
 			}
 			conf.Filesystem = append(conf.Filesystem, b...)
 		}
 		// bind entries in /run
-		if d, err := os.ReadDir("/run"); err != nil {
+		if d, err := a.os.ReadDir("/run"); err != nil {
 			return err
 		} else {
 			b := make([]*FilesystemConfig, 0, len(d))
@@ -162,50 +198,77 @@ func (a *app) Seal(config *Config) error {
 		}
 		// hide nscd from sandbox if present
 		nscd := "/var/run/nscd"
-		if _, err := os.Stat(nscd); !errors.Is(err, os.ErrNotExist) {
-			conf.Tmpfs = append(conf.Tmpfs, bwrap.TmpfsConfig{Size: 8 * 1024, Dir: nscd})
+		if _, err := a.os.Stat(nscd); !errors.Is(err, fs.ErrNotExist) {
+			conf.Override = append(conf.Override, nscd)
 		}
 		// bind GPU stuff
-		if config.Confinement.Enablements.Has(state.EnableX) || config.Confinement.Enablements.Has(state.EnableWayland) {
+		if config.Confinement.Enablements.Has(system.EX11) || config.Confinement.Enablements.Has(system.EWayland) {
 			conf.Filesystem = append(conf.Filesystem, &FilesystemConfig{Src: "/dev/dri", Device: true})
 		}
+		// link host /etc to prevent passwd/group from being overwritten
+		if d, err := a.os.ReadDir("/etc"); err != nil {
+			return err
+		} else {
+			b := make([][2]string, 0, len(d))
+			for _, ent := range d {
+				name := ent.Name()
+				switch name {
+				case "passwd":
+				case "group":
+
+				case "mtab":
+					b = append(b, [2]string{
+						"/proc/mounts",
+						"/etc/" + name,
+					})
+				default:
+					b = append(b, [2]string{
+						"/dev/fortify/etc/" + name,
+						"/etc/" + name,
+					})
+				}
+			}
+			conf.Link = append(conf.Link, b...)
+		}
+
 		config.Confinement.Sandbox = conf
 	}
 	seal.sys.bwrap = config.Confinement.Sandbox.Bwrap()
+	seal.sys.override = config.Confinement.Sandbox.Override
 	if seal.sys.bwrap.SetEnv == nil {
 		seal.sys.bwrap.SetEnv = make(map[string]string)
 	}
 
-	// create wayland client wait channel if mediated wayland is enabled
-	// this channel being set enables mediated wayland setup later on
+	// create wayland struct and client wait channel if mediated wayland is enabled
+	// this field being set enables mediated wayland setup later on
 	if config.Confinement.Sandbox.Wayland {
-		seal.wlDone = make(chan struct{})
+		seal.wl = shim.NewWayland()
 	}
 
 	// open process state store
 	// the simple store only starts holding an open file after first action
 	// store activity begins after Start is called and must end before Wait
-	seal.store = state.NewSimple(seal.SystemConstants.RunDirPath, seal.sys.Uid)
+	seal.store = state.NewSimple(seal.RunDirPath, seal.sys.user.Uid)
 
 	// parse string UID
-	if u, err := strconv.Atoi(seal.sys.Uid); err != nil {
+	if u, err := strconv.Atoi(seal.sys.user.Uid); err != nil {
 		// unreachable unless kernel bug
 		panic("uid parse")
 	} else {
-		seal.sys.uid = u
+		seal.sys.I = system.New(u)
 	}
 
 	// pass through enablements
 	seal.et = config.Confinement.Enablements
 
 	// this method calls all share methods in sequence
-	if err := seal.shareAll([2]*dbus.Config{config.Confinement.SessionBus, config.Confinement.SystemBus}); err != nil {
+	if err := seal.shareAll([2]*dbus.Config{config.Confinement.SessionBus, config.Confinement.SystemBus}, a.os); err != nil {
 		return err
 	}
 
 	// verbose log seal information
-	verbose.Println("created application seal as user",
-		seal.sys.Username, "("+seal.sys.Uid+"),",
+	fmsg.VPrintln("created application seal as user",
+		seal.sys.user.Username, "("+seal.sys.user.Uid+"),",
 		"method:", config.Method+",",
 		"launcher:", seal.toolPath+",",
 		"command:", config.Command)

internal/app/share.dbus.go

@@ -1,15 +1,11 @@
 package app
 
 import (
-	"errors"
-	"fmt"
-	"os"
 	"path"
 
-	"git.ophivana.moe/cat/fortify/acl"
-	"git.ophivana.moe/cat/fortify/dbus"
-	"git.ophivana.moe/cat/fortify/internal/state"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 const (
@@ -17,122 +13,30 @@ const (
 	dbusSystemBusAddress  = "DBUS_SYSTEM_BUS_ADDRESS"
 )
 
-var (
-	ErrDBusConfig = errors.New("dbus config not supplied")
-)
-
-type (
-	SealDBusError   BaseError
-	LookupDBusError BaseError
-	StartDBusError  BaseError
-	CloseDBusError  BaseError
-)
-
 func (seal *appSeal) shareDBus(config [2]*dbus.Config) error {
-	if !seal.et.Has(state.EnableDBus) {
+	if !seal.et.Has(system.EDBus) {
 		return nil
 	}
 
-	// session bus is mandatory
-	if config[0] == nil {
-		return (*SealDBusError)(wrapError(ErrDBusConfig, "attempted to seal session bus proxy with nil config"))
-	}
-
-	// system bus is optional
-	seal.sys.dbusSystem = config[1] != nil
-
-	// upstream address, downstream socket path
-	var sessionBus, systemBus [2]string
-
 	// downstream socket paths
-	sessionBus[1] = path.Join(seal.share, "bus")
-	systemBus[1] = path.Join(seal.share, "system_bus_socket")
+	sessionPath, systemPath := path.Join(seal.share, "bus"), path.Join(seal.share, "system_bus_socket")
 
-	// resolve upstream bus addresses
-	sessionBus[0], systemBus[0] = dbus.Address()
-
-	// create proxy instance
-	seal.sys.dbus = dbus.New(sessionBus, systemBus)
-
-	// seal dbus proxy
-	if err := seal.sys.dbus.Seal(config[0], config[1]); err != nil {
-		return (*SealDBusError)(wrapError(err, "cannot seal message bus proxy:", err))
+	// configure dbus proxy
+	if err := seal.sys.ProxyDBus(config[0], config[1], sessionPath, systemPath); err != nil {
+		return err
 	}
 
-	// store addresses for cleanup and logging
-	seal.sys.dbusAddr = &[2][2]string{sessionBus, systemBus}
-
 	// share proxy sockets
 	sessionInner := path.Join(seal.sys.runtime, "bus")
-	seal.sys.setEnv(dbusSessionBusAddress, "unix:path="+sessionInner)
-	seal.sys.bind(sessionBus[1], sessionInner, true)
-	seal.sys.updatePerm(sessionBus[1], acl.Read, acl.Write)
-	if seal.sys.dbusSystem {
+	seal.sys.bwrap.SetEnv[dbusSessionBusAddress] = "unix:path=" + sessionInner
+	seal.sys.bwrap.Bind(sessionPath, sessionInner)
+	seal.sys.UpdatePerm(sessionPath, acl.Read, acl.Write)
+	if config[1] != nil {
 		systemInner := "/run/dbus/system_bus_socket"
-		seal.sys.setEnv(dbusSystemBusAddress, "unix:path="+systemInner)
-		seal.sys.bind(systemBus[1], systemInner, true)
-		seal.sys.updatePerm(systemBus[1], acl.Read, acl.Write)
+		seal.sys.bwrap.SetEnv[dbusSystemBusAddress] = "unix:path=" + systemInner
+		seal.sys.bwrap.Bind(systemPath, systemInner)
+		seal.sys.UpdatePerm(systemPath, acl.Read, acl.Write)
 	}
 
 	return nil
 }
-
-func (tx *appSealTx) startDBus() error {
-	// ready channel passed to dbus package
-	ready := make(chan error, 1)
-	// used by waiting goroutine to notify process return
-	tx.dbusWait = make(chan struct{})
-
-	// background dbus proxy start
-	if err := tx.dbus.Start(ready, os.Stderr, true); err != nil {
-		return (*StartDBusError)(wrapError(err, "cannot start message bus proxy:", err))
-	}
-	verbose.Println("starting message bus proxy:", tx.dbus)
-	verbose.Println("message bus proxy bwrap args:", tx.dbus.Bwrap())
-
-	// background wait for proxy instance and notify completion
-	go func() {
-		if err := tx.dbus.Wait(); err != nil {
-			fmt.Println("fortify: warn: message bus proxy returned error:", err)
-			go func() { ready <- err }()
-		} else {
-			verbose.Println("message bus proxy exit")
-		}
-
-		// ensure socket removal so ephemeral directory is empty at revert
-		if err := os.Remove(tx.dbusAddr[0][1]); err != nil && !errors.Is(err, os.ErrNotExist) {
-			fmt.Println("fortify: cannot remove dangling session bus socket:", err)
-		}
-		if tx.dbusSystem {
-			if err := os.Remove(tx.dbusAddr[1][1]); err != nil && !errors.Is(err, os.ErrNotExist) {
-				fmt.Println("fortify: cannot remove dangling system bus socket:", err)
-			}
-		}
-
-		// notify proxy completion
-		tx.dbusWait <- struct{}{}
-	}()
-
-	// ready is not nil if the proxy process faulted
-	if err := <-ready; err != nil {
-		// note that err here is either an I/O related error or a predetermined unexpected behaviour error
-		return (*StartDBusError)(wrapError(err, "message bus proxy fault after start:", err))
-	}
-	verbose.Println("message bus proxy ready")
-
-	return nil
-}
-
-func (tx *appSealTx) stopDBus() error {
-	if err := tx.dbus.Close(); err != nil {
-		if errors.Is(err, os.ErrClosed) {
-			return (*CloseDBusError)(wrapError(err, "message bus proxy already closed"))
-		} else {
-			return (*CloseDBusError)(wrapError(err, "cannot close message bus proxy:", err))
-		}
-	}
-
-	// block until proxy wait returns
-	<-tx.dbusWait
-	return nil
-}

internal/app/share.display.go

@@ -2,11 +2,12 @@ package app
 
 import (
 	"errors"
-	"os"
 	"path"
 
-	"git.ophivana.moe/cat/fortify/acl"
-	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 const (
@@ -22,44 +23,44 @@ var (
 	ErrXDisplay = errors.New(display + " unset")
 )
 
-type ErrDisplayEnv BaseError
-
-func (seal *appSeal) shareDisplay() error {
+func (seal *appSeal) shareDisplay(os internal.System) error {
 	// pass $TERM to launcher
 	if t, ok := os.LookupEnv(term); ok {
-		seal.sys.setEnv(term, t)
+		seal.sys.bwrap.SetEnv[term] = t
 	}
 
 	// set up wayland
-	if seal.et.Has(state.EnableWayland) {
+	if seal.et.Has(system.EWayland) {
 		if wd, ok := os.LookupEnv(waylandDisplay); !ok {
-			return (*ErrDisplayEnv)(wrapError(ErrWayland, "WAYLAND_DISPLAY is not set"))
-		} else if seal.wlDone == nil {
+			return fmsg.WrapError(ErrWayland,
+				"WAYLAND_DISPLAY is not set")
+		} else if seal.wl == nil {
 			// hardlink wayland socket
 			wp := path.Join(seal.RuntimePath, wd)
 			wpi := path.Join(seal.shareLocal, "wayland")
 			w := path.Join(seal.sys.runtime, "wayland-0")
-			seal.sys.link(wp, wpi)
-			seal.sys.setEnv(waylandDisplay, w)
-			seal.sys.bind(wpi, w, true)
+			seal.sys.Link(wp, wpi)
+			seal.sys.bwrap.SetEnv[waylandDisplay] = w
+			seal.sys.bwrap.Bind(wpi, w)
 
 			// ensure Wayland socket ACL (e.g. `/run/user/%d/wayland-%d`)
-			seal.sys.updatePermTag(state.EnableWayland, wp, acl.Read, acl.Write, acl.Execute)
+			seal.sys.UpdatePermType(system.EWayland, wp, acl.Read, acl.Write, acl.Execute)
 		} else {
-			// set wayland socket path (e.g. `/run/user/%d/wayland-%d`)
-			seal.wl = path.Join(seal.RuntimePath, wd)
+			// set wayland socket path for mediation (e.g. `/run/user/%d/wayland-%d`)
+			seal.wl.Path = path.Join(seal.RuntimePath, wd)
 		}
 	}
 
 	// set up X11
-	if seal.et.Has(state.EnableX) {
+	if seal.et.Has(system.EX11) {
 		// discover X11 and grant user permission via the `ChangeHosts` command
 		if d, ok := os.LookupEnv(display); !ok {
-			return (*ErrDisplayEnv)(wrapError(ErrXDisplay, "DISPLAY is not set"))
+			return fmsg.WrapError(ErrXDisplay,
+				"DISPLAY is not set")
 		} else {
-			seal.sys.changeHosts(seal.sys.Username)
-			seal.sys.setEnv(display, d)
-			seal.sys.bind("/tmp/.X11-unix", "/tmp/.X11-unix", true)
+			seal.sys.ChangeHosts(seal.sys.user.Username)
+			seal.sys.bwrap.SetEnv[display] = d
+			seal.sys.bwrap.Bind("/tmp/.X11-unix", "/tmp/.X11-unix")
 		}
 	}
 

internal/app/share.pulse.go

@@ -4,10 +4,11 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
-	"os"
 	"path"
 
-	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 const (
@@ -24,13 +25,8 @@ var (
 	ErrPulseMode   = errors.New("unexpected pulse socket mode")
 )
 
-type (
-	PulseCookieAccessError BaseError
-	PulseSocketAccessError BaseError
-)
-
-func (seal *appSeal) sharePulse() error {
-	if !seal.et.Has(state.EnablePulse) {
+func (seal *appSeal) sharePulse(os internal.System) error {
+	if !seal.et.Has(system.EPulse) {
 		return nil
 	}
 
@@ -39,49 +35,50 @@ func (seal *appSeal) sharePulse() error {
 	ps := path.Join(pd, "native")
 	if _, err := os.Stat(pd); err != nil {
 		if !errors.Is(err, fs.ErrNotExist) {
-			return (*PulseSocketAccessError)(wrapError(err,
-				fmt.Sprintf("cannot access PulseAudio directory '%s':", pd), err))
+			return fmsg.WrapErrorSuffix(err,
+				fmt.Sprintf("cannot access PulseAudio directory %q:", pd))
 		}
-		return (*PulseSocketAccessError)(wrapError(ErrPulseSocket,
-			fmt.Sprintf("PulseAudio directory '%s' not found", pd)))
+		return fmsg.WrapError(ErrPulseSocket,
+			fmt.Sprintf("PulseAudio directory %q not found", pd))
 	}
 
 	// check PulseAudio socket permission (e.g. `/run/user/%d/pulse/native`)
 	if s, err := os.Stat(ps); err != nil {
 		if !errors.Is(err, fs.ErrNotExist) {
-			return (*PulseSocketAccessError)(wrapError(err,
-				fmt.Sprintf("cannot access PulseAudio socket '%s':", ps), err))
+			return fmsg.WrapErrorSuffix(err,
+				fmt.Sprintf("cannot access PulseAudio socket %q:", ps))
 		}
-		return (*PulseSocketAccessError)(wrapError(ErrPulseSocket,
-			fmt.Sprintf("PulseAudio directory '%s' found but socket does not exist", pd)))
+		return fmsg.WrapError(ErrPulseSocket,
+			fmt.Sprintf("PulseAudio directory %q found but socket does not exist", pd))
 	} else {
 		if m := s.Mode(); m&0o006 != 0o006 {
-			return (*PulseSocketAccessError)(wrapError(ErrPulseMode,
-				fmt.Sprintf("unexpected permissions on '%s':", ps), m))
+			return fmsg.WrapError(ErrPulseMode,
+				fmt.Sprintf("unexpected permissions on %q:", ps), m)
 		}
 	}
 
 	// hard link pulse socket into target-executable share
 	psi := path.Join(seal.shareLocal, "pulse")
 	p := path.Join(seal.sys.runtime, "pulse", "native")
-	seal.sys.link(ps, psi)
-	seal.sys.bind(psi, p, true)
-	seal.sys.setEnv(pulseServer, "unix:"+p)
+	seal.sys.Link(ps, psi)
+	seal.sys.bwrap.Bind(psi, p)
+	seal.sys.bwrap.SetEnv[pulseServer] = "unix:" + p
 
 	// publish current user's pulse cookie for target user
-	if src, err := discoverPulseCookie(); err != nil {
+	if src, err := discoverPulseCookie(os); err != nil {
 		return err
 	} else {
 		dst := path.Join(seal.share, "pulse-cookie")
-		seal.sys.setEnv(pulseCookie, dst)
-		seal.sys.copyFile(dst, src)
+		seal.sys.bwrap.SetEnv[pulseCookie] = dst
+		seal.sys.CopyFile(dst, src)
+		seal.sys.bwrap.Bind(dst, dst)
 	}
 
 	return nil
 }
 
 // discoverPulseCookie attempts various standard methods to discover the current user's PulseAudio authentication cookie
-func discoverPulseCookie() (string, error) {
+func discoverPulseCookie(os internal.System) (string, error) {
 	if p, ok := os.LookupEnv(pulseCookie); ok {
 		return p, nil
 	}
@@ -91,8 +88,8 @@ func discoverPulseCookie() (string, error) {
 		p = path.Join(p, ".pulse-cookie")
 		if s, err := os.Stat(p); err != nil {
 			if !errors.Is(err, fs.ErrNotExist) {
-				return p, (*PulseCookieAccessError)(wrapError(err,
-					fmt.Sprintf("cannot access PulseAudio cookie '%s':", p), err))
+				return p, fmsg.WrapErrorSuffix(err,
+					fmt.Sprintf("cannot access PulseAudio cookie %q:", p))
 			}
 			// not found, try next method
 		} else if !s.IsDir() {
@@ -105,7 +102,8 @@ func discoverPulseCookie() (string, error) {
 		p = path.Join(p, "pulse", "cookie")
 		if s, err := os.Stat(p); err != nil {
 			if !errors.Is(err, fs.ErrNotExist) {
-				return p, (*PulseCookieAccessError)(wrapError(err, "cannot access PulseAudio cookie", p+":", err))
+				return p, fmsg.WrapErrorSuffix(err,
+					fmt.Sprintf("cannot access PulseAudio cookie %q:", p))
 			}
 			// not found, try next method
 		} else if !s.IsDir() {
@@ -113,7 +111,7 @@ func discoverPulseCookie() (string, error) {
 		}
 	}
 
-	return "", (*PulseCookieAccessError)(wrapError(ErrPulseCookie,
+	return "", fmsg.WrapError(ErrPulseCookie,
 		fmt.Sprintf("cannot locate PulseAudio cookie (tried $%s, $%s/pulse/cookie, $%s/.pulse-cookie)",
-			pulseCookie, xdgConfigHome, home)))
+			pulseCookie, xdgConfigHome, home))
 }

internal/app/share.runtime.go

@@ -3,9 +3,8 @@ package app
 import (
 	"path"
 
-	"git.ophivana.moe/cat/fortify/acl"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
-	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 const (
@@ -17,58 +16,24 @@ const (
 // shareRuntime queues actions for sharing/ensuring the runtime and share directories
 func (seal *appSeal) shareRuntime() {
 	// mount tmpfs on inner runtime (e.g. `/run/user/%d`)
-	seal.sys.bwrap.Tmpfs = append(seal.sys.bwrap.Tmpfs,
-		bwrap.PermConfig[bwrap.TmpfsConfig]{
-			Path: bwrap.TmpfsConfig{
-				Size: 1 * 1024 * 1024,
-				Dir:  "/run/user",
-			},
-		},
-		bwrap.PermConfig[bwrap.TmpfsConfig]{
-			Path: bwrap.TmpfsConfig{
-				Size: 8 * 1024 * 1024,
-				Dir:  seal.sys.runtime,
-			},
-		},
-	)
+	seal.sys.bwrap.Tmpfs("/run/user", 1*1024*1024)
+	seal.sys.bwrap.Tmpfs(seal.sys.runtime, 8*1024*1024)
+
+	// point to inner runtime path `/run/user/%d`
+	seal.sys.bwrap.SetEnv[xdgRuntimeDir] = seal.sys.runtime
+	seal.sys.bwrap.SetEnv[xdgSessionClass] = "user"
+	seal.sys.bwrap.SetEnv[xdgSessionType] = "tty"
 
 	// ensure RunDir (e.g. `/run/user/%d/fortify`)
-	seal.sys.ensure(seal.RunDirPath, 0700)
-	seal.sys.updatePermTag(state.EnableLength, seal.RunDirPath, acl.Execute)
+	seal.sys.Ensure(seal.RunDirPath, 0700)
+	seal.sys.UpdatePermType(system.User, seal.RunDirPath, acl.Execute)
 
 	// ensure runtime directory ACL (e.g. `/run/user/%d`)
-	seal.sys.updatePermTag(state.EnableLength, seal.RuntimePath, acl.Execute)
-
-	// ensure Share (e.g. `/tmp/fortify.%d`)
-	// acl is unnecessary as this directory is world executable
-	seal.sys.ensure(seal.SharePath, 0701)
-
-	// ensure process-specific share (e.g. `/tmp/fortify.%d/%s`)
-	// acl is unnecessary as this directory is world executable
-	seal.share = path.Join(seal.SharePath, seal.id.String())
-	seal.sys.ensureEphemeral(seal.share, 0701)
+	seal.sys.Ensure(seal.RuntimePath, 0700) // ensure this dir in case XDG_RUNTIME_DIR is unset
+	seal.sys.UpdatePermType(system.User, seal.RuntimePath, acl.Execute)
 
 	// ensure process-specific share local to XDG_RUNTIME_DIR (e.g. `/run/user/%d/fortify/%s`)
-	seal.shareLocal = path.Join(seal.RunDirPath, seal.id.String())
-	seal.sys.ensureEphemeral(seal.shareLocal, 0700)
-	seal.sys.updatePerm(seal.shareLocal, acl.Execute)
-}
-
-func (seal *appSeal) shareRuntimeChild() string {
-	// ensure child runtime parent directory (e.g. `/tmp/fortify.%d/runtime`)
-	targetRuntimeParent := path.Join(seal.SharePath, "runtime")
-	seal.sys.ensure(targetRuntimeParent, 0700)
-	seal.sys.updatePermTag(state.EnableLength, targetRuntimeParent, acl.Execute)
-
-	// ensure child runtime directory (e.g. `/tmp/fortify.%d/runtime/%d`)
-	targetRuntime := path.Join(targetRuntimeParent, seal.sys.Uid)
-	seal.sys.ensure(targetRuntime, 0700)
-	seal.sys.updatePermTag(state.EnableLength, targetRuntime, acl.Read, acl.Write, acl.Execute)
-
-	// point to ensured runtime path
-	seal.sys.setEnv(xdgRuntimeDir, targetRuntime)
-	seal.sys.setEnv(xdgSessionClass, "user")
-	seal.sys.setEnv(xdgSessionType, "tty")
-
-	return targetRuntime
+	seal.shareLocal = path.Join(seal.RunDirPath, seal.id)
+	seal.sys.Ephemeral(system.Process, seal.shareLocal, 0700)
+	seal.sys.UpdatePerm(seal.shareLocal, acl.Execute)
 }

internal/app/share.system.go

@@ -1,8 +1,11 @@
 package app
 
 import (
-	"os"
 	"path"
+
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 const (
@@ -11,33 +14,58 @@ const (
 
 // shareSystem queues various system-related actions
 func (seal *appSeal) shareSystem() {
+	// ensure Share (e.g. `/tmp/fortify.%d`)
+	// acl is unnecessary as this directory is world executable
+	seal.sys.Ensure(seal.SharePath, 0701)
+
+	// ensure process-specific share (e.g. `/tmp/fortify.%d/%s`)
+	// acl is unnecessary as this directory is world executable
+	seal.share = path.Join(seal.SharePath, seal.id)
+	seal.sys.Ephemeral(system.Process, seal.share, 0701)
+
+	// ensure child tmpdir parent directory (e.g. `/tmp/fortify.%d/tmpdir`)
+	targetTmpdirParent := path.Join(seal.SharePath, "tmpdir")
+	seal.sys.Ensure(targetTmpdirParent, 0700)
+	seal.sys.UpdatePermType(system.User, targetTmpdirParent, acl.Execute)
+
+	// ensure child tmpdir (e.g. `/tmp/fortify.%d/tmpdir/%d`)
+	targetTmpdir := path.Join(targetTmpdirParent, seal.sys.user.Uid)
+	seal.sys.Ensure(targetTmpdir, 01700)
+	seal.sys.UpdatePermType(system.User, targetTmpdir, acl.Read, acl.Write, acl.Execute)
+	seal.sys.bwrap.Bind(targetTmpdir, "/tmp", false, true)
+
+	// mount tmpfs on inner shared directory (e.g. `/tmp/fortify.%d`)
+	seal.sys.bwrap.Tmpfs(seal.SharePath, 1*1024*1024)
+}
+
+func (seal *appSeal) sharePasswd(os internal.System) {
 	// look up shell
 	sh := "/bin/sh"
 	if s, ok := os.LookupEnv(shell); ok {
-		seal.sys.setEnv(shell, s)
+		seal.sys.bwrap.SetEnv[shell] = s
 		sh = s
 	}
 
 	// generate /etc/passwd
 	passwdPath := path.Join(seal.share, "passwd")
 	username := "chronos"
-	if seal.sys.Username != "" {
-		username = seal.sys.Username
-		seal.sys.setEnv("USER", seal.sys.Username)
+	if seal.sys.user.Username != "" {
+		username = seal.sys.user.Username
+		seal.sys.bwrap.SetEnv["USER"] = seal.sys.user.Username
 	}
 	homeDir := "/var/empty"
-	if seal.sys.HomeDir != "" {
-		homeDir = seal.sys.HomeDir
-		seal.sys.setEnv("HOME", seal.sys.HomeDir)
+	if seal.sys.user.HomeDir != "" {
+		homeDir = seal.sys.user.HomeDir
+		seal.sys.bwrap.SetEnv["HOME"] = seal.sys.user.HomeDir
 	}
 	passwd := username + ":x:65534:65534:Fortify:" + homeDir + ":" + sh + "\n"
-	seal.sys.writeFile(passwdPath, []byte(passwd))
+	seal.sys.Write(passwdPath, passwd)
 
 	// write /etc/group
 	groupPath := path.Join(seal.share, "group")
-	seal.sys.writeFile(groupPath, []byte("fortify:x:65534:\n"))
+	seal.sys.Write(groupPath, "fortify:x:65534:\n")
 
 	// bind /etc/passwd and /etc/group
-	seal.sys.bind(passwdPath, "/etc/passwd", true)
-	seal.sys.bind(groupPath, "/etc/group", true)
+	seal.sys.bwrap.Bind(passwdPath, "/etc/passwd")
+	seal.sys.bwrap.Bind(groupPath, "/etc/group")
 }

internal/app/start.go

@@ -3,27 +3,20 @@ package app
 import (
 	"errors"
 	"fmt"
-	"os"
 	"os/exec"
 	"path"
 	"path/filepath"
-	"strconv"
-	"time"
+	"strings"
 
-	"git.ophivana.moe/cat/fortify/helper"
-	"git.ophivana.moe/cat/fortify/internal/shim"
-	"git.ophivana.moe/cat/fortify/internal/state"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/helper"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/shim"
+	"git.ophivana.moe/security/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
-type (
-	// ProcessError encapsulates errors returned by starting *exec.Cmd
-	ProcessError BaseError
-	// ShimError encapsulates errors returned by shim.ServeConfig.
-	ShimError BaseError
-)
-
-// Start starts the fortified child
+// Start selects a user switcher and starts shim.
+// Note that Wait must be called regardless of error returned by Start.
 func (a *app) Start() error {
 	a.lock.Lock()
 	defer a.lock.Unlock()
@@ -41,17 +34,14 @@ func (a *app) Start() error {
 			if s, err := exec.LookPath(n); err == nil {
 				shimExec[i] = s
 			} else {
-				return (*ProcessError)(wrapError(err, fmt.Sprintf("cannot find %q: %v", n, err)))
+				return fmsg.WrapError(err,
+					fmt.Sprintf("executable file %q not found in $PATH", n))
 			}
 		}
 	}
 
-	if err := a.seal.sys.commit(); err != nil {
-		return err
-	}
-
 	// select command builder
-	var commandBuilder func(shimEnv string) (args []string)
+	var commandBuilder shim.CommandBuilder
 	switch a.seal.launchOption {
 	case LaunchMethodSudo:
 		commandBuilder = a.commandBuilderSudo
@@ -61,51 +51,48 @@ func (a *app) Start() error {
 		panic("unreachable")
 	}
 
-	// configure child process
-	confSockPath := path.Join(a.seal.share, "shim")
-	a.cmd = exec.Command(a.seal.toolPath, commandBuilder(shim.EnvShim+"="+confSockPath)...)
-	a.cmd.Env = []string{}
-	a.cmd.Stdin = os.Stdin
-	a.cmd.Stdout = os.Stdout
-	a.cmd.Stderr = os.Stderr
-	a.cmd.Dir = a.seal.RunDirPath
+	// construct shim manager
+	a.shim = shim.New(a.seal.toolPath, uint32(a.seal.sys.UID()), path.Join(a.seal.share, "shim"), a.seal.wl,
+		&shim.Payload{
+			Argv:  a.seal.command,
+			Exec:  shimExec,
+			Bwrap: a.seal.sys.bwrap,
+			WL:    a.seal.wl != nil,
 
-	if wls, err := shim.ServeConfig(confSockPath, &shim.Payload{
-		Argv:  a.seal.command,
-		Exec:  shimExec,
-		Bwrap: a.seal.sys.bwrap,
-		WL:    a.seal.wlDone != nil,
+			Verbose: fmsg.Verbose(),
+		},
+		// checkPid is impossible at the moment since there is no reliable way to obtain shim's pid
+		// this feature is disabled here until sudo is replaced by fortify suid wrapper
+		false,
+	)
 
-		Verbose: verbose.Get(),
-	}, a.seal.wl, a.seal.wlDone); err != nil {
-		return (*ShimError)(wrapError(err, "cannot listen on shim socket:", err))
+	// startup will go ahead, commit system setup
+	if err := a.seal.sys.Commit(); err != nil {
+		return err
+	}
+	a.seal.sys.needRevert = true
+
+	if startTime, err := a.shim.Start(commandBuilder); err != nil {
+		return err
 	} else {
-		a.wayland = wls
-	}
+		// shim start and setup success, create process state
+		sd := state.State{
+			PID:        a.shim.Unwrap().Process.Pid,
+			Command:    a.seal.command,
+			Capability: a.seal.et,
+			Method:     method[a.seal.launchOption],
+			Argv:       a.shim.Unwrap().Args,
+			Time:       *startTime,
+		}
 
-	// start shim
-	verbose.Println("starting shim as target user:", a.cmd)
-	if err := a.cmd.Start(); err != nil {
-		return (*ProcessError)(wrapError(err, "cannot start process:", err))
+		// register process state
+		var err0 = new(StateStoreError)
+		err0.Inner, err0.DoErr = a.seal.store.Do(func(b state.Backend) {
+			err0.InnerErr = b.Save(&sd)
+		})
+		a.seal.sys.saveState = true
+		return err0.equiv("cannot save process state:")
 	}
-	startTime := time.Now().UTC()
-
-	// create process state
-	sd := state.State{
-		PID:        a.cmd.Process.Pid,
-		Command:    a.seal.command,
-		Capability: a.seal.et,
-		Launcher:   a.seal.toolPath,
-		Argv:       a.cmd.Args,
-		Time:       startTime,
-	}
-
-	// register process state
-	var err = new(StateStoreError)
-	err.Inner, err.DoErr = a.seal.store.Do(func(b state.Backend) {
-		err.InnerErr = b.Save(&sd)
-	})
-	return err.equiv("cannot save process state:", err)
 }
 
 // StateStoreError is returned for a failed state save
@@ -121,10 +108,10 @@ type StateStoreError struct {
 }
 
 func (e *StateStoreError) equiv(a ...any) error {
-	if e.Inner == true && e.DoErr == nil && e.InnerErr == nil && e.Err == nil {
+	if e.Inner && e.DoErr == nil && e.InnerErr == nil && e.Err == nil {
 		return nil
 	} else {
-		return wrapError(e, a...)
+		return fmsg.WrapErrorSuffix(e, a...)
 	}
 }
 
@@ -167,29 +154,40 @@ func (a *app) Wait() (int, error) {
 	a.lock.Lock()
 	defer a.lock.Unlock()
 
-	var r int
-
-	// wait for process and resolve exit code
-	if err := a.cmd.Wait(); err != nil {
-		var exitError *exec.ExitError
-		if !errors.As(err, &exitError) {
-			// should be unreachable
-			a.wait = err
-		}
-
-		// store non-zero return code
-		r = exitError.ExitCode()
-	} else {
-		r = a.cmd.ProcessState.ExitCode()
+	if a.shim == nil {
+		fmsg.VPrintln("shim not initialised, skipping cleanup")
+		return 1, nil
 	}
 
-	verbose.Println("process", strconv.Itoa(a.cmd.Process.Pid), "exited with exit code", r)
+	var r int
+
+	if cmd := a.shim.Unwrap(); cmd == nil {
+		// failure prior to process start
+		r = 255
+	} else {
+		// wait for process and resolve exit code
+		if err := cmd.Wait(); err != nil {
+			var exitError *exec.ExitError
+			if !errors.As(err, &exitError) {
+				// should be unreachable
+				a.waitErr = err
+			}
+
+			// store non-zero return code
+			r = exitError.ExitCode()
+		} else {
+			r = cmd.ProcessState.ExitCode()
+		}
+		fmsg.VPrintf("process %d exited with exit code %d", cmd.Process.Pid, r)
+	}
+
+	// child process exited, resume output
+	fmsg.Resume()
 
 	// close wayland connection
-	if a.wayland != nil {
-		close(a.seal.wlDone)
-		if err := a.wayland.Close(); err != nil {
-			fmt.Println("fortify: cannot close wayland connection:", err)
+	if a.seal.wl != nil {
+		if err := a.seal.wl.Close(); err != nil {
+			fmsg.Println("cannot close wayland connection:", err)
 		}
 	}
 
@@ -198,22 +196,25 @@ func (a *app) Wait() (int, error) {
 	e.Inner, e.DoErr = a.seal.store.Do(func(b state.Backend) {
 		e.InnerErr = func() error {
 			// destroy defunct state entry
-			if err := b.Destroy(a.cmd.Process.Pid); err != nil {
-				return err
+			if cmd := a.shim.Unwrap(); cmd != nil && a.seal.sys.saveState {
+				if err := b.Destroy(cmd.Process.Pid); err != nil {
+					return err
+				}
 			}
 
 			// enablements of remaining launchers
-			rt, tags := new(state.Enablements), new(state.Enablements)
-			tags.Set(state.EnableLength + 1)
+			rt, ec := new(system.Enablements), new(system.Criteria)
+			ec.Enablements = new(system.Enablements)
+			ec.Set(system.Process)
 			if states, err := b.Load(); err != nil {
 				return err
 			} else {
 				if l := len(states); l == 0 {
 					// cleanup globals as the final launcher
-					verbose.Println("no other launchers active, will clean up globals")
-					tags.Set(state.EnableLength)
+					fmsg.VPrintln("no other launchers active, will clean up globals")
+					ec.Set(system.User)
 				} else {
-					verbose.Printf("found %d active launchers, cleaning up without globals\n", l)
+					fmsg.VPrintf("found %d active launchers, cleaning up without globals", l)
 				}
 
 				// accumulate capabilities of other launchers
@@ -222,24 +223,25 @@ func (a *app) Wait() (int, error) {
 				}
 			}
 			// invert accumulated enablements for cleanup
-			for i := state.Enablement(0); i < state.EnableLength; i++ {
+			for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
 				if !rt.Has(i) {
-					tags.Set(i)
+					ec.Set(i)
 				}
 			}
-			if verbose.Get() {
-				ct := make([]state.Enablement, 0, state.EnableLength)
-				for i := state.Enablement(0); i < state.EnableLength; i++ {
-					if tags.Has(i) {
-						ct = append(ct, i)
+			if fmsg.Verbose() {
+				labels := make([]string, 0, system.ELen+1)
+				for i := system.Enablement(0); i < system.Enablement(system.ELen+2); i++ {
+					if ec.Has(i) {
+						labels = append(labels, system.TypeString(i))
 					}
 				}
-				if len(ct) > 0 {
-					verbose.Println("will revert operations tagged", ct, "as no remaining launchers hold these enablements")
+				if len(labels) > 0 {
+					fmsg.VPrintln("reverting operations labelled", strings.Join(labels, ", "))
 				}
 			}
 
-			if err := a.seal.sys.revert(tags); err != nil {
+			a.shim.AbortWait(errors.New("shim exited"))
+			if err := a.seal.sys.Revert(ec); err != nil {
 				return err.(RevertCompoundError)
 			}
 

internal/app/system.go

@@ -1,429 +1,48 @@
 package app
 
 import (
-	"errors"
-	"fmt"
-	"io/fs"
-	"os"
 	"os/user"
 
-	"git.ophivana.moe/cat/fortify/acl"
-	"git.ophivana.moe/cat/fortify/dbus"
-	"git.ophivana.moe/cat/fortify/helper/bwrap"
-	"git.ophivana.moe/cat/fortify/internal"
-	"git.ophivana.moe/cat/fortify/internal/state"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
-	"git.ophivana.moe/cat/fortify/xcb"
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
-// appSeal seals the application with child-related information
-type appSeal struct {
-	// application unique identifier
-	id *appID
-	// wayland socket path if mediated wayland is enabled
-	wl string
-	// wait for wayland client to exit if mediated wayland is enabled,
-	// (wlDone == nil) determines whether mediated wayland setup is performed
-	wlDone chan struct{}
-
-	// freedesktop application ID
-	fid string
-	// argv to start process with in the final confined environment
-	command []string
-	// persistent process state store
-	store state.Store
-
-	// uint8 representation of launch method sealed from config
-	launchOption uint8
-	// process-specific share directory path
-	share string
-	// process-specific share directory path local to XDG_RUNTIME_DIR
-	shareLocal string
-
-	// path to launcher program
-	toolPath string
-	// pass-through enablement tracking from config
-	et state.Enablements
-
-	// prevents sharing from happening twice
-	shared bool
-	// seal system-level component
-	sys *appSealTx
-
-	// used in various sealing operations
-	internal.SystemConstants
-
-	// protected by upstream mutex
-}
-
-// appSealTx contains the system-level component of the app seal
-type appSealTx struct {
+// appSealSys encapsulates app seal behaviour with OS interactions
+type appSealSys struct {
 	bwrap *bwrap.Config
-
-	// reference to D-Bus proxy instance, nil if disabled
-	dbus *dbus.Proxy
-	// notification from goroutine waiting for dbus.Proxy
-	dbusWait chan struct{}
-	// upstream address/downstream path used to initialise dbus.Proxy
-	dbusAddr *[2][2]string
-	// whether system bus proxy is enabled
-	dbusSystem bool
-
-	// paths to append/strip ACLs (of target user) from
-	acl []*appACLEntry
-	// X11 ChangeHosts commands to perform
-	xhost []string
-	// paths of directories to ensure
-	mkdir []appEnsureEntry
-	// dst, data pairs of temporarily available files
-	files [][2]string
-	// dst, src pairs of temporarily shared files
-	tmpfiles [][2]string
-	// dst, src pairs of temporarily hard linked files
-	hardlinks [][2]string
+	// paths to override by mounting tmpfs over them
+	override []string
 
 	// default formatted XDG_RUNTIME_DIR of User
 	runtime string
 	// sealed path to fortify executable, used by shim
 	executable string
-	// target user UID as an integer
-	uid int
 	// target user sealed from config
-	*user.User
+	user *user.User
 
-	// prevents commit from happening twice
-	complete bool
-	// prevents cleanup from happening twice
-	closed bool
+	needRevert bool
+	saveState  bool
+	*system.I
 
 	// protected by upstream mutex
 }
 
-type appEnsureEntry struct {
-	path   string
-	perm   os.FileMode
-	remove bool
-}
-
-// setEnv sets an environment variable for the child process
-func (tx *appSealTx) setEnv(k, v string) {
-	tx.bwrap.SetEnv[k] = v
-}
-
-// bind mounts a directory within the sandbox
-func (tx *appSealTx) bind(src, dest string, ro bool) {
-	if !ro {
-		tx.bwrap.Bind = append(tx.bwrap.Bind, [2]string{src, dest})
-	} else {
-		tx.bwrap.ROBind = append(tx.bwrap.ROBind, [2]string{src, dest})
-	}
-}
-
-// ensure appends a directory ensure action
-func (tx *appSealTx) ensure(path string, perm os.FileMode) {
-	tx.mkdir = append(tx.mkdir, appEnsureEntry{path, perm, false})
-}
-
-// ensureEphemeral appends a directory ensure action with removal in rollback
-func (tx *appSealTx) ensureEphemeral(path string, perm os.FileMode) {
-	tx.mkdir = append(tx.mkdir, appEnsureEntry{path, perm, true})
-}
-
-// appACLEntry contains information for applying/reverting an ACL entry
-type appACLEntry struct {
-	tag   state.Enablement
-	path  string
-	perms []acl.Perm
-}
-
-func (e *appACLEntry) ts() string {
-	switch e.tag {
-	case state.EnableLength:
-		return "Global"
-	case state.EnableLength + 1:
-		return "Process"
-	default:
-		return e.tag.String()
-	}
-}
-
-func (e *appACLEntry) String() string {
-	var s = []byte("---")
-	for _, p := range e.perms {
-		switch p {
-		case acl.Read:
-			s[0] = 'r'
-		case acl.Write:
-			s[1] = 'w'
-		case acl.Execute:
-			s[2] = 'x'
-		}
-	}
-	return string(s)
-}
-
-// updatePerm appends an untagged acl update action
-func (tx *appSealTx) updatePerm(path string, perms ...acl.Perm) {
-	tx.updatePermTag(state.EnableLength+1, path, perms...)
-}
-
-// updatePermTag appends an acl update action
-// Tagging with state.EnableLength sets cleanup to happen at final active launcher exit,
-// while tagging with state.EnableLength+1 will unconditionally clean up on exit.
-func (tx *appSealTx) updatePermTag(tag state.Enablement, path string, perms ...acl.Perm) {
-	tx.acl = append(tx.acl, &appACLEntry{tag, path, perms})
-}
-
-// changeHosts appends target username of an X11 ChangeHosts action
-func (tx *appSealTx) changeHosts(username string) {
-	tx.xhost = append(tx.xhost, username)
-}
-
-// writeFile appends a files action
-func (tx *appSealTx) writeFile(dst string, data []byte) {
-	tx.files = append(tx.files, [2]string{dst, string(data)})
-	tx.updatePerm(dst, acl.Read)
-	tx.bind(dst, dst, true)
-}
-
-// copyFile appends a tmpfiles action
-func (tx *appSealTx) copyFile(dst, src string) {
-	tx.tmpfiles = append(tx.tmpfiles, [2]string{dst, src})
-	tx.updatePerm(dst, acl.Read)
-	tx.bind(dst, dst, true)
-}
-
-// link appends a hardlink action
-func (tx *appSealTx) link(oldname, newname string) {
-	tx.hardlinks = append(tx.hardlinks, [2]string{oldname, newname})
-}
-
-type (
-	ChangeHostsError BaseError
-	EnsureDirError   BaseError
-	TmpfileError     BaseError
-	DBusStartError   BaseError
-	ACLUpdateError   BaseError
-)
-
-// commit applies recorded actions
-// order: xhost, mkdir, files, tmpfiles, hardlinks, dbus, acl
-func (tx *appSealTx) commit() error {
-	if tx.complete {
-		panic("seal transaction committed twice")
-	}
-	tx.complete = true
-
-	txp := &appSealTx{User: tx.User, bwrap: &bwrap.Config{SetEnv: make(map[string]string)}}
-	defer func() {
-		// rollback partial commit
-		if txp != nil {
-			// global changes (x11, ACLs) are always repeated and check for other launchers cannot happen here
-			// attempting cleanup here will cause other fortified processes to lose access to them
-			// a better (and more secure) fix is to proxy access to these resources and eliminate the ACLs altogether
-			tags := new(state.Enablements)
-			for e := state.Enablement(0); e < state.EnableLength+2; e++ {
-				tags.Set(e)
-			}
-			if err := txp.revert(tags); err != nil {
-				fmt.Println("fortify: errors returned reverting partial commit:", err)
-			}
-		}
-	}()
-
-	// insert xhost entries
-	for _, username := range tx.xhost {
-		verbose.Printf("inserting XHost entry SI:localuser:%s\n", username)
-		if err := xcb.ChangeHosts(xcb.HostModeInsert, xcb.FamilyServerInterpreted, "localuser\x00"+username); err != nil {
-			return (*ChangeHostsError)(wrapError(err,
-				fmt.Sprintf("cannot insert XHost entry SI:localuser:%s, %s", username, err)))
-		} else {
-			// register partial commit
-			txp.changeHosts(username)
-		}
-	}
-
-	// ensure directories
-	for _, dir := range tx.mkdir {
-		verbose.Println("ensuring directory mode:", dir.perm.String(), "path:", dir.path)
-		if err := os.Mkdir(dir.path, dir.perm); err != nil && !errors.Is(err, fs.ErrExist) {
-			return (*EnsureDirError)(wrapError(err,
-				fmt.Sprintf("cannot create directory '%s': %s", dir.path, err)))
-		} else {
-			// only ephemeral dirs require rollback
-			if dir.remove {
-				// register partial commit
-				txp.ensureEphemeral(dir.path, dir.perm)
-			}
-		}
-	}
-
-	// write files
-	for _, file := range tx.files {
-		verbose.Println("writing", len(file[1]), "bytes of data to", file[0])
-		if err := os.WriteFile(file[0], []byte(file[1]), 0600); err != nil {
-			return (*TmpfileError)(wrapError(err,
-				fmt.Sprintf("cannot write file '%s': %s", file[0], err)))
-		} else {
-			// register partial commit
-			txp.writeFile(file[0], make([]byte, 0)) // data not necessary for revert
-		}
-	}
-
-	// publish tmpfiles
-	for _, tmpfile := range tx.tmpfiles {
-		verbose.Println("publishing tmpfile", tmpfile[0], "from", tmpfile[1])
-		if err := copyFile(tmpfile[0], tmpfile[1]); err != nil {
-			return (*TmpfileError)(wrapError(err,
-				fmt.Sprintf("cannot publish tmpfile '%s' from '%s': %s", tmpfile[0], tmpfile[1], err)))
-		} else {
-			// register partial commit
-			txp.copyFile(tmpfile[0], tmpfile[1])
-		}
-	}
-
-	// create hardlinks
-	for _, link := range tx.hardlinks {
-		verbose.Println("creating hardlink", link[1], "from", link[0])
-		if err := os.Link(link[0], link[1]); err != nil {
-			return (*TmpfileError)(wrapError(err,
-				fmt.Sprintf("cannot create hardlink '%s' from '%s': %s", link[1], link[0], err)))
-		} else {
-			// register partial commit
-			txp.link(link[0], link[1])
-		}
-	}
-
-	if tx.dbus != nil {
-		// start dbus proxy
-		verbose.Printf("session bus proxy on '%s' for upstream '%s'\n", tx.dbusAddr[0][1], tx.dbusAddr[0][0])
-		if tx.dbusSystem {
-			verbose.Printf("system bus proxy on '%s' for upstream '%s'\n", tx.dbusAddr[1][1], tx.dbusAddr[1][0])
-		}
-		if err := tx.startDBus(); err != nil {
-			return (*DBusStartError)(wrapError(err, "cannot start message bus proxy:", err))
-		} else {
-			txp.dbus = tx.dbus
-			txp.dbusAddr = tx.dbusAddr
-			txp.dbusSystem = tx.dbusSystem
-			txp.dbusWait = tx.dbusWait
-		}
-	}
-
-	// apply ACLs
-	for _, e := range tx.acl {
-		verbose.Println("applying ACL", e, "uid:", tx.Uid, "tag:", e.ts(), "path:", e.path)
-		if err := acl.UpdatePerm(e.path, tx.uid, e.perms...); err != nil {
-			return (*ACLUpdateError)(wrapError(err,
-				fmt.Sprintf("cannot apply ACL to '%s': %s", e.path, err)))
-		} else {
-			// register partial commit
-			txp.updatePermTag(e.tag, e.path, e.perms...)
-		}
-	}
-
-	// disarm partial commit rollback
-	txp = nil
-	return nil
-}
-
-// revert rolls back recorded actions
-// order: acl, dbus, hardlinks, tmpfiles, files, mkdir, xhost
-// errors are printed but not treated as fatal
-func (tx *appSealTx) revert(tags *state.Enablements) error {
-	if tx.closed {
-		panic("seal transaction reverted twice")
-	}
-	tx.closed = true
-
-	// will be slightly over-sized with ephemeral dirs
-	errs := make([]error, 0, len(tx.acl)+1+len(tx.tmpfiles)+len(tx.mkdir)+len(tx.xhost))
-	joinError := func(err error, a ...any) {
-		var e error
-		if err != nil {
-			e = wrapError(err, a...)
-		}
-		errs = append(errs, e)
-	}
-
-	// revert ACLs
-	for _, e := range tx.acl {
-		if tags.Has(e.tag) {
-			verbose.Println("stripping ACL", e, "uid:", tx.Uid, "tag:", e.ts(), "path:", e.path)
-			err := acl.UpdatePerm(e.path, tx.uid)
-			joinError(err, fmt.Sprintf("cannot strip ACL entry from '%s': %s", e.path, err))
-		} else {
-			verbose.Println("skipping ACL", e, "uid:", tx.Uid, "tag:", e.ts(), "path:", e.path)
-		}
-	}
-
-	if tx.dbus != nil {
-		// stop dbus proxy
-		verbose.Println("terminating message bus proxy")
-		err := tx.stopDBus()
-		joinError(err, "cannot stop message bus proxy:", err)
-	}
-
-	// remove hardlinks
-	for _, link := range tx.hardlinks {
-		verbose.Println("removing hardlink", link[1])
-		err := os.Remove(link[1])
-		joinError(err, fmt.Sprintf("cannot remove hardlink '%s': %s", link[1], err))
-	}
-
-	// remove tmpfiles
-	for _, tmpfile := range tx.tmpfiles {
-		verbose.Println("removing tmpfile", tmpfile[0])
-		err := os.Remove(tmpfile[0])
-		joinError(err, fmt.Sprintf("cannot remove tmpfile '%s': %s", tmpfile[0], err))
-	}
-
-	// remove files
-	for _, file := range tx.files {
-		verbose.Println("removing file", file[0])
-		err := os.Remove(file[0])
-		joinError(err, fmt.Sprintf("cannot remove file '%s': %s", file[0], err))
-	}
-
-	// remove (empty) ephemeral directories
-	for i := len(tx.mkdir); i > 0; i-- {
-		dir := tx.mkdir[i-1]
-		if !dir.remove {
-			continue
-		}
-
-		verbose.Println("destroying ephemeral directory mode:", dir.perm.String(), "path:", dir.path)
-		err := os.Remove(dir.path)
-		joinError(err, fmt.Sprintf("cannot remove ephemeral directory '%s': %s", dir.path, err))
-	}
-
-	if tags.Has(state.EnableX) {
-		// rollback xhost insertions
-		for _, username := range tx.xhost {
-			verbose.Printf("deleting XHost entry SI:localuser:%s\n", username)
-			err := xcb.ChangeHosts(xcb.HostModeDelete, xcb.FamilyServerInterpreted, "localuser\x00"+username)
-			joinError(err, "cannot remove XHost entry:", err)
-		}
-	}
-
-	return errors.Join(errs...)
-}
-
 // shareAll calls all share methods in sequence
-func (seal *appSeal) shareAll(bus [2]*dbus.Config) error {
+func (seal *appSeal) shareAll(bus [2]*dbus.Config, os internal.System) error {
 	if seal.shared {
 		panic("seal shared twice")
 	}
 	seal.shared = true
 
-	seal.shareRuntime()
 	seal.shareSystem()
-	targetRuntime := seal.shareRuntimeChild()
-	verbose.Printf("child runtime data dir '%s' configured\n", targetRuntime)
-	if err := seal.shareDisplay(); err != nil {
+	seal.shareRuntime()
+	seal.sharePasswd(os)
+	if err := seal.shareDisplay(os); err != nil {
 		return err
 	}
-	if err := seal.sharePulse(); err != nil {
+	if err := seal.sharePulse(os); err != nil {
 		return err
 	}
 
@@ -434,12 +53,11 @@ func (seal *appSeal) shareAll(bus [2]*dbus.Config) error {
 
 	if err := seal.shareDBus(bus); err != nil {
 		return err
-	} else if seal.sys.dbusAddr != nil { // set if D-Bus enabled and share successful
-		verbose.Println("sealed session proxy", bus[0].Args(seal.sys.dbusAddr[0]))
-		if bus[1] != nil {
-			verbose.Println("sealed system proxy", bus[1].Args(seal.sys.dbusAddr[1]))
-		}
-		verbose.Println("message bus proxy final args:", seal.sys.dbus)
+	}
+
+	// queue overriding tmpfs at the end of seal.sys.bwrap.Filesystem
+	for _, dest := range seal.sys.override {
+		seal.sys.bwrap.Tmpfs(dest, 8*1024)
 	}
 
 	return nil

internal/early.go

@@ -1,34 +0,0 @@
-package internal
-
-import (
-	"errors"
-	"fmt"
-	"io/fs"
-	"os"
-)
-
-const (
-	systemdCheckPath = "/run/systemd/system"
-)
-
-var SdBootedV = func() bool {
-	if v, err := SdBooted(); err != nil {
-		fmt.Println("warn: read systemd marker:", err)
-		return false
-	} else {
-		return v
-	}
-}()
-
-// SdBooted implements https://www.freedesktop.org/software/systemd/man/sd_booted.html
-func SdBooted() (bool, error) {
-	_, err := os.Stat(systemdCheckPath)
-	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
-			err = nil
-		}
-		return false, err
-	}
-
-	return true, nil
-}

internal/environ.go

@@ -1,59 +0,0 @@
-package internal
-
-import (
-	"fmt"
-	"os"
-	"path"
-	"strconv"
-	"sync"
-
-	"git.ophivana.moe/cat/fortify/internal/verbose"
-)
-
-// state that remain constant for the lifetime of the process
-// fetched and cached here
-
-const (
-	xdgRuntimeDir = "XDG_RUNTIME_DIR"
-)
-
-// SystemConstants contains state from the operating system
-type SystemConstants struct {
-	// path to shared directory e.g. /tmp/fortify.%d
-	SharePath string `json:"share_path"`
-	// XDG_RUNTIME_DIR value e.g. /run/user/%d
-	RuntimePath string `json:"runtime_path"`
-	// application runtime directory e.g. /run/user/%d/fortify
-	RunDirPath string `json:"run_dir_path"`
-}
-
-var (
-	scVal  SystemConstants
-	scOnce sync.Once
-)
-
-func copySC() {
-	sc := SystemConstants{
-		SharePath: path.Join(os.TempDir(), "fortify."+strconv.Itoa(os.Geteuid())),
-	}
-
-	verbose.Println("process share directory at", sc.SharePath)
-
-	// runtimePath, runDirPath
-	if r, ok := os.LookupEnv(xdgRuntimeDir); !ok {
-		fmt.Println("Env variable", xdgRuntimeDir, "unset")
-		os.Exit(1)
-	} else {
-		sc.RuntimePath = r
-		sc.RunDirPath = path.Join(sc.RuntimePath, "fortify")
-		verbose.Println("XDG runtime directory at", sc.RunDirPath)
-	}
-
-	scVal = sc
-}
-
-// GetSC returns a populated SystemConstants value
-func GetSC() SystemConstants {
-	scOnce.Do(copySC)
-	return scVal
-}

internal/fmsg/defer.go

@@ -0,0 +1,72 @@
+package fmsg
+
+import (
+	"os"
+	"sync"
+	"sync/atomic"
+)
+
+var (
+	wstate   atomic.Bool
+	withhold = make(chan struct{}, 1)
+	msgbuf   = make(chan dOp, 64) // these ops are tiny so a large buffer is allocated for withholding output
+
+	dequeueOnce sync.Once
+	queueSync   sync.WaitGroup
+)
+
+func dequeue() {
+	go func() {
+		for {
+			select {
+			case op := <-msgbuf:
+				op.Do()
+				queueSync.Done()
+			case <-withhold:
+				<-withhold
+			}
+		}
+	}()
+}
+
+type dOp interface{ Do() }
+
+func Exit(code int) {
+	queueSync.Wait()
+	os.Exit(code)
+}
+
+func Withhold() {
+	dequeueOnce.Do(dequeue)
+	if wstate.CompareAndSwap(false, true) {
+		withhold <- struct{}{}
+	}
+}
+
+func Resume() {
+	dequeueOnce.Do(dequeue)
+	if wstate.CompareAndSwap(true, false) {
+		withhold <- struct{}{}
+	}
+}
+
+type dPrint []any
+
+func (v dPrint) Do() {
+	std.Print(v...)
+}
+
+type dPrintf struct {
+	format string
+	v      []any
+}
+
+func (d *dPrintf) Do() {
+	std.Printf(d.format, d.v...)
+}
+
+type dPrintln []any
+
+func (v dPrintln) Do() {
+	std.Println(v...)
+}

internal/fmsg/errors.go

@@ -1,4 +1,4 @@
-package app
+package fmsg
 
 import (
 	"fmt"
@@ -29,11 +29,32 @@ func (e *BaseError) Message() string {
 	return e.message
 }
 
-func wrapError(err error, a ...any) *BaseError {
-	return &BaseError{
-		message:   fmt.Sprintln(a...),
-		baseError: baseError{err},
+// WrapError wraps an error with a corresponding message.
+func WrapError(err error, a ...any) error {
+	if err == nil {
+		return nil
 	}
+	return wrapError(err, fmt.Sprintln(a...))
+}
+
+// WrapErrorSuffix wraps an error with a corresponding message with err at the end of the message.
+func WrapErrorSuffix(err error, a ...any) error {
+	if err == nil {
+		return nil
+	}
+	return wrapError(err, fmt.Sprintln(append(a, err)...))
+}
+
+// WrapErrorFunc wraps an error with a corresponding message returned by f.
+func WrapErrorFunc(err error, f func(err error) string) error {
+	if err == nil {
+		return nil
+	}
+	return wrapError(err, f(err))
+}
+
+func wrapError(err error, message string) *BaseError {
+	return &BaseError{message, baseError{err}}
 }
 
 var (

internal/fmsg/fmsg.go

@@ -0,0 +1,43 @@
+// Package fmsg provides various functions for output messages.
+package fmsg
+
+import (
+	"log"
+	"os"
+)
+
+var std = log.New(os.Stderr, "fortify: ", 0)
+
+func SetPrefix(prefix string) {
+	prefix += ": "
+	std.SetPrefix(prefix)
+	std.SetPrefix(prefix)
+}
+
+func Print(v ...any) {
+	dequeueOnce.Do(dequeue)
+	queueSync.Add(1)
+	msgbuf <- dPrint(v)
+}
+
+func Printf(format string, v ...any) {
+	dequeueOnce.Do(dequeue)
+	queueSync.Add(1)
+	msgbuf <- &dPrintf{format, v}
+}
+
+func Println(v ...any) {
+	dequeueOnce.Do(dequeue)
+	queueSync.Add(1)
+	msgbuf <- dPrintln(v)
+}
+
+func Fatal(v ...any) {
+	Print(v...)
+	Exit(1)
+}
+
+func Fatalf(format string, v ...any) {
+	Printf(format, v...)
+	Exit(1)
+}

internal/fmsg/verbose.go

@@ -0,0 +1,25 @@
+package fmsg
+
+import "sync/atomic"
+
+var verbose = new(atomic.Bool)
+
+func Verbose() bool {
+	return verbose.Load()
+}
+
+func SetVerbose(v bool) {
+	verbose.Store(v)
+}
+
+func VPrintf(format string, v ...any) {
+	if verbose.Load() {
+		Printf(format, v...)
+	}
+}
+
+func VPrintln(v ...any) {
+	if verbose.Load() {
+		Println(v...)
+	}
+}

internal/init/main.go

@@ -4,64 +4,66 @@ import (
 	"encoding/gob"
 	"errors"
 	"flag"
-	"fmt"
 	"os"
 	"os/exec"
 	"os/signal"
 	"path"
 	"strconv"
 	"syscall"
+	"time"
 
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+const (
+	// time to wait for linger processes after death initial process
+	residualProcessTimeout = 5 * time.Second
 )
 
 // everything beyond this point runs within pid namespace
 // proceed with caution!
 
 func doInit(fd uintptr) {
+	fmsg.SetPrefix("init")
+
 	// re-exec
 	if len(os.Args) > 0 && os.Args[0] != "fortify" && path.IsAbs(os.Args[0]) {
 		if err := syscall.Exec(os.Args[0], []string{"fortify", "init"}, os.Environ()); err != nil {
-			fmt.Println("fortify-init: cannot re-exec self:", err)
+			fmsg.Println("cannot re-exec self:", err)
 			// continue anyway
 		}
 	}
 
-	verbose.Prefix = "fortify-init:"
-
 	var payload Payload
 	p := os.NewFile(fd, "config-stream")
 	if p == nil {
-		fmt.Println("fortify-init: invalid config descriptor")
-		os.Exit(1)
+		fmsg.Fatal("invalid config descriptor")
 	}
 	if err := gob.NewDecoder(p).Decode(&payload); err != nil {
-		fmt.Println("fortify-init: cannot decode init payload:", err)
-		os.Exit(1)
+		fmsg.Fatal("cannot decode init payload:", err)
 	} else {
 		// sharing stdout with parent
 		// USE WITH CAUTION
-		verbose.Set(payload.Verbose)
+		fmsg.SetVerbose(payload.Verbose)
 
 		// child does not need to see this
 		if err = os.Unsetenv(EnvInit); err != nil {
-			fmt.Println("fortify-init: cannot unset", EnvInit+":", err)
+			fmsg.Println("cannot unset", EnvInit+":", err)
 			// not fatal
 		} else {
-			verbose.Println("received configuration")
+			fmsg.VPrintln("received configuration")
 		}
 	}
 
 	// close config fd
 	if err := p.Close(); err != nil {
-		fmt.Println("fortify-init: cannot close config fd:", err)
+		fmsg.Println("cannot close config fd:", err)
 		// not fatal
 	}
 
 	// die with parent
 	if _, _, errno := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, uintptr(syscall.SIGKILL), 0); errno != 0 {
-		fmt.Println("fortify-init: prctl(PR_SET_PDEATHSIG, SIGKILL):", errno.Error())
-		os.Exit(1)
+		fmsg.Fatal("prctl(PR_SET_PDEATHSIG, SIGKILL):", errno.Error())
 	}
 
 	cmd := exec.Command(payload.Argv0)
@@ -78,8 +80,7 @@ func doInit(fd uintptr) {
 	}
 
 	if err := cmd.Start(); err != nil {
-		fmt.Printf("fortify-init: cannot start %q: %v", payload.Argv0, err)
-		os.Exit(1)
+		fmsg.Fatalf("cannot start %q: %v", payload.Argv0, err)
 	}
 
 	sig := make(chan os.Signal, 2)
@@ -115,18 +116,20 @@ func doInit(fd uintptr) {
 			}
 		}
 		if !errors.Is(err, syscall.ECHILD) {
-			fmt.Println("fortify-init: unexpected wait4 response:", err)
+			fmsg.Println("unexpected wait4 response:", err)
 		}
 
 		close(done)
 	}()
 
+	timeout := make(chan struct{})
+
 	r := 2
 	for {
 		select {
 		case s := <-sig:
-			verbose.Println("received", s.String())
-			os.Exit(0)
+			fmsg.VPrintln("received", s.String())
+			fmsg.Exit(0)
 		case w := <-info:
 			if w.wpid == cmd.Process.Pid {
 				switch {
@@ -137,9 +140,17 @@ func doInit(fd uintptr) {
 				default:
 					r = 255
 				}
+
+				go func() {
+					time.Sleep(residualProcessTimeout)
+					close(timeout)
+				}()
 			}
 		case <-done:
-			os.Exit(r)
+			fmsg.Exit(r)
+		case <-timeout:
+			fmsg.Println("timeout exceeded waiting for lingering processes")
+			fmsg.Exit(r)
 		}
 	}
 }
@@ -153,8 +164,7 @@ func Try() {
 	if args := flag.Args(); len(args) == 1 && args[0] == "init" {
 		if s, ok := os.LookupEnv(EnvInit); ok {
 			if fd, err := strconv.Atoi(s); err != nil {
-				fmt.Printf("fortify-init: cannot parse %q: %v", s, err)
-				os.Exit(1)
+				fmsg.Fatalf("cannot parse %q: %v", s, err)
 			} else {
 				doInit(uintptr(fd))
 			}

internal/shim/main.go

@@ -4,37 +4,36 @@ import (
 	"encoding/gob"
 	"errors"
 	"flag"
-	"fmt"
 	"net"
 	"os"
 	"path"
 	"strconv"
 	"syscall"
 
-	"git.ophivana.moe/cat/fortify/helper"
-	init0 "git.ophivana.moe/cat/fortify/internal/init"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/helper"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	init0 "git.ophivana.moe/security/fortify/internal/init"
 )
 
 // everything beyond this point runs as target user
 // proceed with caution!
 
 func doShim(socket string) {
+	fmsg.SetPrefix("shim")
+
 	// re-exec
 	if len(os.Args) > 0 && os.Args[0] != "fortify" && path.IsAbs(os.Args[0]) {
 		if err := syscall.Exec(os.Args[0], []string{"fortify", "shim"}, os.Environ()); err != nil {
-			fmt.Println("fortify-shim: cannot re-exec self:", err)
+			fmsg.Println("cannot re-exec self:", err)
 			// continue anyway
 		}
 	}
 
-	verbose.Prefix = "fortify-shim:"
-
 	// dial setup socket
 	var conn *net.UnixConn
 	if c, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: socket, Net: "unix"}); err != nil {
-		fmt.Println("fortify-shim: cannot dial setup socket:", err)
-		os.Exit(1)
+		fmsg.Fatal("cannot dial setup socket:", err)
+		panic("unreachable")
 	} else {
 		conn = c
 	}
@@ -42,25 +41,22 @@ func doShim(socket string) {
 	// decode payload gob stream
 	var payload Payload
 	if err := gob.NewDecoder(conn).Decode(&payload); err != nil {
-		fmt.Println("fortify-shim: cannot decode shim payload:", err)
-		os.Exit(1)
+		fmsg.Fatal("cannot decode shim payload:", err)
 	} else {
 		// sharing stdout with parent
 		// USE WITH CAUTION
-		verbose.Set(payload.Verbose)
+		fmsg.SetVerbose(payload.Verbose)
 	}
 
 	if payload.Bwrap == nil {
-		fmt.Println("fortify-shim: bwrap config not supplied")
-		os.Exit(1)
+		fmsg.Fatal("bwrap config not supplied")
 	}
 
 	// receive wayland fd over socket
 	wfd := -1
 	if payload.WL {
 		if fd, err := receiveWLfd(conn); err != nil {
-			fmt.Println("fortify-shim: cannot receive wayland fd:", err)
-			os.Exit(1)
+			fmsg.Fatal("cannot receive wayland fd:", err)
 		} else {
 			wfd = fd
 		}
@@ -68,7 +64,7 @@ func doShim(socket string) {
 
 	// close setup socket
 	if err := conn.Close(); err != nil {
-		fmt.Println("fortify-shim: cannot close setup socket:", err)
+		fmsg.Println("cannot close setup socket:", err)
 		// not fatal
 	}
 
@@ -83,8 +79,7 @@ func doShim(socket string) {
 		// no argv, look up shell instead
 		var ok bool
 		if ic.Argv0, ok = os.LookupEnv("SHELL"); !ok {
-			fmt.Println("fortify-shim: no command was specified and $SHELL was unset")
-			os.Exit(1)
+			fmsg.Fatal("no command was specified and $SHELL was unset")
 		}
 
 		ic.Argv = []string{ic.Argv0}
@@ -106,46 +101,42 @@ func doShim(socket string) {
 
 	// share config pipe
 	if r, w, err := os.Pipe(); err != nil {
-		fmt.Println("fortify-shim: cannot pipe:", err)
-		os.Exit(1)
+		fmsg.Fatal("cannot pipe:", err)
 	} else {
 		conf.SetEnv[init0.EnvInit] = strconv.Itoa(3 + len(extraFiles))
 		extraFiles = append(extraFiles, r)
 
-		verbose.Println("transmitting config to init")
+		fmsg.VPrintln("transmitting config to init")
 		go func() {
 			// stream config to pipe
 			if err = gob.NewEncoder(w).Encode(&ic); err != nil {
-				fmt.Println("fortify-shim: cannot transmit init config:", err)
-				os.Exit(1)
+				fmsg.Fatal("cannot transmit init config:", err)
 			}
 		}()
 	}
 
 	helper.BubblewrapName = payload.Exec[1] // resolved bwrap path by parent
 	if b, err := helper.NewBwrap(conf, nil, payload.Exec[0], func(int, int) []string { return []string{"init"} }); err != nil {
-		fmt.Println("fortify-shim: malformed sandbox config:", err)
-		os.Exit(1)
+		fmsg.Fatal("malformed sandbox config:", err)
 	} else {
 		cmd := b.Unwrap()
 		cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
 		cmd.ExtraFiles = extraFiles
 
-		if verbose.Get() {
-			verbose.Println("bwrap args:", conf.Args())
+		if fmsg.Verbose() {
+			fmsg.VPrintln("bwrap args:", conf.Args())
 		}
 
 		// run and pass through exit code
 		if err = b.Start(); err != nil {
-			fmt.Println("fortify-shim: cannot start target process:", err)
-			os.Exit(1)
+			fmsg.Fatal("cannot start target process:", err)
 		} else if err = b.Wait(); err != nil {
-			verbose.Println("wait:", err)
+			fmsg.VPrintln("wait:", err)
 		}
 		if b.Unwrap().ProcessState != nil {
-			os.Exit(b.Unwrap().ProcessState.ExitCode())
+			fmsg.Exit(b.Unwrap().ProcessState.ExitCode())
 		} else {
-			os.Exit(127)
+			fmsg.Exit(127)
 		}
 	}
 }

internal/shim/parent.go

@@ -1,82 +1,200 @@
 package shim
 
 import (
-	"encoding/gob"
 	"errors"
-	"fmt"
 	"net"
 	"os"
+	"os/exec"
+	"sync"
+	"sync/atomic"
 	"syscall"
+	"time"
 
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
-// called in the parent process
+// used by the parent process
 
-func ServeConfig(socket string, payload *Payload, wl string, done chan struct{}) (*net.UnixConn, error) {
-	var ws *net.UnixConn
-	if payload.WL {
-		if f, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: wl, Net: "unix"}); err != nil {
-			return nil, err
-		} else {
-			verbose.Println("connected to wayland at", wl)
-			ws = f
-		}
+type Shim struct {
+	// user switcher process
+	cmd *exec.Cmd
+	// uid of shim target user
+	uid uint32
+	// whether to check shim pid
+	checkPid bool
+	// user switcher executable path
+	executable string
+	// path to setup socket
+	socket string
+	// shim setup abort reason and completion
+	abort     chan error
+	abortErr  atomic.Pointer[error]
+	abortOnce sync.Once
+	// wayland mediation, nil if disabled
+	wl *Wayland
+	// shim setup payload
+	payload *Payload
+}
+
+func New(executable string, uid uint32, socket string, wl *Wayland, payload *Payload, checkPid bool) *Shim {
+	return &Shim{uid: uid, executable: executable, socket: socket, wl: wl, payload: payload, checkPid: checkPid}
+}
+
+func (s *Shim) String() string {
+	if s.cmd == nil {
+		return "(unused shim manager)"
+	}
+	return s.cmd.String()
+}
+
+func (s *Shim) Unwrap() *exec.Cmd {
+	return s.cmd
+}
+
+func (s *Shim) Abort(err error) {
+	s.abortOnce.Do(func() {
+		s.abortErr.Store(&err)
+		// s.abort is buffered so this will never block
+		s.abort <- err
+	})
+}
+
+func (s *Shim) AbortWait(err error) {
+	s.Abort(err)
+	<-s.abort
+}
+
+type CommandBuilder func(shimEnv string) (args []string)
+
+func (s *Shim) Start(f CommandBuilder) (*time.Time, error) {
+	var (
+		cf     chan *net.UnixConn
+		accept func()
+	)
+
+	// listen on setup socket
+	if c, a, err := s.serve(); err != nil {
+		return nil, fmsg.WrapErrorSuffix(err,
+			"cannot listen on shim setup socket:")
+	} else {
+		// accepts a connection after each call to accept
+		// connections are sent to the channel cf
+		cf, accept = c, a
 	}
 
-	if c, err := net.ListenUnix("unix", &net.UnixAddr{Name: socket, Net: "unix"}); err != nil {
-		return nil, err
+	// start user switcher process and save time
+	s.cmd = exec.Command(s.executable, f(EnvShim+"="+s.socket)...)
+	s.cmd.Env = []string{}
+	s.cmd.Stdin, s.cmd.Stdout, s.cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+	s.cmd.Dir = "/"
+	fmsg.VPrintln("starting shim via user switcher:", s.cmd)
+	fmsg.Withhold() // withhold messages to stderr
+	if err := s.cmd.Start(); err != nil {
+		return nil, fmsg.WrapErrorSuffix(err,
+			"cannot start user switcher:")
+	}
+	startTime := time.Now().UTC()
+
+	// kill shim if something goes wrong and an error is returned
+	killShim := func() {
+		if err := s.cmd.Process.Signal(os.Interrupt); err != nil {
+			fmsg.Println("cannot terminate shim on faulted setup:", err)
+		}
+	}
+	defer func() { killShim() }()
+
+	accept()
+	conn := <-cf
+	if conn == nil {
+		return &startTime, fmsg.WrapErrorSuffix(*s.abortErr.Load(), "cannot accept call on setup socket:")
+	}
+
+	// authenticate against called provided uid and shim pid
+	if cred, err := peerCred(conn); err != nil {
+		return &startTime, fmsg.WrapErrorSuffix(*s.abortErr.Load(), "cannot retrieve shim credentials:")
+	} else if cred.Uid != s.uid {
+		fmsg.Printf("process %d owned by user %d tried to connect, expecting %d",
+			cred.Pid, cred.Uid, s.uid)
+		err = errors.New("compromised fortify build")
+		s.Abort(err)
+		return &startTime, err
+	} else if s.checkPid && cred.Pid != int32(s.cmd.Process.Pid) {
+		fmsg.Printf("process %d tried to connect to shim setup socket, expecting shim %d",
+			cred.Pid, s.cmd.Process.Pid)
+		err = errors.New("compromised target user")
+		s.Abort(err)
+		return &startTime, err
+	}
+
+	// serve payload and wayland fd if enabled
+	// this also closes the connection
+	err := s.payload.serve(conn, s.wl)
+	if err == nil {
+		killShim = func() {}
+	}
+	s.Abort(err) // aborting with nil indicates success
+	return &startTime, err
+}
+
+func (s *Shim) serve() (chan *net.UnixConn, func(), error) {
+	if s.abort != nil {
+		panic("attempted to serve shim setup twice")
+	}
+	s.abort = make(chan error, 1)
+
+	cf := make(chan *net.UnixConn)
+	accept := make(chan struct{}, 1)
+
+	if l, err := net.ListenUnix("unix", &net.UnixAddr{Name: s.socket, Net: "unix"}); err != nil {
+		return nil, nil, err
 	} else {
-		verbose.Println("configuring shim on socket", socket)
-		if err = os.Chmod(socket, 0777); err != nil {
-			fmt.Println("fortify: cannot change permissions of shim setup socket:", err)
+		l.SetUnlinkOnClose(true)
+
+		fmsg.VPrintf("listening on shim setup socket %q", s.socket)
+		if err = acl.UpdatePerm(s.socket, int(s.uid), acl.Read, acl.Write, acl.Execute); err != nil {
+			fmsg.Println("cannot append ACL entry to shim setup socket:", err)
+			s.Abort(err) // ensures setup socket cleanup
 		}
 
 		go func() {
-			var conn *net.UnixConn
-			if conn, err = c.AcceptUnix(); err != nil {
-				fmt.Println("fortify: cannot accept connection from shim:", err)
-			} else {
-				if err = gob.NewEncoder(conn).Encode(*payload); err != nil {
-					fmt.Println("fortify: cannot stream shim payload:", err)
-					return
-				}
-
-				if payload.WL {
-					// get raw connection
-					var rc syscall.RawConn
-					if rc, err = ws.SyscallConn(); err != nil {
-						fmt.Println("fortify: cannot obtain raw wayland connection:", err)
-						return
-					} else {
-						go func() {
-							// pass wayland socket fd
-							if err = rc.Control(func(fd uintptr) {
-								if _, _, err = conn.WriteMsgUnix(nil, syscall.UnixRights(int(fd)), nil); err != nil {
-									fmt.Println("fortify: cannot pass wayland connection to shim:", err)
-									return
-								}
-								_ = conn.Close()
-
-								// block until shim exits
-								<-done
-								verbose.Println("releasing wayland connection")
-							}); err != nil {
-								fmt.Println("fortify: cannot obtain wayland connection fd:", err)
-							}
-						}()
+			for {
+				select {
+				case err = <-s.abort:
+					if err != nil {
+						fmsg.VPrintln("aborting shim setup, reason:", err)
+					}
+					if err = l.Close(); err != nil {
+						fmsg.Println("cannot close setup socket:", err)
+					}
+					close(s.abort)
+					close(cf)
+					return
+				case <-accept:
+					if conn, err0 := l.AcceptUnix(); err0 != nil {
+						s.Abort(err0) // does not block, breaks loop
+						cf <- nil     // receiver sees nil value and loads err0 stored during abort
+					} else {
+						cf <- conn
 					}
-				} else {
-					_ = conn.Close()
 				}
 			}
-			if err = c.Close(); err != nil {
-				fmt.Println("fortify: cannot close shim socket:", err)
-			}
-			if err = os.Remove(socket); err != nil && !errors.Is(err, os.ErrNotExist) {
-				fmt.Println("fortify: cannot remove dangling shim socket:", err)
-			}
 		}()
-		return ws, nil
 	}
+
+	return cf, func() { accept <- struct{}{} }, nil
+}
+
+// peerCred fetches peer credentials of conn
+func peerCred(conn *net.UnixConn) (ucred *syscall.Ucred, err error) {
+	var raw syscall.RawConn
+	if raw, err = conn.SyscallConn(); err != nil {
+		return
+	}
+
+	err0 := raw.Control(func(fd uintptr) {
+		ucred, err = syscall.GetsockoptUcred(int(fd), syscall.SOL_SOCKET, syscall.SO_PEERCRED)
+	})
+	err = errors.Join(err, err0)
+	return
 }

internal/shim/payload.go

@@ -1,6 +1,13 @@
 package shim
 
-import "git.ophivana.moe/cat/fortify/helper/bwrap"
+import (
+	"encoding/gob"
+	"errors"
+	"net"
+
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
 
 const EnvShim = "FORTIFY_SHIM"
 
@@ -17,3 +24,19 @@ type Payload struct {
 	// verbosity pass through
 	Verbose bool
 }
+
+func (p *Payload) serve(conn *net.UnixConn, wl *Wayland) error {
+	if err := gob.NewEncoder(conn).Encode(*p); err != nil {
+		return fmsg.WrapErrorSuffix(err,
+			"cannot stream shim payload:")
+	}
+
+	if wl != nil {
+		if err := wl.WriteUnix(conn); err != nil {
+			return errors.Join(err, conn.Close())
+		}
+	}
+
+	return fmsg.WrapErrorSuffix(conn.Close(),
+		"cannot close setup connection:")
+}

internal/shim/wayland.go

@@ -0,0 +1,75 @@
+package shim
+
+import (
+	"fmt"
+	"net"
+	"sync"
+	"syscall"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+// Wayland implements wayland mediation.
+type Wayland struct {
+	// wayland socket path
+	Path string
+
+	// wayland connection
+	conn *net.UnixConn
+
+	connErr error
+	sync.Once
+	// wait for wayland client to exit
+	done chan struct{}
+}
+
+func (wl *Wayland) WriteUnix(conn *net.UnixConn) error {
+	// connect to host wayland socket
+	if f, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: wl.Path, Net: "unix"}); err != nil {
+		return fmsg.WrapErrorSuffix(err,
+			fmt.Sprintf("cannot connect to wayland at %q:", wl.Path))
+	} else {
+		fmsg.VPrintf("connected to wayland at %q", wl.Path)
+		wl.conn = f
+	}
+
+	// set up for passing wayland socket
+	if rc, err := wl.conn.SyscallConn(); err != nil {
+		return fmsg.WrapErrorSuffix(err, "cannot obtain raw wayland connection:")
+	} else {
+		ec := make(chan error)
+		go func() {
+			// pass wayland connection fd
+			if err = rc.Control(func(fd uintptr) {
+				if _, _, err = conn.WriteMsgUnix(nil, syscall.UnixRights(int(fd)), nil); err != nil {
+					ec <- fmsg.WrapErrorSuffix(err, "cannot pass wayland connection to shim:")
+					return
+				}
+				ec <- nil
+
+				// block until shim exits
+				<-wl.done
+				fmsg.VPrintln("releasing wayland connection")
+			}); err != nil {
+				ec <- fmsg.WrapErrorSuffix(err, "cannot obtain wayland connection fd:")
+				return
+			}
+		}()
+		return <-ec
+	}
+}
+
+func (wl *Wayland) Close() error {
+	wl.Do(func() {
+		close(wl.done)
+		wl.connErr = wl.conn.Close()
+	})
+
+	return wl.connErr
+}
+
+func NewWayland() *Wayland {
+	wl := new(Wayland)
+	wl.done = make(chan struct{})
+	return wl
+}

internal/state/print.go

@@ -10,7 +10,8 @@ import (
 	"text/tabwriter"
 	"time"
 
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 // MustPrintLauncherStateSimpleGlobal prints active launcher states of all simple stores
@@ -20,19 +21,18 @@ func MustPrintLauncherStateSimpleGlobal(w **tabwriter.Writer, runDir string) {
 
 	// read runtime directory to get all UIDs
 	if dirs, err := os.ReadDir(path.Join(runDir, "state")); err != nil && !errors.Is(err, os.ErrNotExist) {
-		fmt.Println("cannot read runtime directory:", err)
-		os.Exit(1)
+		fmsg.Fatal("cannot read runtime directory:", err)
 	} else {
 		for _, e := range dirs {
 			// skip non-directories
 			if !e.IsDir() {
-				verbose.Println("skipped non-directory entry", e.Name())
+				fmsg.VPrintf("skipped non-directory entry %q", e.Name())
 				continue
 			}
 
 			// skip non-numerical names
 			if _, err = strconv.Atoi(e.Name()); err != nil {
-				verbose.Println("skipped non-uid entry", e.Name())
+				fmsg.VPrintf("skipped non-uid entry %q", e.Name())
 				continue
 			}
 
@@ -44,7 +44,7 @@ func MustPrintLauncherStateSimpleGlobal(w **tabwriter.Writer, runDir string) {
 
 			// mustPrintLauncherState causes store activity so store needs to be closed
 			if err = s.Close(); err != nil {
-				fmt.Printf("warn: error closing store for user %s: %s\n", e.Name(), err)
+				fmsg.Printf("cannot close store for user %q: %s", e.Name(), err)
 			}
 		}
 	}
@@ -66,8 +66,8 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 				*w = tabwriter.NewWriter(os.Stdout, 0, 1, 4, ' ', 0)
 
 				// write header when initialising
-				if !verbose.Get() {
-					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tUptime\tEnablements\tLauncher\tCommand")
+				if !fmsg.Verbose() {
+					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tUptime\tEnablements\tMethod\tCommand")
 				} else {
 					// argv is emitted in body when verbose
 					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tArgv")
@@ -85,7 +85,7 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 				// build enablements string
 				ets := strings.Builder{}
 				// append enablement strings in order
-				for i := Enablement(0); i < EnableLength; i++ {
+				for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
 					if state.Capability.Has(i) {
 						ets.WriteString(", " + i.String())
 					}
@@ -95,9 +95,9 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 					ets.WriteString("(No enablements)")
 				}
 
-				if !verbose.Get() {
+				if !fmsg.Verbose() {
 					_, _ = fmt.Fprintf(*w, "\t%s\t%d\t%s\t%s\t%s\t%s\n",
-						s.path[len(s.path)-1], state.PID, now.Sub(state.Time).Round(time.Second).String(), strings.TrimPrefix(ets.String(), ", "), state.Launcher,
+						s.path[len(s.path)-1], state.PID, now.Sub(state.Time).Round(time.Second).String(), strings.TrimPrefix(ets.String(), ", "), state.Method,
 						state.Command)
 				} else {
 					// emit argv instead when verbose
@@ -109,15 +109,13 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 			return nil
 		}()
 	}); err != nil {
-		fmt.Printf("cannot perform action on store '%s': %s\n", path.Join(s.path...), err)
+		fmsg.Printf("cannot perform action on store %q: %s", path.Join(s.path...), err)
 		if !ok {
-			fmt.Println("warn: store faulted before printing")
-			os.Exit(1)
+			fmsg.Fatal("store faulted before printing")
 		}
 	}
 
 	if innerErr != nil {
-		fmt.Printf("cannot print launcher state for store '%s': %s\n", path.Join(s.path...), innerErr)
-		os.Exit(1)
+		fmsg.Fatalf("cannot print launcher state for store %q: %s", path.Join(s.path...), innerErr)
 	}
 }

internal/state/state.go

@@ -2,6 +2,8 @@ package state
 
 import (
 	"time"
+
+	"git.ophivana.moe/security/fortify/internal/system"
 )
 
 type Store interface {
@@ -29,10 +31,10 @@ type State struct {
 	// command used to seal the app
 	Command []string
 	// capability enablements applied to child
-	Capability Enablements
+	Capability system.Enablements
 
-	// resolved launcher path
-	Launcher string
+	// user switch method
+	Method string
 	// full argv whe launching
 	Argv []string
 	// process start time

internal/system.go

@@ -0,0 +1,126 @@
+package internal
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"os/exec"
+	"os/user"
+	"path"
+	"strconv"
+	"sync"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+// System provides safe access to operating system resources.
+type System interface {
+	// Geteuid provides [os.Geteuid].
+	Geteuid() int
+	// LookupEnv provides [os.LookupEnv].
+	LookupEnv(key string) (string, bool)
+	// TempDir provides [os.TempDir].
+	TempDir() string
+	// LookPath provides [exec.LookPath].
+	LookPath(file string) (string, error)
+	// Executable provides [os.Executable].
+	Executable() (string, error)
+	// Lookup provides [user.Lookup].
+	Lookup(username string) (*user.User, error)
+	// ReadDir provides [os.ReadDir].
+	ReadDir(name string) ([]fs.DirEntry, error)
+	// Stat provides [os.Stat].
+	Stat(name string) (fs.FileInfo, error)
+	// Open provides [os.Open]
+	Open(name string) (fs.File, error)
+	// Exit provides [os.Exit].
+	Exit(code int)
+
+	// Paths returns a populated [Paths] struct.
+	Paths() Paths
+	// SdBooted implements https://www.freedesktop.org/software/systemd/man/sd_booted.html
+	SdBooted() bool
+}
+
+// Paths contains environment dependent paths used by fortify.
+type Paths struct {
+	// path to shared directory e.g. /tmp/fortify.%d
+	SharePath string `json:"share_path"`
+	// XDG_RUNTIME_DIR value e.g. /run/user/%d
+	RuntimePath string `json:"runtime_path"`
+	// application runtime directory e.g. /run/user/%d/fortify
+	RunDirPath string `json:"run_dir_path"`
+}
+
+// CopyPaths is a generic implementation of [System.Paths].
+func CopyPaths(os System, v *Paths) {
+	v.SharePath = path.Join(os.TempDir(), "fortify."+strconv.Itoa(os.Geteuid()))
+
+	fmsg.VPrintf("process share directory at %q", v.SharePath)
+
+	if r, ok := os.LookupEnv(xdgRuntimeDir); !ok || r == "" || !path.IsAbs(r) {
+		// fall back to path in share since fortify has no hard XDG dependency
+		v.RunDirPath = path.Join(v.SharePath, "run")
+		v.RuntimePath = path.Join(v.RunDirPath, "compat")
+	} else {
+		v.RuntimePath = r
+		v.RunDirPath = path.Join(v.RuntimePath, "fortify")
+	}
+
+	fmsg.VPrintf("runtime directory at %q", v.RunDirPath)
+}
+
+// Std implements System using the standard library.
+type Std struct {
+	paths     Paths
+	pathsOnce sync.Once
+
+	sdBooted     bool
+	sdBootedOnce sync.Once
+}
+
+func (s *Std) Geteuid() int                               { return os.Geteuid() }
+func (s *Std) LookupEnv(key string) (string, bool)        { return os.LookupEnv(key) }
+func (s *Std) TempDir() string                            { return os.TempDir() }
+func (s *Std) LookPath(file string) (string, error)       { return exec.LookPath(file) }
+func (s *Std) Executable() (string, error)                { return os.Executable() }
+func (s *Std) Lookup(username string) (*user.User, error) { return user.Lookup(username) }
+func (s *Std) ReadDir(name string) ([]os.DirEntry, error) { return os.ReadDir(name) }
+func (s *Std) Stat(name string) (fs.FileInfo, error)      { return os.Stat(name) }
+func (s *Std) Open(name string) (fs.File, error)          { return os.Open(name) }
+func (s *Std) Exit(code int)                              { fmsg.Exit(code) }
+
+const xdgRuntimeDir = "XDG_RUNTIME_DIR"
+
+func (s *Std) Paths() Paths {
+	s.pathsOnce.Do(func() { CopyPaths(s, &s.paths) })
+	return s.paths
+}
+
+func (s *Std) SdBooted() bool {
+	s.sdBootedOnce.Do(func() { s.sdBooted = copySdBooted() })
+	return s.sdBooted
+}
+
+const systemdCheckPath = "/run/systemd/system"
+
+func copySdBooted() bool {
+	if v, err := sdBooted(); err != nil {
+		fmsg.Println("cannot read systemd marker:", err)
+		return false
+	} else {
+		return v
+	}
+}
+
+func sdBooted() (bool, error) {
+	_, err := os.Stat(systemdCheckPath)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			err = nil
+		}
+		return false, err
+	}
+
+	return true, nil
+}

internal/system/acl.go

@@ -0,0 +1,70 @@
+package system
+
+import (
+	"fmt"
+	"slices"
+
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+// UpdatePerm appends an ephemeral acl update Op.
+func (sys *I) UpdatePerm(path string, perms ...acl.Perm) *I {
+	sys.UpdatePermType(Process, path, perms...)
+
+	return sys
+}
+
+// UpdatePermType appends an acl update Op.
+func (sys *I) UpdatePermType(et Enablement, path string, perms ...acl.Perm) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &ACL{et, path, perms})
+
+	return sys
+}
+
+type ACL struct {
+	et    Enablement
+	path  string
+	perms acl.Perms
+}
+
+func (a *ACL) Type() Enablement {
+	return a.et
+}
+
+func (a *ACL) apply(sys *I) error {
+	fmsg.VPrintln("applying ACL", a)
+	return fmsg.WrapErrorSuffix(acl.UpdatePerm(a.path, sys.uid, a.perms...),
+		fmt.Sprintf("cannot apply ACL entry to %q:", a.path))
+}
+
+func (a *ACL) revert(sys *I, ec *Criteria) error {
+	if ec.hasType(a) {
+		fmsg.VPrintln("stripping ACL", a)
+		return fmsg.WrapErrorSuffix(acl.UpdatePerm(a.path, sys.uid),
+			fmt.Sprintf("cannot strip ACL entry from %q:", a.path))
+	} else {
+		fmsg.VPrintln("skipping ACL", a)
+		return nil
+	}
+}
+
+func (a *ACL) Is(o Op) bool {
+	a0, ok := o.(*ACL)
+	return ok && a0 != nil &&
+		a.et == a0.et &&
+		a.path == a0.path &&
+		slices.Equal(a.perms, a0.perms)
+}
+
+func (a *ACL) Path() string {
+	return a.path
+}
+
+func (a *ACL) String() string {
+	return fmt.Sprintf("%s type: %s path: %q",
+		a.perms, TypeString(a.et), a.path)
+}

internal/system/acl_test.go

@@ -0,0 +1,90 @@
+package system
+
+import (
+	"testing"
+
+	"git.ophivana.moe/security/fortify/acl"
+)
+
+func TestUpdatePerm(t *testing.T) {
+	testCases := []struct {
+		path  string
+		perms []acl.Perm
+	}{
+		{"/run/user/1971/fortify", []acl.Perm{acl.Execute}},
+		{"/tmp/fortify.1971/tmpdir/150", []acl.Perm{acl.Read, acl.Write, acl.Execute}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path+permSubTestSuffix(tc.perms), func(t *testing.T) {
+			sys := New(150)
+			sys.UpdatePerm(tc.path, tc.perms...)
+			(&tcOp{Process, tc.path}).test(t, sys.ops, []Op{&ACL{Process, tc.path, tc.perms}}, "UpdatePerm")
+		})
+	}
+}
+
+func TestUpdatePermType(t *testing.T) {
+	testCases := []struct {
+		perms []acl.Perm
+		tcOp
+	}{
+		{[]acl.Perm{acl.Execute}, tcOp{User, "/tmp/fortify.1971/tmpdir"}},
+		{[]acl.Perm{acl.Read, acl.Write, acl.Execute}, tcOp{User, "/tmp/fortify.1971/tmpdir/150"}},
+		{[]acl.Perm{acl.Execute}, tcOp{Process, "/run/user/1971/fortify/fcb8a12f7c482d183ade8288c3de78b5"}},
+		{[]acl.Perm{acl.Read}, tcOp{Process, "/tmp/fortify.1971/fcb8a12f7c482d183ade8288c3de78b5/passwd"}},
+		{[]acl.Perm{acl.Read}, tcOp{Process, "/tmp/fortify.1971/fcb8a12f7c482d183ade8288c3de78b5/group"}},
+		{[]acl.Perm{acl.Read, acl.Write, acl.Execute}, tcOp{EWayland, "/run/user/1971/wayland-0"}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path+"_"+TypeString(tc.et)+permSubTestSuffix(tc.perms), func(t *testing.T) {
+			sys := New(150)
+			sys.UpdatePermType(tc.et, tc.path, tc.perms...)
+			tc.test(t, sys.ops, []Op{&ACL{tc.et, tc.path, tc.perms}}, "UpdatePermType")
+		})
+	}
+}
+
+func TestACL_String(t *testing.T) {
+	testCases := []struct {
+		want  string
+		et    Enablement
+		perms []acl.Perm
+	}{
+		{`--- type: Process path: "/nonexistent"`, Process, []acl.Perm{}},
+		{`r-- type: User path: "/nonexistent"`, User, []acl.Perm{acl.Read}},
+		{`-w- type: Wayland path: "/nonexistent"`, EWayland, []acl.Perm{acl.Write}},
+		{`--x type: X11 path: "/nonexistent"`, EX11, []acl.Perm{acl.Execute}},
+		{`rw- type: D-Bus path: "/nonexistent"`, EDBus, []acl.Perm{acl.Read, acl.Write}},
+		{`r-x type: PulseAudio path: "/nonexistent"`, EPulse, []acl.Perm{acl.Read, acl.Execute}},
+		{`rwx type: User path: "/nonexistent"`, User, []acl.Perm{acl.Read, acl.Write, acl.Execute}},
+		{`rwx type: Process path: "/nonexistent"`, Process, []acl.Perm{acl.Read, acl.Write, acl.Write, acl.Execute}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.want, func(t *testing.T) {
+			a := &ACL{et: tc.et, perms: tc.perms, path: "/nonexistent"}
+			if got := a.String(); got != tc.want {
+				t.Errorf("String() = %v, want %v",
+					got, tc.want)
+			}
+		})
+	}
+}
+
+func permSubTestSuffix(perms []acl.Perm) (suffix string) {
+	for _, perm := range perms {
+		switch perm {
+		case acl.Read:
+			suffix += "_read"
+		case acl.Write:
+			suffix += "_write"
+		case acl.Execute:
+			suffix += "_execute"
+		default:
+			panic("unreachable")
+		}
+	}
+	return
+}

internal/system/dbus.go

@@ -0,0 +1,166 @@
+package system
+
+import (
+	"errors"
+	"os"
+
+	"git.ophivana.moe/security/fortify/dbus"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+var (
+	ErrDBusConfig = errors.New("dbus config not supplied")
+)
+
+func (sys *I) MustProxyDBus(sessionPath string, session *dbus.Config, systemPath string, system *dbus.Config) *I {
+	if err := sys.ProxyDBus(session, system, sessionPath, systemPath); err != nil {
+		panic(err.Error())
+	} else {
+		return sys
+	}
+}
+
+func (sys *I) ProxyDBus(session, system *dbus.Config, sessionPath, systemPath string) error {
+	d := new(DBus)
+
+	// used by waiting goroutine to notify process exit
+	d.done = make(chan struct{})
+
+	// session bus is mandatory
+	if session == nil {
+		return fmsg.WrapError(ErrDBusConfig,
+			"attempted to seal message bus proxy without session bus config")
+	}
+
+	// system bus is optional
+	d.system = system == nil
+
+	// upstream address, downstream socket path
+	var sessionBus, systemBus [2]string
+
+	// resolve upstream bus addresses
+	sessionBus[0], systemBus[0] = dbus.Address()
+
+	// set paths from caller
+	sessionBus[1], systemBus[1] = sessionPath, systemPath
+
+	// create proxy instance
+	d.proxy = dbus.New(sessionBus, systemBus)
+
+	defer func() {
+		if fmsg.Verbose() && d.proxy.Sealed() {
+			fmsg.VPrintln("sealed session proxy", session.Args(sessionBus))
+			if system != nil {
+				fmsg.VPrintln("sealed system proxy", system.Args(systemBus))
+			}
+			fmsg.VPrintln("message bus proxy final args:", d.proxy)
+		}
+	}()
+
+	// queue operation
+	sys.ops = append(sys.ops, d)
+
+	// seal dbus proxy
+	return fmsg.WrapErrorSuffix(d.proxy.Seal(session, system),
+		"cannot seal message bus proxy:")
+}
+
+type DBus struct {
+	proxy *dbus.Proxy
+
+	// whether system bus proxy is enabled
+	system bool
+	// notification from goroutine waiting for dbus.Proxy
+	done chan struct{}
+}
+
+func (d *DBus) Type() Enablement {
+	return Process
+}
+
+func (d *DBus) apply(_ *I) error {
+	fmsg.VPrintf("session bus proxy on %q for upstream %q", d.proxy.Session()[1], d.proxy.Session()[0])
+	if d.system {
+		fmsg.VPrintf("system bus proxy on %q for upstream %q", d.proxy.System()[1], d.proxy.System()[0])
+	}
+
+	// ready channel passed to dbus package
+	ready := make(chan error, 1)
+
+	// background dbus proxy start
+	if err := d.proxy.Start(ready, os.Stderr, true); err != nil {
+		return fmsg.WrapErrorSuffix(err,
+			"cannot start message bus proxy:")
+	}
+	fmsg.VPrintln("starting message bus proxy:", d.proxy)
+	if fmsg.Verbose() { // save the extra bwrap arg build when verbose logging is off
+		fmsg.VPrintln("message bus proxy bwrap args:", d.proxy.Bwrap())
+	}
+
+	// background wait for proxy instance and notify completion
+	go func() {
+		if err := d.proxy.Wait(); err != nil {
+			fmsg.Println("message bus proxy exited with error:", err)
+			go func() { ready <- err }()
+		} else {
+			fmsg.VPrintln("message bus proxy exit")
+		}
+
+		// ensure socket removal so ephemeral directory is empty at revert
+		if err := os.Remove(d.proxy.Session()[1]); err != nil && !errors.Is(err, os.ErrNotExist) {
+			fmsg.Println("cannot remove dangling session bus socket:", err)
+		}
+		if d.system {
+			if err := os.Remove(d.proxy.System()[1]); err != nil && !errors.Is(err, os.ErrNotExist) {
+				fmsg.Println("cannot remove dangling system bus socket:", err)
+			}
+		}
+
+		// notify proxy completion
+		close(d.done)
+	}()
+
+	// ready is not nil if the proxy process faulted
+	if err := <-ready; err != nil {
+		// note that err here is either an I/O error or a predetermined unexpected behaviour error
+		return fmsg.WrapErrorSuffix(err,
+			"message bus proxy fault after start:")
+	}
+	fmsg.VPrintln("message bus proxy ready")
+
+	return nil
+}
+
+func (d *DBus) revert(_ *I, _ *Criteria) error {
+	// criteria ignored here since dbus is always process-scoped
+	fmsg.VPrintln("terminating message bus proxy")
+
+	if err := d.proxy.Close(); err != nil {
+		if errors.Is(err, os.ErrClosed) {
+			return fmsg.WrapError(err,
+				"message bus proxy already closed")
+		} else {
+			return fmsg.WrapErrorSuffix(err,
+				"cannot stop message bus proxy:")
+		}
+	}
+
+	// block until proxy wait returns
+	<-d.done
+	return nil
+}
+
+func (d *DBus) Is(o Op) bool {
+	d0, ok := o.(*DBus)
+	return ok && d0 != nil &&
+		((d.proxy == nil && d0.proxy == nil) ||
+			(d.proxy != nil && d0.proxy != nil && d.proxy.String() == d0.proxy.String()))
+}
+
+func (d *DBus) Path() string {
+	return "(dbus proxy)"
+}
+
+func (d *DBus) String() string {
+	return d.proxy.String()
+}

internal/system/enablement.go

@@ -1,4 +1,4 @@
-package state
+package system
 
 type (
 	// Enablement represents an optional system resource
@@ -8,22 +8,25 @@ type (
 )
 
 const (
-	EnableWayland Enablement = iota
-	EnableX
-	EnableDBus
-	EnablePulse
-
-	EnableLength
+	EWayland Enablement = iota
+	EX11
+	EDBus
+	EPulse
 )
 
-var enablementString = [EnableLength]string{
-	"Wayland",
-	"X11",
-	"D-Bus",
-	"PulseAudio",
+var enablementString = [...]string{
+	EWayland: "Wayland",
+	EX11:     "X11",
+	EDBus:    "D-Bus",
+	EPulse:   "PulseAudio",
 }
 
+const ELen = len(enablementString)
+
 func (e Enablement) String() string {
+	if int(e) >= ELen {
+		return "<invalid enablement>"
+	}
 	return enablementString[e]
 }
 

internal/system/mkdir.go

@@ -0,0 +1,88 @@
+package system
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+// Ensure the existence and mode of a directory.
+func (sys *I) Ensure(name string, perm os.FileMode) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &Mkdir{User, name, perm, false})
+
+	return sys
+}
+
+// Ephemeral ensures the temporary existence and mode of a directory through the life of et.
+func (sys *I) Ephemeral(et Enablement, name string, perm os.FileMode) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &Mkdir{et, name, perm, true})
+
+	return sys
+}
+
+type Mkdir struct {
+	et        Enablement
+	path      string
+	perm      os.FileMode
+	ephemeral bool
+}
+
+func (m *Mkdir) Type() Enablement {
+	return m.et
+}
+
+func (m *Mkdir) apply(_ *I) error {
+	fmsg.VPrintln("ensuring directory", m)
+
+	// create directory
+	err := os.Mkdir(m.path, m.perm)
+	if !errors.Is(err, os.ErrExist) {
+		return fmsg.WrapErrorSuffix(err,
+			fmt.Sprintf("cannot create directory %q:", m.path))
+	}
+
+	// directory exists, ensure mode
+	return fmsg.WrapErrorSuffix(os.Chmod(m.path, m.perm),
+		fmt.Sprintf("cannot change mode of %q to %s:", m.path, m.perm))
+}
+
+func (m *Mkdir) revert(_ *I, ec *Criteria) error {
+	if !m.ephemeral {
+		// skip non-ephemeral dir and do not log anything
+		return nil
+	}
+
+	if ec.hasType(m) {
+		fmsg.VPrintln("destroying ephemeral directory", m)
+		return fmsg.WrapErrorSuffix(os.Remove(m.path),
+			fmt.Sprintf("cannot remove ephemeral directory %q:", m.path))
+	} else {
+		fmsg.VPrintln("skipping ephemeral directory", m)
+		return nil
+	}
+}
+
+func (m *Mkdir) Is(o Op) bool {
+	m0, ok := o.(*Mkdir)
+	return ok && m0 != nil && *m == *m0
+}
+
+func (m *Mkdir) Path() string {
+	return m.path
+}
+
+func (m *Mkdir) String() string {
+	t := "Ensure"
+	if m.ephemeral {
+		t = TypeString(m.Type())
+	}
+	return fmt.Sprintf("mode: %s type: %s path: %q", m.perm.String(), t, m.path)
+}

internal/system/mkdir_test.go

@@ -0,0 +1,73 @@
+package system
+
+import (
+	"os"
+	"testing"
+)
+
+func TestEnsure(t *testing.T) {
+	testCases := []struct {
+		name string
+		perm os.FileMode
+	}{
+		{"/tmp/fortify.1971", 0701},
+		{"/tmp/fortify.1971/tmpdir", 0700},
+		{"/tmp/fortify.1971/tmpdir/150", 0700},
+		{"/run/user/1971/fortify", 0700},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name+"_"+tc.perm.String(), func(t *testing.T) {
+			sys := New(150)
+			sys.Ensure(tc.name, tc.perm)
+			(&tcOp{User, tc.name}).test(t, sys.ops, []Op{&Mkdir{User, tc.name, tc.perm, false}}, "Ensure")
+		})
+	}
+}
+
+func TestEphemeral(t *testing.T) {
+	testCases := []struct {
+		perm os.FileMode
+		tcOp
+	}{
+		{0700, tcOp{Process, "/run/user/1971/fortify/ec07546a772a07cde87389afc84ffd13"}},
+		{0701, tcOp{Process, "/tmp/fortify.1971/ec07546a772a07cde87389afc84ffd13"}},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.path+"_"+tc.perm.String()+"_"+TypeString(tc.et), func(t *testing.T) {
+			sys := New(150)
+			sys.Ephemeral(tc.et, tc.path, tc.perm)
+			tc.test(t, sys.ops, []Op{&Mkdir{tc.et, tc.path, tc.perm, true}}, "Ephemeral")
+		})
+	}
+}
+
+func TestMkdir_String(t *testing.T) {
+	testCases := []struct {
+		want      string
+		ephemeral bool
+		et        Enablement
+	}{
+		{"Ensure", false, User},
+		{"Ensure", false, Process},
+		{"Ensure", false, EWayland},
+
+		{"Wayland", true, EWayland},
+		{"X11", true, EX11},
+		{"D-Bus", true, EDBus},
+		{"PulseAudio", true, EPulse},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.want, func(t *testing.T) {
+			m := &Mkdir{
+				et:        tc.et,
+				path:      "/nonexistent",
+				perm:      0701,
+				ephemeral: tc.ephemeral,
+			}
+			want := "mode: " + os.FileMode(0701).String() + " type: " + tc.want + " path: \"/nonexistent\""
+			if got := m.String(); got != want {
+				t.Errorf("String() = %v, want %v", got, want)
+			}
+		})
+	}
+}

internal/system/op.go

@@ -0,0 +1,140 @@
+package system
+
+import (
+	"errors"
+	"sync"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+const (
+	// User type is reverted at final launcher exit.
+	User = Enablement(ELen)
+	// Process type is unconditionally reverted on exit.
+	Process = Enablement(ELen + 1)
+)
+
+type Criteria struct {
+	*Enablements
+}
+
+func (ec *Criteria) hasType(o Op) bool {
+	// nil criteria: revert everything except User
+	if ec.Enablements == nil {
+		return o.Type() != User
+	}
+
+	return ec.Has(o.Type())
+}
+
+// Op is a reversible system operation.
+type Op interface {
+	// Type returns Op's enablement type.
+	Type() Enablement
+
+	// apply the Op
+	apply(sys *I) error
+	// revert reverses the Op if criteria is met
+	revert(sys *I, ec *Criteria) error
+
+	Is(o Op) bool
+	Path() string
+	String() string
+}
+
+func TypeString(e Enablement) string {
+	switch e {
+	case User:
+		return "User"
+	case Process:
+		return "Process"
+	default:
+		return e.String()
+	}
+}
+
+type I struct {
+	uid int
+	ops []Op
+
+	state [2]bool
+	lock  sync.Mutex
+}
+
+func (sys *I) UID() int {
+	return sys.uid
+}
+
+func (sys *I) Equal(v *I) bool {
+	if v == nil || sys.uid != v.uid || len(sys.ops) != len(v.ops) {
+		return false
+	}
+
+	for i, o := range sys.ops {
+		if !o.Is(v.ops[i]) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (sys *I) Commit() error {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	if sys.state[0] {
+		panic("sys instance committed twice")
+	}
+	sys.state[0] = true
+
+	sp := New(sys.uid)
+	sp.ops = make([]Op, 0, len(sys.ops)) // prevent copies during commits
+	defer func() {
+		// sp is set to nil when all ops are applied
+		if sp != nil {
+			// rollback partial commit
+			fmsg.VPrintf("commit faulted after %d ops, rolling back partial commit", len(sp.ops))
+			if err := sp.Revert(&Criteria{nil}); err != nil {
+				fmsg.Println("errors returned reverting partial commit:", err)
+			}
+		}
+	}()
+
+	for _, o := range sys.ops {
+		if err := o.apply(sys); err != nil {
+			return err
+		} else {
+			// register partial commit
+			sp.ops = append(sp.ops, o)
+		}
+	}
+
+	// disarm partial commit rollback
+	sp = nil
+	return nil
+}
+
+func (sys *I) Revert(ec *Criteria) error {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	if sys.state[1] {
+		panic("sys instance reverted twice")
+	}
+	sys.state[1] = true
+
+	// collect errors
+	errs := make([]error, len(sys.ops))
+
+	for i := range sys.ops {
+		errs[i] = sys.ops[len(sys.ops)-i-1].revert(sys, ec)
+	}
+
+	// errors.Join filters nils
+	return errors.Join(errs...)
+}
+
+func New(uid int) *I {
+	return &I{uid: uid}
+}

internal/system/op_internal_test.go

@@ -0,0 +1,79 @@
+package system
+
+import "testing"
+
+type tcOp struct {
+	et   Enablement
+	path string
+}
+
+// test an instance of the Op interface
+func (ptc tcOp) test(t *testing.T, gotOps []Op, wantOps []Op, fn string) {
+	if len(gotOps) != len(wantOps) {
+		t.Errorf("%s: inserted %v Ops, want %v", fn,
+			len(gotOps), len(wantOps))
+		return
+	}
+
+	t.Run("path", func(t *testing.T) {
+		if len(gotOps) > 0 {
+			if got := gotOps[0].Path(); got != ptc.path {
+				t.Errorf("Path() = %q, want %q",
+					got, ptc.path)
+				return
+			}
+		}
+	})
+
+	for i := range gotOps {
+		o := gotOps[i]
+
+		t.Run("is", func(t *testing.T) {
+			if !o.Is(o) {
+				t.Errorf("Is returned false on self")
+				return
+			}
+			if !o.Is(wantOps[i]) {
+				t.Errorf("%s: inserted %#v, want %#v",
+					fn,
+					o, wantOps[i])
+				return
+			}
+		})
+
+		t.Run("criteria", func(t *testing.T) {
+			testCases := []struct {
+				name string
+				ec   *Criteria
+				want bool
+			}{
+				{"nil", newCriteria(), ptc.et != User},
+				{"self", newCriteria(ptc.et), true},
+				{"all", newCriteria(EWayland, EX11, EDBus, EPulse, User, Process), true},
+				{"enablements", newCriteria(EWayland, EX11, EDBus, EPulse), ptc.et != User && ptc.et != Process},
+			}
+
+			for _, tc := range testCases {
+				t.Run(tc.name, func(t *testing.T) {
+					if got := tc.ec.hasType(o); got != tc.want {
+						t.Errorf("hasType: got %v, want %v",
+							got, tc.want)
+					}
+				})
+			}
+		})
+	}
+}
+
+func newCriteria(labels ...Enablement) *Criteria {
+	ec := new(Criteria)
+	if len(labels) == 0 {
+		return ec
+	}
+
+	ec.Enablements = new(Enablements)
+	for _, e := range labels {
+		ec.Set(e)
+	}
+	return ec
+}

internal/system/op_test.go

@@ -0,0 +1,129 @@
+package system_test
+
+import (
+	"strconv"
+	"testing"
+
+	"git.ophivana.moe/security/fortify/internal/system"
+)
+
+func TestNew(t *testing.T) {
+	testCases := []struct {
+		uid int
+	}{
+		{150},
+		{149},
+		{148},
+		{147},
+	}
+
+	for _, tc := range testCases {
+		t.Run("sys initialised with uid "+strconv.Itoa(tc.uid), func(t *testing.T) {
+			if got := system.New(tc.uid); got.UID() != tc.uid {
+				t.Errorf("New(%d) uid = %d, want %d",
+					tc.uid,
+					got.UID(), tc.uid)
+			}
+		})
+	}
+}
+
+func TestTypeString(t *testing.T) {
+	testCases := []struct {
+		e    system.Enablement
+		want string
+	}{
+		{system.EWayland, system.EWayland.String()},
+		{system.EX11, system.EX11.String()},
+		{system.EDBus, system.EDBus.String()},
+		{system.EPulse, system.EPulse.String()},
+		{system.User, "User"},
+		{system.Process, "Process"},
+	}
+
+	for _, tc := range testCases {
+		t.Run("label type string "+tc.want, func(t *testing.T) {
+			if got := system.TypeString(tc.e); got != tc.want {
+				t.Errorf("TypeString(%d) = %v, want %v",
+					tc.e,
+					got, tc.want)
+			}
+		})
+	}
+}
+
+func TestI_Equal(t *testing.T) {
+	testCases := []struct {
+		name string
+		sys  *system.I
+		v    *system.I
+		want bool
+	}{
+		{
+			"simple UID",
+			system.New(150),
+			system.New(150),
+			true,
+		},
+		{
+			"simple UID differ",
+			system.New(150),
+			system.New(151),
+			false,
+		},
+		{
+			"simple UID nil",
+			system.New(150),
+			nil,
+			false,
+		},
+		{
+			"op length mismatch",
+			system.New(150).
+				ChangeHosts("chronos"),
+			system.New(150).
+				ChangeHosts("chronos").
+				Ensure("/run", 0755),
+			false,
+		},
+		{
+			"op value mismatch",
+			system.New(150).
+				ChangeHosts("chronos").
+				Ensure("/run", 0644),
+			system.New(150).
+				ChangeHosts("chronos").
+				Ensure("/run", 0755),
+			false,
+		},
+		{
+			"op type mismatch",
+			system.New(150).
+				ChangeHosts("chronos").
+				CopyFile("/tmp/fortify.1971/30c9543e0a2c9621a8bfecb9d874c347/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie"),
+			system.New(150).
+				ChangeHosts("chronos").
+				Ensure("/run", 0755),
+			false,
+		},
+		{
+			"op equals",
+			system.New(150).
+				ChangeHosts("chronos").
+				Ensure("/run", 0755),
+			system.New(150).
+				ChangeHosts("chronos").
+				Ensure("/run", 0755),
+			true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			if tc.sys.Equal(tc.v) != tc.want {
+				t.Errorf("Equal: got %v; want %v",
+					!tc.want, tc.want)
+			}
+		})
+	}
+}

internal/system/tmpfiles.go

@@ -0,0 +1,145 @@
+package system
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+
+	"git.ophivana.moe/security/fortify/acl"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+// CopyFile registers an Op that copies path dst from src.
+func (sys *I) CopyFile(dst, src string) *I {
+	return sys.CopyFileType(Process, dst, src)
+}
+
+// CopyFileType registers a file copying Op labelled with type et.
+func (sys *I) CopyFileType(et Enablement, dst, src string) *I {
+	sys.lock.Lock()
+	sys.ops = append(sys.ops, &Tmpfile{et, tmpfileCopy, dst, src})
+	sys.lock.Unlock()
+
+	sys.UpdatePermType(et, dst, acl.Read)
+
+	return sys
+}
+
+// Link registers an Op that links dst to src.
+func (sys *I) Link(oldname, newname string) *I {
+	return sys.LinkFileType(Process, oldname, newname)
+}
+
+// LinkFileType registers a file linking Op labelled with type et.
+func (sys *I) LinkFileType(et Enablement, oldname, newname string) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &Tmpfile{et, tmpfileLink, newname, oldname})
+
+	return sys
+}
+
+// Write registers an Op that writes dst with the contents of src.
+func (sys *I) Write(dst, src string) *I {
+	return sys.WriteType(Process, dst, src)
+}
+
+// WriteType registers a file writing Op labelled with type et.
+func (sys *I) WriteType(et Enablement, dst, src string) *I {
+	sys.lock.Lock()
+	sys.ops = append(sys.ops, &Tmpfile{et, tmpfileWrite, dst, src})
+	sys.lock.Unlock()
+
+	sys.UpdatePermType(et, dst, acl.Read)
+
+	return sys
+}
+
+const (
+	tmpfileCopy uint8 = iota
+	tmpfileLink
+	tmpfileWrite
+)
+
+type Tmpfile struct {
+	et       Enablement
+	method   uint8
+	dst, src string
+}
+
+func (t *Tmpfile) Type() Enablement {
+	return t.et
+}
+
+func (t *Tmpfile) apply(_ *I) error {
+	switch t.method {
+	case tmpfileCopy:
+		fmsg.VPrintln("publishing tmpfile", t)
+		return fmsg.WrapErrorSuffix(copyFile(t.dst, t.src),
+			fmt.Sprintf("cannot copy tmpfile %q:", t.dst))
+	case tmpfileLink:
+		fmsg.VPrintln("linking tmpfile", t)
+		return fmsg.WrapErrorSuffix(os.Link(t.src, t.dst),
+			fmt.Sprintf("cannot link tmpfile %q:", t.dst))
+	case tmpfileWrite:
+		fmsg.VPrintln("writing", t)
+		return fmsg.WrapErrorSuffix(os.WriteFile(t.dst, []byte(t.src), 0600),
+			fmt.Sprintf("cannot write tmpfile %q:", t.dst))
+	default:
+		panic("invalid tmpfile method " + strconv.Itoa(int(t.method)))
+	}
+}
+
+func (t *Tmpfile) revert(_ *I, ec *Criteria) error {
+	if ec.hasType(t) {
+		fmsg.VPrintf("removing tmpfile %q", t.dst)
+		return fmsg.WrapErrorSuffix(os.Remove(t.dst),
+			fmt.Sprintf("cannot remove tmpfile %q:", t.dst))
+	} else {
+		fmsg.VPrintf("skipping tmpfile %q", t.dst)
+		return nil
+	}
+}
+
+func (t *Tmpfile) Is(o Op) bool {
+	t0, ok := o.(*Tmpfile)
+	return ok && t0 != nil && *t == *t0
+}
+
+func (t *Tmpfile) Path() string {
+	if t.method == tmpfileWrite {
+		return fmt.Sprintf("(%d bytes of data)", len(t.src))
+	}
+	return t.src
+}
+
+func (t *Tmpfile) String() string {
+	switch t.method {
+	case tmpfileCopy:
+		return fmt.Sprintf("%q from %q", t.dst, t.src)
+	case tmpfileLink:
+		return fmt.Sprintf("%q from %q", t.dst, t.src)
+	case tmpfileWrite:
+		return fmt.Sprintf("%d bytes of data to %q", len(t.src), t.dst)
+	default:
+		panic("invalid tmpfile method " + strconv.Itoa(int(t.method)))
+	}
+}
+
+func copyFile(dst, src string) error {
+	dstD, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+
+	srcD, err := os.Open(src)
+	if err != nil {
+		return errors.Join(err, dstD.Close())
+	}
+
+	_, err = io.Copy(dstD, srcD)
+	return errors.Join(err, dstD.Close(), srcD.Close())
+}

internal/system/tmpfiles_test.go

@@ -0,0 +1,167 @@
+package system
+
+import (
+	"strconv"
+	"testing"
+
+	"git.ophivana.moe/security/fortify/acl"
+)
+
+func TestCopyFile(t *testing.T) {
+	testCases := []struct {
+		dst, src string
+	}{
+		{"/tmp/fortify.1971/f587afe9fce3c8e1ad5b64deb6c41ad5/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie"},
+		{"/tmp/fortify.1971/62154f708b5184ab01f9dcc2bbe7a33b/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie"},
+	}
+	for _, tc := range testCases {
+		t.Run("copy file "+tc.dst+" from "+tc.src, func(t *testing.T) {
+			sys := New(150)
+			sys.CopyFile(tc.dst, tc.src)
+			(&tcOp{Process, tc.src}).test(t, sys.ops, []Op{
+				&Tmpfile{Process, tmpfileCopy, tc.dst, tc.src},
+				&ACL{Process, tc.dst, []acl.Perm{acl.Read}},
+			}, "CopyFile")
+		})
+	}
+}
+
+func TestCopyFileType(t *testing.T) {
+	testCases := []struct {
+		tcOp
+		dst string
+	}{
+		{tcOp{User, "/tmp/fortify.1971/f587afe9fce3c8e1ad5b64deb6c41ad5/pulse-cookie"}, "/home/ophestra/xdg/config/pulse/cookie"},
+		{tcOp{Process, "/tmp/fortify.1971/62154f708b5184ab01f9dcc2bbe7a33b/pulse-cookie"}, "/home/ophestra/xdg/config/pulse/cookie"},
+	}
+	for _, tc := range testCases {
+		t.Run("copy file "+tc.dst+" from "+tc.path+" with type "+TypeString(tc.et), func(t *testing.T) {
+			sys := New(150)
+			sys.CopyFileType(tc.et, tc.dst, tc.path)
+			tc.test(t, sys.ops, []Op{
+				&Tmpfile{tc.et, tmpfileCopy, tc.dst, tc.path},
+				&ACL{tc.et, tc.dst, []acl.Perm{acl.Read}},
+			}, "CopyFileType")
+		})
+	}
+}
+
+func TestLink(t *testing.T) {
+	testCases := []struct {
+		dst, src string
+	}{
+		{"/tmp/fortify.1971/f587afe9fce3c8e1ad5b64deb6c41ad5/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie"},
+		{"/tmp/fortify.1971/62154f708b5184ab01f9dcc2bbe7a33b/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie"},
+	}
+	for _, tc := range testCases {
+		t.Run("link file "+tc.dst+" from "+tc.src, func(t *testing.T) {
+			sys := New(150)
+			sys.Link(tc.src, tc.dst)
+			(&tcOp{Process, tc.src}).test(t, sys.ops, []Op{
+				&Tmpfile{Process, tmpfileLink, tc.dst, tc.src},
+			}, "Link")
+		})
+	}
+}
+
+func TestLinkFileType(t *testing.T) {
+	testCases := []struct {
+		tcOp
+		dst string
+	}{
+		{tcOp{User, "/tmp/fortify.1971/f587afe9fce3c8e1ad5b64deb6c41ad5/pulse-cookie"}, "/home/ophestra/xdg/config/pulse/cookie"},
+		{tcOp{Process, "/tmp/fortify.1971/62154f708b5184ab01f9dcc2bbe7a33b/pulse-cookie"}, "/home/ophestra/xdg/config/pulse/cookie"},
+	}
+	for _, tc := range testCases {
+		t.Run("link file "+tc.dst+" from "+tc.path+" with type "+TypeString(tc.et), func(t *testing.T) {
+			sys := New(150)
+			sys.LinkFileType(tc.et, tc.path, tc.dst)
+			tc.test(t, sys.ops, []Op{
+				&Tmpfile{tc.et, tmpfileLink, tc.dst, tc.path},
+			}, "LinkFileType")
+		})
+	}
+}
+
+func TestWrite(t *testing.T) {
+	testCases := []struct {
+		dst, src string
+	}{
+		{"/etc/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n"},
+		{"/etc/group", "fortify:x:65534:\n"},
+	}
+	for _, tc := range testCases {
+		t.Run("write "+strconv.Itoa(len(tc.src))+" bytes to "+tc.dst, func(t *testing.T) {
+			sys := New(150)
+			sys.Write(tc.dst, tc.src)
+			(&tcOp{Process, "(" + strconv.Itoa(len(tc.src)) + " bytes of data)"}).test(t, sys.ops, []Op{
+				&Tmpfile{Process, tmpfileWrite, tc.dst, tc.src},
+				&ACL{Process, tc.dst, []acl.Perm{acl.Read}},
+			}, "Write")
+		})
+	}
+}
+
+func TestWriteType(t *testing.T) {
+	testCases := []struct {
+		et       Enablement
+		dst, src string
+	}{
+		{Process, "/etc/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n"},
+		{Process, "/etc/group", "fortify:x:65534:\n"},
+		{User, "/etc/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n"},
+		{User, "/etc/group", "fortify:x:65534:\n"},
+	}
+	for _, tc := range testCases {
+		t.Run("write "+strconv.Itoa(len(tc.src))+" bytes to "+tc.dst+" with type "+TypeString(tc.et), func(t *testing.T) {
+			sys := New(150)
+			sys.WriteType(tc.et, tc.dst, tc.src)
+			(&tcOp{tc.et, "(" + strconv.Itoa(len(tc.src)) + " bytes of data)"}).test(t, sys.ops, []Op{
+				&Tmpfile{tc.et, tmpfileWrite, tc.dst, tc.src},
+				&ACL{tc.et, tc.dst, []acl.Perm{acl.Read}},
+			}, "WriteType")
+		})
+	}
+}
+
+func TestTmpfile_String(t *testing.T) {
+	t.Run("invalid method panic", func(t *testing.T) {
+		defer func() {
+			wantPanic := "invalid tmpfile method 255"
+			if r := recover(); r != wantPanic {
+				t.Errorf("String() panic = %v, want %v",
+					r, wantPanic)
+			}
+		}()
+		_ = (&Tmpfile{method: 255}).String()
+	})
+
+	testCases := []struct {
+		method   uint8
+		dst, src string
+		want     string
+	}{
+		{tmpfileCopy, "/tmp/fortify.1971/4b6bdc9182fb2f1d3a965c5fa8b9b66e/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie",
+			`"/tmp/fortify.1971/4b6bdc9182fb2f1d3a965c5fa8b9b66e/pulse-cookie" from "/home/ophestra/xdg/config/pulse/cookie"`},
+		{tmpfileLink, "/run/user/1971/fortify/4b6bdc9182fb2f1d3a965c5fa8b9b66e/wayland", "/run/user/1971/wayland-0",
+			`"/run/user/1971/fortify/4b6bdc9182fb2f1d3a965c5fa8b9b66e/wayland" from "/run/user/1971/wayland-0"`},
+		{tmpfileLink, "/run/user/1971/fortify/4b6bdc9182fb2f1d3a965c5fa8b9b66e/pulse", "/run/user/1971/pulse/native",
+			`"/run/user/1971/fortify/4b6bdc9182fb2f1d3a965c5fa8b9b66e/pulse" from "/run/user/1971/pulse/native"`},
+		{tmpfileWrite, "/tmp/fortify.1971/4b6bdc9182fb2f1d3a965c5fa8b9b66e/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n",
+			`75 bytes of data to "/tmp/fortify.1971/4b6bdc9182fb2f1d3a965c5fa8b9b66e/passwd"`},
+		{tmpfileWrite, "/tmp/fortify.1971/4b6bdc9182fb2f1d3a965c5fa8b9b66e/group", "fortify:x:65534:\n",
+			`17 bytes of data to "/tmp/fortify.1971/4b6bdc9182fb2f1d3a965c5fa8b9b66e/group"`},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.want, func(t *testing.T) {
+			if got := (&Tmpfile{
+				method: tc.method,
+				dst:    tc.dst,
+				src:    tc.src,
+			}).String(); got != tc.want {
+				t.Errorf("String() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}

internal/system/xhost.go

@@ -0,0 +1,54 @@
+package system
+
+import (
+	"fmt"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/xcb"
+)
+
+// ChangeHosts appends an X11 ChangeHosts command Op.
+func (sys *I) ChangeHosts(username string) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, XHost(username))
+
+	return sys
+}
+
+type XHost string
+
+func (x XHost) Type() Enablement {
+	return EX11
+}
+
+func (x XHost) apply(_ *I) error {
+	fmsg.VPrintf("inserting entry %s to X11", x)
+	return fmsg.WrapErrorSuffix(xcb.ChangeHosts(xcb.HostModeInsert, xcb.FamilyServerInterpreted, "localuser\x00"+string(x)),
+		fmt.Sprintf("cannot insert entry %s to X11:", x))
+}
+
+func (x XHost) revert(_ *I, ec *Criteria) error {
+	if ec.hasType(x) {
+		fmsg.VPrintf("deleting entry %s from X11", x)
+		return fmsg.WrapErrorSuffix(xcb.ChangeHosts(xcb.HostModeDelete, xcb.FamilyServerInterpreted, "localuser\x00"+string(x)),
+			fmt.Sprintf("cannot delete entry %s from X11:", x))
+	} else {
+		fmsg.VPrintf("skipping entry %s in X11", x)
+		return nil
+	}
+}
+
+func (x XHost) Is(o Op) bool {
+	x0, ok := o.(XHost)
+	return ok && x == x0
+}
+
+func (x XHost) Path() string {
+	return string(x)
+}
+
+func (x XHost) String() string {
+	return string("SI:localuser:" + x)
+}

internal/system/xhost_test.go

@@ -0,0 +1,34 @@
+package system
+
+import (
+	"testing"
+)
+
+func TestChangeHosts(t *testing.T) {
+	testCases := []string{"chronos", "keyring", "cat", "kbd", "yonah"}
+	for _, tc := range testCases {
+		t.Run("append ChangeHosts operation for "+tc, func(t *testing.T) {
+			sys := New(150)
+			sys.ChangeHosts(tc)
+			(&tcOp{EX11, tc}).test(t, sys.ops, []Op{
+				XHost(tc),
+			}, "ChangeHosts")
+		})
+	}
+}
+
+func TestXHost_String(t *testing.T) {
+	testCases := []struct {
+		username string
+		want     string
+	}{
+		{"chronos", "SI:localuser:chronos"},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.want, func(t *testing.T) {
+			if got := XHost(tc.username).String(); got != tc.want {
+				t.Errorf("String() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}

internal/verbose/print.go

@@ -1,19 +0,0 @@
-package verbose
-
-import (
-	"fmt"
-)
-
-var Prefix = "fortify:"
-
-func Println(a ...any) {
-	if verbose.Load() {
-		fmt.Println(append([]any{Prefix}, a...)...)
-	}
-}
-
-func Printf(format string, a ...any) {
-	if verbose.Load() {
-		fmt.Printf(Prefix+" "+format, a...)
-	}
-}

internal/verbose/print_test.go

@@ -1,67 +0,0 @@
-package verbose_test
-
-import (
-	"os"
-	"os/exec"
-	"strconv"
-	"strings"
-	"testing"
-
-	"git.ophivana.moe/cat/fortify/internal/verbose"
-)
-
-const (
-	testVerbose = "GO_TEST_VERBOSE"
-	wantStdout  = "fortify: println\nfortify: printf"
-)
-
-func TestPrinter(t *testing.T) {
-	switch os.Getenv(testVerbose) {
-	case "0":
-		verbose.Set(false)
-	case "1":
-		verbose.Set(true)
-	default:
-		return
-	}
-
-	verbose.Println("println")
-	verbose.Printf("%s", "printf")
-}
-
-func TestPrintf_Println(t *testing.T) {
-	testPrintfPrintln(t, false)
-	testPrintfPrintln(t, true)
-
-	// make -cover happy
-	stdout := os.Stdout
-	t.Cleanup(func() {
-		os.Stdout = stdout
-	})
-	os.Stdout = nil
-	verbose.Set(true)
-	verbose.Printf("")
-	verbose.Println()
-}
-
-func testPrintfPrintln(t *testing.T, v bool) {
-	t.Run("start verbose printer with verbose "+strconv.FormatBool(v), func(t *testing.T) {
-		stdout, stderr := new(strings.Builder), new(strings.Builder)
-		stdout.Grow(len(wantStdout))
-		cmd := exec.Command(os.Args[0], "-test.run=TestPrinter")
-		cmd.Stdout, cmd.Stderr = stdout, stderr
-		if v {
-			cmd.Env = append(cmd.Env, testVerbose+"=1")
-		} else {
-			cmd.Env = append(cmd.Env, testVerbose+"=0")
-		}
-		if err := cmd.Run(); err != nil {
-			panic("cannot run printer process: " + err.Error() + " stderr: " + stderr.String())
-		}
-
-		if got := stdout.String(); strings.Contains(got, wantStdout) != v {
-			t.Errorf("Print: got %v; want %t",
-				got, v)
-		}
-	})
-}

internal/verbose/state.go

@@ -1,13 +0,0 @@
-package verbose
-
-import "sync/atomic"
-
-var verbose = new(atomic.Bool)
-
-func Get() bool {
-	return verbose.Load()
-}
-
-func Set(v bool) {
-	verbose.Store(v)
-}

internal/verbose/state_test.go

@@ -1,20 +0,0 @@
-package verbose_test
-
-import (
-	"testing"
-
-	"git.ophivana.moe/cat/fortify/internal/verbose"
-)
-
-func TestGetSet(t *testing.T) {
-	verbose.Set(false)
-	if verbose.Get() {
-		t.Errorf("Get() = true, want false")
-	}
-
-	verbose.Set(true)
-	if !verbose.Get() {
-		t.Errorf("Get() = false, want true")
-	}
-
-}

ldd/exec.go

@@ -5,14 +5,37 @@ import (
 	"os"
 	"os/exec"
 	"strings"
+
+	"git.ophivana.moe/security/fortify/helper"
+	"git.ophivana.moe/security/fortify/helper/bwrap"
 )
 
 func Exec(p string) ([]*Entry, error) {
-	t := exec.Command("ldd", p)
-	t.Stdout, t.Stderr = new(strings.Builder), os.Stderr
-	if err := t.Run(); err != nil {
+	var (
+		h   helper.Helper
+		cmd *exec.Cmd
+	)
+
+	if b, err := helper.NewBwrap((&bwrap.Config{
+		Hostname:      "fortify-ldd",
+		Chdir:         "/",
+		NewSession:    true,
+		DieWithParent: true,
+	}).Bind("/", "/").DevTmpfs("/dev"),
+		nil, "ldd", func(_, _ int) []string { return []string{p} }); err != nil {
+		return nil, err
+	} else {
+		cmd = b.Unwrap()
+		h = b
+	}
+
+	cmd.Stdout, cmd.Stderr = new(strings.Builder), os.Stderr
+	if err := h.Start(); err != nil {
+		return nil, err
+	}
+	if err := h.Wait(); err != nil {
 		return nil, err
 	}
 
-	return Parse(t.Stdout.(fmt.Stringer))
+	return Parse(cmd.Stdout.(fmt.Stringer))
 }

ldd/ldd_test.go

@@ -6,7 +6,7 @@ import (
 	"strings"
 	"testing"
 
-	"git.ophivana.moe/cat/fortify/ldd"
+	"git.ophivana.moe/security/fortify/ldd"
 )
 
 func TestParseError(t *testing.T) {

license.go

@@ -4,7 +4,6 @@ import (
 	_ "embed"
 	"flag"
 	"fmt"
-	"os"
 )
 
 var (

main.go

@@ -2,15 +2,13 @@ package main
 
 import (
 	"flag"
-	"fmt"
-	"os"
 	"syscall"
 
-	"git.ophivana.moe/cat/fortify/internal"
-	"git.ophivana.moe/cat/fortify/internal/app"
-	init0 "git.ophivana.moe/cat/fortify/internal/init"
-	"git.ophivana.moe/cat/fortify/internal/shim"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
+	"git.ophivana.moe/security/fortify/internal"
+	"git.ophivana.moe/security/fortify/internal/app"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	init0 "git.ophivana.moe/security/fortify/internal/init"
+	"git.ophivana.moe/security/fortify/internal/shim"
 )
 
 var (
@@ -21,17 +19,19 @@ func init() {
 	flag.BoolVar(&flagVerbose, "v", false, "Verbose output")
 }
 
-func main() {
-	flag.Parse()
-	verbose.Set(flagVerbose)
+var os = new(internal.Std)
 
+func main() {
 	// linux/sched/coredump.h
 	if _, _, errno := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_DUMPABLE, 0, 0); errno != 0 {
-		fmt.Printf("fortify: cannot set SUID_DUMP_DISABLE: %s", errno.Error())
+		fmsg.Printf("fortify: cannot set SUID_DUMP_DISABLE: %s", errno.Error())
 	}
 
-	if internal.SdBootedV {
-		verbose.Println("system booted with systemd as init system")
+	flag.Parse()
+	fmsg.SetVerbose(flagVerbose)
+
+	if os.SdBooted() {
+		fmsg.VPrintln("system booted with systemd as init system")
 	}
 
 	// shim/init early exit
@@ -39,9 +39,9 @@ func main() {
 	shim.Try()
 
 	// root check
-	if os.Getuid() == 0 {
-		fmt.Println("fortify: this program must not run as root")
-		os.Exit(1)
+	if os.Geteuid() == 0 {
+		fmsg.Fatal("this program must not run as root")
+		panic("unreachable")
 	}
 
 	// version/license/template command early exit
@@ -53,20 +53,26 @@ func main() {
 	tryState()
 
 	// invoke app
-	r := 1
-	a := app.New()
-	if err := a.Seal(loadConfig()); err != nil {
-		logBaseError(err, "fortify: cannot seal app:")
+	a, err := app.New(os)
+	if err != nil {
+		fmsg.Fatalf("cannot create app: %s\n", err)
+	} else if err = a.Seal(loadConfig()); err != nil {
+		logBaseError(err, "cannot seal app:")
+		fmsg.Exit(1)
 	} else if err = a.Start(); err != nil {
-		logBaseError(err, "fortify: cannot start app:")
-	} else if r, err = a.Wait(); err != nil {
+		logBaseError(err, "cannot start app:")
+	}
+
+	var r int
+	// wait must be called regardless of result of start
+	if r, err = a.Wait(); err != nil {
 		if r < 1 {
 			r = 1
 		}
 		logWaitError(err)
 	}
-	if err := a.WaitErr(); err != nil {
-		fmt.Println("fortify: inner wait failed:", err)
+	if err = a.WaitErr(); err != nil {
+		fmsg.Println("inner wait failed:", err)
 	}
-	os.Exit(r)
+	fmsg.Exit(r)
 }

package.nix

@@ -10,7 +10,7 @@
 
 buildGoModule rec {
   pname = "fortify";
-  version = "0.0.3";
+  version = "0.0.10";
 
   src = ./.;
   vendorHash = null;
@@ -20,6 +20,8 @@ buildGoModule rec {
     "-w"
     "-X"
     "main.Version=v${version}"
+    "-X"
+    "main.FortifyPath=${placeholder "out"}/bin/.fortify-wrapped"
   ];
 
   buildInputs = [
@@ -36,5 +38,7 @@ buildGoModule rec {
         xdg-dbus-proxy
       ]
     }
+
+    mv $out/bin/fsu $out/bin/.fsu
   '';
 }

state.go

@@ -3,11 +3,10 @@ package main
 import (
 	"flag"
 	"fmt"
-	"os"
 	"text/tabwriter"
 
-	"git.ophivana.moe/cat/fortify/internal"
-	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+	"git.ophivana.moe/security/fortify/internal/state"
 )
 
 var (
@@ -22,15 +21,15 @@ func init() {
 func tryState() {
 	if stateActionEarly {
 		var w *tabwriter.Writer
-		state.MustPrintLauncherStateSimpleGlobal(&w, internal.GetSC().RunDirPath)
+		state.MustPrintLauncherStateSimpleGlobal(&w, os.Paths().RunDirPath)
 		if w != nil {
 			if err := w.Flush(); err != nil {
-				fmt.Println("warn: error formatting output:", err)
+				fmsg.Println("cannot format output:", err)
 			}
 		} else {
 			fmt.Println("No information available")
 		}
 
-		os.Exit(0)
+		fmsg.Exit(0)
 	}
 }

version.go

@@ -3,7 +3,6 @@ package main
 import (
 	"flag"
 	"fmt"
-	"os"
 )
 
 var (