release: 0.2.0

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

.gitea/workflows/release.yml

@@ -33,9 +33,9 @@ jobs:
           go build -v -ldflags '-s -w
           -X git.ophivana.moe/security/fortify/internal.Version=${{ github.ref_name }}
           -X git.ophivana.moe/security/fortify/internal.Fsu=/usr/bin/fsu
-          -X git.ophivana.moe/security/fortify/internal.Fshim=/usr/libexec/fortify/fshim
           -X git.ophivana.moe/security/fortify/internal.Finit=/usr/libexec/fortify/finit
-          -X main.Fmain=/usr/bin/fortify'
+          -X main.Fmain=/usr/bin/fortify
+          -X main.Fshim=/usr/libexec/fortify/fshim'
           -o bin/ ./... &&
           (cd bin && sha512sum --tag -b * > sha512sums)
 

.gitea/workflows/test.yml

@@ -36,8 +36,8 @@ jobs:
           go build -v -ldflags '-s -w
           -X git.ophivana.moe/security/fortify/internal.Version=${{ github.ref_name }}
           -X git.ophivana.moe/security/fortify/internal.Fsu=/usr/bin/fsu
-          -X git.ophivana.moe/security/fortify/internal.Fshim=/usr/libexec/fortify/fshim
           -X git.ophivana.moe/security/fortify/internal.Finit=/usr/libexec/fortify/finit
-          -X main.Fmain=/usr/bin/fortify'
+          -X main.Fmain=/usr/bin/fortify
+          -X main.Fshim=/usr/libexec/fortify/fshim'
           -o bin/ ./... &&
           (cd bin && sha512sum --tag -b * > sha512sums)

README.md

@@ -32,7 +32,9 @@ nix run git+https://git.ophivana.moe/security/fortify -- -h
 
 ## Module usage
 
-The NixOS module currently requires home-manager and impermanence to function correctly.
+The NixOS module currently requires home-manager to function correctly.
+
+Full module documentation can be found [here](options.md).
 
 To use the module, import it into your configuration with
 
@@ -69,37 +71,19 @@ This adds the `environment.fortify` option:
 {
   environment.fortify = {
     enable = true;
-    user = "nixos";
-    stateDir = "/var/lib/persist/module";
-    target = {
-      chronos = {
-        launchers = {
-          weechat.method = "sudo";
-          claws-mail.capability.pulse = false;
-
-          discord = {
-            id = "dev.vencord.Vesktop";
-            command = "vesktop --ozone-platform-hint=wayland";
-            userns = true;
-            useRealUid = true;
-            dbus = {
-              session =
-                f:
-                f {
-                  talk = [ "org.kde.StatusNotifierWatcher" ];
-                  own = [ ];
-                  call = { };
-                  broadcast = { };
-                };
-              system.filter = true;
-            };
-            share = pkgs.vesktop;
+    stateDir = "/var/lib/persist/module/fortify";
+    users = {
+      alice = 0;
+      nixos = 10;
     };
 
-          chromium = {
+    apps = [
+      {
+        name = "chromium";
         id = "org.chromium.Chromium";
+        packages = [ pkgs.chromium ];
         userns = true;
-            useRealUid = true;
+        mapRealUid = true;
         dbus = {
           system = {
             filter = true;
@@ -109,7 +93,9 @@ This adds the `environment.fortify` option:
               "org.freedesktop.UPower"
             ];
           };
-              session = f: f {
+          session =
+            f:
+            f {
               talk = [
                 "org.freedesktop.DBus"
                 "org.freedesktop.FileManager1"
@@ -128,81 +114,59 @@ This adds the `environment.fortify` option:
               broadcast = { };
             };
         };
+      }
+      {
+        name = "claws-mail";
+        id = "org.claws_mail.Claws-Mail";
+        packages = [ pkgs.claws-mail ];
+        gpu = false;
+        capability.pulse = false;
+      }
+      {
+        name = "weechat";
+        packages = [ pkgs.weechat ];
+        capability = {
+          wayland = false;
+          x11 = false;
+          dbus = true;
+          pulse = false;
         };
+      }
+      {
+        name = "discord";
+        id = "dev.vencord.Vesktop";
+        packages = [ pkgs.vesktop ];
+        share = pkgs.vesktop;
+        command = "vesktop --ozone-platform-hint=wayland";
+        userns = true;
+        mapRealUid = true;
+        capability.x11 = true;
+        dbus = {
+          session =
+            f:
+            f {
+              talk = [ "org.kde.StatusNotifierWatcher" ];
+              own = [ ];
+              call = { };
+              broadcast = { };
             };
-        packages = with pkgs; [
-          weechat
-          claws-mail
-          vesktop
-          chromium
-        ];
-        persistence.directories = [
-          ".config/weechat"
-          ".claws-mail"
-          ".config/vesktop"
+          system.filter = true;
+        };
+      }
+      {
+        name = "looking-glass-client";
+        groups = [ "plugdev" ];
+        extraPaths = [
+          {
+            src = "/dev/shm/looking-glass";
+            write = true;
+          }
         ];
         extraConfig = {
           programs.looking-glass-client.enable = true;
         };
-      };
-    };
+      }
+    ];
   };
 }
 ```
-
-* `enable` determines whether the module should be enabled or not. Useful when sharing configurations between graphical
-  and headless systems. Defaults to `false`.
-
-* `user` specifies the privileged user with access to fortified applications.
-
-* `stateDir` is the path to your persistent storage location. It is directly passed through to the impermanence module.
-
-* `target` is an attribute set of submodules, where the attribute name is the username of the unprivileged target user.
-
-  The available options are:
-
-    * `packages`, the list of packages to make available in the target user's environment.
-
-    * `persistence`, user persistence attribute set passed to impermanence.
-
-    * `extraConfig`, extra home-manager configuration for the target user.
-
-    * `launchers`, attribute set where the attribute name is the name of the launcher.
-
-      The available options are:
-
-        * `id`, the freedesktop application ID, primarily used by dbus, null to disable.
-
-        * `command`, the command to run as the target user. Defaults to launcher name.
-
-        * `dbus.session`, D-Bus session proxy custom configuration.
-
-        * `dbus.configSystem`, D-Bus system proxy custom configuration, null to disable.
-
-        * `env`, attrset of environment variables to set for the initial process in the sandbox.
-
-        * `nix`, whether to allow nix daemon connections from within the sandbox.
-
-        * `userns`, whether to allow userns within the sandbox.
-
-        * `useRealUid`, whether to map to the real UID within the sandbox.
-
-        * `net`, whether to allow network access within the sandbox.
-
-        * `gpu`, target process GPU and driver access, null to follow Wayland or X capability.
-
-        * `dev`, whether to allow full device access within the sandbox.
-
-        * `extraPaths`, a list of extra paths to make available inside the sandbox.
-
-        * `capability.wayland`, whether to share the Wayland socket.
-
-        * `capability.x11`, whether to share the X11 socket and allow connection.
-
-        * `capability.dbus`, whether to proxy D-Bus.
-
-        * `capability.pulse`, whether to share the PulseAudio socket and cookie.
-
-        * `share`, package containing desktop/icon files. Defaults to launcher name.
-
-        * `method`, the launch method for the sandboxed program, can be `"sudo"`, `"systemd"`, `"simple"`.

cmd/finit/main.go

@@ -103,7 +103,7 @@ func main() {
 	if err := cmd.Start(); err != nil {
 		fmsg.Fatalf("cannot start %q: %v", payload.Argv0, err)
 	}
-	fmsg.Withhold()
+	fmsg.Suspend()
 
 	// close setup pipe as setup is now complete
 	if err := setup.Close(); err != nil {

cmd/fshim/ipc/shim/shim.go

@@ -5,6 +5,8 @@ import (
 	"net"
 	"os"
 	"os/exec"
+	"os/signal"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"syscall"
@@ -12,6 +14,7 @@ import (
 
 	"git.ophivana.moe/security/fortify/acl"
 	shim0 "git.ophivana.moe/security/fortify/cmd/fshim/ipc"
+	"git.ophivana.moe/security/fortify/internal"
 	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
@@ -24,24 +27,26 @@ type Shim struct {
 	cmd *exec.Cmd
 	// uid of shim target user
 	uid uint32
-	// whether to check shim pid
-	checkPid bool
-	// user switcher executable path
-	executable string
+	// string representation of application id
+	aid string
+	// string representation of supplementary group ids
+	supp []string
 	// path to setup socket
 	socket string
 	// shim setup abort reason and completion
 	abort     chan error
 	abortErr  atomic.Pointer[error]
 	abortOnce sync.Once
+	// fallback exit notifier with error returned killing the process
+	killFallback chan error
 	// wayland mediation, nil if disabled
 	wl *shim0.Wayland
 	// shim setup payload
 	payload *shim0.Payload
 }
 
-func New(executable string, uid uint32, socket string, wl *shim0.Wayland, payload *shim0.Payload, checkPid bool) *Shim {
-	return &Shim{uid: uid, executable: executable, socket: socket, wl: wl, payload: payload, checkPid: checkPid}
+func New(uid uint32, aid string, supp []string, socket string, wl *shim0.Wayland, payload *shim0.Payload) *Shim {
+	return &Shim{uid: uid, aid: aid, supp: supp, socket: socket, wl: wl, payload: payload}
 }
 
 func (s *Shim) String() string {
@@ -68,9 +73,11 @@ func (s *Shim) AbortWait(err error) {
 	<-s.abort
 }
 
-type CommandBuilder func(shimEnv string) (args []string)
+func (s *Shim) WaitFallback() chan error {
+	return s.killFallback
+}
 
-func (s *Shim) Start(f CommandBuilder) (*time.Time, error) {
+func (s *Shim) Start() (*time.Time, error) {
 	var (
 		cf     chan *net.UnixConn
 		accept func()
@@ -87,26 +94,51 @@ func (s *Shim) Start(f CommandBuilder) (*time.Time, error) {
 	}
 
 	// start user switcher process and save time
-	s.cmd = exec.Command(s.executable, f(shim0.Env+"="+s.socket)...)
-	s.cmd.Env = []string{}
+	var fsu string
+	if p, ok := internal.Check(internal.Fsu); !ok {
+		fmsg.Fatal("invalid fsu path, this copy of fshim is not compiled correctly")
+		panic("unreachable")
+	} else {
+		fsu = p
+	}
+	s.cmd = exec.Command(fsu)
+	s.cmd.Env = []string{
+		shim0.Env + "=" + s.socket,
+		"FORTIFY_APP_ID=" + s.aid,
+	}
+	if len(s.supp) > 0 {
+		fmsg.VPrintf("attaching supplementary group ids %s", s.supp)
+		s.cmd.Env = append(s.cmd.Env, "FORTIFY_GROUPS="+strings.Join(s.supp, " "))
+	}
 	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
+	fmsg.VPrintln("starting shim via fsu:", s.cmd)
+	fmsg.Suspend() // withhold messages to stderr
 	if err := s.cmd.Start(); err != nil {
 		return nil, fmsg.WrapErrorSuffix(err,
-			"cannot start user switcher:")
+			"cannot start fsu:")
 	}
 	startTime := time.Now().UTC()
 
 	// kill shim if something goes wrong and an error is returned
+	s.killFallback = make(chan error, 1)
 	killShim := func() {
 		if err := s.cmd.Process.Signal(os.Interrupt); err != nil {
-			fmsg.Println("cannot terminate shim on faulted setup:", err)
+			s.killFallback <- err
 		}
 	}
 	defer func() { killShim() }()
 
+	// take alternative exit path on signal
+	sig := make(chan os.Signal, 2)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		v := <-sig
+		fmsg.Printf("got %s after program start", v)
+		s.killFallback <- nil
+		signal.Ignore(syscall.SIGINT, syscall.SIGTERM)
+	}()
+
 	accept()
 	var conn *net.UnixConn
 	select {
@@ -132,7 +164,7 @@ func (s *Shim) Start(f CommandBuilder) (*time.Time, error) {
 		err = errors.New("compromised fortify build")
 		s.Abort(err)
 		return &startTime, err
-	} else if s.checkPid && cred.Pid != int32(s.cmd.Process.Pid) {
+	} else if 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")

cmd/fshim/main.go

@@ -58,7 +58,7 @@ func main() {
 	// dial setup socket
 	var conn *net.UnixConn
 	if c, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: socketPath, Net: "unix"}); err != nil {
-		fmsg.Fatal("cannot dial setup socket:", err)
+		fmsg.Fatal(err.Error())
 		panic("unreachable")
 	} else {
 		conn = c
@@ -67,7 +67,7 @@ func main() {
 	// decode payload gob stream
 	var payload shim.Payload
 	if err := gob.NewDecoder(conn).Decode(&payload); err != nil {
-		fmsg.Fatal("cannot decode shim payload:", err)
+		fmsg.Fatalf("cannot decode shim payload: %v", err)
 	} else {
 		fmsg.SetVerbose(payload.Verbose)
 	}
@@ -80,7 +80,7 @@ func main() {
 	wfd := -1
 	if payload.WL {
 		if fd, err := receiveWLfd(conn); err != nil {
-			fmsg.Fatal("cannot receive wayland fd:", err)
+			fmsg.Fatalf("cannot receive wayland fd: %v", err)
 		} else {
 			wfd = fd
 		}
@@ -102,7 +102,10 @@ func main() {
 	} else {
 		// no argv, look up shell instead
 		var ok bool
-		if ic.Argv0, ok = os.LookupEnv("SHELL"); !ok {
+		if payload.Bwrap.SetEnv == nil {
+			fmsg.Fatal("no command was specified and environment is unset")
+		}
+		if ic.Argv0, ok = payload.Bwrap.SetEnv["SHELL"]; !ok {
 			fmsg.Fatal("no command was specified and $SHELL was unset")
 		}
 
@@ -125,7 +128,7 @@ func main() {
 
 	// share config pipe
 	if r, w, err := os.Pipe(); err != nil {
-		fmsg.Fatal("cannot pipe:", err)
+		fmsg.Fatalf("cannot pipe: %v", err)
 	} else {
 		conf.SetEnv[init0.Env] = strconv.Itoa(3 + len(extraFiles))
 		extraFiles = append(extraFiles, r)
@@ -134,7 +137,7 @@ func main() {
 		go func() {
 			// stream config to pipe
 			if err = gob.NewEncoder(w).Encode(&ic); err != nil {
-				fmsg.Fatal("cannot transmit init config:", err)
+				fmsg.Fatalf("cannot transmit init config: %v", err)
 			}
 		}()
 	}
@@ -142,7 +145,7 @@ func main() {
 	helper.BubblewrapName = payload.Exec[0] // resolved bwrap path by parent
 	if b, err := helper.NewBwrap(conf, nil, finitPath,
 		func(int, int) []string { return make([]string, 0) }); err != nil {
-		fmsg.Fatal("malformed sandbox config:", err)
+		fmsg.Fatalf("malformed sandbox config: %v", err)
 	} else {
 		cmd := b.Unwrap()
 		cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
@@ -154,7 +157,7 @@ func main() {
 
 		// run and pass through exit code
 		if err = b.Start(); err != nil {
-			fmsg.Fatal("cannot start target process:", err)
+			fmsg.Fatalf("cannot start target process: %v", err)
 		} else if err = b.Wait(); err != nil {
 			fmsg.VPrintln("wait:", err)
 		}

cmd/fsu/main.go

@@ -1,10 +1,12 @@
 package main
 
 import (
-	"bufio"
+	"bytes"
+	"fmt"
 	"log"
 	"os"
 	"path"
+	"slices"
 	"strconv"
 	"strings"
 	"syscall"
@@ -15,9 +17,15 @@ const (
 	fsuConfFile = "/etc/fsurc"
 	envShim     = "FORTIFY_SHIM"
 	envAID      = "FORTIFY_APP_ID"
+	envGroups   = "FORTIFY_GROUPS"
+
+	PR_SET_NO_NEW_PRIVS = 0x26
 )
 
-var Fmain = compPoison
+var (
+	Fmain = compPoison
+	Fshim = compPoison
+)
 
 func main() {
 	log.SetFlags(0)
@@ -33,12 +41,17 @@ func main() {
 		log.Fatal("this program must not be started by root")
 	}
 
-	var fmain string
+	var fmain, fshim string
 	if p, ok := checkPath(Fmain); !ok {
 		log.Fatal("invalid fortify path, this copy of fsu is not compiled correctly")
 	} else {
 		fmain = p
 	}
+	if p, ok := checkPath(Fshim); !ok {
+		log.Fatal("invalid fshim path, this copy of fsu is not compiled correctly")
+	} else {
+		fshim = p
+	}
 
 	pexe := path.Join("/proc", strconv.Itoa(os.Getppid()), "exe")
 	if p, err := os.Readlink(pexe); err != nil {
@@ -61,84 +74,76 @@ func main() {
 		uid += fid * 10000
 	}
 
+	// allowed aid range 0 to 9999
+	if as, ok := os.LookupEnv(envAID); !ok {
+		log.Fatal("FORTIFY_APP_ID not set")
+	} else if aid, err := parseUint32Fast(as); err != nil || aid < 0 || aid > 9999 {
+		log.Fatal("invalid aid")
+	} else {
+		uid += aid
+	}
+
 	// pass through setup path to shim
 	var shimSetupPath string
 	if s, ok := os.LookupEnv(envShim); !ok {
-		log.Fatal("FORTIFY_SHIM not set")
+		// fortify requests target uid
+		// print resolved uid and exit
+		fmt.Print(uid)
+		os.Exit(0)
 	} 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")
+	// supplementary groups
+	var suppGroups, suppCurrent []int
+
+	if gs, ok := os.LookupEnv(envGroups); ok {
+		if cur, err := os.Getgroups(); err != nil {
+			log.Fatalf("cannot get groups: %v", err)
 		} else {
-		uid += aid
+			suppCurrent = cur
 		}
 
+		// parse space-separated list of group ids
+		gss := bytes.Split([]byte(gs), []byte{' '})
+		suppGroups = make([]int, len(gss)+1)
+		for i, s := range gss {
+			if gid, err := strconv.Atoi(string(s)); err != nil {
+				log.Fatalf("cannot parse %q: %v", string(s), err)
+			} else if gid > 0 && gid != uid && gid != os.Getgid() && slices.Contains(suppCurrent, gid) {
+				suppGroups[i] = gid
+			} else {
+				log.Fatalf("invalid gid %d", gid)
+			}
+		}
+		suppGroups[len(suppGroups)-1] = uid
+	} else {
+		suppGroups = []int{uid}
+	}
+
+	// careful! users in the allowlist is effectively allowed to drop groups via fsu
+
 	if err := syscall.Setresgid(uid, uid, uid); err != nil {
 		log.Fatalf("cannot set gid: %v", err)
 	}
+	if err := syscall.Setgroups(suppGroups); err != nil {
+		log.Fatalf("cannot set supplementary groups: %v", err)
+	}
 	if err := syscall.Setresuid(uid, uid, uid); err != nil {
 		log.Fatalf("cannot set uid: %v", err)
 	}
-	if err := syscall.Exec(fmain, []string{"fortify", "shim"}, []string{envShim + "=" + shimSetupPath}); err != nil {
+	if _, _, errno := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_NO_NEW_PRIVS, 1, 0); errno != 0 {
+		log.Fatalf("cannot set no_new_privs flag: %s", errno.Error())
+	}
+	if err := syscall.Exec(fshim, []string{"fshim"}, []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
-	}
-}
-
 func checkPath(p string) (string, bool) {
 	return p, p != compPoison && p != "" && path.IsAbs(p)
 }

cmd/fsu/parse.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"syscall"
+)
+
+func parseUint32Fast(s string) (int, error) {
+	sLen := len(s)
+	if sLen < 1 {
+		return -1, errors.New("zero length string")
+	}
+	if sLen > 10 {
+		return -1, errors.New("string too long")
+	}
+
+	n := 0
+	for i, ch := range []byte(s) {
+		ch -= '0'
+		if ch > 9 {
+			return -1, fmt.Errorf("invalid character '%s' at index %d", string([]byte{ch}), i)
+		}
+		n = n*10 + int(ch)
+	}
+	return n, nil
+}
+
+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 = parseUint32Fast(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 = parseUint32Fast(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
+	}
+}

cmd/fuserdb/main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"path"
+	"strconv"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+func main() {
+	fmsg.SetPrefix("fuserdb")
+
+	const varEmpty = "/var/empty"
+
+	out := flag.String("o", "userdb", "output directory")
+	homeDir := flag.String("d", varEmpty, "parent of home directories")
+	shell := flag.String("s", "/sbin/nologin", "absolute path to subordinate user shell")
+	flag.Parse()
+
+	type user struct {
+		name string
+		fid  int
+	}
+
+	users := make([]user, len(flag.Args()))
+	for i, s := range flag.Args() {
+		f := bytes.SplitN([]byte(s), []byte{':'}, 2)
+		if len(f) != 2 {
+			fmsg.Fatalf("invalid entry at index %d", i)
+		}
+		users[i].name = string(f[0])
+		if fid, err := strconv.Atoi(string(f[1])); err != nil {
+			fmsg.Fatal(err.Error())
+		} else {
+			users[i].fid = fid
+		}
+	}
+
+	if err := os.MkdirAll(*out, 0755); err != nil && !errors.Is(err, os.ErrExist) {
+		fmsg.Fatalf("cannot create output: %v", err)
+	}
+
+	for _, u := range users {
+		fidString := strconv.Itoa(u.fid)
+		for aid := 0; aid < 10000; aid++ {
+			userName := fmt.Sprintf("u%d_a%d", u.fid, aid)
+			uid := 1000000 + u.fid*10000 + aid
+			us := strconv.Itoa(uid)
+			realName := fmt.Sprintf("Fortify subordinate user %d (%s)", aid, u.name)
+			var homeDirectory string
+			if *homeDir != varEmpty {
+				homeDirectory = path.Join(*homeDir, fidString, strconv.Itoa(aid))
+			} else {
+				homeDirectory = varEmpty
+			}
+
+			writeUser(userName, uid, us, realName, homeDirectory, *shell, *out)
+			writeGroup(userName, uid, us, nil, *out)
+		}
+	}
+
+	fmsg.Printf("created %d entries", len(users)*2*10000)
+	fmsg.Exit(0)
+}

cmd/fuserdb/payload.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+type payloadU struct {
+	UserName      string   `json:"userName"`
+	Uid           int      `json:"uid"`
+	Gid           int      `json:"gid"`
+	MemberOf      []string `json:"memberOf,omitempty"`
+	RealName      string   `json:"realName"`
+	HomeDirectory string   `json:"homeDirectory"`
+	Shell         string   `json:"shell"`
+}
+
+func writeUser(userName string, uid int, us string, realName, homeDirectory, shell string, out string) {
+	userFileName := userName + ".user"
+	if f, err := os.OpenFile(path.Join(out, userFileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+		fmsg.Fatalf("cannot create %s: %v", userName, err)
+	} else if err = json.NewEncoder(f).Encode(&payloadU{
+		UserName:      userName,
+		Uid:           uid,
+		Gid:           uid,
+		RealName:      realName,
+		HomeDirectory: homeDirectory,
+		Shell:         shell,
+	}); err != nil {
+		fmsg.Fatalf("cannot serialise %s: %v", userName, err)
+	} else if err = f.Close(); err != nil {
+		fmsg.Printf("cannot close %s: %v", userName, err)
+	}
+	if err := os.Symlink(userFileName, path.Join(out, us+".user")); err != nil {
+		fmsg.Fatalf("cannot link %s: %v", userName, err)
+	}
+}
+
+type payloadG struct {
+	GroupName string   `json:"groupName"`
+	Gid       int      `json:"gid"`
+	Members   []string `json:"members,omitempty"`
+}
+
+func writeGroup(groupName string, gid int, gs string, members []string, out string) {
+	groupFileName := groupName + ".group"
+	if f, err := os.OpenFile(path.Join(out, groupFileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+		fmsg.Fatalf("cannot create %s: %v", groupName, err)
+	} else if err = json.NewEncoder(f).Encode(&payloadG{
+		GroupName: groupName,
+		Gid:       gid,
+		Members:   members,
+	}); err != nil {
+		fmsg.Fatalf("cannot serialise %s: %v", groupName, err)
+	} else if err = f.Close(); err != nil {
+		fmsg.Printf("cannot close %s: %v", groupName, err)
+	}
+	if err := os.Symlink(groupFileName, path.Join(out, gs+".group")); err != nil {
+		fmsg.Fatalf("cannot link %s: %v", groupName, err)
+	}
+}

flake.nix

@@ -42,6 +42,33 @@
             with nixpkgsFor.${system};
             self.packages.${system}.fortify.buildInputs ++ [ self.packages.${system}.fortify ];
         };
+
+        generateDoc =
+          let
+            pkgs = nixpkgsFor.${system};
+            inherit (pkgs) lib;
+
+            doc =
+              let
+                eval = lib.evalModules {
+                  specialArgs = {
+                    inherit pkgs;
+                  };
+                  modules = [ ./options.nix ];
+                };
+                cleanEval = lib.filterAttrsRecursive (n: v: n != "_module") eval;
+              in
+              pkgs.nixosOptionsDoc { inherit (cleanEval) options; };
+            docText = pkgs.runCommand "fortify-module-docs.md" { } ''
+              cat ${doc.optionsCommonMark} > $out
+              sed -i '/*Declared by:*/,+1 d' $out
+            '';
+          in
+          nixpkgsFor.${system}.mkShell {
+            shellHook = ''
+              exec cat ${docText} > options.md
+            '';
+          };
       });
     };
 }

internal/app/app.go

@@ -53,7 +53,7 @@ func (a *app) String() string {
 	}
 
 	if a.seal != nil {
-		return "(sealed fortified app as uid " + a.seal.sys.user.Uid + ")"
+		return "(sealed fortified app as uid " + a.seal.sys.user.us + ")"
 	}
 
 	return "(unsealed fortified app)"

internal/app/app_nixos_test.go

@@ -19,9 +19,12 @@ var testCasesNixos = []sealTestCase{
 	{
 		"nixos permissive defaults no enablements", new(stubNixOS),
 		&app.Config{
-			User:    "chronos",
 			Command: make([]string, 0),
-			Method:  "sudo",
+			Confinement: app.ConfinementConfig{
+				AppID:    0,
+				Username: "chronos",
+				Outer:    "/home/chronos",
+			},
 		},
 		app.ID{
 			0x4a, 0x45, 0x0b, 0x65,
@@ -29,11 +32,11 @@ var testCasesNixos = []sealTestCase{
 			0xbd, 0x01, 0x78, 0x0e,
 			0xb9, 0xa6, 0x07, 0xac,
 		},
-		system.New(150).
-			Ensure("/tmp/fortify.1971", 0701).
-			Ephemeral(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac", 0701).
+		system.New(1000000).
+			Ensure("/tmp/fortify.1971", 0711).
+			Ephemeral(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac", 0711).
 			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("/tmp/fortify.1971/tmpdir/0", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/0", 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).
@@ -43,6 +46,7 @@ var testCasesNixos = []sealTestCase{
 			Net:      true,
 			UserNS:   true,
 			Clearenv: true,
+			Chdir:    "/home/chronos",
 			SetEnv: map[string]string{
 				"HOME":              "/home/chronos",
 				"SHELL":             "/run/current-system/sw/bin/zsh",
@@ -182,10 +186,11 @@ var testCasesNixos = []sealTestCase{
 			Symlink("/fortify/etc/zprofile", "/etc/zprofile").
 			Symlink("/fortify/etc/zshenv", "/etc/zshenv").
 			Symlink("/fortify/etc/zshrc", "/etc/zshrc").
-			Bind("/tmp/fortify.1971/tmpdir/150", "/tmp", false, true).
+			Bind("/tmp/fortify.1971/tmpdir/0", "/tmp", false, true).
 			Tmpfs("/tmp/fortify.1971", 1048576).
 			Tmpfs("/run/user", 1048576).
 			Tmpfs("/run/user/65534", 8388608).
+			Bind("/home/chronos", "/home/chronos", false, true).
 			Bind("/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/passwd", "/etc/passwd").
 			Bind("/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/group", "/etc/group").
 			Tmpfs("/var/run/nscd", 8192),
@@ -194,9 +199,12 @@ var testCasesNixos = []sealTestCase{
 		"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{
+				AppID:    9,
+				Groups:   []string{"video"},
+				Username: "chronos",
+				Outer:    "/home/chronos",
 				SessionBus: &dbus.Config{
 					Talk: []string{
 						"org.freedesktop.Notifications",
@@ -230,7 +238,6 @@ var testCasesNixos = []sealTestCase{
 				},
 				Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
 			},
-			Method: "systemd",
 		},
 		app.ID{
 			0xeb, 0xf0, 0x83, 0xd1,
@@ -238,11 +245,11 @@ var testCasesNixos = []sealTestCase{
 			0x82, 0xd4, 0x13, 0x36,
 			0x9b, 0x64, 0xce, 0x7c,
 		},
-		system.New(150).
-			Ensure("/tmp/fortify.1971", 0701).
-			Ephemeral(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c", 0701).
+		system.New(1000009).
+			Ensure("/tmp/fortify.1971", 0711).
+			Ephemeral(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c", 0711).
 			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("/tmp/fortify.1971/tmpdir/9", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/9", 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).
@@ -287,6 +294,7 @@ var testCasesNixos = []sealTestCase{
 		(&bwrap.Config{
 			Net:      true,
 			UserNS:   true,
+			Chdir:    "/home/chronos",
 			Clearenv: true,
 			SetEnv: map[string]string{
 				"DBUS_SESSION_BUS_ADDRESS": "unix:path=/run/user/65534/bus",
@@ -434,10 +442,11 @@ var testCasesNixos = []sealTestCase{
 			Symlink("/fortify/etc/zprofile", "/etc/zprofile").
 			Symlink("/fortify/etc/zshenv", "/etc/zshenv").
 			Symlink("/fortify/etc/zshrc", "/etc/zshrc").
-			Bind("/tmp/fortify.1971/tmpdir/150", "/tmp", false, true).
+			Bind("/tmp/fortify.1971/tmpdir/9", "/tmp", false, true).
 			Tmpfs("/tmp/fortify.1971", 1048576).
 			Tmpfs("/run/user", 1048576).
 			Tmpfs("/run/user/65534", 8388608).
+			Bind("/home/chronos", "/home/chronos", false, true).
 			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/65534/wayland-0").
@@ -504,23 +513,12 @@ 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
+func (s *stubNixOS) LookupGroup(name string) (*user.Group, error) {
+	switch name {
+	case "video":
+		return &user.Group{Gid: "26", Name: "video"}, nil
 	default:
-		return nil, user.UnknownUserError(username)
+		return nil, user.UnknownGroupError(name)
 	}
 }
 
@@ -586,10 +584,6 @@ func (s *stubNixOS) Stdout() io.Writer {
 	panic("requested stdout")
 }
 
-func (s *stubNixOS) FshimPath() string {
-	return "/nix/store/00000000000000000000000000000000-fortify-0.0.10/bin/.fshim"
-}
-
 func (s *stubNixOS) Paths() linux.Paths {
 	return linux.Paths{
 		SharePath:   "/tmp/fortify.1971",
@@ -598,6 +592,10 @@ func (s *stubNixOS) Paths() linux.Paths {
 	}
 }
 
+func (s *stubNixOS) Uid(aid int) (int, error) {
+	return 1000000 + 0*10000 + aid, nil
+}
+
 func (s *stubNixOS) SdBooted() bool {
 	return true
 }

internal/app/config.go

@@ -15,12 +15,8 @@ const fTmp = "/fortify"
 type Config struct {
 	// D-Bus application ID
 	ID string `json:"id"`
-	// username of the target user to switch to
-	User string `json:"user"`
 	// value passed through to the child process as its argv
 	Command []string `json:"command"`
-	// string representation of the child's launch method
-	Method string `json:"method"`
 
 	// child confinement configuration
 	Confinement ConfinementConfig `json:"confinement"`
@@ -28,6 +24,16 @@ type Config struct {
 
 // ConfinementConfig defines fortified child's confinement
 type ConfinementConfig struct {
+	// numerical application id, determines uid in the init namespace
+	AppID int `json:"app_id"`
+	// list of supplementary groups to inherit
+	Groups []string `json:"groups"`
+	// passwd username in the sandbox, defaults to chronos
+	Username string `json:"username,omitempty"`
+	// home directory in sandbox, empty for outer
+	Inner string `json:"home_inner"`
+	// home directory in init namespace
+	Outer string `json:"home"`
 	// bwrap sandbox confinement configuration
 	Sandbox *SandboxConfig `json:"sandbox"`
 
@@ -55,7 +61,7 @@ type SandboxConfig struct {
 	// do not run in new session
 	NoNewSession bool `json:"no_new_session,omitempty"`
 	// map target user uid to privileged user uid in the user namespace
-	UseRealUID bool `json:"use_real_uid"`
+	MapRealUID bool `json:"map_real_uid"`
 	// mediated access to wayland socket
 	Wayland bool `json:"wayland,omitempty"`
 
@@ -92,7 +98,7 @@ func (s *SandboxConfig) Bwrap(os linux.System) (*bwrap.Config, error) {
 	}
 
 	var uid int
-	if !s.UseRealUID {
+	if !s.MapRealUID {
 		uid = 65534
 	} else {
 		uid = os.Geteuid()
@@ -170,7 +176,6 @@ func (s *SandboxConfig) Bwrap(os linux.System) (*bwrap.Config, error) {
 func Template() *Config {
 	return &Config{
 		ID: "org.chromium.Chromium",
-		User: "chronos",
 		Command: []string{
 			"chromium",
 			"--ignore-gpu-blocklist",
@@ -178,14 +183,18 @@ func Template() *Config {
 			"--enable-features=UseOzonePlatform",
 			"--ozone-platform=wayland",
 		},
-		Method: "sudo",
 		Confinement: ConfinementConfig{
+			AppID:    9,
+			Groups:   []string{"video"},
+			Username: "chronos",
+			Outer:    "/var/lib/persist/home/org.chromium.Chromium",
+			Inner:    "/var/lib/fortify",
 			Sandbox: &SandboxConfig{
 				Hostname:     "localhost",
 				UserNS:       true,
 				Net:          true,
 				NoNewSession: true,
-				UseRealUID:   true,
+				MapRealUID:   true,
 				Dev:          true,
 				Wayland:      false,
 				// example API credentials pulled from Google Chrome

internal/app/launch.machinectl.go

@@ -1,57 +0,0 @@
-package app
-
-import (
-	"strings"
-
-	"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.user.Username)
-
-	// --quiet
-	if !fmsg.Verbose() {
-		args = append(args, "--quiet")
-	}
-
-	// environ
-	envQ := make([]string, 0, len(a.seal.sys.bwrap.SetEnv)+1)
-	for k, v := range a.seal.sys.bwrap.SetEnv {
-		envQ = append(envQ, "-E"+k+"="+v)
-	}
-	// add shim payload to environment for shim path
-	envQ = append(envQ, "-E"+shimEnv)
-	args = append(args, envQ...)
-
-	// -- .host
-	args = append(args, "--", ".host")
-
-	// /bin/sh -c
-	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 {
-		args = append(args, sh, "-c")
-	}
-
-	// build inner command expression ran as target user
-	innerCommand := strings.Builder{}
-
-	// apply custom environment variables to activation environment
-	innerCommand.WriteString("dbus-update-activation-environment --systemd")
-	for k := range a.seal.sys.bwrap.SetEnv {
-		innerCommand.WriteString(" " + k)
-	}
-	innerCommand.WriteString("; ")
-
-	// launch fortify shim
-	innerCommand.WriteString("exec " + a.os.FshimPath())
-
-	// append inner command
-	args = append(args, innerCommand.String())
-
-	return
-}

internal/app/launch.sudo.go

@@ -1,30 +0,0 @@
-package app
-
-import (
-	"git.ophivana.moe/security/fortify/internal/fmsg"
-)
-
-const (
-	sudoAskPass = "SUDO_ASKPASS"
-)
-
-func (a *app) commandBuilderSudo(shimEnv string) (args []string) {
-	args = make([]string, 0, 8)
-
-	// -Hiu $USER
-	args = append(args, "-Hiu", a.seal.sys.user.Username)
-
-	// -A?
-	if _, ok := a.os.LookupEnv(sudoAskPass); ok {
-		fmsg.VPrintln(sudoAskPass, "set, adding askpass flag")
-		args = append(args, "-A")
-	}
-
-	// shim payload
-	args = append(args, shimEnv)
-
-	// -- $@
-	args = append(args, "--", a.os.FshimPath())
-
-	return
-}

internal/app/seal.go

@@ -2,8 +2,8 @@ package app
 
 import (
 	"errors"
+	"fmt"
 	"io/fs"
-	"os/user"
 	"path"
 	"strconv"
 
@@ -15,24 +15,10 @@ import (
 	"git.ophivana.moe/security/fortify/internal/system"
 )
 
-const (
-	LaunchMethodSudo uint8 = iota
-	LaunchMethodMachineCtl
-)
-
-var method = [...]string{
-	LaunchMethodSudo:       "sudo",
-	LaunchMethodMachineCtl: "systemd",
-}
-
 var (
 	ErrConfig = errors.New("no configuration to seal")
-	ErrUser   = errors.New("unknown user")
-	ErrLaunch = errors.New("invalid launch method")
-
-	ErrSudo       = errors.New("sudo not available")
-	ErrSystemd    = errors.New("systemd not available")
-	ErrMachineCtl = errors.New("machinectl not available")
+	ErrUser   = errors.New("invalid aid")
+	ErrHome   = errors.New("invalid home directory")
 )
 
 // appSeal seals the application with child-related information
@@ -51,15 +37,11 @@ type appSeal struct {
 	// 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
 
@@ -98,39 +80,11 @@ func (a *app) Seal(config *Config) error {
 	seal.fid = config.ID
 	seal.command = config.Command
 
-	// parses launch method text and looks up tool path
-	switch config.Method {
-	case method[LaunchMethodSudo]:
-		seal.launchOption = LaunchMethodSudo
-		if sudoPath, err := a.os.LookPath("sudo"); err != nil {
-			return fmsg.WrapError(ErrSudo,
-				"sudo not found")
-		} else {
-			seal.toolPath = sudoPath
-		}
-	case method[LaunchMethodMachineCtl]:
-		seal.launchOption = LaunchMethodMachineCtl
-		if !a.os.SdBooted() {
-			return fmsg.WrapError(ErrSystemd,
-				"system has not been booted with systemd as init system")
-		}
-
-		if machineCtlPath, err := a.os.LookPath("machinectl"); err != nil {
-			return fmsg.WrapError(ErrMachineCtl,
-				"machinectl not found")
-		} else {
-			seal.toolPath = machineCtlPath
-		}
-	default:
-		return fmsg.WrapError(ErrLaunch,
-			"invalid launch method")
-	}
-
 	// create seal system component
 	seal.sys = new(appSealSys)
 
 	// mapped uid
-	if config.Confinement.Sandbox != nil && config.Confinement.Sandbox.UseRealUID {
+	if config.Confinement.Sandbox != nil && config.Confinement.Sandbox.MapRealUID {
 		seal.sys.mappedID = a.os.Geteuid()
 	} else {
 		seal.sys.mappedID = 65534
@@ -138,16 +92,48 @@ func (a *app) Seal(config *Config) error {
 	seal.sys.mappedIDString = strconv.Itoa(seal.sys.mappedID)
 	seal.sys.runtime = path.Join("/run/user", seal.sys.mappedIDString)
 
-	// look up user from system
-	if u, err := a.os.Lookup(config.User); err != nil {
-		if errors.As(err, new(user.UnknownUserError)) {
-			return fmsg.WrapError(ErrUser, "unknown user", config.User)
+	// validate uid and set user info
+	if config.Confinement.AppID < 0 || config.Confinement.AppID > 9999 {
+		return fmsg.WrapError(ErrUser,
+			fmt.Sprintf("aid %d out of range", config.Confinement.AppID))
 	} else {
-			// unreachable
-			panic(err)
+		seal.sys.user = appUser{
+			aid:      config.Confinement.AppID,
+			as:       strconv.Itoa(config.Confinement.AppID),
+			data:     config.Confinement.Outer,
+			home:     config.Confinement.Inner,
+			username: config.Confinement.Username,
 		}
+		if seal.sys.user.username == "" {
+			seal.sys.user.username = "chronos"
+		}
+		if seal.sys.user.data == "" || !path.IsAbs(seal.sys.user.data) {
+			return fmsg.WrapError(ErrHome,
+				fmt.Sprintf("invalid home directory %q", seal.sys.user.data))
+		}
+		if seal.sys.user.home == "" {
+			seal.sys.user.home = seal.sys.user.data
+		}
+
+		// invoke fsu for full uid
+		if u, err := a.os.Uid(seal.sys.user.aid); err != nil {
+			return fmsg.WrapErrorSuffix(err,
+				"cannot obtain uid from fsu:")
 		} else {
-		seal.sys.user = u
+			seal.sys.user.uid = u
+			seal.sys.user.us = strconv.Itoa(u)
+		}
+
+		// resolve supplementary group ids from names
+		seal.sys.user.supp = make([]string, len(config.Confinement.Groups))
+		for i, name := range config.Confinement.Groups {
+			if g, err := a.os.LookupGroup(name); err != nil {
+				return fmsg.WrapError(err,
+					fmt.Sprintf("unknown group %q", name))
+			} else {
+				seal.sys.user.supp[i] = g.Gid
+			}
+		}
 	}
 
 	// map sandbox config to bwrap
@@ -230,15 +216,10 @@ func (a *app) Seal(config *Config) error {
 	// 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.RunDirPath, seal.sys.user.Uid)
+	seal.store = state.NewSimple(seal.RunDirPath, seal.sys.user.as)
 
-	// parse string UID
-	if u, err := strconv.Atoi(seal.sys.user.Uid); err != nil {
-		// unreachable unless kernel bug
-		panic("uid parse")
-	} else {
-		seal.sys.I = system.New(u)
-	}
+	// initialise system interface with full uid
+	seal.sys.I = system.New(seal.sys.user.uid)
 
 	// pass through enablements
 	seal.et = config.Confinement.Enablements
@@ -249,11 +230,8 @@ func (a *app) Seal(config *Config) error {
 	}
 
 	// verbose log seal information
-	fmsg.VPrintln("created application seal as user",
-		seal.sys.user.Username, "("+seal.sys.user.Uid+"),",
-		"method:", config.Method+",",
-		"launcher:", seal.toolPath+",",
-		"command:", config.Command)
+	fmsg.VPrintf("created application seal for uid %s (%s) groups: %v, command: %s",
+		seal.sys.user.us, seal.sys.user.username, config.Confinement.Groups, config.Command)
 
 	// seal app and release lock
 	a.seal = seal

internal/app/share.display.go

@@ -58,7 +58,7 @@ func (seal *appSeal) shareDisplay(os linux.System) error {
 			return fmsg.WrapError(ErrXDisplay,
 				"DISPLAY is not set")
 		} else {
-			seal.sys.ChangeHosts(seal.sys.user.Username)
+			seal.sys.ChangeHosts("#" + seal.sys.user.us)
 			seal.sys.bwrap.SetEnv[display] = d
 			seal.sys.bwrap.Bind("/tmp/.X11-unix", "/tmp/.X11-unix")
 		}

internal/app/share.system.go

@@ -16,12 +16,12 @@ const (
 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)
+	seal.sys.Ensure(seal.SharePath, 0711)
 
 	// 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)
+	seal.sys.Ephemeral(system.Process, seal.share, 0711)
 
 	// ensure child tmpdir parent directory (e.g. `/tmp/fortify.%d/tmpdir`)
 	targetTmpdirParent := path.Join(seal.SharePath, "tmpdir")
@@ -29,7 +29,7 @@ func (seal *appSeal) shareSystem() {
 	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)
+	targetTmpdir := path.Join(targetTmpdirParent, seal.sys.user.as)
 	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)
@@ -49,15 +49,21 @@ func (seal *appSeal) sharePasswd(os linux.System) {
 	// generate /etc/passwd
 	passwdPath := path.Join(seal.share, "passwd")
 	username := "chronos"
-	if seal.sys.user.Username != "" {
-		username = seal.sys.user.Username
-		seal.sys.bwrap.SetEnv["USER"] = seal.sys.user.Username
+	if seal.sys.user.username != "" {
+		username = seal.sys.user.username
 	}
 	homeDir := "/var/empty"
-	if seal.sys.user.HomeDir != "" {
-		homeDir = seal.sys.user.HomeDir
-		seal.sys.bwrap.SetEnv["HOME"] = seal.sys.user.HomeDir
+	if seal.sys.user.home != "" {
+		homeDir = seal.sys.user.home
 	}
+
+	// bind home directory
+	seal.sys.bwrap.Bind(seal.sys.user.data, homeDir, false, true)
+	seal.sys.bwrap.Chdir = homeDir
+
+	seal.sys.bwrap.SetEnv["USER"] = username
+	seal.sys.bwrap.SetEnv["HOME"] = homeDir
+
 	passwd := username + ":x:" + seal.sys.mappedIDString + ":" + seal.sys.mappedIDString + ":Fortify:" + homeDir + ":" + sh + "\n"
 	seal.sys.Write(passwdPath, passwd)
 

internal/app/start.go

@@ -41,19 +41,13 @@ func (a *app) Start() error {
 		}
 	}
 
-	// select command builder
-	var commandBuilder shim.CommandBuilder
-	switch a.seal.launchOption {
-	case LaunchMethodSudo:
-		commandBuilder = a.commandBuilderSudo
-	case LaunchMethodMachineCtl:
-		commandBuilder = a.commandBuilderMachineCtl
-	default:
-		panic("unreachable")
-	}
-
 	// construct shim manager
-	a.shim = shim.New(a.seal.toolPath, uint32(a.seal.sys.UID()), path.Join(a.seal.share, "shim"), a.seal.wl,
+	a.shim = shim.New(
+		uint32(a.seal.sys.UID()),
+		a.seal.sys.user.as,
+		a.seal.sys.user.supp,
+		path.Join(a.seal.share, "shim"),
+		a.seal.wl,
 		&shim0.Payload{
 			Argv:  a.seal.command,
 			Exec:  shimExec,
@@ -62,9 +56,6 @@ func (a *app) Start() error {
 
 			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,
 	)
 
 	// startup will go ahead, commit system setup
@@ -73,7 +64,7 @@ func (a *app) Start() error {
 	}
 	a.seal.sys.needRevert = true
 
-	if startTime, err := a.shim.Start(commandBuilder); err != nil {
+	if startTime, err := a.shim.Start(); err != nil {
 		return err
 	} else {
 		// shim start and setup success, create process state
@@ -81,7 +72,6 @@ func (a *app) Start() error {
 			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,
 		}
@@ -166,8 +156,13 @@ func (a *app) Wait() (int, error) {
 		// failure prior to process start
 		r = 255
 	} else {
+		wait := make(chan error, 1)
+		go func() { wait <- cmd.Wait() }()
+
+		select {
 		// wait for process and resolve exit code
-		if err := cmd.Wait(); err != nil {
+		case err := <-wait:
+			if err != nil {
 				var exitError *exec.ExitError
 				if !errors.As(err, &exitError) {
 					// should be unreachable
@@ -180,6 +175,16 @@ func (a *app) Wait() (int, error) {
 				r = cmd.ProcessState.ExitCode()
 			}
 			fmsg.VPrintf("process %d exited with exit code %d", cmd.Process.Pid, r)
+
+		// alternative exit path when kill was unsuccessful
+		case err := <-a.shim.WaitFallback():
+			r = 255
+			if err != nil {
+				fmsg.Printf("cannot terminate shim on faulted setup: %v", err)
+			} else {
+				fmsg.VPrintln("alternative exit path selected")
+			}
+		}
 	}
 
 	// child process exited, resume output
@@ -250,10 +255,17 @@ func (a *app) Wait() (int, error) {
 				}
 			}
 
+			if a.shim.Unwrap() == nil {
+				fmsg.VPrintln("fault before shim start")
+			} else {
 				a.shim.AbortWait(errors.New("shim exited"))
+			}
+
+			if a.seal.sys.needRevert {
 				if err := a.seal.sys.Revert(ec); err != nil {
 					return err.(RevertCompoundError)
 				}
+			}
 
 			return nil
 		}()

internal/app/system.go

@@ -1,8 +1,6 @@
 package app
 
 import (
-	"os/user"
-
 	"git.ophivana.moe/security/fortify/dbus"
 	"git.ophivana.moe/security/fortify/helper/bwrap"
 	"git.ophivana.moe/security/fortify/internal/linux"
@@ -18,7 +16,7 @@ type appSealSys struct {
 	// default formatted XDG_RUNTIME_DIR of User
 	runtime string
 	// target user sealed from config
-	user *user.User
+	user appUser
 
 	// mapped uid and gid in user namespace
 	mappedID int
@@ -32,6 +30,28 @@ type appSealSys struct {
 	// protected by upstream mutex
 }
 
+type appUser struct {
+	// full uid resolved by fsu
+	uid int
+	// string representation of uid
+	us string
+
+	// supplementary group ids
+	supp []string
+
+	// application id
+	aid int
+	// string representation of aid
+	as string
+
+	// home directory host path
+	data string
+	// app user home directory
+	home string
+	// passwd database username
+	username string
+}
+
 // shareAll calls all share methods in sequence
 func (seal *appSeal) shareAll(bus [2]*dbus.Config, os linux.System) error {
 	if seal.shared {

internal/fmsg/defer.go

@@ -33,16 +33,17 @@ func dequeue() {
 // queue submits ops to msgbuf but drops messages
 // when the buffer is full and dequeue is withholding
 func queue(op dOp) {
+	queueSync.Add(1)
+
 	select {
 	case msgbuf <- op:
-		queueSync.Add(1)
 	default:
 		// send the op anyway if not withholding
 		// as dequeue will get to it eventually
 		if !wstate.Load() {
-			queueSync.Add(1)
 			msgbuf <- op
 		} else {
+			queueSync.Done()
 			// increment dropped message count
 			dropped.Add(1)
 		}
@@ -56,9 +57,10 @@ func Exit(code int) {
 	os.Exit(code)
 }
 
-func Withhold() {
+func Suspend() {
 	dequeueOnce.Do(dequeue)
 	if wstate.CompareAndSwap(false, true) {
+		queueSync.Wait()
 		withhold <- struct{}{}
 	}
 }

internal/linux/interface.go

@@ -22,8 +22,8 @@ type System interface {
 	LookPath(file string) (string, error)
 	// Executable provides [os.Executable].
 	Executable() (string, error)
-	// Lookup provides [user.Lookup].
-	Lookup(username string) (*user.User, error)
+	// LookupGroup provides [user.LookupGroup].
+	LookupGroup(name string) (*user.Group, error)
 	// ReadDir provides [os.ReadDir].
 	ReadDir(name string) ([]fs.DirEntry, error)
 	// Stat provides [os.Stat].
@@ -35,10 +35,10 @@ type System interface {
 	// Stdout provides [os.Stdout].
 	Stdout() io.Writer
 
-	// FshimPath returns an absolute path to the fshim binary.
-	FshimPath() string
 	// Paths returns a populated [Paths] struct.
 	Paths() Paths
+	// Uid invokes fsu and returns target uid.
+	Uid(aid int) (int, error)
 	// SdBooted implements https://www.freedesktop.org/software/systemd/man/sd_booted.html
 	SdBooted() bool
 }

internal/linux/std.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"os/exec"
 	"os/user"
+	"strconv"
 	"sync"
 
 	"git.ophivana.moe/security/fortify/internal"
@@ -21,8 +22,12 @@ type Std struct {
 	sdBooted     bool
 	sdBootedOnce sync.Once
 
-	fshim     string
-	fshimOnce sync.Once
+	uidOnce sync.Once
+	uidCopy map[int]struct {
+		uid int
+		err error
+	}
+	uidMu sync.RWMutex
 }
 
 func (s *Std) Geteuid() int                                 { return os.Geteuid() }
@@ -30,7 +35,7 @@ func (s *Std) LookupEnv(key string) (string, bool)        { return os.LookupEnv(
 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) LookupGroup(name string) (*user.Group, error) { return user.LookupGroup(name) }
 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) }
@@ -39,23 +44,53 @@ func (s *Std) Stdout() io.Writer                          { return os.Stdout }
 
 const xdgRuntimeDir = "XDG_RUNTIME_DIR"
 
-func (s *Std) FshimPath() string {
-	s.fshimOnce.Do(func() {
-		p, ok := internal.Path(internal.Fshim)
-		if !ok {
-			fmsg.Fatal("invalid fshim path, this copy of fortify is not compiled correctly")
-		}
-		s.fshim = p
-	})
-
-	return s.fshim
-}
-
 func (s *Std) Paths() Paths {
 	s.pathsOnce.Do(func() { CopyPaths(s, &s.paths) })
 	return s.paths
 }
 
+func (s *Std) Uid(aid int) (int, error) {
+	s.uidOnce.Do(func() {
+		s.uidCopy = make(map[int]struct {
+			uid int
+			err error
+		})
+	})
+
+	s.uidMu.RLock()
+	if u, ok := s.uidCopy[aid]; ok {
+		s.uidMu.RUnlock()
+		return u.uid, u.err
+	}
+
+	s.uidMu.RUnlock()
+	s.uidMu.Lock()
+	defer s.uidMu.Unlock()
+
+	u := struct {
+		uid int
+		err error
+	}{}
+	defer func() { s.uidCopy[aid] = u }()
+
+	u.uid = -1
+	if fsu, ok := internal.Check(internal.Fsu); !ok {
+		fmsg.Fatal("invalid fsu path, this copy of fshim is not compiled correctly")
+		panic("unreachable")
+	} else {
+		cmd := exec.Command(fsu)
+		cmd.Path = fsu
+		cmd.Stderr = os.Stderr // pass through fatal messages
+		cmd.Env = []string{"FORTIFY_APP_ID=" + strconv.Itoa(aid)}
+		cmd.Dir = "/"
+		var p []byte
+		if p, u.err = cmd.Output(); u.err == nil {
+			u.uid, u.err = strconv.Atoi(string(p))
+		}
+		return u.uid, u.err
+	}
+}
+
 func (s *Std) SdBooted() bool {
 	s.sdBootedOnce.Do(func() { s.sdBooted = copySdBooted() })
 	return s.sdBooted

internal/path.go

@@ -4,7 +4,6 @@ import "path"
 
 var (
 	Fsu   = compPoison
-	Fshim = compPoison
 	Finit = compPoison
 )
 

internal/state/print.go

@@ -67,10 +67,10 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 
 				// write header when initialising
 				if !fmsg.Verbose() {
-					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tUptime\tEnablements\tMethod\tCommand")
+					_, _ = fmt.Fprintln(*w, "\tPID\tApp\tUptime\tEnablements\tCommand")
 				} else {
 					// argv is emitted in body when verbose
-					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tArgv")
+					_, _ = fmt.Fprintln(*w, "\tPID\tApp\tArgv")
 				}
 			}
 
@@ -96,13 +96,13 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 				}
 
 				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.Method,
+					_, _ = fmt.Fprintf(*w, "\t%d\t%s\t%s\t%s\t%s\n",
+						state.PID, s.path[len(s.path)-1], now.Sub(state.Time).Round(time.Second).String(), strings.TrimPrefix(ets.String(), ", "),
 						state.Command)
 				} else {
 					// emit argv instead when verbose
-					_, _ = fmt.Fprintf(*w, "\t%s\t%d\t%s\n",
-						s.path[len(s.path)-1], state.PID, state.Argv)
+					_, _ = fmt.Fprintf(*w, "\t%d\t%s\t%s\n",
+						state.PID, s.path[len(s.path)-1], state.Argv)
 				}
 			}
 

internal/state/state.go

@@ -33,8 +33,6 @@ type State struct {
 	// capability enablements applied to child
 	Capability system.Enablements
 
-	// user switch method
-	Method string
 	// full argv whe launching
 	Argv []string
 	// process start time

main.go

@@ -5,6 +5,9 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
+	"os/user"
+	"strconv"
+	"strings"
 	"text/tabwriter"
 
 	"git.ophivana.moe/security/fortify/dbus"
@@ -29,6 +32,20 @@ func init() {
 
 var os = new(linux.Std)
 
+type gl []string
+
+func (g *gl) String() string {
+	if g == nil {
+		return "<nil>"
+	}
+	return strings.Join(*g, " ")
+}
+
+func (g *gl) Set(v string) error {
+	*g = append(*g, v)
+	return nil
+}
+
 func main() {
 	if err := internal.PR_SET_DUMPABLE__SUID_DUMP_DISABLE(); err != nil {
 		fmsg.Printf("cannot set SUID_DUMP_DISABLE: %s", err)
@@ -135,10 +152,11 @@ func main() {
 			mpris             bool
 			dbusVerbose       bool
 
+			aid         int
+			groups      gl
+			homeDir     string
 			userName    string
 			enablements [system.ELen]bool
-
-			launchMethodText string
 		)
 
 		set.StringVar(&dbusConfigSession, "dbus-config", "builtin", "Path to D-Bus proxy config file, or \"builtin\" for defaults")
@@ -147,29 +165,50 @@ func main() {
 		set.BoolVar(&mpris, "mpris", false, "Allow owning MPRIS D-Bus path, has no effect if custom config is available")
 		set.BoolVar(&dbusVerbose, "dbus-log", false, "Force logging in the D-Bus proxy")
 
-		set.StringVar(&userName, "u", "chronos", "Passwd name of user to run as")
+		set.IntVar(&aid, "a", 0, "Fortify application ID")
+		set.Var(&groups, "g", "Groups inherited by the app process")
+		set.StringVar(&homeDir, "d", "os", "Application home directory")
+		set.StringVar(&userName, "u", "chronos", "Passwd name within sandbox")
 		set.BoolVar(&enablements[system.EWayland], "wayland", false, "Share Wayland socket")
 		set.BoolVar(&enablements[system.EX11], "X", false, "Share X11 socket and allow connection")
 		set.BoolVar(&enablements[system.EDBus], "dbus", false, "Proxy D-Bus connection")
 		set.BoolVar(&enablements[system.EPulse], "pulse", false, "Share PulseAudio socket and cookie")
 
-		methodHelpString := "Method of launching the child process, can be one of \"sudo\""
-		if os.SdBooted() {
-			methodHelpString += ", \"systemd\""
-		}
-		set.StringVar(&launchMethodText, "method", "sudo", methodHelpString)
-
 		// Ignore errors; set is set for ExitOnError.
 		_ = set.Parse(args[1:])
 
 		// initialise config from flags
 		config := &app.Config{
 			ID:      dbusID,
-			User:    userName,
 			Command: set.Args(),
-			Method:  launchMethodText,
 		}
 
+		if aid < 0 || aid > 9999 {
+			fmsg.Fatalf("aid %d out of range", aid)
+			panic("unreachable")
+		}
+
+		// resolve home directory from os when flag is unset
+		if homeDir == "os" {
+			var us string
+			if uid, err := os.Uid(aid); err != nil {
+				fmsg.Fatalf("cannot obtain uid from fsu: %v", err)
+			} else {
+				us = strconv.Itoa(uid)
+			}
+			if u, err := user.LookupId(us); err != nil {
+				fmsg.VPrintf("cannot look up uid %s", us)
+				homeDir = "/var/empty"
+			} else {
+				homeDir = u.HomeDir
+			}
+		}
+
+		config.Confinement.AppID = aid
+		config.Confinement.Groups = groups
+		config.Confinement.Outer = homeDir
+		config.Confinement.Username = userName
+
 		// enablements from flags
 		for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
 			if enablements[i] {

nixos.nix

@@ -7,12 +7,13 @@
 
 let
   inherit (lib)
-    types
-    mkOption
-    mkEnableOption
     mkIf
+    mkDefault
     mapAttrs
     mapAttrsToList
+    mergeAttrsList
+    imap1
+    foldr
     foldlAttrs
     optional
     optionals
@@ -22,263 +23,59 @@ let
 in
 
 {
-  options = {
-    environment.fortify = {
-      enable = mkEnableOption "fortify";
-
-      target = mkOption {
-        default = { };
-        type =
-          let
-            inherit (types)
-              str
-              enum
-              bool
-              package
-              anything
-              submodule
-              listOf
-              attrsOf
-              nullOr
-              functionTo
-              ;
-          in
-          attrsOf (submodule {
-            options = {
-              packages = mkOption {
-                type = listOf package;
-                default = [ ];
-                description = ''
-                  List of extra packages to install via home-manager.
-                '';
-              };
-
-              launchers = mkOption {
-                type = attrsOf (submodule {
-                  options = {
-                    id = mkOption {
-                      type = nullOr str;
-                      default = null;
-                      description = ''
-                        Freedesktop application ID.
-                      '';
-                    };
-
-                    command = mkOption {
-                      type = nullOr str;
-                      default = null;
-                      description = ''
-                        Command to run as the target user.
-                        Setting this to null will default command to wrapper name.
-                      '';
-                    };
-
-                    method = mkOption {
-                      type = enum [
-                        "simple"
-                        "sudo"
-                        "systemd"
-                      ];
-                      default = "systemd";
-                      description = ''
-                        Launch method for the sandboxed program.
-                      '';
-                    };
-
-                    dbus = {
-                      session = mkOption {
-                        type = nullOr (functionTo anything);
-                        default = null;
-                        description = ''
-                          D-Bus session bus custom configuration.
-                          Setting this to null will enable built-in defaults.
-                        '';
-                      };
-
-                      system = mkOption {
-                        type = nullOr anything;
-                        default = null;
-                        description = ''
-                          D-Bus system bus custom configuration.
-                          Setting this to null will disable the system bus proxy.
-                        '';
-                      };
-                    };
-
-                    env = mkOption {
-                      type = nullOr (attrsOf str);
-                      default = null;
-                      description = ''
-                        Environment variables to set for the initial process in the sandbox.
-                      '';
-                    };
-
-                    nix = mkEnableOption ''
-                      Whether to allow nix daemon connections from within sandbox.
-                    '';
-
-                    userns = mkEnableOption ''
-                      Whether to allow userns within sandbox.
-                    '';
-
-                    useRealUid = mkEnableOption ''
-                      Whether to map to fortify's real UID within the sandbox.
-                    '';
-
-                    net =
-                      mkEnableOption ''
-                        Whether to allow network access within sandbox.
-                      ''
-                      // {
-                        default = true;
-                      };
-
-                    gpu = mkOption {
-                      type = nullOr bool;
-                      default = null;
-                      description = ''
-                        Target process GPU and driver access.
-                        Setting this to null will enable GPU whenever X or Wayland is enabled.
-                      '';
-                    };
-
-                    dev = mkEnableOption ''
-                      Whether to allow access to all devices within sandbox.
-                    '';
-
-                    extraPaths = mkOption {
-                      type = listOf anything;
-                      default = [ ];
-                      description = ''
-                        Extra paths to make available inside the sandbox.
-                      '';
-                    };
-
-                    capability = {
-                      wayland = mkOption {
-                        type = bool;
-                        default = true;
-                        description = ''
-                          Whether to share the Wayland socket.
-                        '';
-                      };
-
-                      x11 = mkOption {
-                        type = bool;
-                        default = false;
-                        description = ''
-                          Whether to share the X11 socket and allow connection.
-                        '';
-                      };
-
-                      dbus = mkOption {
-                        type = bool;
-                        default = true;
-                        description = ''
-                          Whether to proxy D-Bus.
-                        '';
-                      };
-
-                      pulse = mkOption {
-                        type = bool;
-                        default = true;
-                        description = ''
-                          Whether to share the PulseAudio socket and cookie.
-                        '';
-                      };
-                    };
-
-                    share = mkOption {
-                      type = nullOr package;
-                      default = null;
-                      description = ''
-                        Package containing share files.
-                        Setting this to null will default package name to wrapper name.
-                      '';
-                    };
-                  };
-                });
-                default = { };
-              };
-
-              persistence = mkOption {
-                type = submodule {
-                  options = {
-                    directories = mkOption {
-                      type = listOf anything;
-                      default = [ ];
-                    };
-
-                    files = mkOption {
-                      type = listOf anything;
-                      default = [ ];
-                    };
-                  };
-                };
-                description = ''
-                  Per-user state passed to github:nix-community/impermanence.
-                '';
-              };
-
-              extraConfig = mkOption {
-                type = anything;
-                default = { };
-                description = "Extra home-manager configuration.";
-              };
-            };
-          });
-      };
-
-      package = mkOption {
-        type = types.package;
-        default = pkgs.callPackage ./package.nix { };
-        description = "Package providing fortify.";
-      };
-
-      user = mkOption {
-        type = types.str;
-        description = "Privileged user account.";
-      };
-
-      stateDir = mkOption {
-        type = types.str;
-        description = ''
-          The path to persistent storage where per-user state should be stored.
-        '';
-      };
-    };
-  };
+  imports = [ ./options.nix ];
 
   config = mkIf cfg.enable {
-    environment.persistence.${cfg.stateDir}.users = mapAttrs (_: target: target.persistence) cfg.target;
+    security.wrappers.fsu = {
+      source = "${cfg.package}/libexec/fsu";
+      setuid = true;
+      owner = "root";
+      setgid = true;
+      group = "root";
+    };
 
-    home-manager.users =
-      mapAttrs (_: target: target.extraConfig // { home.packages = target.packages; }) cfg.target
-      // {
-        ${cfg.user}.home.packages =
+    environment.etc = {
+      fsurc = {
+        mode = "0400";
+        text = foldlAttrs (
+          acc: username: fid:
+          "${toString config.users.users.${username}.uid} ${toString fid}\n" + acc
+        ) "" cfg.users;
+      };
+
+      userdb.source = pkgs.runCommand "fortify-userdb" { } ''
+        ${cfg.package}/libexec/fuserdb -o $out ${
+          foldlAttrs (
+            acc: username: fid:
+            acc + " ${username}:${toString fid}"
+          ) "-s /run/current-system/sw/bin/nologin -d ${cfg.stateDir}" cfg.users
+        }
+      '';
+    };
+
+    services.userdbd.enable = mkDefault true;
+
+    home-manager =
       let
-            wrap =
-              user: launchers:
-              mapAttrsToList (
-                name: launcher:
-                with launcher.capability;
+        privPackages = mapAttrs (username: fid: {
+          home.packages =
+            let
+              # aid 0 is reserved
+              wrappers = imap1 (
+                aid: app:
                 let
                   extendDBusDefault = id: ext: {
                     filter = true;
 
                     talk = [ "org.freedesktop.Notifications" ] ++ ext.talk;
                     own =
-                      (optionals (launcher.id != null) [
+                      (optionals (app.id != null) [
                         "${id}.*"
                         "org.mpris.MediaPlayer2.${id}.*"
                       ])
                       ++ ext.own;
-                    call = {
-                      "org.freedesktop.portal.*" = "*";
-                    } // ext.call;
-                    broadcast = {
-                      "org.freedesktop.portal.*" = "@/org/freedesktop/portal/*";
-                    } // ext.broadcast;
+
+                    inherit (ext) call broadcast;
                   };
                   dbusConfig =
                     let
@@ -291,34 +88,41 @@ in
                     in
                     {
                       session_bus =
-                        if launcher.dbus.session != null then
-                          (launcher.dbus.session (extendDBusDefault launcher.id))
+                        if app.dbus.session != null then
+                          (app.dbus.session (extendDBusDefault app.id))
                         else
-                          (extendDBusDefault launcher.id default);
-                      system_bus = launcher.dbus.system;
+                          (extendDBusDefault app.id default);
+                      system_bus = app.dbus.system;
                     };
-                  command = if launcher.command == null then name else launcher.command;
+                  command = if app.command == null then app.name else app.command;
+                  script = if app.script == null then ("exec " + command + " $@") else app.script;
                   enablements =
+                    with app.capability;
                     (if wayland then 1 else 0)
                     + (if x11 then 2 else 0)
                     + (if dbus then 4 else 0)
                     + (if pulse then 8 else 0);
                   conf = {
-                    inherit (launcher) id method;
-                    inherit user;
+                    inherit (app) id;
                     command = [
-                      "/run/current-system/sw/bin/zsh"
-                      (pkgs.writeShellScript "${name}-start" ("exec " + command + " $@"))
+                      (pkgs.writeScript "${app.name}-start" ''
+                        #!${pkgs.zsh}${pkgs.zsh.shellPath}
+                        ${script}
+                      '')
                     ];
                     confinement = {
+                      app_id = aid;
+                      inherit (app) groups;
+                      username = "u${toString fid}_a${toString aid}";
+                      home = "${cfg.stateDir}/${toString fid}/${toString aid}";
                       sandbox = {
-                        inherit (launcher)
+                        inherit (app)
                           userns
                           net
                           dev
                           env
                           ;
-                        use_real_uid = launcher.useRealUid;
+                        map_real_uid = app.mapRealUid;
                         filesystem =
                           [
                             { src = "/bin"; }
@@ -345,24 +149,19 @@ in
                               src = "/sys/devices";
                               require = false;
                             }
-                            {
-                              src = "/home/${user}";
-                              write = true;
-                              require = true;
-                            }
                           ]
-                          ++ optionals launcher.nix [
+                          ++ optionals app.nix [
                             { src = "/nix/var"; }
                             { src = "/var/db/nix-channels"; }
                           ]
-                          ++ optionals (if launcher.gpu != null then launcher.gpu else wayland || x11) [
+                          ++ optionals (if app.gpu != null then app.gpu else app.capability.wayland || app.capability.x11) [
                             { src = "/run/opengl-driver"; }
                             {
                               src = "/dev/dri";
                               dev = true;
                             }
                           ]
-                          ++ launcher.extraPaths;
+                          ++ app.extraPaths;
                         auto_etc = true;
                         override = [ "/var/run/nscd" ];
                       };
@@ -371,54 +170,49 @@ in
                     };
                   };
                 in
-                pkgs.writeShellScriptBin name (
-                  if launcher.method == "simple" then
+                pkgs.writeShellScriptBin app.name ''
+                  exec fortify app ${pkgs.writeText "fortify-${app.name}.json" (builtins.toJSON conf)} $@
                 ''
-                      exec sudo -u ${user} -i ${command} $@
-                    ''
-                  else
-                    ''
-                      exec fortify app ${pkgs.writeText "fortify-${name}.json" (builtins.toJSON conf)} $@
-                    ''
-                )
-              ) launchers;
+              ) cfg.apps;
             in
-          foldlAttrs (
-            acc: user: target:
-            acc
-            ++ (foldlAttrs (
-              shares: name: launcher:
+            foldr (
+              app: acc:
               let
-                pkg = if launcher.share != null then launcher.share else pkgs.${name};
-                link = source: "[ -d '${source}' ] && ln -sv '${source}' $out/share || true";
+                pkg = if app.share != null then app.share else pkgs.${app.name};
+                copy = source: "[ -d '${source}' ] && cp -Lrv '${source}' $out/share || true";
               in
-              shares
-              ++
-                optional (launcher.method != "simple" && (launcher.capability.wayland || launcher.capability.x11))
-                  (
-                    pkgs.runCommand "${name}-share" { } ''
+              optional (app.capability.wayland || app.capability.x11) (
+                pkgs.runCommand "${app.name}-share" { } ''
                   mkdir -p $out/share
-                      ${link "${pkg}/share/applications"}
-                      ${link "${pkg}/share/icons"}
-                      ${link "${pkg}/share/man"}
+                  ${copy "${pkg}/share/applications"}
+                  ${copy "${pkg}/share/pixmaps"}
+                  ${copy "${pkg}/share/icons"}
+                  ${copy "${pkg}/share/man"}
+
+                  substituteInPlace $out/share/applications/* \
+                    --replace-warn '${pkg}/bin/' "" \
+                    --replace-warn '${pkg}/libexec/' ""
                 ''
               )
-            ) (wrap user target.launchers) target.launchers)
-          ) [ cfg.package ] cfg.target;
-      };
-
-    security.polkit.extraConfig =
-      let
-        allowList = builtins.toJSON (mapAttrsToList (name: _: name) cfg.target);
+              ++ acc
+            ) (wrappers ++ [ cfg.package ]) cfg.apps;
+        }) cfg.users;
       in
-      ''
-        polkit.addRule(function(action, subject) {
-          if (action.id == "org.freedesktop.machine1.host-shell" &&
-            ${allowList}.indexOf(action.lookup("user")) > -1 &&
-            subject.user == "${cfg.user}") {
-                return polkit.Result.YES;
-          }
-        });
-      '';
+      {
+        useUserPackages = false; # prevent users.users entries from being added
+
+        users = foldlAttrs (
+          acc: _: fid:
+          mergeAttrsList (
+            # aid 0 is reserved
+            imap1 (aid: app: {
+              "u${toString fid}_a${toString aid}" = app.extraConfig // {
+                home.packages = app.packages;
+              };
+            }) cfg.apps
+          )
+          // acc
+        ) privPackages cfg.users;
+      };
   };
 }

options.md

@@ -0,0 +1,531 @@
+## environment\.fortify\.enable
+
+
+
+Whether to enable fortify\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` false `
+
+
+
+*Example:*
+` true `
+
+
+
+
+## environment\.fortify\.package
+
+
+
+The fortify package to use\.
+
+
+
+*Type:*
+package
+
+
+
+*Default:*
+` <derivation fortify-0.1.0> `
+
+
+
+
+## environment\.fortify\.apps
+
+Declarative fortify apps\.
+
+
+
+*Type:*
+list of (submodule)
+
+
+
+*Default:*
+` [ ] `
+
+
+
+
+## environment\.fortify\.apps\.\*\.packages
+
+
+
+List of extra packages to install via home-manager\.
+
+
+
+*Type:*
+list of package
+
+
+
+*Default:*
+` [ ] `
+
+
+
+
+## environment\.fortify\.apps\.\*\.capability\.dbus
+
+
+
+Whether to proxy D-Bus\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.capability\.pulse
+
+
+
+Whether to share the PulseAudio socket and cookie\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.capability\.wayland
+
+
+
+Whether to share the Wayland socket\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.capability\.x11
+
+
+
+Whether to share the X11 socket and allow connection\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` false `
+
+
+
+
+## environment\.fortify\.apps\.\*\.command
+
+
+
+Command to run as the target user\.
+Setting this to null will default command to launcher name\.
+Has no effect when script is set\.
+
+
+
+*Type:*
+null or string
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.dbus\.session
+
+
+
+D-Bus session bus custom configuration\.
+Setting this to null will enable built-in defaults\.
+
+
+
+*Type:*
+null or (function that evaluates to a(n) anything)
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.dbus\.system
+
+
+
+D-Bus system bus custom configuration\.
+Setting this to null will disable the system bus proxy\.
+
+
+
+*Type:*
+null or anything
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.dev
+
+
+
+Whether to enable access to all devices within the sandbox\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` false `
+
+
+
+*Example:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.env
+
+
+
+Environment variables to set for the initial process in the sandbox\.
+
+
+
+*Type:*
+null or (attribute set of string)
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.extraConfig
+
+
+
+Extra home-manager configuration\.
+
+
+
+*Type:*
+anything
+
+
+
+*Default:*
+` { } `
+
+
+
+
+## environment\.fortify\.apps\.\*\.extraPaths
+
+
+
+Extra paths to make available to the sandbox\.
+
+
+
+*Type:*
+list of anything
+
+
+
+*Default:*
+` [ ] `
+
+
+
+
+## environment\.fortify\.apps\.\*\.gpu
+
+
+
+Target process GPU and driver access\.
+Setting this to null will enable GPU whenever X or Wayland is enabled\.
+
+
+
+*Type:*
+null or boolean
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.groups
+
+
+
+List of groups to inherit from the privileged user\.
+
+
+
+*Type:*
+list of string
+
+
+
+*Default:*
+` [ ] `
+
+
+
+
+## environment\.fortify\.apps\.\*\.id
+
+
+
+Freedesktop application ID\.
+
+
+
+*Type:*
+null or string
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.mapRealUid
+
+
+
+Whether to enable mapping to fortify’s real UID within the sandbox\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` false `
+
+
+
+*Example:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.name
+
+
+
+Name of the app’s launcher script\.
+
+
+
+*Type:*
+string
+
+
+
+
+## environment\.fortify\.apps\.\*\.net
+
+
+
+Whether to enable network access within the sandbox\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` true `
+
+
+
+*Example:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.nix
+
+
+
+Whether to enable nix daemon access within the sandbox\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` false `
+
+
+
+*Example:*
+` true `
+
+
+
+
+## environment\.fortify\.apps\.\*\.script
+
+
+
+Application launch script\.
+
+
+
+*Type:*
+null or string
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.share
+
+
+
+Package containing share files\.
+Setting this to null will default package name to wrapper name\.
+
+
+
+*Type:*
+null or package
+
+
+
+*Default:*
+` null `
+
+
+
+
+## environment\.fortify\.apps\.\*\.userns
+
+
+
+Whether to enable userns within the sandbox\.
+
+
+
+*Type:*
+boolean
+
+
+
+*Default:*
+` false `
+
+
+
+*Example:*
+` true `
+
+
+
+
+## environment\.fortify\.stateDir
+
+
+
+The state directory where app home directories are stored\.
+
+
+
+*Type:*
+string
+
+
+
+
+## environment\.fortify\.users
+
+
+
+Users allowed to spawn fortify apps and their corresponding fortify fid\.
+
+
+
+*Type:*
+attribute set of integer between 0 and 99 (both inclusive)
+
+
+

options.nix

@@ -0,0 +1,214 @@
+{ lib, pkgs, ... }:
+
+let
+  inherit (lib) types mkOption mkEnableOption;
+in
+
+{
+  options = {
+    environment.fortify = {
+      enable = mkEnableOption "fortify";
+
+      package = mkOption {
+        type = types.package;
+        default = pkgs.callPackage ./package.nix { };
+        description = "The fortify package to use.";
+      };
+
+      users = mkOption {
+        type =
+          let
+            inherit (types) attrsOf ints;
+          in
+          attrsOf (ints.between 0 99);
+        description = ''
+          Users allowed to spawn fortify apps and their corresponding fortify fid.
+        '';
+      };
+
+      apps = mkOption {
+        type =
+          let
+            inherit (types)
+              str
+              enum
+              bool
+              package
+              anything
+              submodule
+              listOf
+              attrsOf
+              nullOr
+              functionTo
+              ;
+          in
+          listOf (submodule {
+            options = {
+              name = mkOption {
+                type = str;
+                description = ''
+                  Name of the app's launcher script.
+                '';
+              };
+
+              id = mkOption {
+                type = nullOr str;
+                default = null;
+                description = ''
+                  Freedesktop application ID.
+                '';
+              };
+
+              packages = mkOption {
+                type = listOf package;
+                default = [ ];
+                description = ''
+                  List of extra packages to install via home-manager.
+                '';
+              };
+
+              extraConfig = mkOption {
+                type = anything;
+                default = { };
+                description = ''
+                  Extra home-manager configuration.
+                '';
+              };
+
+              script = mkOption {
+                type = nullOr str;
+                default = null;
+                description = ''
+                  Application launch script.
+                '';
+              };
+
+              command = mkOption {
+                type = nullOr str;
+                default = null;
+                description = ''
+                  Command to run as the target user.
+                  Setting this to null will default command to launcher name.
+                  Has no effect when script is set.
+                '';
+              };
+
+              groups = mkOption {
+                type = listOf str;
+                default = [ ];
+                description = ''
+                  List of groups to inherit from the privileged user.
+                '';
+              };
+
+              dbus = {
+                session = mkOption {
+                  type = nullOr (functionTo anything);
+                  default = null;
+                  description = ''
+                    D-Bus session bus custom configuration.
+                    Setting this to null will enable built-in defaults.
+                  '';
+                };
+
+                system = mkOption {
+                  type = nullOr anything;
+                  default = null;
+                  description = ''
+                    D-Bus system bus custom configuration.
+                    Setting this to null will disable the system bus proxy.
+                  '';
+                };
+              };
+
+              env = mkOption {
+                type = nullOr (attrsOf str);
+                default = null;
+                description = ''
+                  Environment variables to set for the initial process in the sandbox.
+                '';
+              };
+
+              nix = mkEnableOption "nix daemon access within the sandbox";
+              userns = mkEnableOption "userns within the sandbox";
+              mapRealUid = mkEnableOption "mapping to fortify's real UID within the sandbox";
+              dev = mkEnableOption "access to all devices within the sandbox";
+
+              net = mkEnableOption "network access within the sandbox" // {
+                default = true;
+              };
+
+              gpu = mkOption {
+                type = nullOr bool;
+                default = null;
+                description = ''
+                  Target process GPU and driver access.
+                  Setting this to null will enable GPU whenever X or Wayland is enabled.
+                '';
+              };
+
+              extraPaths = mkOption {
+                type = listOf anything;
+                default = [ ];
+                description = ''
+                  Extra paths to make available to the sandbox.
+                '';
+              };
+
+              capability = {
+                wayland = mkOption {
+                  type = bool;
+                  default = true;
+                  description = ''
+                    Whether to share the Wayland socket.
+                  '';
+                };
+
+                x11 = mkOption {
+                  type = bool;
+                  default = false;
+                  description = ''
+                    Whether to share the X11 socket and allow connection.
+                  '';
+                };
+
+                dbus = mkOption {
+                  type = bool;
+                  default = true;
+                  description = ''
+                    Whether to proxy D-Bus.
+                  '';
+                };
+
+                pulse = mkOption {
+                  type = bool;
+                  default = true;
+                  description = ''
+                    Whether to share the PulseAudio socket and cookie.
+                  '';
+                };
+              };
+
+              share = mkOption {
+                type = nullOr package;
+                default = null;
+                description = ''
+                  Package containing share files.
+                  Setting this to null will default package name to wrapper name.
+                '';
+              };
+            };
+          });
+        default = [ ];
+        description = "Declarative fortify apps.";
+      };
+
+      stateDir = mkOption {
+        type = types.str;
+        description = ''
+          The state directory where app home directories are stored.
+        '';
+      };
+    };
+  };
+}

package.nix

@@ -10,7 +10,7 @@
 
 buildGoModule rec {
   pname = "fortify";
-  version = "0.1.0";
+  version = "0.2.0";
 
   src = ./.;
   vendorHash = null;
@@ -29,13 +29,14 @@ buildGoModule rec {
         "-s"
         "-w"
         "-X"
-        "main.Fmain=${placeholder "out"}/bin/.fortify-wrapped"
+        "main.Fmain=${placeholder "out"}/libexec/fortify"
+        "-X"
+        "main.Fshim=${placeholder "out"}/libexec/fshim"
       ]
       {
         Version = "v${version}";
         Fsu = "/run/wrappers/bin/fsu";
-        Fshim = "${placeholder "out"}/bin/.fshim";
-        Finit = "${placeholder "out"}/bin/.finit";
+        Finit = "${placeholder "out"}/libexec/finit";
       };
 
   buildInputs = [
@@ -46,15 +47,15 @@ buildGoModule rec {
   nativeBuildInputs = [ makeBinaryWrapper ];
 
   postInstall = ''
-    wrapProgram $out/bin/${pname} --prefix PATH : ${
+    mkdir "$out/libexec"
+    mv "$out"/bin/* "$out/libexec/"
+
+    makeBinaryWrapper "$out/libexec/fortify" "$out/bin/fortify" \
+      --inherit-argv0 --prefix PATH : ${
         lib.makeBinPath [
           bubblewrap
           xdg-dbus-proxy
         ]
       }
-
-    mv $out/bin/fsu $out/bin/.fsu
-    mv $out/bin/fshim $out/bin/.fshim
-    mv $out/bin/finit $out/bin/.finit
   '';
 }