update README document

We have a highly configurable sandbox now, just not really the Android sandbox.

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

.gitea/workflows/release.yml

@@ -21,8 +21,8 @@ jobs:
 
       - 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

.gitea/workflows/test.yml

@@ -20,8 +20,8 @@ jobs:
 
       - 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

README.md

@@ -3,7 +3,7 @@ Fortify
 
 [![Go Reference](https://pkg.go.dev/badge/git.ophivana.moe/cat/fortify.svg)](https://pkg.go.dev/git.ophivana.moe/cat/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:
 

flake.nix

@@ -34,6 +34,12 @@
 
       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 ];

internal/app/app.go

@@ -7,26 +7,39 @@ import (
 )
 
 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
+	// underlying user switcher process
+	cmd *exec.Cmd
 	// 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)"
@@ -47,9 +60,11 @@ func (a *app) String() string {
 }
 
 func (a *app) WaitErr() error {
-	return a.wait
+	return a.waitErr
 }
 
-func New() App {
-	return new(app)
+func New() (App, error) {
+	a := new(app)
+	a.id = new(ID)
+	return a, newAppID(a.id)
 }

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/seal.go

@@ -21,6 +21,11 @@ const (
 	LaunchMethodMachineCtl
 )
 
+var method = [...]string{
+	LaunchMethodSudo:       "sudo",
+	LaunchMethodMachineCtl: "systemd",
+}
+
 var (
 	ErrConfig = errors.New("no configuration to seal")
 	ErrUser   = errors.New("unknown user")
@@ -48,24 +53,17 @@ func (a *app) Seal(config *Config) error {
 	// create seal
 	seal := new(appSeal)
 
-	// generate application ID
-	if id, err := newAppID(); err != nil {
-		return fmsg.WrapErrorSuffix(err,
-			"cannot generate application ID:")
-	} else {
-		seal.id = id
-	}
-
 	// fetch system constants
 	seal.SystemConstants = internal.GetSC()
 
 	// 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 fmsg.WrapError(ErrSudo,
@@ -73,7 +71,7 @@ func (a *app) Seal(config *Config) error {
 		} else {
 			seal.toolPath = sudoPath
 		}
-	case "systemd":
+	case method[LaunchMethodMachineCtl]:
 		seal.launchOption = LaunchMethodMachineCtl
 		if !internal.SdBootedV {
 			return fmsg.WrapError(ErrSystemd,

internal/app/share.runtime.go

@@ -31,17 +31,8 @@ func (seal *appSeal) shareRuntime() {
 	// ensure runtime directory ACL (e.g. `/run/user/%d`)
 	seal.sys.UpdatePermType(system.User, 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.Ephemeral(system.Process, seal.share, 0701)
-
 	// 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.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

@@ -14,6 +14,31 @@ 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() {
 	// look up shell
 	sh := "/bin/sh"
 	if s, ok := os.LookupEnv(shell); ok {
@@ -44,21 +69,3 @@ func (seal *appSeal) shareSystem() {
 	seal.sys.bwrap.Bind(passwdPath, "/etc/passwd")
 	seal.sys.bwrap.Bind(groupPath, "/etc/group")
 }
-
-func (seal *appSeal) shareTmpdirChild() string {
-	// 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)
-
-	return targetTmpdir
-}

internal/app/start.go

@@ -94,7 +94,7 @@ func (a *app) Start() error {
 		PID:        a.cmd.Process.Pid,
 		Command:    a.seal.command,
 		Capability: a.seal.et,
-		Launcher:   a.seal.toolPath,
+		Method:     method[a.seal.launchOption],
 		Argv:       a.cmd.Args,
 		Time:       startTime,
 	}
@@ -173,7 +173,7 @@ func (a *app) Wait() (int, error) {
 		var exitError *exec.ExitError
 		if !errors.As(err, &exitError) {
 			// should be unreachable
-			a.wait = err
+			a.waitErr = err
 		}
 
 		// store non-zero return code

internal/app/system.go

@@ -8,19 +8,18 @@ import (
 	"git.ophivana.moe/cat/fortify/internal"
 	"git.ophivana.moe/cat/fortify/internal/state"
 	"git.ophivana.moe/cat/fortify/internal/system"
-	"git.ophivana.moe/cat/fortify/internal/verbose"
 )
 
 // 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{}
 
+	// app unique ID string representation
+	id string
 	// freedesktop application ID
 	fid string
 	// argv to start process with in the final confined environment
@@ -76,10 +75,9 @@ func (seal *appSeal) shareAll(bus [2]*dbus.Config) error {
 	}
 	seal.shared = true
 
-	targetTmpdir := seal.shareTmpdirChild()
-	verbose.Printf("child tmpdir %q configured\n", targetTmpdir)
-	seal.shareRuntime()
 	seal.shareSystem()
+	seal.shareRuntime()
+	seal.sharePasswd()
 	if err := seal.shareDisplay(); err != nil {
 		return err
 	}

internal/init/main.go

@@ -145,11 +145,12 @@ func doInit(fd uintptr) {
 				default:
 					r = 255
 				}
-			}
+
 				go func() {
 					time.Sleep(residualProcessTimeout)
 					close(timeout)
 				}()
+			}
 		case <-done:
 			os.Exit(r)
 		case <-timeout:

internal/state/print.go

@@ -68,7 +68,7 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 
 				// write header when initialising
 				if !verbose.Get() {
-					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tUptime\tEnablements\tLauncher\tCommand")
+					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tUptime\tEnablements\tMethod\tCommand")
 				} else {
 					// argv is emitted in body when verbose
 					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tArgv")
@@ -98,7 +98,7 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 
 				if !verbose.Get() {
 					_, _ = 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

internal/state/state.go

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

internal/system/acl_test.go

@@ -0,0 +1,89 @@
+package system
+
+import (
+	"testing"
+
+	"git.ophivana.moe/cat/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
+		perms []acl.Perm
+	}{
+		{"---", []acl.Perm{}},
+		{"r--", []acl.Perm{acl.Read}},
+		{"-w-", []acl.Perm{acl.Write}},
+		{"--x", []acl.Perm{acl.Execute}},
+		{"rw-", []acl.Perm{acl.Read, acl.Write}},
+		{"r-x", []acl.Perm{acl.Read, acl.Execute}},
+		{"rwx", []acl.Perm{acl.Read, acl.Write, acl.Execute}},
+		{"rwx", []acl.Perm{acl.Read, acl.Write, acl.Write, acl.Execute}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.want, func(t *testing.T) {
+			a := &ACL{perms: tc.perms}
+			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/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_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 +1,53 @@
+package system_test
+
+import (
+	"strconv"
+	"testing"
+
+	"git.ophivana.moe/cat/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)
+			}
+		})
+	}
+}

internal/system/tmpfiles_test.go

@@ -0,0 +1,167 @@
+package system
+
+import (
+	"strconv"
+	"testing"
+
+	"git.ophivana.moe/cat/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_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)
+			}
+		})
+	}
+}

main.go

@@ -54,8 +54,10 @@ func main() {
 
 	// invoke app
 	r := 1
-	a := app.New()
-	if err := a.Seal(loadConfig()); err != nil {
+	a, err := app.New()
+	if err != nil {
+		fatalf("cannot create app: %s\n", err)
+	} else if err = a.Seal(loadConfig()); err != nil {
 		logBaseError(err, "fortify: cannot seal app:")
 	} else if err = a.Start(); err != nil {
 		logBaseError(err, "fortify: cannot start app:")
@@ -65,7 +67,7 @@ func main() {
 		}
 		logWaitError(err)
 	}
-	if err := a.WaitErr(); err != nil {
+	if err = a.WaitErr(); err != nil {
 		fmt.Println("fortify: inner wait failed:", err)
 	}
 	os.Exit(r)

package.nix

@@ -10,7 +10,7 @@
 
 buildGoModule rec {
   pname = "fortify";
-  version = "0.0.4";
+  version = "0.0.6";
 
   src = ./.;
   vendorHash = null;