clean up setup/launcher code and enable better control over shares

In the past Wayland, X and PulseAudio are shared unconditionally. This can unnecessarily increase attack surface as some of these resources might not be needed at all. This commit moves all environment preparation code to the internal app package and selectively call them based on flags.

An "enablements" bitfield is introduced tracking all enabled shares. This value is registered after successful child process launch and stored in launcher states.

Code responsible for running the child process is isolated to its own app/run file and cleaned up. Launch method selection is also extensively cleaned up.

The internal state/track readLaunchers function now takes uid as an argument. Launcher state is now printed using text/tabwriter and argv is only emitted when verbose.

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

7 files changed, 343 insertions, 151 deletions

diff --git a/internal/app/dbus.go b/internal/app/dbus.go
new file mode 100644
index 00000000..89394f15
--- /dev/null
+++ b/internal/app/dbus.go
@@ -0,0 +1,14 @@
+package app
+
+import (
+	"fmt"
+
+	"git.ophivana.moe/cat/fortify/internal/state"
+)
+
+func (a *App) ShareDBus() {
+	a.setEnablement(state.EnableDBus)
+
+	// TODO: start xdg-dbus-proxy
+	fmt.Println("warn: dbus proxy not implemented")
+}
diff --git a/internal/app/launch.go b/internal/app/launch.go
index ab48baad..02204aae 100644
--- a/internal/app/launch.go
+++ b/internal/app/launch.go
@@ -10,14 +10,10 @@ import (
 	"syscall"
 
 	"git.ophivana.moe/cat/fortify/internal/state"
-	"git.ophivana.moe/cat/fortify/internal/system"
 	"git.ophivana.moe/cat/fortify/internal/util"
 )
 
-const (
-	sudoAskPass     = "SUDO_ASKPASS"
-	launcherPayload = "FORTIFY_LAUNCHER_PAYLOAD"
-)
+const launcherPayload = "FORTIFY_LAUNCHER_PAYLOAD"
 
 func (a *App) launcherPayloadEnv() string {
 	r := &bytes.Buffer{}
@@ -75,80 +71,3 @@ func Early(printVersion bool) {
 		}
 	}
 }
-
-func (a *App) launchBySudo() (args []string) {
-	args = make([]string, 0, 4+len(a.env)+len(a.command))
-
-	// -Hiu $USER
-	args = append(args, "-Hiu", a.Username)
-
-	// -A?
-	if _, ok := os.LookupEnv(sudoAskPass); ok {
-		if system.V.Verbose {
-			fmt.Printf("%s set, adding askpass flag\n", sudoAskPass)
-		}
-		args = append(args, "-A")
-	}
-
-	// environ
-	args = append(args, a.env...)
-
-	// -- $@
-	args = append(args, "--")
-	args = append(args, a.command...)
-
-	return
-}
-
-func (a *App) launchByMachineCtl(bare bool) (args []string) {
-	args = make([]string, 0, 9+len(a.env))
-
-	// shell --uid=$USER
-	args = append(args, "shell", "--uid="+a.Username)
-
-	// --quiet
-	if !system.V.Verbose {
-		args = append(args, "--quiet")
-	}
-
-	// environ
-	envQ := make([]string, len(a.env)+1)
-	for i, e := range a.env {
-		envQ[i] = "-E" + e
-	}
-	envQ[len(a.env)] = "-E" + a.launcherPayloadEnv()
-	args = append(args, envQ...)
-
-	// -- .host
-	args = append(args, "--", ".host")
-
-	// /bin/sh -c
-	if sh, ok := util.Which("sh"); !ok {
-		state.Fatal("Did not find 'sh' in PATH")
-	} else {
-		args = append(args, sh, "-c")
-	}
-
-	if len(a.command) == 0 { // execute shell if command is not provided
-		a.command = []string{"$SHELL"}
-	}
-
-	innerCommand := strings.Builder{}
-
-	if !bare {
-		innerCommand.WriteString("dbus-update-activation-environment --systemd")
-		for _, e := range a.env {
-			innerCommand.WriteString(" " + strings.SplitN(e, "=", 2)[0])
-		}
-		innerCommand.WriteString("; systemctl --user start xdg-desktop-portal-gtk; ")
-	}
-
-	if executable, err := os.Executable(); err != nil {
-		state.Fatal("Error reading executable path:", err)
-	} else {
-		innerCommand.WriteString("exec " + executable + " -V")
-	}
-	args = append(args, innerCommand.String())
-
-	return
-}
diff --git a/internal/app/pulse.go b/internal/app/pulse.go
new file mode 100644
index 00000000..848ac717
--- /dev/null
+++ b/internal/app/pulse.go
@@ -0,0 +1,68 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+
+	"git.ophivana.moe/cat/fortify/internal/acl"
+	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/cat/fortify/internal/system"
+	"git.ophivana.moe/cat/fortify/internal/util"
+)
+
+func (a *App) SharePulse() {
+	a.setEnablement(state.EnablePulse)
+
+	// ensure PulseAudio directory ACL (e.g. `/run/user/%d/pulse`)
+	pulse := path.Join(system.V.Runtime, "pulse")
+	pulseS := path.Join(pulse, "native")
+	if s, err := os.Stat(pulse); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			state.Fatal("Error accessing PulseAudio directory:", err)
+		}
+		state.Fatal(fmt.Sprintf("PulseAudio dir '%s' not found", pulse))
+	} else {
+		// add environment variable for new process
+		a.AppendEnv(util.PulseServer, "unix:"+pulseS)
+		if err = acl.UpdatePerm(pulse, a.UID(), acl.Execute); err != nil {
+			state.Fatal("Error preparing PulseAudio:", err)
+		} else {
+			state.RegisterRevertPath(pulse)
+		}
+
+		// ensure PulseAudio socket permission (e.g. `/run/user/%d/pulse/native`)
+		if s, err = os.Stat(pulseS); err != nil {
+			if errors.Is(err, fs.ErrNotExist) {
+				state.Fatal("PulseAudio directory found but socket does not exist")
+			}
+			state.Fatal("Error accessing PulseAudio socket:", err)
+		} else {
+			if m := s.Mode(); m&0o006 != 0o006 {
+				state.Fatal(fmt.Sprintf("Unexpected permissions on '%s':", pulseS), m)
+			}
+		}
+
+		// Publish current user's pulse-cookie for target user
+		pulseCookieSource := util.DiscoverPulseCookie()
+		pulseCookieFinal := path.Join(system.V.Share, "pulse-cookie")
+		a.AppendEnv(util.PulseCookie, pulseCookieFinal)
+		if system.V.Verbose {
+			fmt.Printf("Publishing PulseAudio cookie '%s' to '%s'\n", pulseCookieSource, pulseCookieFinal)
+		}
+		if err = util.CopyFile(pulseCookieFinal, pulseCookieSource); err != nil {
+			state.Fatal("Error copying PulseAudio cookie:", err)
+		}
+		if err = acl.UpdatePerm(pulseCookieFinal, a.UID(), acl.Read); err != nil {
+			state.Fatal("Error publishing PulseAudio cookie:", err)
+		} else {
+			state.RegisterRevertPath(pulseCookieFinal)
+		}
+
+		if system.V.Verbose {
+			fmt.Printf("PulseAudio dir '%s' configured\n", pulse)
+		}
+	}
+}
diff --git a/internal/app/run.go b/internal/app/run.go
new file mode 100644
index 00000000..bd3bd9bf
--- /dev/null
+++ b/internal/app/run.go
@@ -0,0 +1,178 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/cat/fortify/internal/system"
+	"git.ophivana.moe/cat/fortify/internal/util"
+)
+
+const (
+	term        = "TERM"
+	sudoAskPass = "SUDO_ASKPASS"
+)
+const (
+	LaunchMethodSudo = iota
+	LaunchMethodMachineCtl
+
+	LaunchBare
+	launchOptionLength
+)
+
+var (
+	// LaunchOptions is set in main's cli.go
+	LaunchOptions [launchOptionLength]bool
+)
+
+func (a *App) Run() {
+	// pass $TERM to launcher
+	if t, ok := os.LookupEnv(term); ok {
+		a.AppendEnv(term, t)
+	}
+
+	commandBuilder := a.commandBuilderSudo
+
+	var toolPath string
+
+	// dependency checks
+	const sudoFallback = "Falling back to 'sudo', some desktop integration features may not work"
+	if LaunchOptions[LaunchMethodMachineCtl] && !LaunchOptions[LaunchMethodSudo] { // sudo argument takes priority
+		if !util.SdBooted() {
+			fmt.Println("This system was not booted through systemd")
+			fmt.Println(sudoFallback)
+		} else if machineCtlPath, ok := util.Which("machinectl"); !ok {
+			fmt.Println("Did not find 'machinectl' in PATH")
+			fmt.Println(sudoFallback)
+		} else {
+			toolPath = machineCtlPath
+			commandBuilder = a.commandBuilderMachineCtl
+		}
+	} else if sudoPath, ok := util.Which("sudo"); !ok {
+		state.Fatal("Did not find 'sudo' in PATH")
+	} else {
+		toolPath = sudoPath
+	}
+
+	if system.V.Verbose {
+		fmt.Printf("Selected launcher '%s' bare=%t\n", toolPath, LaunchOptions[LaunchBare])
+	}
+
+	cmd := exec.Command(toolPath, commandBuilder(LaunchOptions[LaunchBare])...)
+	cmd.Env = a.env
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Dir = system.V.RunDir
+
+	if system.V.Verbose {
+		fmt.Println("Executing:", cmd)
+	}
+
+	if err := cmd.Start(); err != nil {
+		state.Fatal("Error starting process:", err)
+	}
+
+	state.RegisterEnablement(a.enablements)
+
+	if err := state.SaveProcess(a.Uid, cmd); err != nil {
+		// process already started, shouldn't be fatal
+		fmt.Println("Error registering process:", err)
+	}
+
+	var r int
+	if err := cmd.Wait(); err != nil {
+		var exitError *exec.ExitError
+		if !errors.As(err, &exitError) {
+			state.Fatal("Error running process:", err)
+		}
+	}
+
+	if system.V.Verbose {
+		fmt.Println("Process exited with exit code", r)
+	}
+	state.BeforeExit()
+	os.Exit(r)
+}
+
+func (a *App) commandBuilderSudo(bare bool) (args []string) {
+	args = make([]string, 0, 4+len(a.env)+len(a.command))
+
+	// -Hiu $USER
+	args = append(args, "-Hiu", a.Username)
+
+	// -A?
+	if _, ok := os.LookupEnv(sudoAskPass); ok {
+		if system.V.Verbose {
+			fmt.Printf("%s set, adding askpass flag\n", sudoAskPass)
+		}
+		args = append(args, "-A")
+	}
+
+	// environ
+	args = append(args, a.env...)
+
+	// -- $@
+	args = append(args, "--")
+	args = append(args, a.command...)
+
+	return
+}
+
+func (a *App) commandBuilderMachineCtl(bare bool) (args []string) {
+	args = make([]string, 0, 9+len(a.env))
+
+	// shell --uid=$USER
+	args = append(args, "shell", "--uid="+a.Username)
+
+	// --quiet
+	if !system.V.Verbose {
+		args = append(args, "--quiet")
+	}
+
+	// environ
+	envQ := make([]string, len(a.env)+1)
+	for i, e := range a.env {
+		envQ[i] = "-E" + e
+	}
+	envQ[len(a.env)] = "-E" + a.launcherPayloadEnv()
+	args = append(args, envQ...)
+
+	// -- .host
+	args = append(args, "--", ".host")
+
+	// /bin/sh -c
+	if sh, ok := util.Which("sh"); !ok {
+		state.Fatal("Did not find 'sh' in PATH")
+	} else {
+		args = append(args, sh, "-c")
+	}
+
+	if len(a.command) == 0 { // execute shell if command is not provided
+		a.command = []string{"$SHELL"}
+	}
+
+	innerCommand := strings.Builder{}
+
+	if !bare {
+		innerCommand.WriteString("dbus-update-activation-environment --systemd")
+		for _, e := range a.env {
+			innerCommand.WriteString(" " + strings.SplitN(e, "=", 2)[0])
+		}
+		innerCommand.WriteString("; ")
+		//innerCommand.WriteString("systemctl --user start xdg-desktop-portal-gtk; ")
+	}
+
+	if executable, err := os.Executable(); err != nil {
+		state.Fatal("Error reading executable path:", err)
+	} else {
+		innerCommand.WriteString("exec " + executable + " -V")
+	}
+	args = append(args, innerCommand.String())
+
+	return
+}
diff --git a/internal/app/setup.go b/internal/app/setup.go
index 7b5cd2ec..82765dfb 100644
--- a/internal/app/setup.go
+++ b/internal/app/setup.go
@@ -4,13 +4,11 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"os/exec"
 	"os/user"
 	"strconv"
 
 	"git.ophivana.moe/cat/fortify/internal/state"
 	"git.ophivana.moe/cat/fortify/internal/system"
-	"git.ophivana.moe/cat/fortify/internal/util"
 )
 
 type App struct {
@@ -18,78 +16,19 @@ type App struct {
 	env     []string
 	command []string
 
+	enablements state.Enablements
 	*user.User
-}
-
-func (a *App) Run() {
-	f := a.launchBySudo
-	m, b := false, false
-	switch {
-	case system.MethodFlags[0]: // sudo
-	case system.MethodFlags[1]: // bare
-		m, b = true, true
-	default: // machinectl
-		m, b = true, false
-	}
-
-	var toolPath string
-
-	// dependency checks
-	const sudoFallback = "Falling back to 'sudo', some desktop integration features may not work"
-	if m {
-		if !util.SdBooted() {
-			fmt.Println("This system was not booted through systemd")
-			fmt.Println(sudoFallback)
-		} else if tp, ok := util.Which("machinectl"); !ok {
-			fmt.Println("Did not find 'machinectl' in PATH")
-			fmt.Println(sudoFallback)
-		} else {
-			toolPath = tp
-			f = func() []string { return a.launchByMachineCtl(b) }
-		}
-	} else if tp, ok := util.Which("sudo"); !ok {
-		state.Fatal("Did not find 'sudo' in PATH")
-	} else {
-		toolPath = tp
-	}
-
-	if system.V.Verbose {
-		fmt.Printf("Selected launcher '%s' bare=%t\n", toolPath, b)
-	}
 
-	cmd := exec.Command(toolPath, f()...)
-	cmd.Env = a.env
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	cmd.Dir = system.V.RunDir
-
-	if system.V.Verbose {
-		fmt.Println("Executing:", cmd)
-	}
-
-	if err := cmd.Start(); err != nil {
-		state.Fatal("Error starting process:", err)
-	}
-
-	if err := state.SaveProcess(a.Uid, cmd); err != nil {
-		// process already started, shouldn't be fatal
-		fmt.Println("Error registering process:", err)
-	}
+	// absolutely *no* method of this type is thread-safe
+	// so don't treat it as if it is
+}
 
-	var r int
-	if err := cmd.Wait(); err != nil {
-		var exitError *exec.ExitError
-		if !errors.As(err, &exitError) {
-			state.Fatal("Error running process:", err)
-		}
+func (a *App) setEnablement(e state.Enablement) {
+	if a.enablements.Has(e) {
+		panic("enablement " + e.String() + " set twice")
 	}
 
-	if system.V.Verbose {
-		fmt.Println("Process exited with exit code", r)
-	}
-	state.BeforeExit()
-	os.Exit(r)
+	a.enablements |= e.Mask()
 }
 
 func New(userName string, args []string) *App {
diff --git a/internal/app/wayland.go b/internal/app/wayland.go
new file mode 100644
index 00000000..1cabdbdb
--- /dev/null
+++ b/internal/app/wayland.go
@@ -0,0 +1,39 @@
+package app
+
+import (
+	"fmt"
+	"os"
+	"path"
+
+	"git.ophivana.moe/cat/fortify/internal/acl"
+	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/cat/fortify/internal/system"
+)
+
+const (
+	// https://manpages.debian.org/experimental/libwayland-doc/wl_display_connect.3.en.html
+	waylandDisplay = "WAYLAND_DISPLAY"
+)
+
+func (a *App) ShareWayland() {
+	a.setEnablement(state.EnableWayland)
+
+	// ensure Wayland socket ACL (e.g. `/run/user/%d/wayland-%d`)
+	if w, ok := os.LookupEnv(waylandDisplay); !ok {
+		if system.V.Verbose {
+			fmt.Println("Wayland: WAYLAND_DISPLAY not set, skipping")
+		}
+	} else {
+		// add environment variable for new process
+		wp := path.Join(system.V.Runtime, w)
+		a.AppendEnv(waylandDisplay, wp)
+		if err := acl.UpdatePerm(wp, a.UID(), acl.Read, acl.Write, acl.Execute); err != nil {
+			state.Fatal(fmt.Sprintf("Error preparing Wayland '%s':", w), err)
+		} else {
+			state.RegisterRevertPath(wp)
+		}
+		if system.V.Verbose {
+			fmt.Printf("Wayland socket '%s' configured\n", w)
+		}
+	}
+}
diff --git a/internal/app/x.go b/internal/app/x.go
new file mode 100644
index 00000000..02c40a68
--- /dev/null
+++ b/internal/app/x.go
@@ -0,0 +1,35 @@
+package app
+
+import (
+	"fmt"
+	"os"
+
+	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/cat/fortify/internal/system"
+	"git.ophivana.moe/cat/fortify/internal/xcb"
+)
+
+const display = "DISPLAY"
+
+func (a *App) ShareX() {
+	a.setEnablement(state.EnableX)
+
+	// discovery X11 and grant user permission via the `ChangeHosts` command
+	if d, ok := os.LookupEnv(display); !ok {
+		if system.V.Verbose {
+			fmt.Println("X11: DISPLAY not set, skipping")
+		}
+	} else {
+		// add environment variable for new process
+		a.AppendEnv(display, d)
+
+		if system.V.Verbose {
+			fmt.Printf("X11: Adding XHost entry SI:localuser:%s to display '%s'\n", a.Username, d)
+		}
+		if err := xcb.ChangeHosts(xcb.HostModeInsert, xcb.FamilyServerInterpreted, "localuser\x00"+a.Username); err != nil {
+			state.Fatal(fmt.Sprintf("Error adding XHost entry to '%s':", d), err)
+		} else {
+			state.XcbActionComplete()
+		}
+	}
+}