system: move sd_booted implementation to os abstraction

This implements lazy loading of the systemd marker (they are not accessed in init and shim) and ensures consistent behaviour when running with a stub.

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

config.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 
 	"git.ophivana.moe/security/fortify/dbus"
-	"git.ophivana.moe/security/fortify/internal"
 	"git.ophivana.moe/security/fortify/internal/app"
 	"git.ophivana.moe/security/fortify/internal/fmsg"
 	"git.ophivana.moe/security/fortify/internal/system"
@@ -50,7 +49,7 @@ func init() {
 
 func init() {
 	methodHelpString := "Method of launching the child process, can be one of \"sudo\""
-	if internal.SdBootedV {
+	if os.SdBooted() {
 		methodHelpString += ", \"systemd\""
 	}
 

internal/app/app_nixos_test.go

@@ -586,3 +586,7 @@ func (s *stubNixOS) Paths() internal.Paths {
 		RunDirPath:  "/run/user/1971/fortify",
 	}
 }
+
+func (s *stubNixOS) SdBooted() bool {
+	return true
+}

internal/app/seal.go

@@ -108,7 +108,7 @@ func (a *app) Seal(config *Config) error {
 		}
 	case method[LaunchMethodMachineCtl]:
 		seal.launchOption = LaunchMethodMachineCtl
-		if !internal.SdBootedV {
+		if !a.os.SdBooted() {
 			return fmsg.WrapError(ErrSystemd,
 				"system has not been booted with systemd as init system")
 		}

internal/early.go

@@ -1,35 +0,0 @@
-package internal
-
-import (
-	"errors"
-	"io/fs"
-	"os"
-
-	"git.ophivana.moe/security/fortify/internal/fmsg"
-)
-
-const (
-	systemdCheckPath = "/run/systemd/system"
-)
-
-var SdBootedV = func() bool {
-	if v, err := SdBooted(); err != nil {
-		fmsg.Println("cannot read systemd marker:", err)
-		return false
-	} else {
-		return v
-	}
-}()
-
-// SdBooted implements https://www.freedesktop.org/software/systemd/man/sd_booted.html
-func SdBooted() (bool, error) {
-	_, err := os.Stat(systemdCheckPath)
-	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
-			err = nil
-		}
-		return false, err
-	}
-
-	return true, nil
-}

internal/system.go

@@ -1,6 +1,7 @@
 package internal
 
 import (
+	"errors"
 	"io/fs"
 	"os"
 	"os/exec"
@@ -37,6 +38,8 @@ type System interface {
 
 	// Paths returns a populated [Paths] struct.
 	Paths() Paths
+	// SdBooted implements https://www.freedesktop.org/software/systemd/man/sd_booted.html
+	SdBooted() bool
 }
 
 // Paths contains environment dependent paths used by fortify.
@@ -71,46 +74,21 @@ func CopyPaths(os System, v *Paths) {
 type Std struct {
 	paths     Paths
 	pathsOnce sync.Once
+
+	sdBooted     bool
+	sdBootedOnce sync.Once
 }
 
-func (s *Std) Geteuid() int {
-	return os.Geteuid()
-}
-
-func (s *Std) LookupEnv(key string) (string, bool) {
-	return os.LookupEnv(key)
-}
-
-func (s *Std) TempDir() string {
-	return os.TempDir()
-}
-
-func (s *Std) LookPath(file string) (string, error) {
-	return exec.LookPath(file)
-}
-
-func (s *Std) Executable() (string, error) {
-	return os.Executable()
-}
-
-func (s *Std) Lookup(username string) (*user.User, error) {
-	return user.Lookup(username)
-}
-
-func (s *Std) ReadDir(name string) ([]os.DirEntry, error) {
-	return os.ReadDir(name)
-}
-
-func (s *Std) Stat(name string) (fs.FileInfo, error) {
-	return os.Stat(name)
-}
-
-func (s *Std) Open(name string) (fs.File, error) {
-	return os.Open(name)
-}
-func (s *Std) Exit(code int) {
-	fmsg.Exit(code)
-}
+func (s *Std) Geteuid() int                               { return os.Geteuid() }
+func (s *Std) LookupEnv(key string) (string, bool)        { return os.LookupEnv(key) }
+func (s *Std) TempDir() string                            { return os.TempDir() }
+func (s *Std) LookPath(file string) (string, error)       { return exec.LookPath(file) }
+func (s *Std) Executable() (string, error)                { return os.Executable() }
+func (s *Std) Lookup(username string) (*user.User, error) { return user.Lookup(username) }
+func (s *Std) ReadDir(name string) ([]os.DirEntry, error) { return os.ReadDir(name) }
+func (s *Std) Stat(name string) (fs.FileInfo, error)      { return os.Stat(name) }
+func (s *Std) Open(name string) (fs.File, error)          { return os.Open(name) }
+func (s *Std) Exit(code int)                              { fmsg.Exit(code) }
 
 const xdgRuntimeDir = "XDG_RUNTIME_DIR"
 
@@ -118,3 +96,31 @@ func (s *Std) Paths() Paths {
 	s.pathsOnce.Do(func() { CopyPaths(s, &s.paths) })
 	return s.paths
 }
+
+func (s *Std) SdBooted() bool {
+	s.sdBootedOnce.Do(func() { s.sdBooted = copySdBooted() })
+	return s.sdBooted
+}
+
+const systemdCheckPath = "/run/systemd/system"
+
+func copySdBooted() bool {
+	if v, err := sdBooted(); err != nil {
+		fmsg.Println("cannot read systemd marker:", err)
+		return false
+	} else {
+		return v
+	}
+}
+
+func sdBooted() (bool, error) {
+	_, err := os.Stat(systemdCheckPath)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			err = nil
+		}
+		return false, err
+	}
+
+	return true, nil
+}

main.go

@@ -30,7 +30,7 @@ func main() {
 	flag.Parse()
 	fmsg.SetVerbose(flagVerbose)
 
-	if internal.SdBootedV {
+	if os.SdBooted() {
 		fmsg.VPrintln("system booted with systemd as init system")
 	}