.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.Fshim=/usr/libexec/fortify/fshim'
+          -X main.Fmain=/usr/bin/fortify'
           -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.Fshim=/usr/libexec/fortify/fshim'
+          -X main.Fmain=/usr/bin/fortify'
           -o bin/ ./... &&
           (cd bin && sha512sum --tag -b * > sha512sums)

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.Suspend()
+	fmsg.Withhold()
 
 	// close setup pipe as setup is now complete
 	if err := setup.Close(); err != nil {

cmd/fshim/ipc/shim/shim.go

@@ -5,7 +5,6 @@ import (
 	"net"
 	"os"
 	"os/exec"
-	"strings"
 	"sync"
 	"sync/atomic"
 	"syscall"
@@ -13,7 +12,6 @@ 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"
 )
 
@@ -26,26 +24,24 @@ type Shim struct {
 	cmd *exec.Cmd
 	// uid of shim target user
 	uid uint32
-	// string representation of application id
-	aid string
-	// string representation of supplementary group ids
-	supp []string
+	// whether to check shim pid
+	checkPid bool
+	// user switcher executable path
+	executable string
 	// path to setup socket
 	socket string
 	// shim setup abort reason and completion
 	abort     chan error
 	abortErr  atomic.Pointer[error]
 	abortOnce sync.Once
-	// 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(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 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 (s *Shim) String() string {
@@ -72,11 +68,9 @@ func (s *Shim) AbortWait(err error) {
 	<-s.abort
 }
 
-func (s *Shim) WaitFallback() chan error {
-	return s.killFallback
-}
+type CommandBuilder func(shimEnv string) (args []string)
 
-func (s *Shim) Start() (*time.Time, error) {
+func (s *Shim) Start(f CommandBuilder) (*time.Time, error) {
 	var (
 		cf     chan *net.UnixConn
 		accept func()
@@ -93,37 +87,22 @@ func (s *Shim) Start() (*time.Time, error) {
 	}
 
 	// start user switcher process and save time
-	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 = exec.Command(s.executable, f(shim0.Env+"="+s.socket)...)
+	s.cmd.Env = []string{}
 	s.cmd.Stdin, s.cmd.Stdout, s.cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
 	s.cmd.Dir = "/"
-	fmsg.VPrintln("starting shim via fsu:", s.cmd)
-	fmsg.Suspend() // withhold messages to stderr
+	fmsg.VPrintln("starting shim via user switcher:", s.cmd)
+	fmsg.Withhold() // withhold messages to stderr
 	if err := s.cmd.Start(); err != nil {
 		return nil, fmsg.WrapErrorSuffix(err,
-			"cannot start fsu:")
+			"cannot start user switcher:")
 	}
 	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 {
-			s.killFallback <- err
+			fmsg.Println("cannot terminate shim on faulted setup:", err)
 		}
 	}
 	defer func() { killShim() }()
@@ -153,7 +132,7 @@ func (s *Shim) Start() (*time.Time, error) {
 		err = errors.New("compromised fortify build")
 		s.Abort(err)
 		return &startTime, err
-	} else if cred.Pid != int32(s.cmd.Process.Pid) {
+	} else if s.checkPid && cred.Pid != int32(s.cmd.Process.Pid) {
 		fmsg.Printf("process %d tried to connect to shim setup socket, expecting shim %d",
 			cred.Pid, s.cmd.Process.Pid)
 		err = errors.New("compromised target user")

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(err.Error())
+		fmsg.Fatal("cannot dial setup socket:", err)
 		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.Fatalf("cannot decode shim payload: %v", err)
+		fmsg.Fatal("cannot decode shim payload:", 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.Fatalf("cannot receive wayland fd: %v", err)
+			fmsg.Fatal("cannot receive wayland fd:", err)
 		} else {
 			wfd = fd
 		}
@@ -102,10 +102,7 @@ func main() {
 	} else {
 		// no argv, look up shell instead
 		var ok bool
-		if payload.Bwrap.SetEnv == nil {
-			fmsg.Fatal("no command was specified and environment is unset")
-		}
-		if ic.Argv0, ok = payload.Bwrap.SetEnv["SHELL"]; !ok {
+		if ic.Argv0, ok = os.LookupEnv("SHELL"); !ok {
 			fmsg.Fatal("no command was specified and $SHELL was unset")
 		}
 
@@ -128,7 +125,7 @@ func main() {
 
 	// share config pipe
 	if r, w, err := os.Pipe(); err != nil {
-		fmsg.Fatalf("cannot pipe: %v", err)
+		fmsg.Fatal("cannot pipe:", err)
 	} else {
 		conf.SetEnv[init0.Env] = strconv.Itoa(3 + len(extraFiles))
 		extraFiles = append(extraFiles, r)
@@ -137,7 +134,7 @@ func main() {
 		go func() {
 			// stream config to pipe
 			if err = gob.NewEncoder(w).Encode(&ic); err != nil {
-				fmsg.Fatalf("cannot transmit init config: %v", err)
+				fmsg.Fatal("cannot transmit init config:", err)
 			}
 		}()
 	}
@@ -145,7 +142,7 @@ 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.Fatalf("malformed sandbox config: %v", err)
+		fmsg.Fatal("malformed sandbox config:", err)
 	} else {
 		cmd := b.Unwrap()
 		cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
@@ -157,7 +154,7 @@ func main() {
 
 		// run and pass through exit code
 		if err = b.Start(); err != nil {
-			fmsg.Fatalf("cannot start target process: %v", err)
+			fmsg.Fatal("cannot start target process:", err)
 		} else if err = b.Wait(); err != nil {
 			fmsg.VPrintln("wait:", err)
 		}

cmd/fsu/main.go

@@ -1,12 +1,10 @@
 package main
 
 import (
-	"bytes"
-	"fmt"
+	"bufio"
 	"log"
 	"os"
 	"path"
-	"slices"
 	"strconv"
 	"strings"
 	"syscall"
@@ -17,15 +15,11 @@ const (
 	fsuConfFile = "/etc/fsurc"
 	envShim     = "FORTIFY_SHIM"
 	envAID      = "FORTIFY_APP_ID"
-	envGroups   = "FORTIFY_GROUPS"
 
 	PR_SET_NO_NEW_PRIVS = 0x26
 )
 
-var (
-	Fmain = compPoison
-	Fshim = compPoison
-)
+var Fmain = compPoison
 
 func main() {
 	log.SetFlags(0)
@@ -41,17 +35,12 @@ func main() {
 		log.Fatal("this program must not be started by root")
 	}
 
-	var fmain, fshim string
+	var fmain 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 {
@@ -74,76 +63,87 @@ 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 {
-		// fortify requests target uid
-		// print resolved uid and exit
-		fmt.Print(uid)
-		os.Exit(0)
+		log.Fatal("FORTIFY_SHIM not set")
 	} else if !path.IsAbs(s) {
 		log.Fatal("FORTIFY_SHIM is not absolute")
 	} else {
 		shimSetupPath = s
 	}
 
-	// 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 {
-			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
+	// allowed aid range 0 to 9999
+	if as, ok := os.LookupEnv(envAID); !ok {
+		log.Fatal("FORTIFY_APP_ID not set")
+	} else if aid, err := strconv.Atoi(as); err != nil || aid < 0 || aid > 9999 {
+		log.Fatal("invalid aid")
 	} else {
-		suppGroups = []int{uid}
+		uid += aid
 	}
 
-	// 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 _, _, 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 {
+	if err := syscall.Exec(fmain, []string{"fortify", "shim"}, []string{envShim + "=" + shimSetupPath}); err != nil {
 		log.Fatalf("cannot start shim: %v", err)
 	}
 
 	panic("unreachable")
 }
 
+func parseConfig(p string, puid int) (fid int, ok bool) {
+	// refuse to run if fsurc is not protected correctly
+	if s, err := os.Stat(p); err != nil {
+		log.Fatal(err)
+	} else if s.Mode().Perm() != 0400 {
+		log.Fatal("bad fsurc perm")
+	} else if st := s.Sys().(*syscall.Stat_t); st.Uid != 0 || st.Gid != 0 {
+		log.Fatal("fsurc must be owned by uid 0")
+	}
+
+	if r, err := os.Open(p); err != nil {
+		log.Fatal(err)
+		return -1, false
+	} else {
+		s := bufio.NewScanner(r)
+		var line int
+		for s.Scan() {
+			line++
+
+			// <puid> <fid>
+			lf := strings.SplitN(s.Text(), " ", 2)
+			if len(lf) != 2 {
+				log.Fatalf("invalid entry on line %d", line)
+			}
+
+			var puid0 int
+			if puid0, err = strconv.Atoi(lf[0]); err != nil || puid0 < 1 {
+				log.Fatalf("invalid parent uid on line %d", line)
+			}
+
+			ok = puid0 == puid
+			if ok {
+				// allowed fid range 0 to 99
+				if fid, err = strconv.Atoi(lf[1]); err != nil || fid < 0 || fid > 99 {
+					log.Fatalf("invalid fortify uid on line %d", line)
+				}
+				return
+			}
+		}
+		if err = s.Err(); err != nil {
+			log.Fatalf("cannot read fsurc: %v", err)
+		}
+		return -1, false
+	}
+}
+
 func checkPath(p string) (string, bool) {
 	return p, p != compPoison && p != "" && path.IsAbs(p)
 }

cmd/fsu/parse.go

@@ -1,77 +0,0 @@
-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

@@ -1,69 +0,0 @@
-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

@@ -1,64 +0,0 @@
-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)
-	}
-}

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.us + ")"
+		return "(sealed fortified app as uid " + a.seal.sys.user.Uid + ")"
 	}
 
 	return "(unsealed fortified app)"

internal/app/app_nixos_test.go

@@ -19,12 +19,9 @@ var testCasesNixos = []sealTestCase{
 	{
 		"nixos permissive defaults no enablements", new(stubNixOS),
 		&app.Config{
+			User:    "chronos",
 			Command: make([]string, 0),
-			Confinement: app.ConfinementConfig{
-				AppID:    0,
-				Username: "chronos",
-				Outer:    "/home/chronos",
-			},
+			Method:  "sudo",
 		},
 		app.ID{
 			0x4a, 0x45, 0x0b, 0x65,
@@ -32,11 +29,11 @@ var testCasesNixos = []sealTestCase{
 			0xbd, 0x01, 0x78, 0x0e,
 			0xb9, 0xa6, 0x07, 0xac,
 		},
-		system.New(1000000).
-			Ensure("/tmp/fortify.1971", 0711).
-			Ephemeral(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac", 0711).
+		system.New(150).
+			Ensure("/tmp/fortify.1971", 0701).
+			Ephemeral(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac", 0701).
 			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
-			Ensure("/tmp/fortify.1971/tmpdir/0", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/0", acl.Read, acl.Write, acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/150", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/150", acl.Read, acl.Write, acl.Execute).
 			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
 			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
 			Ephemeral(system.Process, "/run/user/1971/fortify/4a450b6596d7bc15bd01780eb9a607ac", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/4a450b6596d7bc15bd01780eb9a607ac", acl.Execute).
@@ -46,7 +43,6 @@ 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",
@@ -186,11 +182,10 @@ 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/0", "/tmp", false, true).
+			Bind("/tmp/fortify.1971/tmpdir/150", "/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),
@@ -199,12 +194,9 @@ 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",
@@ -238,6 +230,7 @@ var testCasesNixos = []sealTestCase{
 				},
 				Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
 			},
+			Method: "systemd",
 		},
 		app.ID{
 			0xeb, 0xf0, 0x83, 0xd1,
@@ -245,11 +238,11 @@ var testCasesNixos = []sealTestCase{
 			0x82, 0xd4, 0x13, 0x36,
 			0x9b, 0x64, 0xce, 0x7c,
 		},
-		system.New(1000009).
-			Ensure("/tmp/fortify.1971", 0711).
-			Ephemeral(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c", 0711).
+		system.New(150).
+			Ensure("/tmp/fortify.1971", 0701).
+			Ephemeral(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c", 0701).
 			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
-			Ensure("/tmp/fortify.1971/tmpdir/9", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/9", acl.Read, acl.Write, acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/150", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/150", acl.Read, acl.Write, acl.Execute).
 			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
 			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
 			Ephemeral(system.Process, "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c", acl.Execute).
@@ -294,7 +287,6 @@ 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",
@@ -442,11 +434,10 @@ 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/9", "/tmp", false, true).
+			Bind("/tmp/fortify.1971/tmpdir/150", "/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").
@@ -513,12 +504,23 @@ func (s *stubNixOS) Executable() (string, error) {
 	return "/home/ophestra/.nix-profile/bin/fortify", nil
 }
 
-func (s *stubNixOS) LookupGroup(name string) (*user.Group, error) {
-	switch name {
-	case "video":
-		return &user.Group{Gid: "26", Name: "video"}, nil
+func (s *stubNixOS) Lookup(username string) (*user.User, error) {
+	if s.usernameErr != nil {
+		if err, ok := s.usernameErr[username]; ok {
+			return nil, err
+		}
+	}
+
+	switch username {
+	case "chronos":
+		return &user.User{
+			Uid:      "150",
+			Gid:      "101",
+			Username: "chronos",
+			HomeDir:  "/home/chronos",
+		}, nil
 	default:
-		return nil, user.UnknownGroupError(name)
+		return nil, user.UnknownUserError(username)
 	}
 }
 
@@ -584,6 +586,10 @@ 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",
@@ -592,10 +598,6 @@ 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

@@ -15,8 +15,12 @@ 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"`
@@ -24,16 +28,6 @@ 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"`
 
@@ -175,7 +169,8 @@ func (s *SandboxConfig) Bwrap(os linux.System) (*bwrap.Config, error) {
 // Template returns a fully populated instance of Config.
 func Template() *Config {
 	return &Config{
-		ID: "org.chromium.Chromium",
+		ID:   "org.chromium.Chromium",
+		User: "chronos",
 		Command: []string{
 			"chromium",
 			"--ignore-gpu-blocklist",
@@ -183,12 +178,8 @@ 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,

internal/app/launch.machinectl.go

@@ -0,0 +1,57 @@
+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

@@ -0,0 +1,30 @@
+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"
 
@@ -15,10 +15,24 @@ 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("invalid aid")
-	ErrHome   = errors.New("invalid home directory")
+	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")
 )
 
 // appSeal seals the application with child-related information
@@ -37,11 +51,15 @@ 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
 
@@ -80,6 +98,34 @@ 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)
 
@@ -92,48 +138,16 @@ 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)
 
-	// 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 {
-		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:")
+	// 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)
 		} else {
-			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
-			}
+			// unreachable
+			panic(err)
 		}
+	} else {
+		seal.sys.user = u
 	}
 
 	// map sandbox config to bwrap
@@ -216,10 +230,15 @@ 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.as)
+	seal.store = state.NewSimple(seal.RunDirPath, seal.sys.user.Uid)
 
-	// initialise system interface with full uid
-	seal.sys.I = system.New(seal.sys.user.uid)
+	// 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)
+	}
 
 	// pass through enablements
 	seal.et = config.Confinement.Enablements
@@ -230,8 +249,11 @@ func (a *app) Seal(config *Config) error {
 	}
 
 	// verbose log seal information
-	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)
+	fmsg.VPrintln("created application seal as user",
+		seal.sys.user.Username, "("+seal.sys.user.Uid+"),",
+		"method:", config.Method+",",
+		"launcher:", seal.toolPath+",",
+		"command:", 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.us)
+			seal.sys.ChangeHosts(seal.sys.user.Username)
 			seal.sys.bwrap.SetEnv[display] = d
 			seal.sys.bwrap.Bind("/tmp/.X11-unix", "/tmp/.X11-unix")
 		}

internal/app/share.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, 0711)
+	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, 0711)
+	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")
@@ -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.as)
+	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)
@@ -49,21 +49,15 @@ 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
+	if seal.sys.user.Username != "" {
+		username = seal.sys.user.Username
+		seal.sys.bwrap.SetEnv["USER"] = seal.sys.user.Username
 	}
 	homeDir := "/var/empty"
-	if seal.sys.user.home != "" {
-		homeDir = seal.sys.user.home
+	if seal.sys.user.HomeDir != "" {
+		homeDir = seal.sys.user.HomeDir
+		seal.sys.bwrap.SetEnv["HOME"] = seal.sys.user.HomeDir
 	}
-
-	// 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

@@ -41,13 +41,19 @@ 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(
-		uint32(a.seal.sys.UID()),
-		a.seal.sys.user.as,
-		a.seal.sys.user.supp,
-		path.Join(a.seal.share, "shim"),
-		a.seal.wl,
+	a.shim = shim.New(a.seal.toolPath, uint32(a.seal.sys.UID()), path.Join(a.seal.share, "shim"), a.seal.wl,
 		&shim0.Payload{
 			Argv:  a.seal.command,
 			Exec:  shimExec,
@@ -56,6 +62,9 @@ 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
@@ -64,7 +73,7 @@ func (a *app) Start() error {
 	}
 	a.seal.sys.needRevert = true
 
-	if startTime, err := a.shim.Start(); err != nil {
+	if startTime, err := a.shim.Start(commandBuilder); err != nil {
 		return err
 	} else {
 		// shim start and setup success, create process state
@@ -72,6 +81,7 @@ 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,
 		}
@@ -156,31 +166,20 @@ 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
-		case err := <-wait:
-			if err != nil {
-				var exitError *exec.ExitError
-				if !errors.As(err, &exitError) {
-					// should be unreachable
-					a.waitErr = err
-				}
-
-				// store non-zero return code
-				r = exitError.ExitCode()
-			} else {
-				r = cmd.ProcessState.ExitCode()
+		if err := cmd.Wait(); err != nil {
+			var exitError *exec.ExitError
+			if !errors.As(err, &exitError) {
+				// should be unreachable
+				a.waitErr = err
 			}
-			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
-			fmsg.Printf("cannot terminate shim on faulted setup: %v", err)
+			// store non-zero return code
+			r = exitError.ExitCode()
+		} else {
+			r = cmd.ProcessState.ExitCode()
 		}
+		fmsg.VPrintf("process %d exited with exit code %d", cmd.Process.Pid, r)
 	}
 
 	// child process exited, resume output
@@ -251,16 +250,9 @@ 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)
-				}
+			a.shim.AbortWait(errors.New("shim exited"))
+			if err := a.seal.sys.Revert(ec); err != nil {
+				return err.(RevertCompoundError)
 			}
 
 			return nil

internal/app/system.go

@@ -1,6 +1,8 @@
 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"
@@ -16,7 +18,7 @@ type appSealSys struct {
 	// default formatted XDG_RUNTIME_DIR of User
 	runtime string
 	// target user sealed from config
-	user appUser
+	user *user.User
 
 	// mapped uid and gid in user namespace
 	mappedID int
@@ -30,28 +32,6 @@ 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

@@ -33,17 +33,16 @@ 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)
 		}
@@ -57,10 +56,9 @@ func Exit(code int) {
 	os.Exit(code)
 }
 
-func Suspend() {
+func Withhold() {
 	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)
-	// LookupGroup provides [user.LookupGroup].
-	LookupGroup(name string) (*user.Group, error)
+	// Lookup provides [user.Lookup].
+	Lookup(username string) (*user.User, error)
 	// ReadDir provides [os.ReadDir].
 	ReadDir(name string) ([]fs.DirEntry, error)
 	// Stat provides [os.Stat].
@@ -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

@@ -7,7 +7,6 @@ import (
 	"os"
 	"os/exec"
 	"os/user"
-	"strconv"
 	"sync"
 
 	"git.ophivana.moe/security/fortify/internal"
@@ -22,75 +21,41 @@ type Std struct {
 	sdBooted     bool
 	sdBootedOnce sync.Once
 
-	uidOnce sync.Once
-	uidCopy map[int]struct {
-		uid int
-		err error
-	}
-	uidMu sync.RWMutex
+	fshim     string
+	fshimOnce 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) 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) }
-func (s *Std) Exit(code int)                                { fmsg.Exit(code) }
-func (s *Std) Stdout() io.Writer                            { return os.Stdout }
+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) 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

@@ -4,6 +4,7 @@ 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, "\tPID\tApp\tUptime\tEnablements\tCommand")
+					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tUptime\tEnablements\tMethod\tCommand")
 				} else {
 					// argv is emitted in body when verbose
-					_, _ = fmt.Fprintln(*w, "\tPID\tApp\tArgv")
+					_, _ = fmt.Fprintln(*w, "\tUID\tPID\tArgv")
 				}
 			}
 
@@ -96,13 +96,13 @@ func (s *simpleStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time
 				}
 
 				if !fmsg.Verbose() {
-					_, _ = 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(), ", "),
+					_, _ = 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,
 						state.Command)
 				} else {
 					// emit argv instead when verbose
-					_, _ = fmt.Fprintf(*w, "\t%d\t%s\t%s\n",
-						state.PID, s.path[len(s.path)-1], state.Argv)
+					_, _ = fmt.Fprintf(*w, "\t%s\t%d\t%s\n",
+						s.path[len(s.path)-1], state.PID, state.Argv)
 				}
 			}
 

internal/state/state.go

@@ -33,6 +33,8 @@ 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

@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
-	"strings"
 	"text/tabwriter"
 
 	"git.ophivana.moe/security/fortify/dbus"
@@ -30,20 +29,6 @@ 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)
@@ -150,11 +135,10 @@ 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")
@@ -163,34 +147,29 @@ 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.IntVar(&aid, "a", 0, "Fortify application ID")
-		set.Var(&groups, "g", "Groups inherited by the app process")
-		set.StringVar(&homeDir, "d", "/var/empty", "Application home directory")
-		set.StringVar(&userName, "u", "chronos", "Passwd name within sandbox")
+		set.StringVar(&userName, "u", "chronos", "Passwd name of user to run as")
 		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")
-		}
-
-		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

@@ -11,12 +11,8 @@ let
     mkOption
     mkEnableOption
     mkIf
-    mkDefault
     mapAttrs
     mapAttrsToList
-    mergeAttrsList
-    imap1
-    foldr
     foldlAttrs
     optional
     optionals
@@ -30,24 +26,8 @@ in
     environment.fortify = {
       enable = mkEnableOption "fortify";
 
-      package = mkOption {
-        type = types.package;
-        default = pkgs.callPackage ./package.nix { };
-        description = "Package providing fortify.";
-      };
-
-      users = mkOption {
-        type =
-          let
-            inherit (types) attrsOf ints;
-          in
-          attrsOf (ints.between 0 99);
-        description = ''
-          Users allowed to spawn fortify apps, as well as their fortify ID value.
-        '';
-      };
-
-      apps = mkOption {
+      target = mkOption {
+        default = { };
         type =
           let
             inherit (types)
@@ -63,23 +43,8 @@ in
               functionTo
               ;
           in
-          listOf (submodule {
+          attrsOf (submodule {
             options = {
-              name = mkOption {
-                type = str;
-                description = ''
-                  App name, typically command.
-                '';
-              };
-
-              id = mkOption {
-                type = nullOr str;
-                default = null;
-                description = ''
-                  Freedesktop application ID.
-                '';
-              };
-
               packages = mkOption {
                 type = listOf package;
                 default = [ ];
@@ -88,153 +53,200 @@ in
                 '';
               };
 
+              launchers = mkOption {
+                type = attrsOf (submodule {
+                  options = {
+                    id = mkOption {
+                      type = nullOr str;
+                      default = null;
+                      description = ''
+                        Freedesktop application ID.
+                      '';
+                    };
+
+                    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 wrapper name.
+                        Has no effect when script is set.
+                      '';
+                    };
+
+                    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.
+                    '';
+
+                    mapRealUid = 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.";
               };
-
-              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 wrapper 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 ''
-                Whether to allow nix daemon connections from within sandbox.
-              '';
-
-              userns = mkEnableOption ''
-                Whether to allow userns within sandbox.
-              '';
-
-              mapRealUid = 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 = [ ];
-        description = "Applications managed by fortify.";
+      };
+
+      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 {
@@ -247,50 +259,25 @@ in
   };
 
   config = mkIf cfg.enable {
-    security.wrappers.fsu = {
-      source = "${cfg.package}/libexec/fsu";
-      setuid = true;
-      owner = "root";
-      setgid = true;
-      group = "root";
-    };
+    environment.persistence.${cfg.stateDir}.users = mapAttrs (_: target: target.persistence) cfg.target;
 
-    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 "generate-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
-        privPackages = mapAttrs (username: fid: {
-          home.packages =
-            let
-              # aid 0 is reserved
-              wrappers = imap1 (
-                aid: app:
+    home-manager.users =
+      mapAttrs (_: target: target.extraConfig // { home.packages = target.packages; }) cfg.target
+      // {
+        ${cfg.user}.home.packages =
+          let
+            wrap =
+              user: launchers:
+              mapAttrsToList (
+                name: launcher:
+                with launcher.capability;
                 let
                   extendDBusDefault = id: ext: {
                     filter = true;
 
                     talk = [ "org.freedesktop.Notifications" ] ++ ext.talk;
                     own =
-                      (optionals (app.id != null) [
+                      (optionals (launcher.id != null) [
                         "${id}.*"
                         "org.mpris.MediaPlayer2.${id}.*"
                       ])
@@ -309,41 +296,37 @@ in
                     in
                     {
                       session_bus =
-                        if app.dbus.session != null then
-                          (app.dbus.session (extendDBusDefault app.id))
+                        if launcher.dbus.session != null then
+                          (launcher.dbus.session (extendDBusDefault launcher.id))
                         else
-                          (extendDBusDefault app.id default);
-                      system_bus = app.dbus.system;
+                          (extendDBusDefault launcher.id default);
+                      system_bus = launcher.dbus.system;
                     };
-                  command = if app.command == null then app.name else app.command;
-                  script = if app.script == null then ("exec " + command + " $@") else app.script;
+                  command = if launcher.command == null then name else launcher.command;
+                  script = if launcher.script == null then ("exec " + command + " $@") else launcher.script;
                   enablements =
-                    with app.capability;
                     (if wayland then 1 else 0)
                     + (if x11 then 2 else 0)
                     + (if dbus then 4 else 0)
                     + (if pulse then 8 else 0);
                   conf = {
-                    inherit (app) id;
+                    inherit (launcher) id method;
+                    inherit user;
                     command = [
-                      (pkgs.writeScript "${app.name}-start" ''
+                      (pkgs.writeScript "${name}-start" ''
                         #!${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 (app)
+                        inherit (launcher)
                           userns
                           net
                           dev
                           env
                           ;
-                        map_real_uid = app.mapRealUid;
+                        map_real_uid = launcher.mapRealUid;
                         filesystem =
                           [
                             { src = "/bin"; }
@@ -370,19 +353,24 @@ in
                               src = "/sys/devices";
                               require = false;
                             }
+                            {
+                              src = "/home/${user}";
+                              write = true;
+                              require = true;
+                            }
                           ]
-                          ++ optionals app.nix [
+                          ++ optionals launcher.nix [
                             { src = "/nix/var"; }
                             { src = "/var/db/nix-channels"; }
                           ]
-                          ++ optionals (if app.gpu != null then app.gpu else app.capability.wayland || app.capability.x11) [
+                          ++ optionals (if launcher.gpu != null then launcher.gpu else wayland || x11) [
                             { src = "/run/opengl-driver"; }
                             {
                               src = "/dev/dri";
                               dev = true;
                             }
                           ]
-                          ++ app.extraPaths;
+                          ++ launcher.extraPaths;
                         auto_etc = true;
                         override = [ "/var/run/nscd" ];
                       };
@@ -391,48 +379,58 @@ in
                     };
                   };
                 in
-                pkgs.writeShellScriptBin app.name ''
-                  exec fortify app ${pkgs.writeText "fortify-${app.name}.json" (builtins.toJSON conf)} $@
-                ''
-              ) cfg.apps;
-            in
-            foldr (
-              app: acc:
+                pkgs.writeShellScriptBin name (
+                  if launcher.method == "simple" then
+                    ''
+                      exec sudo -u ${user} -i ${command} $@
+                    ''
+                  else
+                    ''
+                      exec fortify app ${pkgs.writeText "fortify-${name}.json" (builtins.toJSON conf)} $@
+                    ''
+                )
+              ) launchers;
+          in
+          foldlAttrs (
+            acc: user: target:
+            acc
+            ++ (foldlAttrs (
+              shares: name: launcher:
               let
-                pkg = if app.share != null then app.share else pkgs.${app.name};
+                pkg = if launcher.share != null then launcher.share else pkgs.${name};
                 copy = source: "[ -d '${source}' ] && cp -Lrv '${source}' $out/share || true";
               in
-              optional (app.capability.wayland || app.capability.x11) (
-                pkgs.runCommand "${app.name}-share" { } ''
-                  mkdir -p $out/share
-                  ${copy "${pkg}/share/applications"}
-                  ${copy "${pkg}/share/icons"}
-                  ${copy "${pkg}/share/man"}
+              shares
+              ++
+                optional (launcher.method != "simple" && (launcher.capability.wayland || launcher.capability.x11))
+                  (
+                    pkgs.runCommand "${name}-share" { } ''
+                      mkdir -p $out/share
+                      ${copy "${pkg}/share/applications"}
+                      ${copy "${pkg}/share/icons"}
+                      ${copy "${pkg}/share/man"}
 
-                  substituteInPlace $out/share/applications/* \
-                    --replace-warn '${pkg}/bin/' "" \
-                    --replace-warn '${pkg}/libexec/' ""
-                ''
-              )
-              ++ acc
-            ) (wrappers ++ [ cfg.package ]) cfg.apps;
-        }) cfg.users;
-      in
-      {
-        useUserPackages = false; # prevent users.users entries from being added
-
-        users = foldlAttrs (
-          acc: _: fid:
-          mergeAttrsList (
-            # aid 0 is reserved
-            imap1 (aid: app: {
-              "u${toString fid}_a${toString aid}" = app.extraConfig // {
-                home.packages = app.packages;
-              };
-            }) cfg.apps
-          )
-          // acc
-        ) privPackages cfg.users;
+                      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);
+      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;
+          }
+        });
+      '';
   };
 }

package.nix

@@ -30,13 +30,12 @@ buildGoModule rec {
         "-w"
         "-X"
         "main.Fmain=${placeholder "out"}/bin/.fortify-wrapped"
-        "-X"
-        "main.Fshim=${placeholder "out"}/libexec/fshim"
       ]
       {
         Version = "v${version}";
         Fsu = "/run/wrappers/bin/fsu";
-        Finit = "${placeholder "out"}/libexec/finit";
+        Fshim = "${placeholder "out"}/bin/fshim";
+        Finit = "${placeholder "out"}/bin/finit";
       };
 
   buildInputs = [
@@ -54,7 +53,6 @@ buildGoModule rec {
       ]
     }
 
-    mkdir $out/libexec
-    (cd $out/bin && mv fsu fshim finit fuserdb ../libexec/)
+    mv $out/bin/fsu $out/bin/.fsu
   '';
 }