system/wayland: sync file at caller specified address

Storing this in sys is incredibly ugly: sys should be stateless and Ops must keep track of their state.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/app_pd_test.go

@@ -1,6 +1,8 @@
 package app_test
 
 import (
+	"os"
+
 	"git.gensokyo.uk/security/fortify/acl"
 	"git.gensokyo.uk/security/fortify/dbus"
 	"git.gensokyo.uk/security/fortify/fst"
@@ -217,7 +219,7 @@ var testCasesPd = []sealTestCase{
 			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).
 			Ensure("/tmp/fortify.1971/wayland", 0711).
-			Wayland("/tmp/fortify.1971/wayland/ebf083d1b175911782d413369b64ce7c", "/run/user/1971/wayland-0", "org.chromium.Chromium", "ebf083d1b175911782d413369b64ce7c").
+			Wayland(new(*os.File), "/tmp/fortify.1971/wayland/ebf083d1b175911782d413369b64ce7c", "/run/user/1971/wayland-0", "org.chromium.Chromium", "ebf083d1b175911782d413369b64ce7c").
 			Link("/run/user/1971/pulse/native", "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/pulse").
 			CopyFile(new([]byte), "/home/ophestra/xdg/config/pulse/cookie", 256, 256).
 			MustProxyDBus("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", &dbus.Config{

internal/app/share.go

@@ -163,7 +163,7 @@ func (seal *appSeal) setupShares(bus [2]*dbus.Config, os linux.System) error {
 				// use instance ID in case app id is not set
 				appID = "uk.gensokyo.fortify." + seal.id
 			}
-			seal.sys.Wayland(outerPath, socketPath, appID, seal.id)
+			seal.sys.Wayland(&seal.sys.sp, outerPath, socketPath, appID, seal.id)
 			seal.sys.bwrap.Bind(outerPath, innerPath)
 		} else { // bind mount wayland socket (insecure)
 			fmsg.Verbose("direct wayland access, PROCEED WITH CAUTION")

internal/app/start.go

@@ -58,7 +58,7 @@ func (a *app) Run(ctx context.Context, rs *RunState) error {
 	if startTime, err := a.shim.Start(
 		a.seal.sys.user.as,
 		a.seal.sys.user.supp,
-		a.seal.sys.Sync(),
+		a.seal.sys.sp,
 	); err != nil {
 		return err
 	} else {

internal/app/system.go

@@ -1,6 +1,8 @@
 package app
 
 import (
+	"os"
+
 	"git.gensokyo.uk/security/fortify/helper/bwrap"
 	"git.gensokyo.uk/security/fortify/internal/system"
 )
@@ -8,6 +10,8 @@ import (
 // appSealSys encapsulates app seal behaviour with OS interactions
 type appSealSys struct {
 	bwrap *bwrap.Config
+	// bwrap sync fd
+	sp *os.File
 	// paths to override by mounting tmpfs over them
 	override []string
 

internal/system/op.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"log"
-	"os"
 	"sync"
 
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
@@ -60,8 +59,6 @@ type I struct {
 	uid int
 	ops []Op
 	ctx context.Context
-	// sync fd passed to bwrap
-	sp *os.File
 
 	// whether sys has been reverted
 	state bool
@@ -73,10 +70,6 @@ func (sys *I) UID() int {
 	return sys.uid
 }
 
-func (sys *I) Sync() *os.File {
-	return sys.sp
-}
-
 func (sys *I) Equal(v *I) bool {
 	if v == nil || sys.uid != v.uid || len(sys.ops) != len(v.ops) {
 		return false

internal/system/wayland.go

@@ -11,79 +11,80 @@ import (
 )
 
 // Wayland sets up a wayland socket with a security context attached.
-func (sys *I) Wayland(dst, src, appID, instanceID string) *I {
+func (sys *I) Wayland(syncFd **os.File, dst, src, appID, instanceID string) *I {
 	sys.lock.Lock()
 	defer sys.lock.Unlock()
 
-	sys.ops = append(sys.ops, Wayland{[2]string{dst, src}, new(wl.Conn), appID, instanceID})
+	sys.ops = append(sys.ops, &Wayland{syncFd, dst, src, appID, instanceID, wl.Conn{}})
 
 	return sys
 }
 
 type Wayland struct {
-	pair [2]string
-	conn *wl.Conn
-
+	sync              **os.File
+	dst, src          string
 	appID, instanceID string
+
+	conn wl.Conn
 }
 
-func (w Wayland) Type() Enablement {
-	return Process
+func (w *Wayland) Type() Enablement { return Process }
+
+func (w *Wayland) apply(sys *I) error {
+	if w.sync == nil {
+		// this is a misuse of the API; do not return an error message
+		return errors.New("invalid sync")
 	}
 
-func (w Wayland) apply(sys *I) error {
 	// the Wayland op is not repeatable
-	if sys.sp != nil {
+	if *w.sync != nil {
+		// this is a misuse of the API; do not return an error message
 		return errors.New("attempted to attach multiple wayland sockets")
 	}
 
-	if err := w.conn.Attach(w.pair[1]); err != nil {
+	if err := w.conn.Attach(w.src); err != nil {
 		// make console output less nasty
 		if errors.Is(err, os.ErrNotExist) {
 			err = os.ErrNotExist
 		}
 		return fmsg.WrapErrorSuffix(err,
-			fmt.Sprintf("cannot attach to wayland on %q:", w.pair[1]))
+			fmt.Sprintf("cannot attach to wayland on %q:", w.src))
 	} else {
-		fmsg.Verbosef("wayland attached on %q", w.pair[1])
+		fmsg.Verbosef("wayland attached on %q", w.src)
 	}
 
-	if sp, err := w.conn.Bind(w.pair[0], w.appID, w.instanceID); err != nil {
+	if sp, err := w.conn.Bind(w.dst, w.appID, w.instanceID); err != nil {
 		return fmsg.WrapErrorSuffix(err,
-			fmt.Sprintf("cannot bind to socket on %q:", w.pair[0]))
+			fmt.Sprintf("cannot bind to socket on %q:", w.dst))
 	} else {
-		sys.sp = sp
-		fmsg.Verbosef("wayland listening on %q", w.pair[0])
-		return fmsg.WrapErrorSuffix(errors.Join(os.Chmod(w.pair[0], 0), acl.UpdatePerm(w.pair[0], sys.uid, acl.Read, acl.Write, acl.Execute)),
-			fmt.Sprintf("cannot chmod socket on %q:", w.pair[0]))
+		*w.sync = sp
+		fmsg.Verbosef("wayland listening on %q", w.dst)
+		return fmsg.WrapErrorSuffix(errors.Join(os.Chmod(w.dst, 0), acl.UpdatePerm(w.dst, sys.uid, acl.Read, acl.Write, acl.Execute)),
+			fmt.Sprintf("cannot chmod socket on %q:", w.dst))
 	}
 }
 
-func (w Wayland) revert(_ *I, ec *Criteria) error {
+func (w *Wayland) revert(_ *I, ec *Criteria) error {
 	if ec.hasType(w) {
-		fmsg.Verbosef("removing wayland socket on %q", w.pair[0])
-		if err := os.Remove(w.pair[0]); err != nil && !errors.Is(err, os.ErrNotExist) {
+		fmsg.Verbosef("removing wayland socket on %q", w.dst)
+		if err := os.Remove(w.dst); err != nil && !errors.Is(err, os.ErrNotExist) {
 			return err
 		}
 
-		fmsg.Verbosef("detaching from wayland on %q", w.pair[1])
+		fmsg.Verbosef("detaching from wayland on %q", w.src)
 		return fmsg.WrapErrorSuffix(w.conn.Close(),
-			fmt.Sprintf("cannot detach from wayland on %q:", w.pair[1]))
+			fmt.Sprintf("cannot detach from wayland on %q:", w.src))
 	} else {
-		fmsg.Verbosef("skipping wayland cleanup on %q", w.pair[0])
+		fmsg.Verbosef("skipping wayland cleanup on %q", w.dst)
 		return nil
 	}
 }
 
-func (w Wayland) Is(o Op) bool {
-	w0, ok := o.(Wayland)
-	return ok && w.pair == w0.pair
+func (w *Wayland) Is(o Op) bool {
+	w0, ok := o.(*Wayland)
+	return ok && w.dst == w0.dst && w.src == w0.src &&
+		w.appID == w0.appID && w.instanceID == w0.instanceID
 }
 
-func (w Wayland) Path() string {
-	return w.pair[0]
-}
-
-func (w Wayland) String() string {
-	return fmt.Sprintf("wayland socket at %q", w.pair[0])
-}
+func (w *Wayland) Path() string   { return w.dst }
+func (w *Wayland) String() string { return fmt.Sprintf("wayland socket at %q", w.dst) }