internal/wayland: check pathname size

This avoids passing a truncated pathname to the kernel.

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

internal/wayland/conn_test.go

@@ -0,0 +1,54 @@
+package wayland
+
+import (
+	"errors"
+	"os"
+	"reflect"
+	"syscall"
+	"testing"
+
+	"hakurei.app/container/check"
+)
+
+func TestSecurityContextClose(t *testing.T) {
+	t.Parallel()
+
+	if err := (*SecurityContext)(nil).Close(); !reflect.DeepEqual(err, os.ErrInvalid) {
+		t.Fatalf("Close: error = %v", err)
+	}
+
+	var ctx SecurityContext
+	if err := syscall.Pipe2(ctx.closeFds[0:], syscall.O_CLOEXEC); err != nil {
+		t.Fatalf("Pipe: error = %v", err)
+	}
+	t.Cleanup(func() { _ = syscall.Close(ctx.closeFds[0]); _ = syscall.Close(ctx.closeFds[1]) })
+
+	if err := ctx.Close(); err != nil {
+		t.Fatalf("Close: error = %v", err)
+	}
+
+	wantErr := errors.Join(syscall.EBADF, syscall.EBADF)
+	if err := ctx.Close(); !reflect.DeepEqual(err, wantErr) {
+		t.Fatalf("Close: error = %#v, want %#v", err, wantErr)
+	}
+}
+
+func TestNewEnsure(t *testing.T) {
+	existingDirPath := check.MustAbs(t.TempDir()).Append("dir")
+	if err := os.MkdirAll(existingDirPath.String(), 0700); err != nil {
+		t.Fatal(err)
+	}
+	nonexistent := check.MustAbs("/proc/nonexistent")
+
+	wantErr := &Error{RCreate, existingDirPath.String(), nonexistent.String(), &os.PathError{
+		Op:   "open",
+		Path: existingDirPath.String(),
+		Err:  syscall.EISDIR,
+	}}
+	if _, err := New(
+		nonexistent,
+		existingDirPath, "", "",
+	); !reflect.DeepEqual(err, wantErr) {
+		t.Fatalf("New: error = %#v, want %#v", err, wantErr)
+	}
+}

internal/wayland/wayland-client-helper.c

@@ -3,7 +3,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
-#include <sys/un.h>
 #include <unistd.h>
 
 #include "security-context-v1-protocol.h"

internal/wayland/wayland-client-helper.h

@@ -1,3 +1,6 @@
+#include <stdbool.h>
+#include <sys/un.h>
+
 typedef enum {
   HAKUREI_WAYLAND_SUCCESS,
   /* wl_display_connect_to_fd failed, errno */
@@ -29,3 +32,9 @@ hakurei_wayland_res hakurei_security_context_bind(
     const char *app_id,
     const char *instance_id,
     int close_fd);
+
+/* returns whether the specified size fits in the sun_path field of sockaddr_un */
+static inline bool hakurei_is_valid_size_sun_path(size_t sz) {
+  struct sockaddr_un sockaddr;
+  return sz <= sizeof(sockaddr.sun_path);
+};

internal/wayland/wayland.go

@@ -12,8 +12,8 @@ package wayland
 */
 import "C"
 import (
+	"errors"
 	"strings"
-	"syscall"
 )
 
 const (
@@ -134,8 +134,11 @@ func securityContextBind(
 	appID, instanceID string,
 	closeFd int,
 ) error {
-	if hasNull(appID) || hasNull(instanceID) {
-		return syscall.EINVAL
+	if hasNull(socketPath) || hasNull(appID) || hasNull(instanceID) {
+		return &Error{Cause: RBind, Path: socketPath, Errno: errors.New("argument contains NUL character")}
+	}
+	if !C.hakurei_is_valid_size_sun_path(C.size_t(len(socketPath))) {
+		return &Error{Cause: RBind, Path: socketPath, Errno: errors.New("socket pathname too long")}
 	}
 
 	var e Error

internal/wayland/wayland_test.go

@@ -1,12 +1,13 @@
-package wayland_test
+package wayland
 
 import (
+	"errors"
 	"os"
+	"reflect"
 	"syscall"
 	"testing"
 
 	"hakurei.app/container/stub"
-	"hakurei.app/internal/wayland"
 )
 
 func TestError(t *testing.T) {
@@ -14,88 +15,88 @@ func TestError(t *testing.T) {
 
 	testCases := []struct {
 		name string
-		err  wayland.Error
+		err  Error
 		want string
 	}{
-		{"success", wayland.Error{
-			Cause: wayland.RSuccess,
+		{"success", Error{
+			Cause: RSuccess,
 		}, "success"},
 
-		{"success errno", wayland.Error{
-			Cause: wayland.RSuccess,
+		{"success errno", Error{
+			Cause: RSuccess,
 			Errno: stub.UniqueError(0),
 		}, "unique error 0 injected by the test suite"},
 
-		{"wl_display_connect_to_fd", wayland.Error{
-			Cause: wayland.RConnect,
+		{"wl_display_connect_to_fd", Error{
+			Cause: RConnect,
 			Errno: stub.UniqueError(1),
 		}, "wl_display_connect_to_fd failed: unique error 1 injected by the test suite"},
 
-		{"wl_registry_add_listener", wayland.Error{
-			Cause: wayland.RListener,
+		{"wl_registry_add_listener", Error{
+			Cause: RListener,
 			Errno: stub.UniqueError(2),
 		}, "wl_registry_add_listener failed: unique error 2 injected by the test suite"},
 
-		{"wl_display_roundtrip", wayland.Error{
-			Cause: wayland.RRoundtrip,
+		{"wl_display_roundtrip", Error{
+			Cause: RRoundtrip,
 			Errno: stub.UniqueError(3),
 		}, "wl_display_roundtrip failed: unique error 3 injected by the test suite"},
 
-		{"not available", wayland.Error{
-			Cause: wayland.RNotAvail,
+		{"not available", Error{
+			Cause: RNotAvail,
 		}, "compositor does not implement security_context_v1"},
 
-		{"not available errno", wayland.Error{
-			Cause: wayland.RNotAvail,
+		{"not available errno", Error{
+			Cause: RNotAvail,
 			Errno: syscall.EAGAIN,
 		}, "compositor does not implement security_context_v1"},
 
-		{"socket", wayland.Error{
-			Cause: wayland.RSocket,
+		{"socket", Error{
+			Cause: RSocket,
 			Errno: stub.UniqueError(4),
 		}, "socket: unique error 4 injected by the test suite"},
 
-		{"bind", wayland.Error{
-			Cause: wayland.RBind,
+		{"bind", Error{
+			Cause: RBind,
 			Path:  "/hakurei.0/18783d07791f2460dbbcffb76c24c9e6/wayland",
 			Errno: stub.UniqueError(5),
 		}, "cannot bind /hakurei.0/18783d07791f2460dbbcffb76c24c9e6/wayland: unique error 5 injected by the test suite"},
 
-		{"listen", wayland.Error{
-			Cause: wayland.RListen,
+		{"listen", Error{
+			Cause: RListen,
 			Path:  "/hakurei.0/18783d07791f2460dbbcffb76c24c9e6/wayland",
 			Errno: stub.UniqueError(6),
 		}, "cannot listen on /hakurei.0/18783d07791f2460dbbcffb76c24c9e6/wayland: unique error 6 injected by the test suite"},
 
-		{"socket invalid", wayland.Error{
-			Cause: wayland.RSocket,
+		{"socket invalid", Error{
+			Cause: RSocket,
 		}, "socket operation failed"},
 
-		{"create", wayland.Error{
-			Cause: wayland.RCreate,
+		{"create", Error{
+			Cause: RCreate,
 		}, "cannot ensure wayland pathname socket"},
 
-		{"create path", wayland.Error{
-			Cause: wayland.RCreate,
+		{"create path", Error{
+			Cause: RCreate,
 			Errno: &os.PathError{Op: "create", Path: "/proc/nonexistent", Err: syscall.EEXIST},
 		}, "create /proc/nonexistent: file exists"},
 
-		{"host socket", wayland.Error{
-			Cause: wayland.RHostSocket,
+		{"host socket", Error{
+			Cause: RHostSocket,
 			Errno: stub.UniqueError(7),
 		}, "socket: unique error 7 injected by the test suite"},
 
-		{"host connect", wayland.Error{
-			Cause: wayland.RHostConnect,
+		{"host connect", Error{
+			Cause: RHostConnect,
 			Host:  "/run/user/1971/wayland-1",
 			Errno: stub.UniqueError(8),
 		}, "cannot connect to /run/user/1971/wayland-1: unique error 8 injected by the test suite"},
 
-		{"invalid", wayland.Error{
+		{"invalid", Error{
 			Cause: 0xbad,
 		}, "impossible outcome"},
 
-		{"invalid errno", wayland.Error{
+		{"invalid errno", Error{
 			Cause: 0xbad,
 			Errno: stub.UniqueError(9),
 		}, "impossible outcome: unique error 9 injected by the test suite"},
@@ -110,3 +111,27 @@ func TestError(t *testing.T) {
 		})
 	}
 }
+
+func TestSecurityContextBindValidate(t *testing.T) {
+	t.Parallel()
+
+	t.Run("NUL", func(t *testing.T) {
+		t.Parallel()
+
+		want := &Error{Cause: RBind, Path: "\x00", Errno: errors.New("argument contains NUL character")}
+		if got := securityContextBind("\x00", -1, "\x00", "\x00", -1); !reflect.DeepEqual(got, want) {
+			t.Fatalf("securityContextBind: error = %#v, want %#v", got, want)
+		}
+	})
+
+	t.Run("long", func(t *testing.T) {
+		t.Parallel()
+		// 256 bytes
+		const oversizedPath = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+
+		want := &Error{Cause: RBind, Path: oversizedPath, Errno: errors.New("socket pathname too long")}
+		if got := securityContextBind(oversizedPath, -1, "", "", -1); !reflect.DeepEqual(got, want) {
+			t.Fatalf("securityContextBind: error = %#v, want %#v", got, want)
+		}
+	})
+}