From 83a1c75f1ac4d2d611b3a96474ed07df3cb557b6 Mon Sep 17 00:00:00 2001 From: Ophestra Date: Mon, 18 Aug 2025 02:24:56 +0900 Subject: app: set up acl on X11 socket The socket is typically owned by the priv-user, and inaccessible by the target user, so just allowing access to the directory is not enough. This change fixes this oversight and add checks that will also be useful for merging https://git.gensokyo.uk/security/hakurei/pulls/1. Signed-off-by: Ophestra --- internal/app/seal_linux.go | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) (limited to 'internal') diff --git a/internal/app/seal_linux.go b/internal/app/seal_linux.go index 49ef78f7..c7293720 100644 --- a/internal/app/seal_linux.go +++ b/internal/app/seal_linux.go @@ -12,6 +12,7 @@ import ( "path" "regexp" "slices" + "strconv" "strings" "sync/atomic" "syscall" @@ -386,9 +387,34 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co return hlog.WrapErr(ErrXDisplay, "DISPLAY is not set") } else { + socketDir := container.AbsFHSTmp.Append(".X11-unix") + + // the socket file at `/tmp/.X11-unix/X%d` is typically owned by the priv user + // and not accessible by the target user + var socketPath *container.Absolute + if len(d) > 1 && d[0] == ':' { // `:%d` + if n, err := strconv.Atoi(d[1:]); err == nil && n >= 0 { + socketPath = socketDir.Append("X" + strconv.Itoa(n)) + } + } else if len(d) > 5 && strings.HasPrefix(d, "unix:") { // `unix:%s` + if a, err := container.NewAbs(d[5:]); err == nil { + socketPath = a + } + } + if socketPath != nil { + if _, err := sys.Stat(socketPath.String()); err != nil { + if !errors.Is(err, fs.ErrNotExist) { + return hlog.WrapErrSuffix(err, + fmt.Sprintf("cannot access X11 socket %q:", socketPath)) + } + } else { + seal.sys.UpdatePermType(system.EX11, socketPath.String(), acl.Read, acl.Write, acl.Execute) + d = "unix:" + socketPath.String() + } + } + seal.sys.ChangeHosts("#" + seal.user.uid.String()) seal.env[display] = d - socketDir := container.AbsFHSTmp.Append(".X11-unix") seal.container.Bind(socketDir, socketDir, 0) } } -- cgit v1.3.1