From 7a5b4524431110fde4e9336f64ade73ab2c26b6b Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Tue, 19 Apr 2016 10:23:49 +0200 Subject: [PATCH] Disallow S_ISGID on directories without default ACL entries We can't handle the S_ISGID bit if the child didn't inherit a NULL SID ACE with the S_ISGID bit set. On directories without default ACL entries we would have to add an inheritable NULL SID ACE and nothing else. This in turn results in permission problems when calling set_file_sd from set_created_file_access. That's fixable, but it would only work for files created from Cygwin while files created from native Windows tools end up with really ugly permissions. This patch only makes sure that the S_ISGID bit is reset for a directory if it has no inheritable ACEs. Still having the 's' bit shown in ls or getfacl output would be misleading. So, calling `setfacl -k' on a dir also removes the S_ISGID bit now. * sec_acl.cc (set_posix_access): Drop S_ISGID bit on directories without inheritable ACEs. Explain why. Signed-off-by: Corinna Vinschen --- winsup/cygwin/sec_acl.cc | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/winsup/cygwin/sec_acl.cc b/winsup/cygwin/sec_acl.cc index 8dd73b195..cf0f89d80 100644 --- a/winsup/cygwin/sec_acl.cc +++ b/winsup/cygwin/sec_acl.cc @@ -334,7 +334,19 @@ set_posix_access (mode_t attr, uid_t uid, gid_t gid, other_obj = aclbufp[tmp_idx].a_perm; /* ... class_obj. Create NULL deny ACE. Only the S_ISGID attribute gets - inherited. */ + inherited. For directories check if we are also going to generate + default entries. If not we have a problem. We can't generate only a + single, inheritable NULL SID ACE because that leads to (fixable, TODO) + access problems when trying to create the matching child permissions. + Therefore we remove the S_ISGID bit on the directory because having it + set would be misleading. */ + if (!def && S_ISDIR (attr) && (attr & S_ISGID)) + { + /* Check for a required entry per POSIX. */ + tmp_idx = searchace (aclbufp, nentries, DEF_USER_OBJ); + if (tmp_idx < 0) + attr &= ~S_ISGID; + } access = CYG_ACE_ISBITS_TO_WIN (def ? attr & S_ISGID : attr) | CYG_ACE_NEW_STYLE; tmp_idx = searchace (aclbufp, nentries, def | CLASS_OBJ);