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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 <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2016-04-19 10:23:49 +02:00
parent 97d0449325
commit 7a5b452443
1 changed files with 13 additions and 1 deletions
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14
winsup/cygwin/sec_acl.cc
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@ -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);