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Fix up POSIX permission handling

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* fhandler_disk_file.cc (fhandler_disk_file::fchmod): Disable
	deviation from POSIX 1003.1e in terms of GROUP_OBJ/CLASS_OBJ
	permissions.  Follow POSIX 1003.1e again.  Keep old code in
	for future reference.
	* sec_acl.cc: Accommodate changes in ACE creation in leading
	comment.
	(set_posix_access): Fix user deny ACE creation.  Split group
	deny ACE creation into two steps, one to reflect CLASS_OBJ,
	the other to reflect OTHER_OBJ.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2015-09-01 22:23:59 +02:00
parent 7972e63402
commit 7edb6b8d3e
3 changed files with 67 additions and 9 deletions
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12
winsup/cygwin/ChangeLog
View File

@ -1,3 +1,15 @@
2015-11-18 Corinna Vinschen <corinna@vinschen.de>
* fhandler_disk_file.cc (fhandler_disk_file::fchmod): Disable
deviation from POSIX 1003.1e in terms of GROUP_OBJ/CLASS_OBJ
permissions. Follow POSIX 1003.1e again. Keep old code in
for future reference.
* sec_acl.cc: Accommodate changes in ACE creation in leading
comment.
(set_posix_access): Fix user deny ACE creation. Split group
deny ACE creation into two steps, one to reflect CLASS_OBJ,
the other to reflect OTHER_OBJ.
2015-11-18 Corinna Vinschen <corinna@vinschen.de>
* sec_acl.cc (getacl): Use Authz to fetch correct user permissions.

10
winsup/cygwin/fhandler_disk_file.cc
View File

@ -915,6 +915,7 @@ fhandler_disk_file::fchmod (mode_t mode)
/* Overwrite ACL permissions as required by POSIX 1003.1e
draft 17. */
aclp[0].a_perm = (mode >> 6) & S_IRWXO;
#if 0
/* Deliberate deviation from POSIX 1003.1e here. We're not
writing CLASS_OBJ *or* GROUP_OBJ, but both. Otherwise we're
going to be in constant trouble with user expectations. */
@ -923,6 +924,15 @@ fhandler_disk_file::fchmod (mode_t mode)
if (nentries > MIN_ACL_ENTRIES
&& (idx = searchace (aclp, nentries, CLASS_OBJ)) >= 0)
aclp[idx].a_perm = (mode >> 3) & S_IRWXO;
#else
/* POSIXly correct: If CLASS_OBJ is present, chmod only modifies
CLASS_OBJ, not GROUP_OBJ. */
if (nentries > MIN_ACL_ENTRIES
&& (idx = searchace (aclp, nentries, CLASS_OBJ)) >= 0)
aclp[idx].a_perm = (mode >> 3) & S_IRWXO;
else if ((idx = searchace (aclp, nentries, GROUP_OBJ)) >= 0)
aclp[idx].a_perm = (mode >> 3) & S_IRWXO;
#endif
if ((idx = searchace (aclp, nentries, OTHER_OBJ)) >= 0)
aclp[idx].a_perm = mode & S_IRWXO;
if (pc.isdir ())

54
winsup/cygwin/sec_acl.cc
View File

@ -37,25 +37,30 @@ details. */
or
USER_OBJ deny ACE == ~USER_OBJ & (GROUP_OBJ | OTHER_OBJ)
- USER deny. If a user has different permissions from CLASS_OBJ, or if the
- USER deny. If a user has more permissions than CLASS_OBJ, or if the
user has less permissions than OTHER_OBJ, deny the excess permissions.
USER deny ACE == (USER ^ CLASS_OBJ) | (~USER & OTHER_OBJ)
USER deny ACE == (USER & ~CLASS_OBJ) | (~USER & OTHER_OBJ)
- USER_OBJ allow ACE
- USER allow ACEs
The POSIX permissions returned for a USER entry are the allow bits alone!
The POSIX permissions returned for a USER entry are the allow bits alone!
- GROUP{_OBJ} deny. If a group has more permissions than CLASS_OBJ,
or less permissions than OTHER_OBJ, deny the excess permissions.
GROUP{_OBJ} deny ACEs == (GROUP & ~CLASS_OBJ) | (~GROUP & OTHER_OBJ)
GROUP{_OBJ} deny ACEs == (GROUP & ~CLASS_OBJ)
- GROUP_OBJ allow ACE
- GROUP allow ACEs
The POSIX permissions returned for a GROUP entry are the allow bits alone!
The POSIX permissions returned for a GROUP entry are the allow bits alone!
- 2. GROUP{_OBJ} deny. If a group has less permissions than OTHER_OBJ,
deny the excess permissions.
2. GROUP{_OBJ} deny ACEs == (~GROUP & OTHER_OBJ)
- OTHER_OBJ allow ACE
@ -311,7 +316,9 @@ set_posix_access (mode_t attr, uid_t uid, gid_t gid,
check_types < CLASS_OBJ;
check_types <<= 2)
{
/* Create deny ACEs for users, then groups. */
/* Create deny ACEs for users, then 1st run for groups. For groups,
only take CLASS_OBJ permissions into account. Class permissions
are handled in the 2nd deny loop below. */
for (start_idx = idx;
idx < nentries && aclbufp[idx].a_type & check_types;
++idx)
@ -327,7 +334,7 @@ set_posix_access (mode_t attr, uid_t uid, gid_t gid,
if (aclbufp[idx].a_type & USER_OBJ)
deny = ~aclbufp[idx].a_perm & (class_obj | other_obj);
else if (aclbufp[idx].a_type & USER)
deny = (aclbufp[idx].a_perm ^ class_obj)
deny = (aclbufp[idx].a_perm & ~class_obj)
| (~aclbufp[idx].a_perm & other_obj);
/* Accommodate Windows: Only generate deny masks for SYSTEM
and the Administrators group in terms of the execute bit,
@ -337,8 +344,7 @@ set_posix_access (mode_t attr, uid_t uid, gid_t gid,
|| aclsid[idx] == well_known_admins_sid))
deny = aclbufp[idx].a_perm & ~(class_obj | S_IROTH | S_IWOTH);
else
deny = (aclbufp[idx].a_perm & ~class_obj)
| (~aclbufp[idx].a_perm & other_obj);
deny = (aclbufp[idx].a_perm & ~class_obj);
if (!deny)
continue;
access = 0;
@ -391,6 +397,36 @@ set_posix_access (mode_t attr, uid_t uid, gid_t gid,
inherit))
return NULL;
}
/* 2nd deny loop: Create deny ACEs for groups when they have less
permissions than OTHER_OBJ. */
if (check_types == (GROUP_OBJ | GROUP))
for (idx = start_idx;
idx < nentries && aclbufp[idx].a_type & check_types;
++idx)
{
if (aclbufp[idx].a_type & GROUP && aclsid[idx] == group)
continue;
/* Only generate deny masks for SYSTEM and the Administrators
group if they are the primary group. */
if (aclbufp[idx].a_type & GROUP
&& (aclsid[idx] == well_known_system_sid
|| aclsid[idx] == well_known_admins_sid))
deny = 0;
else
deny = (~aclbufp[idx].a_perm & other_obj);
if (!deny)
continue;
access = 0;
if (deny & S_IROTH)
access |= FILE_DENY_READ;
if (deny & S_IWOTH)
access |= FILE_DENY_WRITE;
if (deny & S_IXOTH)
access |= FILE_DENY_EXEC;
if (!add_access_denied_ace (acl, access, aclsid[idx], acl_len,
inherit))
return NULL;
}
}
/* For ptys if the admins group isn't in the ACL, add an ACE to make
sure the group has WRITE_DAC and WRITE_OWNER perms. */