Bug 1122013 - pam_systemd causes AVC for ThinLinc
Summary: pam_systemd causes AVC for ThinLinc
Alias: None
Product: Fedora
Classification: Fedora
Component: selinux-policy
Version: 20
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Lukas Vrabec
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2014-07-22 11:08 UTC by Pierre Ossman
Modified: 2015-06-30 01:36 UTC (History)
5 users (show)

Fixed In Version: selinux-policy-3.12.1-182.fc20
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2015-06-30 01:36:11 UTC
Type: Bug

Attachments (Terms of Use)
Policy file for ThinLinc (4.68 KB, text/plain)
2014-08-20 10:39 UTC, Pierre Ossman
no flags Details

Description Pierre Ossman 2014-07-22 11:08:58 UTC
pam_systemd is messing around with the given $DISPLAY, causing this AVC:

> type=AVC msg=audit(1406027132.689:67802): avc:  denied  { search } for  pid=4487 comm="tl-session" name=".X11-unix" dev="tmpfs" ino=18235 scontext=system_u:system_r:thinlinc_session_t:s0 tcontext=system_u:object_r:xdm_tmp_t:s0 tclass=dir

Commenting out pam_systemd gets rid of the audit message.

Comment 1 Daniel Walsh 2014-08-04 22:03:01 UTC
Where did the thinlinc_session_t type come from?  It is not something we ship?

Looks like thinlinc ships their own policy, you have to work with them.

Comment 2 Pierre Ossman 2014-08-20 10:36:21 UTC
Yes, it is an external policy. I was in a rush and should have been clearer.

The point was that I believe the auth_use_pam() macro needs to be adjusted as (apparently) some PAM modules now need more access to do their work.

Comment 3 Pierre Ossman 2014-08-20 10:39:04 UTC
Created attachment 928755 [details]
Policy file for ThinLinc

This is the policy that defines the thinlinc_session_t type, and also calls auth_login_pgm_domain() to indicate that it needs to be allowed to perform a login.

(I was also unable to reset the assignee back properly :/)

Comment 4 Daniel Walsh 2014-08-20 14:46:42 UTC
What is it searching for in /tmp/.X11-unix?

Adding this to auth_use_pam seems like it is streting it, since I am not sure pam is causing this AVC.  Seems to be X Specific.

Comment 5 Pierre Ossman 2014-08-20 15:15:20 UTC
Well, I haven't dug around in pam_systemd to figure out what it's up to, but I assume that the triggering condition is that PAM_XDISPLAY is set. Perhaps pam_systemd tries to verify the X11 socket? Or add some root window properties?

One question is why this isn't seen with anything shipped with Fedora. I suspect that only display managers have PAM_XDISPLAY set. And they most likely run in a context where they need access to X11 anyway. If you put the non-graphical portions of GDM in a different context, then you might see similar problems.

tl-session is more specialised and more or less only does the login.
(It also runs before the X server is started, so whatever pam_systemd is up to will probably fail. But that's a separate matter.)

Comment 6 Daniel Walsh 2014-08-21 12:02:44 UTC
Is the search all that is needed?  Have you run in permissive mode, to see if it actually does any other access?

Comment 7 Pierre Ossman 2014-08-21 13:03:52 UTC
This is the only AVC I see, even in permissive mode.

Comment 8 Daniel Walsh 2014-08-22 13:08:43 UTC
d0c04a625cd235b9c362a4bc17acfc7e2c5aca52 fixes this in git.

Comment 9 Lukas Vrabec 2014-08-27 12:19:35 UTC
commit d0c04a625cd235b9c362a4bc17acfc7e2c5aca52
Author: Dan Walsh <dwalsh@redhat.com>
Date:   Fri Aug 22 09:08:23 2014 -0400

    Allow programs to use pam to search through user_tmp_t dires (/tmp/.X11-unix)


Comment 10 Fedora Update System 2014-08-27 14:52:53 UTC
selinux-policy-3.12.1-182.fc20 has been submitted as an update for Fedora 20.

Comment 11 Fedora Update System 2014-08-28 15:30:43 UTC
Package selinux-policy-3.12.1-182.fc20:
* should fix your issue,
* was pushed to the Fedora 20 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing selinux-policy-3.12.1-182.fc20'
as soon as you are able to.
Please go to the following url:
then log in and leave karma (feedback).

Comment 12 Fedora Update System 2014-08-30 03:54:51 UTC
selinux-policy-3.12.1-182.fc20 has been pushed to the Fedora 20 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 13 Pierre Ossman 2014-09-09 07:56:03 UTC
Confirmed that the issue is solved. Thank you. :)

Comment 14 Pierre Ossman 2014-09-09 15:20:36 UTC
I spoke too soon. Not sure why the AVC didn't show up the first time. Still getting:

> type=AVC msg=audit(1410275853.495:53011): avc:  denied  { search } for  pid=8600 comm="tl-session" name=".X11-unix" dev="tmpfs" ino=18622 scontext=system_u:system_r:thinlinc_session_t:s0 tcontext=system_u:object_r:xdm_tmp_t:s0 tclass=dir


Comment 15 Pierre Ossman 2014-09-09 15:41:21 UTC
Ah. The problem is that the X11 files are xdm_tmp_t, not normal tmp_t. You need a call to xserver_search_xdm_tmp_dirs() rather than userdom_search_user_tmp_dirs().

Comment 16 Pierre Ossman 2014-09-29 07:47:29 UTC

Comment 17 Miroslav Grepl 2014-09-29 09:48:38 UTC
We get it as user_tmp_t in F21. It needs to be allowed by thinlinc policy which we don't ship.

Comment 18 Pierre Ossman 2014-09-29 10:25:45 UTC
So F20 is already too old to be adjusted?

$ ls -Z /tmp/.X11-unix/
srwxrwxrwx. root root system_u:object_r:xdm_tmp_t:s0   X0

Comment 19 Miroslav Grepl 2014-09-29 10:43:30 UTC
could you add a fix for f20? We want to have


together with 


in F20.

Comment 20 Lukas Vrabec 2014-09-29 10:57:28 UTC
commit d3b075499ae66359bfda64aec6d3ef881502c71f
Author: Lukas Vrabec <lvrabec@redhat.com>
Date:   Mon Sep 29 12:56:34 2014 +0200

     Allow programs to use pam to search through xdm_tmp_t dires. BZ (#1122013)


Comment 21 Fedora Update System 2014-09-30 08:36:17 UTC
selinux-policy-3.12.1-188.fc20 has been submitted as an update for Fedora 20.

Comment 22 Fedora Update System 2014-10-01 04:22:49 UTC
Package selinux-policy-3.12.1-188.fc20:
* should fix your issue,
* was pushed to the Fedora 20 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing selinux-policy-3.12.1-188.fc20'
as soon as you are able to.
Please go to the following url:
then log in and leave karma (feedback).

Comment 23 Fedora End Of Life 2015-05-29 12:26:03 UTC
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