Bug 1009668 - SELinux targeted policy preventing pam_mount from mounting home directory
SELinux targeted policy preventing pam_mount from mounting home directory
Product: Fedora
Classification: Fedora
Component: selinux-policy-targeted (Show other bugs)
x86_64 Linux
unspecified Severity medium
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Assigned To: Miroslav Grepl
Ben Levenson
: Reopened
Depends On:
  Show dependency treegraph
Reported: 2013-09-18 16:09 EDT by lapseofreason0
Modified: 2015-02-18 06:28 EST (History)
1 user (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2015-02-18 06:28:11 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
AVC denial log (15.84 KB, text/plain)
2013-09-25 15:39 EDT, lapseofreason0
no flags Details

  None (edit)
Description lapseofreason0 2013-09-18 16:09:28 EDT
pam_mount fails to mount home directory when SELinux is enabled and the user is in user_u or staff_u.

Mounting works fine for unconfined_u.

Here is the relevant SELinux troubleshooting entry:

SELinux is preventing /usr/libexec/gdm-session-worker from entrypoint access on the file /usr/bin/mount.

*****  Plugin catchall (100. confidence) suggests  ***************************

If you believe that gdm-session-worker should be allowed entrypoint access on the mount file by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
allow this access for now by executing:
# grep gdm-session-wor /var/log/audit/audit.log | audit2allow -M mypol
# semodule -i mypol.pp

Additional Information:
Source Context                user_u:user_r:user_t:s0
Target Context                system_u:object_r:mount_exec_t:s0
Target Objects                /usr/bin/mount [ file ]
Source                        gdm-session-wor
Source Path                   /usr/libexec/gdm-session-worker
Port                          <Unknown>
Host                          notebook
Source RPM Packages           gdm-3.8.4-2.fc19.x86_64
Target RPM Packages           util-linux-2.23.2-4.fc19.x86_64
Policy RPM                    selinux-policy-3.12.1-74.3.fc19.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     fedora
Platform                      Linux fedora 3.10.11-200.fc19.x86_64 #1 SMP Mon
                              Sep 9 13:03:01 UTC 2013 x86_64 x86_64
Alert Count                   1
First Seen                    2013-09-18 21:50:31 CEST
Last Seen                     2013-09-18 21:50:31 CEST
Local ID                      [redacted]

Raw Audit Messages
type=AVC msg=audit(1379533831.874:657): avc:  denied  { entrypoint } for  pid=11284 comm="gdm-session-wor" path="/usr/bin/mount" dev="dm-0" ino=161878 scontext=user_u:user_r:user_t:s0 tcontext=system_u:object_r:mount_exec_t:s0 tclass=file

type=SYSCALL msg=audit(1379533831.874:657): arch=x86_64 syscall=execve success=no exit=EACCES a0=7fffcd2c73b0 a1=7facd286c2c0 a2=7facd28703a0 a3=7facd00042e0 items=0 ppid=11272 pid=11284 auid=1000 uid=0 gid=1000 euid=0 suid=0 fsuid=0 egid=1000 sgid=1000 fsgid=1000 ses=8 tty=(none) comm=gdm-session-wor exe=/usr/libexec/gdm-session-worker subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 key=(null)

Hash: gdm-session-wor,user_t,mount_exec_t,file,entrypoint
Comment 1 Daniel Walsh 2013-09-24 13:01:57 EDT
user_t and staff_t for that matter are prevented from mounting of file systems.  I guess the best way to handle this would be to use automount.
Comment 2 lapseofreason0 2013-09-25 13:37:39 EDT
I understand, but automount is not a good alternative if you want the user to use the user password on mount (i.e. for a network share or an encrypted folder).

Any chance you could point me towards how to change the policy to allow mounting using pam_mount?
Comment 3 Daniel Walsh 2013-09-25 13:56:11 EDT
Simplest thing would be to gather AVC's for what is required, then we could look at adding a boolean for this.

setenforce 0


ausearch -m avc -ts recent.

We can look at that.

Another option would be to allow a confined user to transition to the mount_t domain.

mount_run(user_t, user_r)
Comment 4 lapseofreason0 2013-09-25 15:39:11 EDT
Created attachment 803044 [details]
AVC denial log
Comment 5 lapseofreason0 2013-09-25 15:43:16 EDT
I added the relevant output of ausearch. Basically gdm-session-worker calls mount (or any other command defined in /etc/security/pam_mount.xml), which then calls mount.crypt. This calls cryptsetup to set up the LUKS mapping and then mounts the filesystem.

How would I allow staff_t to transition to mount_t to test if that would work?
Comment 6 Miroslav Grepl 2013-09-25 16:20:36 EDT
Ok, so it is not just about mount_run() but also about lvm_run() which we don't want to allow by default. I am also sceptic about a boolean. We could think about it for staff_u but definitely not for user_u.
Comment 7 Miroslav Grepl 2013-09-25 16:22:35 EDT
Maybe there could be involved a helper script.
Comment 8 lapseofreason0 2013-09-25 16:28:11 EDT
I'm not sure whether you meant this as a question, but in my case there is a helper script involved. It is simply a bash script that gets called by mount when it is called with a special fstype. The script just feeds the password to cryptsetup and then calls mount.
Comment 9 Fedora End Of Life 2015-01-09 17:18:26 EST
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Comment 10 Fedora End Of Life 2015-02-18 06:28:11 EST
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