Bug 1001871 - SELinux allows user_u to obtain quasi root prompt
SELinux allows user_u to obtain quasi root prompt
Product: Fedora
Classification: Fedora
Component: selinux-policy-targeted (Show other bugs)
x86_64 Linux
unspecified Severity high
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Assigned To: Miroslav Grepl
Ben Levenson
Depends On:
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Reported: 2013-08-27 22:44 EDT by JR
Modified: 2015-02-17 11:57 EST (History)
1 user (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2015-02-17 11:57:01 EST
Type: Bug
Regression: ---
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RHEL 7.3 requirements from Atomic Host:
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Description JR 2013-08-27 22:44:47 EDT
Description of problem:
A user confined as user_u (id -Z yields user_u:user_r:user_t:s0) can now get a quasi-root prompt as shown below.  This is on Fedora 19 x86_64 XFCE Spin install with a 'fixfiles onboot' completed and rebooted.

$ su -
-bash: /root/.bash_profile: Permission denied
-bash-4.2# dmesg
dmesg: read kernel buffer failed: Permission denied
-bash-4.2# logout
-bash: /root/.bash_logout: Permission denied


$ su -
-bash: /root/.bash_profile: Permission denied
-bash-4.2# whoami
-bash-4.2# logout
-bash: /root/.bash_logout: Permission denied

Version-Release number of selected component (if applicable):
$ rpm -qa | grep selinux

How reproducible:
Always with packages listed above.

Steps to Reproduce:
1. Create a user and confine them to user_u
2. Log out and log back in as user
3. Open a terminal and execute su -

Actual results:
After accepting the password, a quasi-root prompt is available.

Expected results:
The su command should return an error and not even prompt for password. (This is how it worked until the most recent SELinux update.)

Additional info:
A few of the denied AVC messages:

type=AVC msg=audit(1377657010.371:726): avc:  denied  { read } for  pid=2560 comm="bash" name=".bash_profile" dev="sda7" ino=523269 scontext=user_u:user_r:user_t:s0 tcontext=system_u:object_r:admin_home_t:s0 tclass=file

type=AVC msg=audit(1377657010.371:727): avc:  denied  { read } for  pid=2560 comm="bash" name=".bash_history" dev="sda7" ino=523294 scontext=user_u:user_r:user_t:s0 tcontext=system_u:object_r:admin_home_t:s0 tclass=file

# rpm -qa | grep kernel

SELinux is in enforcing mode:
# getenforce
Comment 1 Daniel Walsh 2013-08-28 15:11:44 EDT
Do you have the selinuxuser_use_ssh_chroot boolean turned on?
Comment 2 JR 2013-08-28 19:24:35 EDT
Yes, it is still at the default for a Fedora 19 installation:

selinuxuser_use_ssh_chroot     (on   ,   on)  Allow user  to use ssh chroot environment.

Thanks in advance!
Comment 3 Miroslav Grepl 2013-08-29 05:41:44 EDT
Should be turned off by default.

# getsebool selinuxuser_use_ssh_chroot
selinuxuser_use_ssh_chroot --> off
Comment 4 Daniel Walsh 2013-08-29 08:57:32 EDT
Was this ever defaulted to on?
Comment 5 Miroslav Grepl 2013-08-29 09:18:32 EDT
It was not, AFAIK.
Comment 6 Fedora End Of Life 2015-01-09 14:37:12 EST
This message is a notice that Fedora 19 is now at end of life. Fedora 
has stopped maintaining and issuing updates for Fedora 19. It is 
Fedora's policy to close all bug reports from releases that are no 
longer maintained. Approximately 4 (four) weeks from now this bug will
be closed as EOL if it remains open with a Fedora 'version' of '19'.

Package Maintainer: If you wish for this bug to remain open because you
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version prior this bug is closed as described in the policy above.

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Comment 7 Fedora End Of Life 2015-02-17 11:57:01 EST
Fedora 19 changed to end-of-life (EOL) status on 2015-01-06. Fedora 19 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

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