Bug 1663692 - SElinux prevents dnsmasq from running
Summary: SElinux prevents dnsmasq from running
Keywords:
Status: CLOSED EOL
Alias: None
Product: Fedora
Classification: Fedora
Component: dnsmasq
Version: 29
Hardware: x86_64
OS: Linux
unspecified
low
Target Milestone: ---
Assignee: Petr Menšík
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2019-01-06 16:07 UTC by Edgar
Modified: 2023-05-10 02:29 UTC (History)
10 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed: 2019-11-27 21:34:15 UTC
Type: Bug
Embargoed:


Attachments (Terms of Use)

Description Edgar 2019-01-06 16:07:34 UTC
Description of problem: SElinux prevents dnsmasq from running


Version-Release number of selected component (if applicable):
Dnsmasq version 2.79  Copyright (c) 2000-2018 Simon Kelley
Compile time options: IPv6 GNU-getopt DBus no-i18n IDN2 DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth DNSSEC loop-detect inotify

This software comes with ABSOLUTELY NO WARRANTY.
Dnsmasq is free software, and you are welcome to redistribute it
under the terms of the GNU General Public License, version 2 or 3.


How reproducible:
If a "log-facility=/var/log/dnsmasq.log" has been defined in /etc/dnsmasq.conf, the issue is always present.
If the log-facility is commented out, dnsmasq runs correct.

Steps to Reproduce:
1. Install a minimum Fedora 29 server
2. Install dnsmasq
3. Create/adjust /etc/dnsmasq.conf to include "log-facility=/var/log/dnsmasq.log"
4. Run: systemctl enable dnsmasq
5. Run: systemctl start dnsmasq
6. Run: systemctl status dnsmasq

Actual results:
1. -------------- "systemctl status dnsmasq" shows:
● dnsmasq.service - DNS caching server.
   Loaded: loaded (/usr/lib/systemd/system/dnsmasq.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sun 2019-01-06 16:58:45 CET; 2s ago
  Process: 3776 ExecStart=/usr/sbin/dnsmasq -k (code=exited, status=3)
 Main PID: 3776 (code=exited, status=3)

Jan 06 16:58:44 ns2.edgar-matzinger.nl systemd[1]: Started DNS caching server..
Jan 06 16:58:45 ns2.edgar-matzinger.nl dnsmasq[3776]: dnsmasq: cannot open log /var/log/dnsmasq.log: Permission denied
Jan 06 16:58:45 ns2.edgar-matzinger.nl dnsmasq[3776]: cannot open log /var/log/dnsmasq.log: Permission denied
Jan 06 16:58:45 ns2.edgar-matzinger.nl dnsmasq[3776]: FAILED to start up
Jan 06 16:58:45 ns2.edgar-matzinger.nl systemd[1]: dnsmasq.service: Main process exited, code=exited, status=3/NOTIMPLE>
Jan 06 16:58:45 ns2.edgar-matzinger.nl systemd[1]: dnsmasq.service: Failed with result 'exit-code'.

2. -------------- audit2why shows:
type=AVC msg=audit(1546789506.693:901): avc:  denied  { dac_override } for  pid=3751 comm="dnsmasq" capability=1  scontext=system_u:system_r:dnsmasq_t:s0 tcontext=system_u:system_r:dnsmasq_t:s0 tclass=capability permissive=0

	Was caused by:
		Missing type enforcement (TE) allow rule.

		You can use audit2allow to generate a loadable module to allow this access.

3. -------------- SELinux contexts:
[root@ns2 audit]# ls -ldZ /etc/dnsmasq.conf /etc/dnsmasq.d /etc/dnsmasq.d/dnsmasq.dhcp.conf /var/log/dnsmasq.log
-rw-r--r--. 1 root    dnsmasq system_u:object_r:dnsmasq_etc_t:s0     26924 Jan  6 17:00 /etc/dnsmasq.conf
drwxr-xr-x. 2 root    dnsmasq system_u:object_r:dnsmasq_etc_t:s0        31 Jan  6 16:19 /etc/dnsmasq.d
-rw-r--r--. 1 root    root    unconfined_u:object_r:dnsmasq_etc_t:s0   543 Jan  6 16:19 /etc/dnsmasq.d/dnsmasq.dhcp.conf
-rw-r-----. 1 dnsmasq dnsmasq system_u:object_r:dnsmasq_var_log_t:s0  9322 Jan  6 16:43 /var/log/dnsmasq.log

Expected results:
Running dnsmasq configuration with logging to /var/log/dnsmasq.log

Additional info:
Switching SELinux to permissive, allows dnsmasq to start correctly using systemctl.

Comment 1 Petr Menšík 2019-03-18 16:44:53 UTC
Dnsmasq is denied right to override unix permissions in /var/log directory. It can work, just /var/log/dnsmasq.log has to be created first with right to write to it. Daemon running network services runs under dnsmasq user, which has no right to write into /var/log.

If you first create file writeable by that user, dnsmasq should be able to write there.

Can you try (as root):
touch /var/log/dnsmasq.log
chgrp dnsmasq /var/log/dnsmasq.log
chmod g+w /var/log/dnsmasq.log
systemctl restart dnsmasq

This should work also with selinux set to enforcing.

Comment 2 Ben Cotton 2019-10-31 19:45:58 UTC
This message is a reminder that Fedora 29 is nearing its end of life.
Fedora will stop maintaining and issuing updates for Fedora 29 on 2019-11-26.
It is Fedora's policy to close all bug reports from releases that are no longer
maintained. At that time this bug will be closed as EOL if it remains open with a
Fedora 'version' of '29'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not 
able to fix it before Fedora 29 is end of life. If you would still like 
to see this bug fixed and are able to reproduce it against a later version 
of Fedora, you are encouraged  change the 'version' to a later Fedora 
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events. Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.

Comment 3 Ben Cotton 2019-11-27 21:34:15 UTC
Fedora 29 changed to end-of-life (EOL) status on 2019-11-26. Fedora 29 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.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this
bug.

Thank you for reporting this bug and we are sorry it could not be fixed.


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