Just when I thought I was getting near to switching on strict and all of
a sudden my cron jobs are throwing AVCs all over.
The gist of it is all the same, for example:
scontext=user_u:user_r:cronjob_t tcontext=system_u:object_r:crond_tmp_t.
This is from /etc/crontab and has USER=root, so it should be run as a
system crontab and therefore be system_cronjob_t? Here are a couple of
specific AVCs that show this but there are many more similar or
otherwise to do with cron jobs that worked alright until recently:
----
time->Mon Jan 30 13:00:01 2017
type=AVC msg=audit(1485781201.744:14756): avc: denied { write open }
for pid=26263 comm="touch" path="/var/spool/cron/lastrun/cron.hourly"
dev="dm-0" ino=787203 scontext=user_u:user_r:cronjob_t
tcontext=user_u:object_r:crond_tmp_t tclass=file permissive=1
type=AVC msg=audit(1485781201.744:14756): avc: denied { create } for
pid=26263 comm="touch" name="cron.hourly"
scontext=user_u:user_r:cronjob_t tcontext=user_u:object_r:crond_tmp_t
tclass=file permissive=1
type=AVC msg=audit(1485781201.744:14756): avc: denied { add_name }
for pid=26263 comm="touch" name="cron.hourly"
scontext=user_u:user_r:cronjob_t tcontext=system_u:object_r:crond_tmp_t
tclass=dir permissive=1
----
time->Mon Jan 30 15:40:01 2017
type=PROCTITLE msg=audit(1485790801.293:14758):
proctitle=2F62696E2F7368002F7573722F7362696E2F72756E2D63726F6E73
type=PATH msg=audit(1485790801.293:14758): item=0
name="/var/lock/cron.hourly" inode=5592510 dev=00:11 mode=0120777 ouid=0
ogid=0 rdev=00:00 obj=user_u:object_r:var_lock_t nametype=NORMAL
type=CWD msg=audit(1485790801.293:14758): cwd="/"
type=SYSCALL msg=audit(1485790801.293:14758): arch=c000003e syscall=6
success=yes exit=0 a0=1626565d30 a1=3b84123bb70 a2=3b84123bb70 a3=40
items=1 ppid=26697 pid=26698 auid=4294967295 uid=0 gid=0 euid=0 suid=0
fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="run-crons"
exe="/bin/bash" subj=user_u:user_r:cronjob_t key=(null)
type=AVC msg=audit(1485790801.293:14758): avc: denied { getattr } for
pid=26698 comm="run-crons" path="/run/lock/cron.hourly" dev="tmpfs"
ino=5592510 scontext=user_u:user_r:cronjob_t
tcontext=user_u:object_r:var_lock_t tclass=lnk_file permissive=1
Also, I noticed that the files in /var/spool/cron/lastrun/ have the
following contexts:
-rw-r--r--. 1 root root user_u:object_r:crond_tmp_t 0 Jan 30
03:10 cron.daily
-rw-r--r--. 1 root root user_u:object_r:crond_tmp_t 0 Jan 30
15:00 cron.hourly
-rw-r--r--. 1 root root system_u:object_r:system_cronjob_tmp_t 0 Jan 1
05:30 cron.monthly
-rw-r--r--. 1 root root user_u:object_r:crond_tmp_t 0 Jan 28
04:20 cron.weekly
the cron.monthly looks like I would expect (system_cronjob_t) but the
rest have been changed since then.
I have just checked the logs and it confirms that this behaviour started
on 11th Jan, when I updated sec-policy/selinux-base-policy to
2.20161023-r3. So either something got reset that I need to change, I
haven't restarted something or there is some sort of error in the cron
policy that is causing this?
Any ideas?
Thanks - Robert Sharp
