AVC Denial

alan_ri · 03-29-2008, 08:17 AM

Summary
SELinux is preventing /usr/sbin/useradd (useradd_t) "read write" to (var_log_t).

Detailed Description
SELinux denied access requested by /usr/sbin/useradd. It is not expected that this access is required by /usr/sbin/useradd and this access may signal an intrusion attempt. It is also possible that the specific version or configuration of the application is causing it to require additional access.

Allowing Access
Sometimes labeling problems can cause SELinux denials. You could try to restore the default system file context for , restorecon -v If this does not work, there is currently no automatic way to allow this access. Instead, you can generate a local policy module to allow this access - see FAQ.Or you can disable SELinux protection altogether. Disabling SELinux protection is not recommended. Please file a bug report against this package.

Additional Information

Code:

Source Context:  system_u:system_r:useradd_t:s0
Target Context:  system_u:object_r:var_log_t:s0
Target Objects:  None [ file ]
Affected RPM Packages:  shadow-utils-4.0.18.1-18.fc8 [application]
Policy RPM:  selinux-policy-3.0.8-44.fc8
Selinux Enabled:  True
Policy Type:  targeted
MLS Enabled:  True
Enforcing Mode:  Enforcing
Plugin Name:  plugins.catchall_file
Host Name:  localhost.localdomain
Platform:  Linux localhost.localdomain 2.6.23.1-42.fc8 #1 SMP Tue Oct 30 13:55:12 EDT 2007 i686 i686
Alert Count:  2
First Seen:  Fri 28 Mar 2008 05:06:20 PM CET
Last Seen:  Fri 28 Mar 2008 05:06:34 PM CET
Local ID:  1bc9d871-7a93-4bdf-9e06-9522313b8f0d
Line Numbers:  
Raw Audit Messages :
avc: denied { read write } for comm=useradd dev=sda5 
egid=0 euid=0 exe=/usr/sbin/useradd exit=-13 
fsgid=0 fsuid=0 gid=0 items=0 name=faillog pid=7595 
scontext=system_u:system_r:useradd_t:s0 
sgid=0 subj=system_u:system_r:useradd_t:s0 suid=0 tclass=file tcontext=system_u:object_r:var_log_t:s0 tty=(none) uid=0

I didn't add any new user to the system,it's just two of us,me and me as root.I would like to know your opinion about this.Thanks.

unSpawn · 03-31-2008, 08:52 AM

Quote:

Originally Posted by alan_ri

SELinux is preventing /usr/sbin/useradd (useradd_t) "read write" to (var_log_t).

AFAIK /var/log/faillog should not have type "var_log_t" but "faillog_t". Correct with 'chcon -t faillog_t /var/log/faillog'.

Quote:

Originally Posted by alan_ri

I didn't add any new user to the system

Installing a package may include adding a system or unprivileged user. For example if the package was Apache (httpd.*.rpm) you could check running 'rpm -q --scripts httpd|less' and check where it reads "postinstall scriptlet". It may also have been something else like configuring the failure counter or limits ('man fiallog' for more nfo).

alan_ri · 03-31-2008, 09:43 AM

Quote:

Originally Posted by unSpawn

AFAIK /var/log/faillog should not have type "var_log_t" but "faillog_t". Correct with 'chcon -t faillog_t /var/log/faillog'.

I don't think that I have to correct this,because application that I have installed(and I don't know yet which one it was that caused this AVC denial) "wanted" to write something in the /var/log,create a file and give some name to that file.It wasn't something that should go in /var/log/faillog.

Quote:

Originally Posted by unSpawn

Installing a package may include adding a system or unprivileged user.

I knew that,I just wanted to make clear that no user(no app)was added to the system.

'rpm -q --scripts httpd|less'.It wasn't Apache,but I will use this command(with different input)and try to find out which application was responsible for this AVC denial.I'm still learning the command line.

Thanks for your help and interest.

unSpawn · 03-31-2008, 10:26 AM

Quote:

Originally Posted by alan_ri

application that I have installed (and I don't know yet which one it was that caused this AVC denial) "wanted" to write something in the /var/log, create a file and give some name to that file. It wasn't something that should go in /var/log/faillog.

The listed shadow-utils package doesn't execute scripts and the AVC message lists the source process as "comm=useradd, exe=/usr/sbin/useradd, scontext=system_u:system_r:useradd_t" and the target as "name=faillog, tclass=file and tcontext=system_u

bject_r:var_log_t". So I'd be interested to know what other file there is in /var/log that would show up as "tclass=file, name=faillog"... Best start by checking which packages got installed recently. If you don't have 'rpm --last' then 'rpm -qa --qf='%{INSTALLTIME:date} %{NAME}\n'|sort -r|head -30' should work.

alan_ri · 03-31-2008, 02:25 PM

You're right.I didn't think this through as I should.Will try that sweet little command.