On 10/01/2009 05:51 AM, Dominick Grift wrote:
> On Wed, Sep 30, 2009 at 05:21:56PM -0700, Vadym Chepkov wrote:
>> Hi,
>>
>> I am puzzled, what could have caused this kind of AVC:
>>
>> type=SYSCALL msg=audit(1254270789.862:74347): arch=c000003e syscall=2 success=no exit=-13 a0=7f2929f52532 a1=0 a2=d a3=7fff325c4270 items=0 ppid=18807 pid=18808 auid=500 uid=48 gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none) comm="uptime" exe="/usr/bin/uptime" subj=user_u:system_r:httpd_t:s0 key=(null)
>> type=AVC msg=audit(1254270789.862:74347): avc: denied { read } for pid=18808 comm="uptime" name="utmp" dev=sda1 ino=2474106 scontext=user_u:system_r:httpd_t:s0 tcontext=system_u:object_r:initrc_var_run_t:s0 tclass=file
>
> Well uptime runs in the httpd_t domain and the httpd domain (uptime) tried to read /var/run/utmp file. /var/run/utmp has a object type that is owned by init scripts for object in /var/run.
>
> you can and should check first to see whether the types are correct: should "uptime" in this scenario run in the httpd_t domain (is it called from a webapp (non-cgi) also is the target object labelled properly (matchpathcon /var/run/utmp)
>
> Once that is established you can verify whether httpd_t should be able to access the target type:
>
> sesearch --allow -s httpd_t -t initrc_var_run_t -c file -p read
>
> With this information you are going to have to make your security decision.
>
> should you allow it or deny it?
>
> I can tell you that in my configuration /var/run/utmp also has type initrc_var_run_t. So i guess that is what it should be.
>
> What i cannot tell you is why and how uptime is executed in this scenario.
> All i know is that it runs in the httpd_t domain.
>>
>>
>> Sincerely yours,
>> Vadym Chepkov
>>
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>>
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You would need to add policy to be able to do this. Apache being able to read utmp could allow a hacker to figure out all the user names that have logged onto a system. It is denied by default.
You can easily add custom policy using audit2allow.
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