auditing syscalls made 'by' an inode?

[Casey Schaufler]

On 6/8/2012 7:49 AM, Daniel J Walsh wrote:
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> On 06/08/2012 09:51 AM, Steve Grubb wrote:
>> On Friday, June 08, 2012 09:35:01 AM Steve Grubb wrote:
>>> On Thursday, June 07, 2012 06:31:47 PM Peter Moody wrote:
>>>> Is there anyway to audit syscalls made by a particular, not yet 
>>>> running, application?
>>> No...its one of the things I've been interested in for a long time.
>>> About as close as you get is using the selinux process context. But if
>>> its bin_t...there's a couple thousand processes with the same label.
>>>
>>>> For example, if I'm interested in seeing all exec's by google-chrome,
>>>> can I do something like the following?
>>>>
>>>> auditctl -a exit,always -F arch=b64 -S execve -F success=1 -F 
>>>> inode=inode-of-chrome
>>>>
>>>> experimenting seems to indicate that will only tell me when 
>>>> inode-of-chrome is exec'd, basically a watch rule.
>>>>
>>>> The sort of inverse of this rule that got me thinking about this 
>>>> initially was auditing a syscall and seeing if it was/wasn't called by 
>>>> a particular program. For example, audting all bind() calls which 
>>>> *aren't* made by chrome (a silly rule to be sure, but just thrown out 
>>>> as a hypothetical)
>>>>
>>>> If it's not possible to do this now, is there interest in adding this 
>>>> feature?
>>> Yes. I'd be interested in seeing this available. But if you do implement 
>>> it, its more natural to express the rule by process name. But the kernel 
>>> does not do string comparisons. So, what you would likely need to do is 
>>> lookup the path to get the inode, then when it executes a new kind of
>>> pid rule gets created probably off the list like watches do. There are
>>> some apps like apache which fork multiple copies and that adds a wrinkle 
>>> because you would want to audit all of them. And then there are 
>>> threads...
>> The other thing that was discussed a lot maybe 5 years ago (and I don't
>> think it was ever created) was the ability to audit syscalls of a processes
>> children and their children...on and on.  I think Al Viro mentioned he had
>> some ideas about how to do this. But if you add audit by process name, its
>> only natural to optionally track all child processes, too.
>>
>> Where you might want this is like setting a rule on apache for any EPERM or
>> any access to /home. Same could go for bind.
>>
>> -Steve
>>
>> -- Linux-audit mailing list Linux-audit at redhat.com 
>> https://www.redhat.com/mailman/listinfo/linux-audit
>>
> On thing you could do would be to write a simple SELinux domain, like
> auditproc_t and have unconfined_t transition to it using runcon.
>
> type auditproc_t;
> domain_type(auditproc_t);
> unconfined_domain(auditproc_t)
> gen_require(`
>         type unconfined_t;
> 	type unconfined_r;
> ')
>
> allow unconfined_t auditproc_t:process transition;
> role unconfined_r types auditproc_t;
>
>
>
> Setup audit rules to watch SELinux context auditproc_t.
>
>
> Then use runcon -t auditproc_t chrome
>
> Above is totally untested.
>
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It seems that an audit mask attribute on the program file,
much like the file capability attribute, would be on obvious
enhancement to address the original problem statement. The
file capability code could serve as a template. This would be
a generally useful facility in today's application oriented
environments.

I expect that the SELinux based suggestions will work so long
as you're OK with running SELinux and you're sufficiently
confident in your policy writing skills that you can feel
safe changing the policy on important applications. I have
no doubts that Daniel could fix up any policy under the sun
to get auditing without breaking any other enforcement. I
also know that I would never try it.


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