Re: sshd constraint violation issue
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On 08/29/2011 10:43 AM, Stephen Smalley wrote:
On Mon, 2011-08-29 at 10:36 -0400, Christopher J. PeBenito wrote:
> On 08/29/11 11:10, Miroslav Grepl wrote:
>> On 08/29/2011 12:52 PM, Christopher J. PeBenito wrote:
>>> On 08/29/11 08:33, Stephen Smalley wrote:
>>>> On Fri, 2011-08-26 at 20:51 +0200, Miroslav Grepl wrote:
>>>>> Together with Dan Walsh, Jan Chadima we made some changes
>>>>> in the openssh package.
>>>>>
>>>>> But we have the following issue with the following code
>>>>>
>>>>> ...
>>>>>
>>>>> if (internal-sftp) setuid() getexecon(&scon)
>>>>> setcon(scon) freecon(scon)
>>>>>
>>>>> ...
>>>>>
>>>>> We have
>>>>>
>>>>> allow sshd_t unpriv_userdomain:process dyntransition
>>>>>
>>>>> rule but we get a constraint violation with the following
>>>>> AVC msg
>>>>>
>>>>> type=AVC msg=audit(1314348650.561:7910): avc: denied {
>>>>> dyntransition } for pid=555 comm="sshd"
>>>>> scontext=unconfined_u:system_r:sshd_t:s0-s0:c0.c1023
>>>>> tcontext=staff_u:staff_r:staff_t:s0
>>>>>
>>>>> because of
>>>>>
>>>>> constrain process dyntransition ( u1 == u2 and r1 == r2
>>>>> )
>>>>>
>>>>> My question is why dyntrans is not allowed to change USER
>>>>> or ROLE.
>>>>>
>>>>>
>>>>> https://bugzilla.redhat.com/show_bug.cgi?id=729648
>>>> I think just because we haven't previously had a system
>>>> program using setcon(3) to switch its user/role.
>>> Also because the theory we would be reproducing privilege
>>> bracketed domains, so you'd be going to a different privilege
>>> in eg httpd_t -> httpd_mycgi_t, and that would not require
>>> user or role changes.
>>>
>> Ok, I understand. Thanks.
>>
>> Could we add an attribute to break this?
>
> Yes, we could add one. The question is if we want the same
> attribute as the regular transition or a new one. i.e. I'm
> thinking
>
> constran process dyntranstion ( u1 == u2 or ( t1 ==
> can_change_process_identity and t2 == process_user_target ) );
>
> constran process dyntranstion ( r1 == r2 or ( t1 ==
> can_change_process_identity and t2 == process_user_target ) );
>
> do we want can_change_process_identity attribute or a new one?
If so, then might as well just coalesce into the existing
constraint on transition permission.
Ok I like Stephen's better.
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