execve silently blocked

execve silently blocked

[Ian Pilcher]

I am writing an SELinux policy for a daemon that needs to exec an
external program.  The execve call is being denied (permission denied),
but no denial is being logged, even after disabling dontaudit rules
(semodule -DB).

(The execve call does succeed in permissive mode.)

How can I troubleshoot this?

Thanks!

-- 
========================================================================
Ian Pilcher                                         arequipeno@gmail.com
-------- "I grew up before Mark Zuckerberg invented friendship" --------
========================================================================

Re: execve silently blocked

[Dominick Grift]

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On Wed, Oct 02, 2019 at 02:25:22PM -0500, Ian Pilcher wrote:
> I am writing an SELinux policy for a daemon that needs to exec an
> external program.  The execve call is being denied (permission denied),
> but no denial is being logged, even after disabling dontaudit rules
> (semodule -DB).

Are you also looking for "selinux_err" records?

`ausearch -m avc,user_avc,selinux_err -i`

will return avc, user_avc and selinux_err records if auditd is running.

> 
> (The execve call does succeed in permissive mode.)
> 
> How can I troubleshoot this?
> 
> Thanks!
> 
> -- 
> ========================================================================
> Ian Pilcher                                         arequipeno@gmail.com
> -------- "I grew up before Mark Zuckerberg invented friendship" --------
> ========================================================================

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Dominick Grift

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Re: execve silently blocked

[Ian Pilcher]

On 10/2/19 2:41 PM, Dominick Grift wrote:
> Are you also looking for "selinux_err" records?

Nope, because I had never heard of them before.  :-)

That found the error:

   type=SELINUX_ERR msg=audit(1570044939.773:845):
   op=security_compute_sid
   invalid_context=system_u:system_r:denatc_sudo_t:s0
   scontext=system_u:system_r:denatc_t:s0
   tcontext=system_u:object_r:sudo_exec_t:s0 tclass=process

It seems that I was missing a role-type statement:

   role system_r types denatc_sudo_t;

Adding that gets me back to more conventional denials, which I know how
to deal with.

Thanks!

-- 
========================================================================
Ian Pilcher                                         arequipeno@gmail.com
-------- "I grew up before Mark Zuckerberg invented friendship" --------
========================================================================