Re: [PATCH] capabilities: do not audit log BPRM_FCAPS on set*id

On 2017-04-11 15:36, Paul Moore wrote: > On Wed, Mar 29, 2017 at 6:29 AM, Richard Guy Briggs <rgb(a)redhat.com&gt;

> > On 2017-03-09 09:34, Steve Grubb wrote: > >> On Tuesday, March 7, 2017 4:10:49 PM EST Richard Guy Briggs wrote: > >> > > > > > one possibly audit-worth case which (if I read correctly) > >> > > > > > this will > >> > > > > > skip is where a setuid-root binary has filecaps which *limit* > >> > > > > > its > >> > > > > > privs. > >> > > > > > Does that matter? > >> > > > > > >> > > > > I hadn't thought of that case, but I did consider in the setuid > >> > > > > case > >> > > > > comparing before and after without setuid forcing the drop of > >> > > > > all > >> > > > > capabilities via "ambient". Mind you, this bug has been around > >> > > > > before > >> > > > > Luto's patch that adds the ambient capabilities set. > >> > > > > >> > > > Can you suggest a scenario where that might happen? > >> > > > >> > > Sorry, do you mean the case I brought up, or the one you mentioned? > >> > > I > >> > > don't quite understnad the one you brought up. For mine it's > >> > > pretty > >> > > simple to reproduce, just > >> > > >> > I was talking about the case you brought up, but they could be the > >> > same > >> > case. > >> > > >> > I was thinking of a case where the caps actually change, but are > >> > overridden by the blanket full permissions of setuid. > >> > >> If there actually is a change in capability bits besides the implied > >> change of capabilities based on the change of the uid alone, then it > >> should be logged.> > > > Are you speaking of a change in pP' only from pI, or also pI', pE' and > > pA'? > > > > Something like ( pP' xor pI ) not empty? > > > > The previous patch I'd sent was reasonably easy to understand, but I'm > > having trouble adding this new twist to the logic expression in question > > due to the inverted combination of pre-existing items. I'm having > > trouble visualizing a 5 or more-dimensional Karnaugh map... > > > > While I am at it, I notice pA is missing from the audit record. The > > record contains fields "old_pp", "old_pi", "old_pe", "new_pp", "new_pi", > > "new_pe" so in keeping with the previous record normalizations, I'd like > > to change the "new_*" variants to simply drop the "new_" prefix. > > > > https://github.com/linux-audit/audit-kernel/issues/40 > > Yes, there is the separate ambient capabilities record patch, but > where do we stand with this patch? From what I gather there is still > some uncertainty here? Yes, I put this on my back burner thinking about how best to re-approach this, hoping others would offer some insight or advice how to attack this, otherwise I'm going to end up with a horrendous conditional expression, I fear. Steve, I was hoping to get a clarification from you about which capability bits had changed.