Re: [PATCH ghak90 V8 07/16] audit: add contid support for signalling the audit daemon

On Wed, Mar 18, 2020 at 5:56 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > On 2020-03-18 17:42, Paul Moore wrote: > > On Wed, Mar 18, 2020 at 5:27 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > On 2020-03-18 16:56, Paul Moore wrote: > > > > On Fri, Mar 13, 2020 at 2:59 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > > On 2020-03-13 12:29, Paul Moore wrote: > > > > > > On Thu, Mar 12, 2020 at 3:30 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > > > > On 2020-02-13 16:44, Paul Moore wrote: > > > > > > > > This is a bit of a thread-hijack, and for that I apologize, but > > > > > > > > another thought crossed my mind while thinking about this issue > > > > > > > > further ... Once we support multiple auditd instances, including the > > > > > > > > necessary record routing and duplication/multiple-sends (the host > > > > > > > > always sees *everything*), we will likely need to find a way to "trim" > > > > > > > > the audit container ID (ACID) lists we send in the records. The > > > > > > > > auditd instance running on the host/initns will always see everything, > > > > > > > > so it will want the full container ACID list; however an auditd > > > > > > > > instance running inside a container really should only see the ACIDs > > > > > > > > of any child containers. > > > > > > > > > > > > > > Agreed. This should be easy to check and limit, preventing an auditd > > > > > > > from seeing any contid that is a parent of its own contid. > > > > > > > > > > > > > > > For example, imagine a system where the host has containers 1 and 2, > > > > > > > > each running an auditd instance. Inside container 1 there are > > > > > > > > containers A and B. Inside container 2 there are containers Y and Z. > > > > > > > > If an audit event is generated in container Z, I would expect the > > > > > > > > host's auditd to see a ACID list of "1,Z" but container 1's auditd > > > > > > > > should only see an ACID list of "Z". The auditd running in container > > > > > > > > 2 should not see the record at all (that will be relatively > > > > > > > > straightforward). Does that make sense? Do we have the record > > > > > > > > formats properly designed to handle this without too much problem (I'm > > > > > > > > not entirely sure we do)? > > > > > > > > > > > > > > I completely agree and I believe we have record formats that are able to > > > > > > > handle this already. > > > > > > > > > > > > I'm not convinced we do. What about the cases where we have a field > > > > > > with a list of audit container IDs? How do we handle that? > > > > > > > > > > I don't understand the problem. (I think you crossed your 1/2 vs > > > > > A/B/Y/Z in your example.) ... > > > > > > > > It looks like I did, sorry about that. > > > > > > > > > ... Clarifying the example above, if as you > > > > > suggest an event happens in container Z, the hosts's auditd would report > > > > > Z,^2 > > > > > and the auditd in container 2 would report > > > > > Z,^2 > > > > > but if there were another auditd running in container Z it would report > > > > > Z > > > > > while the auditd in container 1 or A/B would see nothing. > > > > > > > > Yes. My concern is how do we handle this to minimize duplicating and > > > > rewriting the records? It isn't so much about the format, although > > > > the format is a side effect. > > > > > > Are you talking about caching, or about divulging more information than > > > necessary or even information leaks? Or even noticing that records that > > > need to be generated to two audit daemons share the same contid field > > > values and should be generated at the same time or information shared > > > between them? I'd see any of these as optimizations that don't affect > > > the api. > > > > Imagine a record is generated in a container which has more than one > > auditd in it's ancestry that should receive this record, how do we > > handle that without completely killing performance? That's my > > concern. If you've already thought up a plan for this - excellent, > > please share :) > > No, I haven't given that much thought other than the correctness and > security issues of making sure that each audit daemon is sufficiently > isolated to do its job but not jeopardize another audit domain. Audit > already kills performance, according to some... > > We currently won't have that problem since there can only be one so far. > Fixing and optimizing this is part of the next phase of the challenge of > adding a second audit daemon. > > Let's work on correctness and reasonable efficiency for this phase and > not focus on a problem we don't yet have. I wouldn't consider this > incurring technical debt at this point. I agree, one stage at a time, but the choice we make here is going to have a significant impact on what we can do later. We need to get this as "right" as possible; this isn't something we should dismiss with a hand-wave as a problem for the next stage. We don't need an implementation, but I would like to see a rough design of how we would address this problem. > I could see cacheing a contid string from one starting point, but it may > be more work to search that cached string to truncate it or add to it > when another audit daemon requests a copy of a similar string. I > suppose every full contid string could be generated the first time it is > used and parts of it used (start/finish) as needed but that > search/indexing may not be worth it. I hope we can do better than string manipulations in the kernel. I'd much rather defer generating the ACID list (if possible), than generating a list only to keep copying and editing it as the record is sent.

paul moore