Re: RFC(V3): Audit Kernel Container IDs

Casey Schaufler
2018-02-03T19:05:32Z

On 2/2/2018 3:24 PM, Paul Moore wrote:
> On Fri, Feb 2, 2018 at 5:19 PM, Simo Sorce <simo@redhat.com> wrote:
>> On Fri, 2018-02-02 at 16:24 -0500, Paul Moore wrote:
>>> On Wed, Jan 10, 2018 at 2:00 AM, Richard Guy Briggs <rgb@redhat.com> wrote:
>>>> On 2018-01-09 11:18, Simo Sorce wrote:
>>>>> On Tue, 2018-01-09 at 07:16 -0500, Richard Guy Briggs wrote:
> ..
>
>>>> Paul, can you justify this somewhat larger inconvenience for some
>>>> relatively minor convenience on our part?
>>> Done in direct response to Simo.
>> Sorry but your response sounds more like waving away then addressing
>> them, the excuse being: we can't please everyone, so we are going to
>> please no one.
> I obviously disagree with the take on my comments but you're free to
> your opinion.
>
> I believe saying we are pleasing no one isn't really fair now is it?
> Is there any type of audit container ID now? How would you go about
> associating audit events with containers now? (spoiler alert: it ain't
> pretty, and there are gaps I don't believe you can cover) This
> proposal provides a mechanism to do this in a way that isn't tied to
> any one particular concept of a container and is manageable inside the
> kernel.
>
> If you have a need to track audit events for containers, I find it
> extremely hard to believe that you are not at least partially pleased
> by the solutions presented here. It may not be everything on your
> wishlist, but when did you ever get *everything* on your wishlist?

I am going to back Paul 100% on this point. The container
community's emphatic position that containers are strictly
a user-space construct makes it impossible for the kernel
to provide any data more sophisticated than an integer, and
any processing based on that data cleverer than a check
for equality.

>>> But to be clear Richard, we've talked about this a few times, it's not
>>> a "minor convenience" on our part, it's a pretty big convenience once
>>> we starting having to route audit events and make decisions based on
>>> the audit container ID information. Audit performance is less than
>>> awesome now, I'm working hard to not make it worse.
>> Sounds like a security vs performance trade off to me.

Without the kernel having a "container" policy to work with there
is no "security" it can possibly enforce.

> Welcome to software development. It's generally a pretty terrible
> hobby and/or occupation, but we make up for it with long hours and
> endless frustration.
>
>>>> u64 vs u128 is easy for us to
>>>> accomodate in terms of scalar comparisons. It doubles the information
>>>> in every container id field we print in audit records.
>>> ... and slows down audit container ID checks.
>> Are you saying a cmp on a u128 is slower than a comparison on a u64 and
>> this is something that will be noticeable ?
> Do you have a 128 bit system? I don't. I've got a bunch of 64 bit
> systems, and a couple of 32 bit systems too. People that use audit
> have a tendency to really hammer on it, to the point that we get
> performance complaints on a not infrequent basis. I don't know the
> exact number of times we are going to need to check the audit
> container ID, but it's reasonable to think that we'll expose it as a
> filter-able field which adds a few checks, we'll use it for record
> routing so that's a few more, and if we're running multiple audit
> daemons we will probably want to include LSM checks which could result
> in a few more audit container ID checks. If it was one comparison I
> wouldn't be too worried about it, but the point I'm trying to make is
> that we don't know what the implementation is going to look like yet
> and I suspect this ID is going to be leveraged in several places in
> the audit subsystem and I would much rather start small to save
> headaches later.
>
> We can always expand the ID to a larger integer at a later date, but
> we can't make it smaller.
>
>>>> A c36 is a bigger step.
>>> Yeah, we're not doing that, no way.
>> Ok, I can see your point though I do not agree with it.
>>
>> I can see why you do not want to have arbitrary length strings, but a
>> u128 sounded like a reasonable compromise to me as it has enough room
>> to be able to have unique cluster-wide IDs which a u64 definitely makes
>> a lot harder to provide w/o tight coordination.
> I originally wanted it to be a 32-bit integer, but Richard managed to
> talk me into 64-bits, that was my compromise :)
>
> As I said earlier, if you are doing container auditing you're going to
> need coordination with the orchestrator, regardless of the audit
> container ID size.
>