Re: [PATCH ghak90 V7 20/21] audit: add capcontid to set contid outside init_user_ns

On Mon, Oct 21, 2019 at 7:58 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > On 2019-10-21 17:43, Paul Moore wrote: > > On Mon, Oct 21, 2019 at 5:38 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > On 2019-10-21 15:53, Paul Moore wrote: > > > > On Fri, Oct 18, 2019 at 9:39 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > > On 2019-09-18 21:22, Richard Guy Briggs wrote: > > > > > > Provide a mechanism similar to CAP_AUDIT_CONTROL to explicitly give a > > > > > > process in a non-init user namespace the capability to set audit > > > > > > container identifiers. > > > > > > > > > > > > Use audit netlink message types AUDIT_GET_CAPCONTID 1027 and > > > > > > AUDIT_SET_CAPCONTID 1028. The message format includes the data > > > > > > structure: > > > > > > struct audit_capcontid_status { > > > > > > pid_t pid; > > > > > > u32 enable; > > > > > > }; > > > > > > > > > > Paul, can I get a review of the general idea here to see if you're ok > > > > > with this way of effectively extending CAP_AUDIT_CONTROL for the sake of > > > > > setting contid from beyond the init user namespace where capable() can't > > > > > reach and ns_capable() is meaningless for these purposes? > > > > > > > > I think my previous comment about having both the procfs and netlink > > > > interfaces apply here. I don't see why we need two different APIs at > > > > the start; explain to me why procfs isn't sufficient. If the argument > > > > is simply the desire to avoid mounting procfs in the container, how > > > > many container orchestrators can function today without a valid /proc? > > > > > > Ok, sorry, I meant to address that question from a previous patch > > > comment at the same time. > > > > > > It was raised by Eric Biederman that the proc filesystem interface for > > > audit had its limitations and he had suggested an audit netlink > > > interface made more sense. > > > > I'm sure you've got it handy, so I'm going to be lazy and ask: archive > > pointer to Eric's comments? Just a heads-up, I'm really *not* a fan > > of using the netlink interface for this, so unless Eric presents a > > super compelling reason for why we shouldn't use procfs I'm inclined > > to stick with /proc. > > It was actually a video call with Eric and Steve where that was > recommended, so I can't provide you with any first-hand communication > about it. I'll get more details... Yeah, that sort of information really needs to be on the list. > So, with that out of the way, could you please comment on the general > idea of what was intended to be the central idea of this mechanism to be > able to nest containers beyond the initial user namespace (knowing that > a /proc interface is available and the audit netlink interface isn't > necessary for it to work and the latter can be easily removed)? I'm not entirely clear what you are asking about, are you asking why I care about nesting container orchestrators? Simply put, it is not uncommon for the LXC/LXD folks to see nested container orchestrators, so I felt it was important to support that use case. When we originally started this effort we probably should have done a better job reaching out to the LXC/LXD folks, we may have caught this earlier. Regardless, we caught it, and it looks like we are on our way to supporting it (that's good).

Are you asking why I prefer the procfs approach to setting/getting the audit container ID? For one, it makes it easier for a LSM to enforce the audit container ID operations independent of the other audit control APIs. It also provides a simpler interface for container orchestrators. Both seem like desirable traits as far as I'm concerned.

> > > The intent was to switch to the audit netlink interface for contid, > > > capcontid and to add the audit netlink interface for loginuid and > > > sessionid while deprecating the proc interface for loginuid and > > > sessionid. This was alluded to in the cover letter, but not very clear, > > > I'm afraid. I have patches to remove the contid and loginuid/sessionid > > > interfaces in another tree which is why I had forgotten to outline that > > > plan more explicitly in the cover letter. paul moore