Re: [PATCH RFC] audit: provide namespace information in user originated records

Eric Paris
2013-03-21T01:46:03Z

On Wed, 2013-03-20 at 16:23 -0700, Eric W. Biederman wrote:
> Eric Paris <eparis-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> writes:
>
> > On Wed, 2013-03-20 at 13:49 -0500, Serge Hallyn wrote:
> >> Quoting Eric Paris (eparis-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org):
> >> > On Wed, 2013-03-20 at 13:36 -0500, Serge Hallyn wrote:
> >> > > Quoting Aristeu Rozanski (arozansk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org):
> >> > > > This is a bit fuzzy to me, perhaps due I'm not fully understanding
> >> > > > userns implementation yet, so bear with me:
> >> > > > I thought of changing so userns would not grant CAP_AUDIT_WRITE and
> >> > > > CAP_AUDIT_CONTROL unless the process already has it (i.e. it'd require
> >> > >
> >> > > Seems like CAP_AUDIT_WRITE should be targeted against the
> >> > > skb->netns->userns. Then CAP_AUDIT_WRITE can be treated like any other
> >> > > capability. Last I knew (long time ago) you had to be in init_user_ns
> >> > > to talk audit, but that's ok - this would just do the right thing in
> >> > > any case.
> >> >
> >> > kauditd should be considered as existing in the init user namespace. So
> >> > I'd think we'd want to check if the process had CAP_AUDIT_WRITE in the
> >> > init user namespace and if so, allow it to send messages. Who care what
> >> > *ns the process exists in. If it has it in the init namespace, go
> >> > ahead. Thus the process that created the container would need
> >> > CAP_AUDIT_WRITE in the init namespace for this to all work, right?
> >>
> >> Yes. What I was suggesting is intended to work if that situation ever
> >> changes. But I have zero complaints about doing it as you say, as I
> >> doubt it ever will/ought to change.
> >>
> >> That basically means CAP_AUDIT_WRITE would be worthless in a non-init
> >> userns. That's fine - at least the rules would be consistent.
> >
> > [veering away from this particular patch]
> >
> > We are also talking about adding a CAP_AUDIT_READ and sending messages
> > via multicast on the audit socket. The problem is I don't know how the
> > audit socket could work in the network namespace world.
>
> Hmm. I don't quite know how CAP_AUDIT_READ could work. When delivering
> a message to a socket you really don't know who is on the other end.
>
> > Right now kauditd has:
> >
> > audit_sock = netlink_kernel_create(&init_net, NETLINK_AUDIT, &cfg);
> >
> > So there won't ever be anything on the kernel side of the audit socket
> > in a non-init network namespace. Lets say that is fixed somehow (I
> > assume it's possible? something? magic pixies?)
>
> One socket for each network namespace... It is a pain but doable.
>
> > I think we'd somehow
> > need to do the CAP_AUDIT_READ check against the user namespace
> > associated with the network namespace in question? But what messages
> > should go to this userspace auditd?
>
> Messages generated by processes in that user namespace?

So the kernel socket(s) would be per network namespace, but we divide
messages per user namespace? Which socket do I send them on,
considering the possible crazy many<->many mappings between user and
network namespaces. It all makes me cry a little.

> > Going to have to have audit namespaces to. But only CAP_AUDIT_READ
> > would make sense in the new audit namespace...
>
> Given the connection of audit and security I think if we add support for
> a non-global auditd the user namespace seems to fit. The user namespace
> is certainly where all of the security connected bits go.
>
> Architecturally it gets a little tricky as it seems to make sense to
> generate audit messages that make sense to the process receiving them,
> which would mean actually generating a different audit message for
> different receiving contexts.

Assuming as today, we only have 1 auditd and it is system wide. We just
attach consistent identifiable information (aka proc inode number, which
people already use) to the audit records (this patch only does user
messages, but attaching to all messages needs to be done).

Moving to multiple auditd's starts to get really hard, and we might not
ever pursue it :)

> I find the auditsc code odd. We log file descriptor numbers when a file
> is mmaped? What is something so process relative good to anyone?

When an earlier record showed that fd being opened? I dunno....

> On a slightly different tangent. Do we want to update the AUDIT_CAPSET
> message to report the user namespace whose caps we are changing or
> perhaps to surpress the message outside of the initial user namespace.

The extension of Aris's patch to syscall audit instead of just userspace
audit would take care of this.