Re: RFC(v2): Audit Kernel Container IDs

[Aleksa Sarai]

> > > > The registration is a pseudo filesystem (proc, since PID tree already
> > > > exists) write of a u8[16] UUID representing the container ID to a file
> > > > representing a process that will become the first process in a new
> > > > container. This write might place restrictions on mount namespaces
> > > > required to define a container, or at least careful checking of
> > > > namespaces in the kernel to verify permissions of the orchestrator 
> > > > so it
> > > > can't change its own container ID. A bind mount of nsfs may be
> > > > necessary in the container orchestrator's mntNS.
> > > > Note: Use a 128-bit scalar rather than a string to make compares faster
> > > > and simpler.
> > > >
> > > > Require a new CAP_CONTAINER_ADMIN to be able to carry out the
> > > > registration.
> > >
> > > Wouldn't CAP_AUDIT_WRITE be sufficient? After all, this is for auditing.
> >
> > No, because then any process with that capability (vsftpd) could change
> > its own container ID. This is discussed more in other parts of the
> > thread...
>
> Not if we make the container ID append-only (to support nesting), or 
> write-once (the other idea thrown around). In that case, you can't move 
> "out" from a particular container ID, you can only go "deeper". These 
> semantics don't make sense for generic containers, but since the point 
> of this facility is *specifically* for audit I imagine that not being 
> able to move a process from a sub-container's ID is a benefit.

[This assumes it's CAP_AUDIT_CONTROL which is what we are discussing in 
a sister thread.]

--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/