Re: [RFC] IMA Log Snapshotting Design Proposal

Mimi Zohar
2023-08-30T23:07:56Z

On Wed, 2023-08-30 at 18:23 -0400, Paul Moore wrote:
> On Wed, Aug 30, 2023 at 6:21 PM Paul Moore <paul@paul-moore.com> wrote:
> > On Wed, Aug 30, 2023 at 5:50 PM Mimi Zohar <zohar@linux.ibm.com> wrote:
> > > On Wed, 2023-08-30 at 16:47 -0400, Paul Moore wrote:
> > > > On Wed, Aug 30, 2023 at 4:25 PM Mimi Zohar <zohar@linux.ibm.com> wrote:
> > > > > Your initial question was "what happens if the file/filesystem becomes
> > > > > inaccessible at some point and an attestation client attempts to read
> > > > > the entire log?". For what reason would it be inaccessible? For the
> > > > > original single tmpfs file, what would make it inaccessible?
> > > >
> > > > In your reply that I had responded to you had mentioned that the
> > > > kernel was simply being passed a fd and taking ownership of it, the fd
> > > > could either be a tmpfs backed file or some form of persistent storage
> > > > as both were discussed in this thread. I imagine a tmpfs filesystem
> > > > could still be forcibly unmounted, resulting in problems, but I can't
> > > > say that for certain. However, there are definitely cases where a fd
> > > > backed against an arbitrary filesystem could run into problems:
> > > > storage device issues for local filesystems, networking issues for
> > > > network filesystems, and good old fashioned user/admin intervention in
> > > > both cases.
> > >
> > > "I imagine tmpfs filesystem could still be forcibly unmounted" sounds
> > > like an attack. Not being able to verify the measurement list against a
> > > quote is probably a good thing.
> >
> > Okay, can you answer the question for an arbitrary persistent
> > filesystem? That was always the more important question, ...

The original proposal, not mine, suggested using a tmpfs file. The
idea of writing the measurements to a file on a persistent filesystem
wasn't mine either. Sush/Tushar were pushing for writing to a
persistent file(s). No argument from me that writing to a file on an
arbitrary persistent filesystem is not a good idea.

--
thanks,

Mimi