Re: [PATCH v3 0/9] bpf-lsm: Extend interoperability with IMA

Mimi Zohar
2022-03-07T20:45:27Z

On Mon, 2022-03-07 at 14:17 +0100, KP Singh wrote:
> On Mon, Mar 7, 2022 at 3:57 AM Mimi Zohar <zohar@linux.ibm.com> wrote:
> >
> > On Thu, 2022-03-03 at 14:39 -0800, Alexei Starovoitov wrote:
> >
> > > . There is no such thing as "eBPF modules". There are BPF programs.
> > > They cannot be signed the same way as kernel modules.
> > > We've been working on providing a way to sign them for more
> > > than a year now. That work is still ongoing.
> > >
> > > . IMA cannot be used for integrity check of BPF programs for the same
> > > reasons why kernel module like signing cannot be used.
> >
> > I assume the issue isn't where the signature is stored (e.g. appended,
> > xattr), but of calculating the hash. Where is the discussion taking
>
> This has the relevant background: https://lwn.net/Articles/853489/

Thanks, Jon!

>
> We had some more discussions in one of our BSC meeting:
>
> https://github.com/ebpf-io/bsc/blob/master/minutes.md
>
> and we expect the discussions to continue over conferences this year
> (e.g. LSF/MM/BPF, Linux Plumbers). As I mentioned on another thread
> we don't have to wait for conferences and we can discuss this in the BPF
> office hours. Please feel free to add an agenda at:
>
> https://docs.google.com/spreadsheets/d/1LfrDXZ9-fdhvPEp_LHkxAMYyxxpwBXjywWa0AejEveU/edit#gid=0
>
> (best is to give some notice so that interested folks can join).

Right, but probably a good idea to understand the issues at least at a
high level, before a meeting.

>
> > place? Are there any summaries of what has been discussed?
> >
> > FYI, IMA isn't limited to measuring files. Support was added for
> > buffer measurements (e.g kexec boot command line, certificates) and
> > measuring kernel critical data (e.g. SELinux in memory policy & state,
> > device mapper).
>
> Nice. I need to look at how this is implemented.

ima_measure_critical_data() is of kernel state info, so signature
verification is currently not needed or supported, only measurement.

thanks,

Mimi