Re: [PATCH 0/2] ima: add dont_audit and fs_subtype to policy language

[Mimi Zohar <zohar@linux.ibm.com>]

On Tue, 2025-09-30 at 16:26 +0200, Jann Horn wrote:
> On Tue, Sep 30, 2025 at 12:23 PM Mimi Zohar <zohar@linux.ibm.com> wrote:
> > On Fri, 2025-09-26 at 01:45 +0200, Jann Horn wrote:
> > > This series adds a "dont_audit" action that cancels out following
> > > "audit" actions (as we already have for other action types), and also
> > > adds an "fs_subtype" that can be used to distinguish between FUSE
> > > filesystems.
> > > 
> > > With these two patches applied, as a toy example, you can use the
> > > following policy:
> > > ```
> > > dont_audit fsname=fuse fs_subtype=sshfs
> > > audit func=BPRM_CHECK fsname=fuse
> > > ```
> > > 
> > > I have tested that with this policy, executing a binary from a
> > > "fuse-zip" FUSE filesystem results in an audit log entry:
> > > ```
> > > type=INTEGRITY_RULE msg=audit([...]): file="/home/user/ima/zipmount/usr/bin/echo" hash="sha256:1d82e8[...]
> > > ```
> > > while executing a binary from an "sshfs" FUSE filesystem does not
> > > generate any audit log entries.
> > > 
> > > Signed-off-by: Jann Horn <jannh@google.com>
> > 
> > 
> > Thanks, Jann.  The patches look fine.  Assuming the "toy" test program creates
> > and mounts the fuse filesystems, not just loads the IMA policy rules, could you
> > share it?
> 
> Thanks for the quick review! To clarify, by "toy example" I meant that
> while I was using real FUSE filesystems, the policy I was using is not
> very sensible.
> 
> I used real FUSE filesystems for this since I figured that would be
> the easiest way to test, https://github.com/libfuse/sshfs and
> https://bitbucket.org/agalanin/fuse-zip. These are packaged in distros
> like Debian (as "sshfs" and "fuse-zip"). I mounted sshfs with these
> commands (mounting the home directory over ssh at ~/mnt/ssh):
> 
> user@vm:~$ cp /usr/bin/echo ~/ima/
> user@vm:~$ sshfs localhost: ~/mnt/ssh
> 
> and mounted fuse-zip with:
> 
> user@vm:~/ima$ zip -rD echo.zip /usr/bin/echo
>   adding: usr/bin/echo (deflated 62%)
> user@vm:~/ima$ mkdir zipmount
> user@vm:~/ima$ fuse-zip echo.zip zipmount/
> 
> I then ran the executables ~/ima/zipmount/usr/bin/echo and ~/mnt/ssh/ima/echo.

Thank you for the instructions.  Due to the holidays, there was a delay. The
patches are now queued in next-integrity for 6.19.

Mimi