On Thu, 2024-06-20 at 10:48 -0400, Paul Moore wrote: > On Thu, Jun 20, 2024 at 5:12 AM Roberto Sassu > <[email protected]> wrote: > > On Wed, 2024-06-19 at 14:43 -0400, Paul Moore wrote: > > > On Wed, Jun 19, 2024 at 12:38 PM Roberto Sassu > > > <[email protected]> wrote: > > > > > > > > Making it a kernel subsystem would likely mean replicating what the LSM > > > > infrastructure is doing, inode (security) blob and being notified about > > > > file/directory changes. > > > > > > Just because the LSM framework can be used for something, perhaps it > > > even makes the implementation easier, it doesn't mean the framework > > > should be used for everything. > > > > It is supporting 3 LSMs: IMA, IPE and BPF LSM. > > > > That makes it a clear target for the security subsystem, and as you > > suggested to start for IMA, if other kernel subsystems require them, we > > can make it as an independent subsystem. > > Have you discussed the file digest cache functionality with either the > IPE or BPF LSM maintainers? While digest_cache may support these
Well, yes. I was in a discussion since long time ago with Deven and Fan. The digest_cache LSM is listed in the Use Case section of the IPE cover letter: https://lore.kernel.org/linux-integrity/[email protected]/ I also developed an IPE module back in the DIGLIM days: https://lore.kernel.org/linux-integrity/[email protected]/ As for eBPF, I just need to make the digest_cache LSM API callable by eBPF programs, very likely not requiring any change on the eBPF infrastructure itself. As an example of the modification needed, you could have a look at: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/bpf_trace.c?h=v6.10-rc4#n1381 Once the digest_cache LSM API is exposed in eBPF, you could write a simple file integrity check (taken from my DIGLIM eBPF), not tested: SEC("lsm.s/bprm_creds_for_exec") int BPF_PROG(exec, struct linux_binprm *bprm) { u8 digest[MAX_DIGEST_SIZE] = { 0 }; digest_cache_found_t found; struct digest_cache; int algo; algo = bpf_ima_file_hash(bprm->file, digest, sizeof(digest)); if (algo < 0) return -EPERM; digest_cache = bpf_digest_cache_get(bprm->file->f_path.dentry); if (!digest_cache) return -EPERM; found = bpf_digest_cache_lookup(bprm->file->f_path.dentry, digest_cache, digest, algo); bpf_digest_cache_put(digest_cache); return found ? 0 : -EPERM; } Roberto > LSMs, I don't recall seeing any comments from the other LSM > developers; if you are going to advocate for this as something outside > of IMA, it would be good to see a show of support for the other LSMs. >
