On Thu, Dec 02, 2021 at 05:13:15PM -0500, Mimi Zohar wrote: > On Thu, 2021-12-02 at 14:07 -0800, Eric Biggers wrote: > > On Thu, Dec 02, 2021 at 04:55:06PM -0500, Mimi Zohar wrote: > > > case IMA_VERITY_DIGSIG: > > > - fallthrough; > > > + set_bit(IMA_DIGSIG, &iint->atomic_flags); > > > + > > > + /* > > > + * The IMA signature is based on a hash of IMA_VERITY_DIGSIG > > > + * and the fs-verity file digest, not directly on the > > > + * fs-verity file digest. Both digests should probably be > > > + * included in the IMA measurement list, but for now this > > > + * digest is only used for verifying the IMA signature. > > > + */ > > > + verity_digest[0] = IMA_VERITY_DIGSIG; > > > + memcpy(verity_digest + 1, iint->ima_hash->digest, > > > + iint->ima_hash->length); > > > + > > > + hash.hdr.algo = iint->ima_hash->algo; > > > + hash.hdr.length = iint->ima_hash->length; > > > > This is still wrong because the bytes being signed don't include the hash > > algorithm. Unless you mean for it to be implicitly always SHA-256? fs-verity > > supports SHA-512 too, and it may support other hash algorithms in the future. > > The signature stored in security.ima is prefixed with a header > (signature_v2_hdr). Yes, but the byte that identifies the hash algorithm is not included in the bytes that are actually signed, as far as I can tell. - Eric
