On Mon, 2021-11-29 at 18:33 -0800, Eric Biggers wrote: > On Mon, Nov 29, 2021 at 12:00:55PM -0500, Mimi Zohar wrote: > > To differentiate between a regular file hash and an fs-verity file digest > > based signature stored as security.ima xattr, define a new signature type > > named IMA_VERITY_DIGSIG. > > > > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> > > For this new signature type, what bytes are actually signed? It looks like it's > just the raw digest, which isn't sufficient since it is ambiguous. It needs to > include information that makes it clear what the signer is actually signing, > such as "this is an fs-verity SHA-256 file digest". See > 'struct fsverity_formatted_digest' for an example of this (but it isn't > necessary to use that exact structure). > > I think the existing IMA signatures have the same problem (but it is hard for me > to understand the code). However, a new signature type doesn't have > backwards-compatibility concerns, so it could be done right. As this change should probably be applicable to all signature types, the signature version in the signature_v2_hdr should be bumped. The existing signature version could co-exist with the new signature version. thanks, Mimi
