sigstore
Support timestamp responses during both signing and verification?
Sigstore has an RFC 3161 TSA now, and signers can request a TSR from it while signing.
During signing, this would probably look like:
- Doing signing as normal;
- Submitting a timestamp request (probably the digest of the signature) to Sigstore's TSA (or a custom TSA), and retrieving the TSR
- Uploading the TSR to Rekor
and then, for verification:
- Checking if a TSR is present (
{input}.tsr); - If present, verifying it against the TSA's public material;
- Confirming that the TSR was entered into Rekor during the certificate's validity period
(I think I got that right, but I might be missing a few details.)
cc @di for thoughts on whether we should support this.
xref https://github.com/sigstore/root-signing/issues/466: this is probably blocked for us on the fact that the TSA's cert chain isn't included in the TUF repo yet.
Edit: Scheduled for v7 of the TUF root: https://github.com/sigstore/root-signing/issues/616
Should be unblocked now.
Triage: this might be worth scheduling for the 2.0, although nobody is currently assigned to it.
Hey @woodruffw, just wondering, are there any major blockers for this? Is there python support for rfc3161 timestamping?
Hey @woodruffw, just wondering, are there any major blockers for this? Is there python support for rfc3161 timestamping?
I don't know of a good client implementation, unfortunately 😞 -- there are a few public ones, but most seem pretty small:
- https://github.com/pyauth/tsp-client
- https://github.com/trbs/rfc3161ng
(tsp-client looks promising, but I haven't looked closely at it yet.)
Another option here would be to add TSR/RFC 3161 support to Cryptography, or potentially reuse the existing PKCS#7/CMS support (since, IIRC, RFC 3161 boils down to a CMS envelope anyways).