Bump sigstore-go, support alternative hash algorithms with keys #4386

haydentherapper · 2025-09-04T22:49:51Z

sigstore-go now handles non-ECDSA-P-256 signatures with Rekor v2. To support verification, we also need a way to provide alternative hash algorithms to the default SHA-256. cosign verify already had a flag for this, so I added the flag to all verify commands. In the future, when we are only processing bundles, we can lookup the default hash algorithm given the key.

Summary

Release Note

Documentation

haydentherapper · 2025-09-04T22:50:35Z

Tested with:

openssl ecparam -genkey -name secp521r1 -noout -out ecdsa-p521-private.pem
cosign import-key-pair --key ecdsa-p521-private.pem
cosign sign-blob --new-bundle-format --bundle artifact.sigstore.json --yes --use-signing-config --key cosign.key README.md
cosign verify-blob --new-bundle-format --bundle artifact.sigstore.json --key cosign.pub --signature-digest-algorithm sha512 README.md

go.mod

codecov · 2025-09-04T22:52:04Z

Codecov Report

❌ Patch coverage is 41.30435% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 34.35%. Comparing base (2ef6022) to head (5701322).
⚠️ Report is 514 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/cosign/cli/verify.go	0.00%	15 Missing ⚠️
cmd/cosign/cli/sign/sign.go	0.00%	4 Missing ⚠️
internal/key/svkeypair.go	55.55%	3 Missing and 1 partial ⚠️
cmd/cosign/cli/options/verify.go	0.00%	3 Missing ⚠️
cmd/cosign/cli/verify/verify_attestation.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4386      +/-   ##
==========================================
- Coverage   40.10%   34.35%   -5.76%     
==========================================
  Files         155      217      +62     
  Lines       10044    15537    +5493     
==========================================
+ Hits         4028     5337    +1309     
- Misses       5530     9508    +3978     
- Partials      486      692     +206

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steiza · 2025-09-08T14:14:25Z

So in sigstore/sigstore-go#520 (comment) we decided to not support ed25519ph with Fulcio for now, but with #4050 we implemented adaptSignerVerifierToFulcio in cmd/cosign/cli/sign/sign.go.

As part of these changes, should we partially roll back the adaptSignerVerifierToFulcio changes that were made in #4050? cc @ret2libc

haydentherapper · 2025-09-08T18:12:41Z

So in sigstore/sigstore-go#520 (comment) we decided to not support ed25519ph with Fulcio for now, but with #4050 we implemented adaptSignerVerifierToFulcio in cmd/cosign/cli/sign/sign.go.

As part of these changes, should we partially roll back the adaptSignerVerifierToFulcio changes that were made in #4050? cc @ret2libc

I'm fine with leaving this in, and documenting this is a change between Cosign v2 and v3 when we switch over signing to sigstore-go.

steiza · 2025-09-09T02:20:04Z

The test coverage shows up as high, but I don't think we have an automated test that covers verifying with a SHA512 digest? We should have at least one test that covers that case (if we don't already!)

I'm fine with leaving this in, and documenting this is a change between Cosign v2 and v3 when we switch over signing to sigstore-go.

I'm not wild about releasing a feature we plan to immediately deprecate 🙃 but I'm also not sure how easy it is to untangle these things.

haydentherapper · 2025-09-09T02:26:53Z

Oh sorry, I was thinking we had merged the adapter in an earlier PR and it was already in a released version. Lemme take a pass at this tomorrow.

sigstore-go now handles non-ECDSA-P-256 signatures with Rekor v2. To support verification, we also need a way to provide alternative hash algorithms to the default SHA-256. cosign verify already had a flag for this, so I added the flag to all verify commands. In the future, when we are only processing bundles, we can lookup the default hash algorithm given the key. Signed-off-by: Hayden <[email protected]>

Signed-off-by: Hayden <[email protected]>

We've chosen to not support this in sigstore-go, so we'll also remove this from Cosign. This is a niche edge case where a user provides an ed25519 key or algorithm and requests a cert and logs it to Rekor. We'll revisit this if there's demand or when we support the prehash variant in Fulcio. Signed-off-by: Hayden <[email protected]>

steiza

This is great - thanks!

This MR contains the following updates: | Package | Update | Change | |---|---|---| | [cosign](https://github.com/sigstore/cosign) | minor | `2.5.3` -> `2.6.0` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>sigstore/cosign (cosign)</summary> ### [`v2.6.0`](https://github.com/sigstore/cosign/blob/HEAD/CHANGELOG.md#v260) [Compare Source](sigstore/cosign@v2.5.3...v2.6.0) v2.6.0 introduces a number of new features, including: - Signing an in-toto statement rather than Cosign constructing one from a predicate, along with verifying a statement's subject using a digest and digest algorithm rather than providing a file reference ([#4306](sigstore/cosign#4306)) - Uploading a signature and its verification material (a ["bundle"](https://github.com/sigstore/protobuf-specs/blob/main/protos/sigstore_bundle.proto)) as an OCI Image 1.1 referring artifact, completing [#3927](sigstore/cosign#3927) ([#4316](sigstore/cosign#4316)) - Providing service URLs for signing and attesting using a [SigningConfig](https://github.com/sigstore/protobuf-specs/blob/4df5baadcdb582a70c2bc032e042c0a218eb3841/protos/sigstore_trustroot.proto#L185). Note that this is required when using a [Rekor v2](https://github.com/sigstore/rekor-tiles) instance ([#4319](sigstore/cosign#4319)) Example generation and verification of a signed in-toto statement: ``` cosign attest-blob --new-bundle-format=true --bundle="digest-key-test.sigstore.json" --key="cosign.key" --statement="../sigstore-go/examples/sigstore-go-signing/intoto.txt" cosign verify-blob-attestation --bundle="digest-key-test.sigstore.json" --key=cosign.pub --type=unused --digest="b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9" --digestAlg="sha256" ``` Example container signing and verification using the new bundle format and referring artifacts: ``` cosign sign --new-bundle-format=true ghcr.io/user/alpine@sha256:a19367999603840546b8612572e338ec076c6d1f2fec61760a9e11410f546733 cosign verify --new-bundle-format=true ghcr.io/user/alpine@sha256:a19367999603840546b8612572e338ec076c6d1f2fec61760a9e11410f546733 ``` Example usage of a signing config provided by the public good instance's TUF repository: ``` cosign sign-blob --use-signing-config --bundle sigstore.json README.md cosign verify-blob --new-bundle-format --bundle sigstore.json --certificate-identity $EMAIL --certificate-oidc-issuer $ISSUER --use-signed-timestamps README.md ``` v2.6.0 leverages sigstore-go's signing and verification APIs gated behind these new flags. In an upcoming major release, we will be updating Cosign to default to producing and consuming bundles to align with all other Sigstore SDKs. #### Features - Add to `attest-blob` the ability to supply a complete in-toto statement, and add to `verify-blob-attestation` the ability to verify with just a digest ([#4306](sigstore/cosign#4306)) - Have cosign sign support bundle format ([#4316](sigstore/cosign#4316)) - Add support for SigningConfig for sign-blob/attest-blob, support Rekor v2 ([#4319](sigstore/cosign#4319)) - Add support for SigningConfig in sign/attest ([#4371](sigstore/cosign#4371)) - Support self-managed keys when signing with sigstore-go ([#4368](sigstore/cosign#4368)) - Don't require timestamps when verifying with a key ([#4337](sigstore/cosign#4337)) - Don't load content from TUF if trusted root path is specified ([#4347](sigstore/cosign#4347)) - Add a terminal spinner while signing with sigstore-go ([#4402](sigstore/cosign#4402)) - Require exclusively a SigningConfig or service URLs when signing ([#4403](sigstore/cosign#4403)) - Remove SHA256 assumption in sign-blob/verify-blob ([#4050](sigstore/cosign#4050)) - Bump sigstore-go, support alternative hash algorithms with keys ([#4386](sigstore/cosign#4386)) #### Breaking API Changes - `sign.SignerFromKeyOpts` no longer generates a key. Instead, it returns whether or not the client needs to generate a key, and if so, clients should call `sign.KeylessSigner`. This allows clients to more easily manage key generation. #### Bug Fixes - Verify subject with bundle only when checking claims ([#4320](sigstore/cosign#4320)) - Fixes to cosign sign / verify for the new bundle format ([#4346](sigstore/cosign#4346)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this MR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this MR, check this box --- This MR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).

haydentherapper requested a review from steiza September 4, 2025 22:49

haydentherapper commented Sep 4, 2025

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haydentherapper force-pushed the bump-sgo branch from 910b222 to e8f915a Compare September 8, 2025 18:08

haydentherapper marked this pull request as ready for review September 8, 2025 18:09

haydentherapper requested review from a team as code owners September 8, 2025 18:09

haydentherapper force-pushed the bump-sgo branch from e8f915a to ff13a5d Compare September 8, 2025 18:12

haydentherapper force-pushed the bump-sgo branch from ff13a5d to 6a01c50 Compare September 8, 2025 18:14

haydentherapper added 2 commits September 10, 2025 16:42

lint fmt

1ac5785

Signed-off-by: Hayden <[email protected]>

haydentherapper force-pushed the bump-sgo branch from 5b92546 to d58dd15 Compare September 10, 2025 23:53

haydentherapper force-pushed the bump-sgo branch from d58dd15 to 5701322 Compare September 11, 2025 06:02

steiza approved these changes Sep 11, 2025

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haydentherapper merged commit 11163ae into sigstore:main Sep 11, 2025
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haydentherapper deleted the bump-sgo branch September 11, 2025 15:32

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Bump sigstore-go, support alternative hash algorithms with keys #4386

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Bump sigstore-go, support alternative hash algorithms with keys #4386

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haydentherapper commented Sep 4, 2025

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