feat(REQ-27): from_sigstore_bundle — ingest cosign/Sigstore bundles (#260) - #264
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feat(REQ-27): from_sigstore_bundle — ingest cosign/Sigstore bundles (#260)#264avrabe wants to merge 1 commit into
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…260) varve (#260) already produces cosign bundles (keyless, GitHub-OIDC) but wsc could only verify artifacts it signed itself — SigstoreBundle can emit wsc signatures but nothing converts an existing cosign bundle back into a KeylessSignature. Adds KeylessSignature::from_sigstore_bundle(json) parsing BOTH wire shapes: - Legacy `rekorBundle` JSON (cosign v2.4.x — what varve's v0.28.0 ships): {base64Signature, cert, rekorBundle:{SignedEntryTimestamp, Payload}}. - Protobuf `bundle.sigstore.dev/v0.3+json` envelope (verificationMaterial + messageSignature + tlogEntries). Faithful extraction (verified against two REAL fixtures committed here): - module_hash is read from the hashedrekord body's spec.data.hash.value, never recomputed; the negative-control test flips one hex char and asserts the extracted hash changes. - integratedTime (unix int) -> RFC3339, the form RekorEntry documents and verify_cert_chain parses (confirmed: cert-chain + body-binding both accept the ingested varve bundle). - v0.3 requires a Fulcio certificate; a raw-public-key (non-keyless) bundle is rejected with a specific error, proven on a real cosign v0.3 bundle. Round-trip fidelity test: from_sigstore_bundle -> from_keyless_signature -> to_json -> from_json preserves signature, module_hash, cert chain and rekor fields (uuid/inclusion_proof intentionally empty for legacy — documented). KNOWN LIMITATION → REQ-28 (#231, the verify half): cosign emits ECDSA signatures in ASN.1 DER (varve's is 71 bytes, 3045…), but the offline verifier's verify_crypto uses P256Signature::from_slice (fixed 64-byte P1363), so it currently rejects an ingested DER signature. Making the verifier accept DER (from_der fallback) and handling the empty Rekor uuid on the offline path is REQ-28's scope — that is where "verify an ingested cosign bundle offline" completes. from_sigstore_bundle here is the faithful ingestion half. Fixtures: legacy = varve v0.28.0 public release; v0.3 = real cosign --new-bundle-format output (see fixtures README). Tests: wsc lib 610 pass/3 ignored; sigstore_bundle 7 pass. Refs: #260, #231 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012aR3Md1h46K9wAUWMQiESH
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Closes the ingestion half of #260: wsc could only verify artifacts it signed itself —
SigstoreBundlecan emit wsc signatures but nothing converted an existing cosign bundle back into aKeylessSignature. varve already ships cosign bundles (keyless, GitHub-OIDC).Change
KeylessSignature::from_sigstore_bundle(json)parses both wire shapes:rekorBundleJSON (cosign v2.4.x — varve's v0.28.0 shape).bundle.sigstore.dev/v0.3+jsonenvelope.Verified against two REAL fixtures (committed)
legacy_rekorbundle_keyless.json— varve v0.28.0's actual public bundle. Internally consistent (body digest =sha256(SHA256SUMS.txt)).protobuf_v0.3_localkey.json— realcosign --new-bundle-formatoutput.Faithful extraction, non-vacuously tested:
module_hashread from the hashedrekord body'sspec.data.hash.value, never recomputed — the negative control flips one hex char and asserts the extracted hash changes.integratedTime(unix int) → RFC3339 (the formverify_cert_chainparses; confirmed cert-chain and body-binding both accept the ingested varve bundle).cosign emits ECDSA signatures in ASN.1 DER (varve's is 71 bytes,
3045…), but the offline verifier'sverify_cryptousesP256Signature::from_slice(fixed 64-byte P1363), so it rejects an ingested DER signature today. Making the verifier accept DER (from_derfallback) + handling the empty Rekoruuidon the offline path is REQ-28's scope — that's where "verify an ingested cosign bundle offline" completes. This PR is the faithful ingestion half; it does not claim the ingested bundle fully verifies (and no test says so).Evidence
wsclib 610 pass/3 ignored;sigstore_bundle7 pass; vacuous-oracle gate clean.Part of the v0.12.0 varve-interop line (plan #261). Refs #260, #231.
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