add new @actions/attest package

Signed-off-by: Brian DeHamer <[email protected]>
2026-08-27 00:00:33 +02:00 · 2024-02-26 08:52:20 -08:00
parent 415c42d27c
commit 6079dea4c4
24 changed files with 4224 additions and 3 deletions
@@ -0,0 +1,96 @@
+import {Bundle, bundleToJSON} from '@sigstore/bundle'
+import {X509Certificate} from 'crypto'
+import {SigstoreInstance, signingEndpoints} from './endpoints'
+import {buildIntotoStatement} from './intoto'
+import {Payload, signPayload} from './sign'
+import {writeAttestation} from './store'
+
+import type {Attestation, Predicate, Subject} from './shared.types'
+
+const INTOTO_PAYLOAD_TYPE = 'application/vnd.in-toto+json'
+
+/**
+ * Options for attesting a subject / predicate.
+ */
+export type AttestOptions = {
+  // The name of the subject to be attested.
+  subjectName: string
+  // The digest of the subject to be attested. Should be a map of digest
+  // algorithms to their hex-encoded values.
+  subjectDigest: Record<string, string>
+  // Content type of the predicate being attested.
+  predicateType: string
+  // Predicate to be attested.
+  predicate: object
+  // GitHub token for writing attestations.
+  token: string
+  // Sigstore instance to use for signing. Must be one of "public-good" or
+  // "github".
+  sigstore?: SigstoreInstance
+  // Whether to skip writing the attestation to the GH attestations API.
+  skipWrite?: boolean
+}
+
+/**
+ * Generates an attestation for the given subject and predicate. The subject and
+ * predicate are combined into an in-toto statement, which is then signed using
+ * the identified Sigstore instance and stored as an attestation.
+ * @param options - The options for attestation.
+ * @returns A promise that resolves to the attestation.
+ */
+export async function attest(options: AttestOptions): Promise<Attestation> {
+  const subject: Subject = {
+    name: options.subjectName,
+    digest: options.subjectDigest
+  }
+  const predicate: Predicate = {
+    type: options.predicateType,
+    params: options.predicate
+  }
+  const statement = buildIntotoStatement(subject, predicate)
+
+  // Sign the provenance statement
+  const payload: Payload = {
+    body: Buffer.from(JSON.stringify(statement)),
+    type: INTOTO_PAYLOAD_TYPE
+  }
+  const endpoints = signingEndpoints(options.sigstore)
+  const bundle = await signPayload(payload, endpoints)
+
+  // Store the attestation
+  let attestationID: string | undefined
+  if (options.skipWrite !== true) {
+    attestationID = await writeAttestation(bundleToJSON(bundle), options.token)
+  }
+
+  return toAttestation(bundle, attestationID)
+}
+
+function toAttestation(bundle: Bundle, attestationID?: string): Attestation {
+  let certBytes: Buffer
+  switch (bundle.verificationMaterial.content.$case) {
+    case 'x509CertificateChain':
+      certBytes =
+        bundle.verificationMaterial.content.x509CertificateChain.certificates[0]
+          .rawBytes
+      break
+    case 'certificate':
+      certBytes = bundle.verificationMaterial.content.certificate.rawBytes
+      break
+    default:
+      throw new Error('Bundle must contain an x509 certificate')
+  }
+
+  const signingCert = new X509Certificate(certBytes)
+
+  // Collect transparency log ID if available
+  const tlogEntries = bundle.verificationMaterial.tlogEntries
+  const tlogID = tlogEntries.length > 0 ? tlogEntries[0].logIndex : undefined
+
+  return {
+    bundle: bundleToJSON(bundle),
+    certificate: signingCert.toString(),
+    tlogID,
+    attestationID
+  }
+}