add new @actions/attest package

Signed-off-by: Brian DeHamer <[email protected]>

packages/attest/src/sign.ts

@@ -0,0 +1,107 @@
+import {Bundle} from '@sigstore/bundle'
+import {
+  BundleBuilder,
+  CIContextProvider,
+  DSSEBundleBuilder,
+  FulcioSigner,
+  RekorWitness,
+  TSAWitness,
+  Witness
+} from '@sigstore/sign'
+
+const OIDC_AUDIENCE = 'sigstore'
+const DEFAULT_TIMEOUT = 10000
+const DEFAULT_RETRIES = 3
+
+/**
+ * The payload to be signed (body) and its media type (type).
+ */
+export type Payload = {
+  body: Buffer
+  type: string
+}
+
+/**
+ * Options for signing a document.
+ */
+export type SignOptions = {
+  /**
+   * The URL of the Fulcio service.
+   */
+  fulcioURL: string
+  /**
+   * The URL of the Rekor service.
+   */
+  rekorURL?: string
+  /**
+   * The URL of the TSA (Time Stamping Authority) server.
+   */
+  tsaServerURL?: string
+  /**
+   * The timeout duration in milliseconds when communicating with Sigstore
+   * services.
+   */
+  timeout?: number
+  /**
+   * The number of retry attempts.
+   */
+  retry?: number
+}
+
+/**
+ * Signs the provided payload with a Sigstore-issued certificate and returns the
+ * signature bundle.
+ * @param payload Payload to be signed.
+ * @param options Signing options.
+ * @returns A promise that resolves to the Sigstore signature bundle.
+ */
+export const signPayload = async (
+  payload: Payload,
+  options: SignOptions
+): Promise<Bundle> => {
+  const artifact = {
+    data: payload.body,
+    type: payload.type
+  }
+
+  // Sign the artifact and build the bundle
+  return initBundleBuilder(options).create(artifact)
+}
+
+// Assembles the Sigstore bundle builder with the appropriate options
+const initBundleBuilder = (opts: SignOptions): BundleBuilder => {
+  const identityProvider = new CIContextProvider(OIDC_AUDIENCE)
+  const timeout = opts.timeout || DEFAULT_TIMEOUT
+  const retry = opts.retry || DEFAULT_RETRIES
+  const witnesses: Witness[] = []
+
+  const signer = new FulcioSigner({
+    identityProvider,
+    fulcioBaseURL: opts.fulcioURL,
+    timeout,
+    retry
+  })
+
+  if (opts.rekorURL) {
+    witnesses.push(
+      new RekorWitness({
+        rekorBaseURL: opts.rekorURL,
+        entryType: 'dsse',
+        timeout,
+        retry
+      })
+    )
+  }
+
+  if (opts.tsaServerURL) {
+    witnesses.push(
+      new TSAWitness({
+        tsaBaseURL: opts.tsaServerURL,
+        timeout,
+        retry
+      })
+    )
+  }
+
+  return new DSSEBundleBuilder({signer, witnesses})
+}