support multi-subject attestations

Signed-off-by: Brian DeHamer <bdehamer@github.com>

packages/attest/README.md

@@ -32,8 +32,7 @@ async function run() {
     const ghToken = core.getInput('gh-token');
 
     const attestation = await attest({
-        subjectName: 'my-artifact-name',
+        subjects: [{name: 'my-artifact-name', digest: { 'sha256': '36ab4667...'}}],
-        subjectDigest: { 'sha256': '36ab4667...'},
         predicateType: 'https://in-toto.io/attestation/release',
         predicate: { . . . },
         token: ghToken
@@ -49,11 +48,12 @@ The `attest` function supports the following options:
 
 ```typescript
 export type AttestOptions = {
-  // The name of the subject to be attested.
+  // Deprecated. Use 'subjects' instead.
-  subjectName: string
+  subjectName?: string
-  // The digest of the subject to be attested. Should be a map of digest
+  // Deprecated. Use 'subjects' instead.
-  // algorithms to their hex-encoded values.
+  subjectDigest?: Record<string, string>
-  subjectDigest: Record<string, string>
+  // Collection of subjects to be attested
+  subjects?: Subject[]
   // URI identifying the content type of the predicate being attested.
   predicateType: string
   // Predicate to be attested.
@@ -68,6 +68,13 @@ export type AttestOptions = {
   // Whether to skip writing the attestation to the GH attestations API.
   skipWrite?: boolean
 }
+
+export type Subject = {
+   // Name of the subject.
+  name: string
+   // Digests of the subject. Should be a map of digest algorithms to their hex-encoded values.
+  digest: Record<string, string>
+}
 ```
 
 ### `attestProvenance`
@@ -105,12 +112,13 @@ The `attestProvenance` function supports the following options:
 
 ```typescript
 export type AttestProvenanceOptions = {
-  // The name of the subject to be attested.
+  // Deprecated. Use 'subjects' instead.
-  subjectName: string
+  subjectName?: string
-  // The digest of the subject to be attested. Should be a map of digest
+  // Deprecated. Use 'subjects' instead.
-  // algorithms to their hex-encoded values.
+  subjectDigest?: Record<string, string>
-  subjectDigest: Record<string, string>
+  // Collection of subjects to be attested
-  // GitHub token for writing attestations.
+  subjects?: Subject[]
+  // URI identifying the content type of the predicate being attested.
   token: string
   // Sigstore instance to use for signing. Must be one of "public-good" or
   // "github".

packages/attest/__tests__/attest.test.ts

@@ -0,0 +1,16 @@
+import {attest} from '../src/attest'
+
+describe('attest', () => {
+  describe('when no subject information is provided', () => {
+    it('throws an error', async () => {
+      const options = {
+        predicateType: 'foo',
+        predicate: {bar: 'baz'},
+        token: 'token'
+      }
+      expect(attest(options)).rejects.toThrowError(
+        'Must provide either subjectName and subjectDigest or subjects'
+      )
+    })
+  })
+})

packages/attest/__tests__/intoto.test.ts

@@ -17,7 +17,7 @@ describe('buildIntotoStatement', () => {
   }
 
   it('returns an intoto statement', () => {
-    const statement = buildIntotoStatement(subject, predicate)
+    const statement = buildIntotoStatement([subject], predicate)
     expect(statement).toMatchSnapshot()
   })
 })

packages/attest/__tests__/provenance.test.ts

@@ -115,8 +115,7 @@ describe('provenance functions', () => {
       describe('when the sigstore instance is explicitly set', () => {
         it('attests provenance', async () => {
           const attestation = await attestProvenance({
-            subjectName,
+            subjects: [{name: subjectName, digest: subjectDigest}],
-            subjectDigest,
             token: 'token',
             sigstore: 'github'
           })
@@ -143,8 +142,7 @@ describe('provenance functions', () => {
 
         it('attests provenance', async () => {
           const attestation = await attestProvenance({
-            subjectName,
+            subjects: [{name: subjectName, digest: subjectDigest}],
-            subjectDigest,
             token: 'token'
           })
 
@@ -178,8 +176,7 @@ describe('provenance functions', () => {
       describe('when the sigstore instance is explicitly set', () => {
         it('attests provenance', async () => {
           const attestation = await attestProvenance({
-            subjectName,
+            subjects: [{name: subjectName, digest: subjectDigest}],
-            subjectDigest,
             token: 'token',
             sigstore: 'public-good'
           })
@@ -206,8 +203,7 @@ describe('provenance functions', () => {
 
         it('attests provenance', async () => {
           const attestation = await attestProvenance({
-            subjectName,
+            subjects: [{name: subjectName, digest: subjectDigest}],
-            subjectDigest,
             token: 'token'
           })
 

packages/attest/src/attest.ts

@@ -14,11 +14,16 @@ 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
+   * @deprecated Use `subjects` instead.
-  // The digest of the subject to be attested. Should be a map of digest
+   **/
-  // algorithms to their hex-encoded values.
+  subjectName?: string
-  subjectDigest: Record<string, string>
+  /**
+   * @deprecated Use `subjects` instead.
+   **/
+  subjectDigest?: Record<string, string>
+  // Subjects to be attested.
+  subjects?: Subject[]
   // Content type of the predicate being attested.
   predicateType: string
   // Predicate to be attested.
@@ -42,15 +47,24 @@ export type AttestOptions = {
  * @returns A promise that resolves to the attestation.
  */
 export async function attest(options: AttestOptions): Promise<Attestation> {
-  const subject: Subject = {
+  let subjects: Subject[]
-    name: options.subjectName,
+
-    digest: options.subjectDigest
+  if (options.subjects) {
+    subjects = options.subjects
+  } else if (options.subjectName && options.subjectDigest) {
+    subjects = [{name: options.subjectName, digest: options.subjectDigest}]
+  } else {
+    throw new Error(
+      'Must provide either subjectName and subjectDigest or subjects'
+    )
   }
+
   const predicate: Predicate = {
     type: options.predicateType,
     params: options.predicate
   }
-  const statement = buildIntotoStatement(subject, predicate)
+
+  const statement = buildIntotoStatement(subjects, predicate)
 
   // Sign the provenance statement
   const payload: Payload = {

packages/attest/src/intoto.ts

@@ -20,12 +20,12 @@ export type InTotoStatement = {
  * @returns The constructed in-toto statement.
  */
 export const buildIntotoStatement = (
-  subject: Subject,
+  subjects: Subject[],
   predicate: Predicate
 ): InTotoStatement => {
   return {
     _type: INTOTO_STATEMENT_V1_TYPE,
-    subject: [subject],
+    subject: subjects,
     predicateType: predicate.type,
     predicate: predicate.params
   }