Move component count test to verifier suite & update to 7 components

tests/assertions.js

@@ -111,7 +111,7 @@ export const shouldNotUseCborTags = ({proof}) => {
 
 export const baseProofShouldHaveElementCount = ({
   proof,
-  expectedLengths = [5, 6],
+  expectedLengths = [5, 6, 7],
   reason = 'Expected baseProof to have expected number of components'
 }) => {
   let error;

tests/setup.js

@@ -14,6 +14,10 @@ import {
   getMultikeys,
   issueCredentials
 } from './vc-generator/index.js';
+import {
+  encodeProofValue,
+  parseDisclosureProofValue
+} from './vc-generator/stubMethods.js';
 import {generators} from 'data-integrity-test-suite-assertion';
 import {writeFile} from 'node:fs/promises';
 
@@ -144,6 +148,21 @@ export async function verifySetup({credentials, keyTypes, suite}) {
     }
   }
   disclosed.invalid.valuePrefix = valuePrefix;
+  // invalid element count means less than 4 components
+  const componentCount = disclosed.invalid.componentCount = new Map();
+  // use the basic disclosed vc
+  for(const [keyType, versions] of disclosed?.basic) {
+    componentCount.set(keyType, new Map());
+    for(const [vcVersion, vc] of versions) {
+      const modifiedVc = structuredClone(vc);
+      const params = parseDisclosureProofValue({proof: modifiedVc.proof});
+      // create a payload with only 2 components
+      const payload = [params.bbsProof, params.presentationHeader];
+      // replace the existing proofValue with the smaller payload
+      modifiedVc.proof.proofValue = encodeProofValue({payload});
+      componentCount.get(keyType).set(vcVersion, modifiedVc);
+    }
+  }
   return {
     base,
     disclosed

tests/suites/create.js

@@ -4,7 +4,6 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 import {
-  baseProofShouldHaveElementCount,
   checkEncoding,
   checkHmacKeyLength,
   shouldBeMultibaseEncoded,
@@ -266,23 +265,12 @@ export function createSuite({
           }
         });
         it('The transformation options MUST contain an array of mandatory ' +
-        'JSON pointers (mandatoryPointers)', function() {
+        'JSON pointers (mandatoryPointers).', function() {
           this.test.link = 'https://w3c.github.io/vc-di-bbs/#:~:text=The%20transformation%20options%20MUST%20contain%20an%20array%20of%20mandatory%20JSON%20pointers%20(mandatoryPointers)';
           for(const proof of bbsProofs) {
             shouldHaveMandatoryPointers({proof});
           }
         });
-        it('Initialize components to an array that is the result of ' +
-        'CBOR-decoding the bytes that follow the three-byte BBS disclosure ' +
-        'proof header. If the result is not an array of five or six elements ' +
-        '— a byte array, a map of integers to integers, two arrays of ' +
-        'integers, and one or two byte arrays; an error MUST be raised and ' +
-        'SHOULD convey an error type of PROOF_VERIFICATION_ERROR.', function() {
-          this.test.link = 'https://w3c.github.io/vc-di-bbs/#:~:text=%22pseudonym_hidden_pid%22.-,Initialize%20components%20to%20an%20array%20that%20is%20the%20result%20of%20CBOR,be%20raised%20and%20SHOULD%20convey%20an%20error%20type%20of%20PROOF_VERIFICATION_ERROR.,-Replace%20the%20second';
-          for(const proof of bbsProofs) {
-            baseProofShouldHaveElementCount({proof});
-          }
-        });
         it.skip(' If featureOption is set to "anonymous_holder_binding" or ' +
         '"pseudonym_hidden_pid", the commitment_with_proof input MUST be ' +
         'supplied.', async function() {

tests/suites/verify.js

@@ -144,6 +144,18 @@ export function verifySuite({
           const credential = cloneTestVector(disclosed?.invalid?.valuePrefix);
           await verificationFail({credential, verifier});
         });
+        it('If the result is not an array of five, six, or seven elements ' +
+          '— a byte array, a map of integers to integers, two arrays of ' +
+          'integers, and one or two byte arrays — an error MUST be raised ' +
+          'and SHOULD convey an error type of PROOF_VERIFICATION_ERROR.',
+        async function() {
+          this.test.link = 'https://w3c.github.io/vc-di-bbs/#:~:text=If%20the%20result%20is%20not%20an%20array%20of%20five%2C%20six%2C%20or%20seven%20elements%20%E2%80%94%20a%20byte%20array%2C%20a%20map%20of%20integers%20to%20integers%2C%20two%20arrays%20of%20integers%2C%20and%20one%20or%20two%20byte%20arrays%3B%20an%20error%20MUST%20be%20raised%20and%20SHOULD%20convey%20an%20error%20type%20of%20PROOF_VERIFICATION_ERROR';
+          await verificationFail({
+            credential: cloneTestVector(disclosed?.invalid?.componentCount),
+            verifier,
+            reason: 'Should not verify a disclosed VC w/ less than 4 components'
+          });
+        });
       });
     }
   });

tests/vc-generator/stubMethods.js

@@ -392,6 +392,10 @@ function serializeDisclosureProofValue({
     // Uint8Array
     presentationHeader
   ];
+  return encodeProofValue({payload, typeEncoders});
+}
+
+export function encodeProofValue({payload, typeEncoders}) {
   const cbor = concatBuffers([
     CBOR_PREFIX_DERIVED, cborg.encode(payload, {useMaps: true, typeEncoders})
   ]);
@@ -435,3 +439,58 @@ async function _findProof({proofId, proofSet, dataIntegrityProof}) {
 export function stringToUtf8Bytes({str, utfOffset = 0}) {
   return TEXT_ENCODER.encode(str).map(b => b + utfOffset);
 }
+
+export function parseDisclosureProofValue({proof} = {}) {
+  try {
+    if(typeof proof?.proofValue !== 'string') {
+      throw new TypeError('"proof.proofValue" must be a string.');
+    }
+    if(proof.proofValue[0] !== 'u') {
+      throw new Error('Only base64url multibase encoding is supported.');
+    }
+
+    // decode from base64url
+    const proofValue = base64url.decode(proof.proofValue.slice(1));
+    if(!_startsWithBytes(proofValue, CBOR_PREFIX_DERIVED)) {
+      throw new TypeError('"proof.proofValue" must be a derived proof.');
+    }
+
+    const payload = proofValue.subarray(CBOR_PREFIX_DERIVED.length);
+    const [
+      bbsProof,
+      compressedLabelMap,
+      mandatoryIndexes,
+      selectiveIndexes,
+      presentationHeader
+    ] = cborg.decode(payload, {useMaps: true, tags: TAGS});
+
+    const labelMap = _decompressLabelMap(compressedLabelMap);
+    const params = {
+      bbsProof, labelMap, mandatoryIndexes, selectiveIndexes,
+      presentationHeader
+    };
+    return params;
+  } catch(e) {
+    const err = new TypeError(
+      'The proof does not include a valid "proofValue" property.');
+    err.cause = e;
+    throw err;
+  }
+}
+
+function _decompressLabelMap(compressedLabelMap) {
+  const map = new Map();
+  for(const [k, v] of compressedLabelMap.entries()) {
+    map.set(`c14n${k}`, `b${v}`);
+  }
+  return map;
+}
+
+function _startsWithBytes(buffer, prefix) {
+  for(let i = 0; i < prefix.length; ++i) {
+    if(buffer[i] !== prefix[i]) {
+      return false;
+    }
+  }
+  return true;
+}