refactor merkle tree inclusion proof verification (#579)

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

.changeset/happy-panthers-dance.md

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+---
+---

packages/client/src/__tests__/tlog/verify/merkle.test.ts

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+/*
+Copyright 2023 The Sigstore Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+import { VerificationError } from '../../../error';
+import { verifyMerkleInclusion } from '../../../tlog/verify/merkle';
+import * as sigstore from '../../../types/sigstore';
+
+describe('verifyMerkleInclusion', () => {
+  // Test data comes from https://rekor.sigstore.dev/api/v1/log/entries?logIndex=25591465
+  const canonicalizedBody = Buffer.from(
+    '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',
+    'base64'
+  );
+  const inclusionProof = {
+    logIndex: '21428034',
+    treeSize: '21476367',
+    hashes: [
+      Buffer.from(
+        '19d3dbf73de6aefabc91f0b0e143b98aa85a09da0fe425ec5f1cd6d156f71618',
+        'hex'
+      ),
+      Buffer.from(
+        'd1142137fddf94069fea54345b912823d6b58b6c11988056581e14328cc1030f',
+        'hex'
+      ),
+      Buffer.from(
+        '93dc3b1aa26f0abe487597beae4e195e906e749e8e4ddeee27e79dbde5b91402',
+        'hex'
+      ),
+      Buffer.from(
+        '39f0b7d480d19cf281a3fd1bb9e22d2e00c4439872b4bbf93356761ff7924d01',
+        'hex'
+      ),
+      Buffer.from(
+        'c4dbc3de6933e3adec550dd14c7fee8959ae510524e8028c3e755c3c6b865be4',
+        'hex'
+      ),
+      Buffer.from(
+        'fb0c3969556c47a5da58cb9cd58de783f1d133f145b2a24ff6c7767ad0557b20',
+        'hex'
+      ),
+      Buffer.from(
+        '8a8f4d600381615d5a9ebc191241cffa65299e80a5f48562f63d72630aedf0c6',
+        'hex'
+      ),
+      Buffer.from(
+        '6e3cfb0b5ac7d32e7e58f51324748e12600d03fe293049fe36247fed3fb2fa65',
+        'hex'
+      ),
+      Buffer.from(
+        'ea20898f9069a9d85faf515f20b062b56b1ff4c1750ce4d741acead08b254b4a',
+        'hex'
+      ),
+      Buffer.from(
+        '3c0c2711b5709e116362413734eebf10b2dcd81cadd2325502254585f5408a93',
+        'hex'
+      ),
+      Buffer.from(
+        '293213bbbac895205eb11b6a4f905eeb2632182aa8022fc96c109d5fa9d9ea31',
+        'hex'
+      ),
+      Buffer.from(
+        'f6f08053bc2277b800e3bfbc74db76a24015f1f38a17e438fac9f3e3a49aa1d4',
+        'hex'
+      ),
+      Buffer.from(
+        '0be5c7bbcf481d1efcfc63a27fce447cf6345f7bb3155cf5de39de592c16d52d',
+        'hex'
+      ),
+      Buffer.from(
+        'f597f4bae8df3d6fc6eebfe3eabd7d393e08781f6f16b42398eca8512398fff1',
+        'hex'
+      ),
+      Buffer.from(
+        '4e35fcb3c0a59e7f329994002b38db35f5d511f499ba009e10b31f5d27563607',
+        'hex'
+      ),
+      Buffer.from(
+        '47044b7ac3aab820e44f0010538d7de71e17a11f4140cbbe9eeb37f78b77cc7d',
+        'hex'
+      ),
+      Buffer.from(
+        'a096e8b56b363e063fb47944b05535e10247eae804325cc5c5df3d024b61e9bf',
+        'hex'
+      ),
+      Buffer.from(
+        'ff41aa21106dbe03996b4335dd158c7ffafd144e45022193de19b2b9136c3e42',
+        'hex'
+      ),
+      Buffer.from(
+        'e6ebdeef2e23335d8d7049ba5a0049a90593efdfe9c1b4548946b44a19d7214f',
+        'hex'
+      ),
+      Buffer.from(
+        'dd51e840e892d70093ad7e1db1e2dea3d50334c7345d360e444d22fc49ed9f5e',
+        'hex'
+      ),
+      Buffer.from(
+        'ad712c98424de0f1284d4f144b8a95b5d22c181d4c0a246518e7a9a220bdf643',
+        'hex'
+      ),
+    ],
+    rootHash: Buffer.from(
+      'd5c395a44b9537f8fa2524a6e93071969dd475ac40e87e2b1231b2aebd9a138b',
+      'hex'
+    ),
+  };
+
+  describe('when the inclusion proof is valid', () => {
+    const entry = {
+      canonicalizedBody,
+      inclusionProof,
+    } as sigstore.TransparencyLogEntry;
+
+    it('returns true', () => {
+      expect(verifyMerkleInclusion(entry)).toBe(true);
+    });
+  });
+
+  describe('when the entry does NOT match the inclusion proof', () => {
+    const invalidEntry = {
+      canonicalizedBody: Buffer.from('invalid'),
+      inclusionProof,
+    } as sigstore.TransparencyLogEntry;
+
+    it('returns false', () => {
+      expect(verifyMerkleInclusion(invalidEntry)).toBe(false);
+    });
+  });
+
+  describe('when the log index is invalid', () => {
+    const invalidEntry = {
+      canonicalizedBody,
+      inclusionProof: { ...inclusionProof, logIndex: '-1' },
+    } as sigstore.TransparencyLogEntry;
+
+    it('throws an error', () => {
+      expect(() => verifyMerkleInclusion(invalidEntry)).toThrow(
+        VerificationError
+      );
+    });
+  });
+
+  describe('when the entry does NOT contain an inclusion proof', () => {
+    const invalidEntry = {
+      canonicalizedBody,
+      inclusionProof: undefined,
+    } as sigstore.TransparencyLogEntry;
+
+    it('throws an error', () => {
+      expect(() => verifyMerkleInclusion(invalidEntry)).toThrow(
+        VerificationError
+      );
+    });
+  });
+
+  describe('when the inclusion proof log index is greather than the tree size', () => {
+    const invalidEntry = {
+      canonicalizedBody,
+      inclusionProof: { ...inclusionProof, treeSize: '99', logIndex: '100' },
+    } as sigstore.TransparencyLogEntry;
+
+    it('throws an error true', () => {
+      expect(() => verifyMerkleInclusion(invalidEntry)).toThrow(
+        VerificationError
+      );
+    });
+  });
+
+  describe('when the inclusion proof is missing hashes', () => {
+    const invalidEntry = {
+      canonicalizedBody: Buffer.from('foo'),
+      inclusionProof: {
+        ...inclusionProof,
+        hashes: inclusionProof.hashes.slice(0, 1),
+      },
+    } as sigstore.TransparencyLogEntry;
+
+    it('throws an error true', () => {
+      expect(() => verifyMerkleInclusion(invalidEntry)).toThrow(
+        VerificationError
+      );
+    });
+  });
+});