// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/crypto/signature_verifier.h"
#include "testing/gtest/include/gtest/gtest.h"

TEST(SignatureVerifierTest, BasicTest) {
  // The input data in this test comes from real certificates.
  //
  // tbs_certificate ("to-be-signed certificate", the part of a certificate
  // that is signed), signature_algorithm, and algorithm come from the
  // certificate of bugs.webkit.org.
  //
  // public_key_info comes from the certificate of the issuer, Go Daddy Secure
  // Certification Authority.
  //
  // The bytes in the array initializers are formatted to expose the DER
  // encoding of the ASN.1 structures.

  // The data that is signed is the following ASN.1 structure:
  //    TBSCertificate  ::=  SEQUENCE  {
  //        ...  -- omitted, not important
  //        }
  const uint8 tbs_certificate[1017] = {
    0x30, 0x82, 0x03, 0xf5,  // a SEQUENCE of length 1013 (0x3f5)
    0xa0, 0x03, 0x02, 0x01, 0x02, 0x02, 0x03, 0x43, 0xdd, 0x63, 0x30, 0x0d,
    0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x05, 0x05,
    0x00, 0x30, 0x81, 0xca, 0x31, 0x0b, 0x30, 0x09, 0x06, 0x03, 0x55, 0x04,
    0x06, 0x13, 0x02, 0x55, 0x53, 0x31, 0x10, 0x30, 0x0e, 0x06, 0x03, 0x55,
    0x04, 0x08, 0x13, 0x07, 0x41, 0x72, 0x69, 0x7a, 0x6f, 0x6e, 0x61, 0x31,
    0x13, 0x30, 0x11, 0x06, 0x03, 0x55, 0x04, 0x07, 0x13, 0x0a, 0x53, 0x63,
    0x6f, 0x74, 0x74, 0x73, 0x64, 0x61, 0x6c, 0x65, 0x31, 0x1a, 0x30, 0x18,
    0x06, 0x03, 0x55, 0x04, 0x0a, 0x13, 0x11, 0x47, 0x6f, 0x44, 0x61, 0x64,
    0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2c, 0x20, 0x49, 0x6e, 0x63, 0x2e,
    0x31, 0x33, 0x30, 0x31, 0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x2a, 0x68,
    0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x65, 0x72, 0x74, 0x69, 0x66,
    0x69, 0x63, 0x61, 0x74, 0x65, 0x73, 0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64,
    0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73,
    0x69, 0x74, 0x6f, 0x72, 0x79, 0x31, 0x30, 0x30, 0x2e, 0x06, 0x03, 0x55,
    0x04, 0x03, 0x13, 0x27, 0x47, 0x6f, 0x20, 0x44, 0x61, 0x64, 0x64, 0x79,
    0x20, 0x53, 0x65, 0x63, 0x75, 0x72, 0x65, 0x20, 0x43, 0x65, 0x72, 0x74,
    0x69, 0x66, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x20, 0x41, 0x75,
    0x74, 0x68, 0x6f, 0x72, 0x69, 0x74, 0x79, 0x31, 0x11, 0x30, 0x0f, 0x06,
    0x03, 0x55, 0x04, 0x05, 0x13, 0x08, 0x30, 0x37, 0x39, 0x36, 0x39, 0x32,
    0x38, 0x37, 0x30, 0x1e, 0x17, 0x0d, 0x30, 0x38, 0x30, 0x33, 0x31, 0x38,
    0x32, 0x33, 0x33, 0x35, 0x31, 0x39, 0x5a, 0x17, 0x0d, 0x31, 0x31, 0x30,
    0x33, 0x31, 0x38, 0x32, 0x33, 0x33, 0x35, 0x31, 0x39, 0x5a, 0x30, 0x79,
    0x31, 0x0b, 0x30, 0x09, 0x06, 0x03, 0x55, 0x04, 0x06, 0x13, 0x02, 0x55,
    0x53, 0x31, 0x13, 0x30, 0x11, 0x06, 0x03, 0x55, 0x04, 0x08, 0x13, 0x0a,
    0x43, 0x61, 0x6c, 0x69, 0x66, 0x6f, 0x72, 0x6e, 0x69, 0x61, 0x31, 0x12,
    0x30, 0x10, 0x06, 0x03, 0x55, 0x04, 0x07, 0x13, 0x09, 0x43, 0x75, 0x70,
    0x65, 0x72, 0x74, 0x69, 0x6e, 0x6f, 0x31, 0x13, 0x30, 0x11, 0x06, 0x03,
    0x55, 0x04, 0x0a, 0x13, 0x0a, 0x41, 0x70, 0x70, 0x6c, 0x65, 0x20, 0x49,
    0x6e, 0x63, 0x2e, 0x31, 0x15, 0x30, 0x13, 0x06, 0x03, 0x55, 0x04, 0x0b,
    0x13, 0x0c, 0x4d, 0x61, 0x63, 0x20, 0x4f, 0x53, 0x20, 0x46, 0x6f, 0x72,
    0x67, 0x65, 0x31, 0x15, 0x30, 0x13, 0x06, 0x03, 0x55, 0x04, 0x03, 0x13,
    0x0c, 0x2a, 0x2e, 0x77, 0x65, 0x62, 0x6b, 0x69, 0x74, 0x2e, 0x6f, 0x72,
    0x67, 0x30, 0x81, 0x9f, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
    0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x81, 0x8d, 0x00, 0x30,
    0x81, 0x89, 0x02, 0x81, 0x81, 0x00, 0xa7, 0x62, 0x79, 0x41, 0xda, 0x28,
    0xf2, 0xc0, 0x4f, 0xe0, 0x25, 0xaa, 0xa1, 0x2e, 0x3b, 0x30, 0x94, 0xb5,
    0xc9, 0x26, 0x3a, 0x1b, 0xe2, 0xd0, 0xcc, 0xa2, 0x95, 0xe2, 0x91, 0xc0,
    0xf0, 0x40, 0x9e, 0x27, 0x6e, 0xbd, 0x6e, 0xde, 0x7c, 0xb6, 0x30, 0x5c,
    0xb8, 0x9b, 0x01, 0x2f, 0x92, 0x04, 0xa1, 0xef, 0x4a, 0xb1, 0x6c, 0xb1,
    0x7e, 0x8e, 0xcd, 0xa6, 0xf4, 0x40, 0x73, 0x1f, 0x2c, 0x96, 0xad, 0xff,
    0x2a, 0x6d, 0x0e, 0xba, 0x52, 0x84, 0x83, 0xb0, 0x39, 0xee, 0xc9, 0x39,
    0xdc, 0x1e, 0x34, 0xd0, 0xd8, 0x5d, 0x7a, 0x09, 0xac, 0xa9, 0xee, 0xca,
    0x65, 0xf6, 0x85, 0x3a, 0x6b, 0xee, 0xe4, 0x5c, 0x5e, 0xf8, 0xda, 0xd1,
    0xce, 0x88, 0x47, 0xcd, 0x06, 0x21, 0xe0, 0xb9, 0x4b, 0xe4, 0x07, 0xcb,
    0x57, 0xdc, 0xca, 0x99, 0x54, 0xf7, 0x0e, 0xd5, 0x17, 0x95, 0x05, 0x2e,
    0xe9, 0xb1, 0x02, 0x03, 0x01, 0x00, 0x01, 0xa3, 0x82, 0x01, 0xce, 0x30,
    0x82, 0x01, 0xca, 0x30, 0x09, 0x06, 0x03, 0x55, 0x1d, 0x13, 0x04, 0x02,
    0x30, 0x00, 0x30, 0x0b, 0x06, 0x03, 0x55, 0x1d, 0x0f, 0x04, 0x04, 0x03,
    0x02, 0x05, 0xa0, 0x30, 0x1d, 0x06, 0x03, 0x55, 0x1d, 0x25, 0x04, 0x16,
    0x30, 0x14, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x03, 0x01,
    0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x03, 0x02, 0x30, 0x57,
    0x06, 0x03, 0x55, 0x1d, 0x1f, 0x04, 0x50, 0x30, 0x4e, 0x30, 0x4c, 0xa0,
    0x4a, 0xa0, 0x48, 0x86, 0x46, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f,
    0x63, 0x65, 0x72, 0x74, 0x69, 0x66, 0x69, 0x63, 0x61, 0x74, 0x65, 0x73,
    0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64, 0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d,
    0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73, 0x69, 0x74, 0x6f, 0x72, 0x79, 0x2f,
    0x67, 0x6f, 0x64, 0x61, 0x64, 0x64, 0x79, 0x65, 0x78, 0x74, 0x65, 0x6e,
    0x64, 0x65, 0x64, 0x69, 0x73, 0x73, 0x75, 0x69, 0x6e, 0x67, 0x33, 0x2e,
    0x63, 0x72, 0x6c, 0x30, 0x52, 0x06, 0x03, 0x55, 0x1d, 0x20, 0x04, 0x4b,
    0x30, 0x49, 0x30, 0x47, 0x06, 0x0b, 0x60, 0x86, 0x48, 0x01, 0x86, 0xfd,
    0x6d, 0x01, 0x07, 0x17, 0x02, 0x30, 0x38, 0x30, 0x36, 0x06, 0x08, 0x2b,
    0x06, 0x01, 0x05, 0x05, 0x07, 0x02, 0x01, 0x16, 0x2a, 0x68, 0x74, 0x74,
    0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x65, 0x72, 0x74, 0x69, 0x66, 0x69, 0x63,
    0x61, 0x74, 0x65, 0x73, 0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64, 0x64, 0x79,
    0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73, 0x69, 0x74,
    0x6f, 0x72, 0x79, 0x30, 0x7f, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05,
    0x07, 0x01, 0x01, 0x04, 0x73, 0x30, 0x71, 0x30, 0x23, 0x06, 0x08, 0x2b,
    0x06, 0x01, 0x05, 0x05, 0x07, 0x30, 0x01, 0x86, 0x17, 0x68, 0x74, 0x74,
    0x70, 0x3a, 0x2f, 0x2f, 0x6f, 0x63, 0x73, 0x70, 0x2e, 0x67, 0x6f, 0x64,
    0x61, 0x64, 0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x30, 0x4a, 0x06, 0x08,
    0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x30, 0x02, 0x86, 0x3e, 0x68, 0x74,
    0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x65, 0x72, 0x74, 0x69, 0x66, 0x69,
    0x63, 0x61, 0x74, 0x65, 0x73, 0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64, 0x64,
    0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73, 0x69,
    0x74, 0x6f, 0x72, 0x79, 0x2f, 0x67, 0x64, 0x5f, 0x69, 0x6e, 0x74, 0x65,
    0x72, 0x6d, 0x65, 0x64, 0x69, 0x61, 0x74, 0x65, 0x2e, 0x63, 0x72, 0x74,
    0x30, 0x1d, 0x06, 0x03, 0x55, 0x1d, 0x0e, 0x04, 0x16, 0x04, 0x14, 0x48,
    0xdf, 0x60, 0x32, 0xcc, 0x89, 0x01, 0xb6, 0xdc, 0x2f, 0xe3, 0x73, 0xb5,
    0x9c, 0x16, 0x58, 0x32, 0x68, 0xa9, 0xc3, 0x30, 0x1f, 0x06, 0x03, 0x55,
    0x1d, 0x23, 0x04, 0x18, 0x30, 0x16, 0x80, 0x14, 0xfd, 0xac, 0x61, 0x32,
    0x93, 0x6c, 0x45, 0xd6, 0xe2, 0xee, 0x85, 0x5f, 0x9a, 0xba, 0xe7, 0x76,
    0x99, 0x68, 0xcc, 0xe7, 0x30, 0x23, 0x06, 0x03, 0x55, 0x1d, 0x11, 0x04,
    0x1c, 0x30, 0x1a, 0x82, 0x0c, 0x2a, 0x2e, 0x77, 0x65, 0x62, 0x6b, 0x69,
    0x74, 0x2e, 0x6f, 0x72, 0x67, 0x82, 0x0a, 0x77, 0x65, 0x62, 0x6b, 0x69,
    0x74, 0x2e, 0x6f, 0x72, 0x67
  };

  // The signature algorithm is specified as the following ASN.1 structure:
  //    AlgorithmIdentifier  ::=  SEQUENCE  {
  //        algorithm               OBJECT IDENTIFIER,
  //        parameters              ANY DEFINED BY algorithm OPTIONAL  }
  //
  const uint8 signature_algorithm[15] = {
    0x30, 0x0d,  // a SEQUENCE of length 13 (0xd)
      0x06, 0x09,  // an OBJECT IDENTIFIER of length 9
        // 1.2.840.113549.1.1.5 - sha1WithRSAEncryption
        0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x05,
      0x05, 0x00,  // a NULL of length 0
  };

  // RSA signature, a big integer in the big-endian byte order.
  const uint8 signature[256] = {
    0x1e, 0x6a, 0xe7, 0xe0, 0x4f, 0xe7, 0x4d, 0xd0, 0x69, 0x7c, 0xf8, 0x8f,
    0x99, 0xb4, 0x18, 0x95, 0x36, 0x24, 0x0f, 0x0e, 0xa3, 0xea, 0x34, 0x37,
    0xf4, 0x7d, 0xd5, 0x92, 0x35, 0x53, 0x72, 0x76, 0x3f, 0x69, 0xf0, 0x82,
    0x56, 0xe3, 0x94, 0x7a, 0x1d, 0x1a, 0x81, 0xaf, 0x9f, 0xc7, 0x43, 0x01,
    0x64, 0xd3, 0x7c, 0x0d, 0xc8, 0x11, 0x4e, 0x4a, 0xe6, 0x1a, 0xc3, 0x01,
    0x74, 0xe8, 0x35, 0x87, 0x5c, 0x61, 0xaa, 0x8a, 0x46, 0x06, 0xbe, 0x98,
    0x95, 0x24, 0x9e, 0x01, 0xe3, 0xe6, 0xa0, 0x98, 0xee, 0x36, 0x44, 0x56,
    0x8d, 0x23, 0x9c, 0x65, 0xea, 0x55, 0x6a, 0xdf, 0x66, 0xee, 0x45, 0xe8,
    0xa0, 0xe9, 0x7d, 0x9a, 0xba, 0x94, 0xc5, 0xc8, 0xc4, 0x4b, 0x98, 0xff,
    0x9a, 0x01, 0x31, 0x6d, 0xf9, 0x2b, 0x58, 0xe7, 0xe7, 0x2a, 0xc5, 0x4d,
    0xbb, 0xbb, 0xcd, 0x0d, 0x70, 0xe1, 0xad, 0x03, 0xf5, 0xfe, 0xf4, 0x84,
    0x71, 0x08, 0xd2, 0xbc, 0x04, 0x7b, 0x26, 0x1c, 0xa8, 0x0f, 0x9c, 0xd8,
    0x12, 0x6a, 0x6f, 0x2b, 0x67, 0xa1, 0x03, 0x80, 0x9a, 0x11, 0x0b, 0xe9,
    0xe0, 0xb5, 0xb3, 0xb8, 0x19, 0x4e, 0x0c, 0xa4, 0xd9, 0x2b, 0x3b, 0xc2,
    0xca, 0x20, 0xd3, 0x0c, 0xa4, 0xff, 0x93, 0x13, 0x1f, 0xfc, 0xba, 0x94,
    0x93, 0x8c, 0x64, 0x15, 0x2e, 0x28, 0xa9, 0x55, 0x8c, 0x2c, 0x48, 0xd3,
    0xd3, 0xc1, 0x50, 0x69, 0x19, 0xe8, 0x34, 0xd3, 0xf1, 0x04, 0x9f, 0x0a,
    0x7a, 0x21, 0x87, 0xbf, 0xb9, 0x59, 0x37, 0x2e, 0xf4, 0x71, 0xa5, 0x3e,
    0xbe, 0xcd, 0x70, 0x83, 0x18, 0xf8, 0x8a, 0x72, 0x85, 0x45, 0x1f, 0x08,
    0x01, 0x6f, 0x37, 0xf5, 0x2b, 0x7b, 0xea, 0xb9, 0x8b, 0xa3, 0xcc, 0xfd,
    0x35, 0x52, 0xdd, 0x66, 0xde, 0x4f, 0x30, 0xc5, 0x73, 0x81, 0xb6, 0xe8,
    0x3c, 0xd8, 0x48, 0x8a
  };

  // The public key is specified as the following ASN.1 structure:
  //   SubjectPublicKeyInfo  ::=  SEQUENCE  {
  //       algorithm            AlgorithmIdentifier,
  //       subjectPublicKey     BIT STRING  }
  const uint8 public_key_info[294] = {
    0x30, 0x82, 0x01, 0x22,  // a SEQUENCE of length 290 (0x122)
      // algorithm
      0x30, 0x0d,  // a SEQUENCE of length 13
        0x06, 0x09,  // an OBJECT IDENTIFIER of length 9
          0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01,
        0x05, 0x00,  // a NULL of length 0
      // subjectPublicKey
      0x03, 0x82, 0x01, 0x0f,  // a BIT STRING of length 271 (0x10f)
        0x00,  // number of unused bits
        0x30, 0x82, 0x01, 0x0a,  // a SEQUENCE of length 266 (0x10a)
          // modulus
          0x02, 0x82, 0x01, 0x01,  // an INTEGER of length 257 (0x101)
            0x00, 0xc4, 0x2d, 0xd5, 0x15, 0x8c, 0x9c, 0x26, 0x4c, 0xec,
            0x32, 0x35, 0xeb, 0x5f, 0xb8, 0x59, 0x01, 0x5a, 0xa6, 0x61,
            0x81, 0x59, 0x3b, 0x70, 0x63, 0xab, 0xe3, 0xdc, 0x3d, 0xc7,
            0x2a, 0xb8, 0xc9, 0x33, 0xd3, 0x79, 0xe4, 0x3a, 0xed, 0x3c,
            0x30, 0x23, 0x84, 0x8e, 0xb3, 0x30, 0x14, 0xb6, 0xb2, 0x87,
            0xc3, 0x3d, 0x95, 0x54, 0x04, 0x9e, 0xdf, 0x99, 0xdd, 0x0b,
            0x25, 0x1e, 0x21, 0xde, 0x65, 0x29, 0x7e, 0x35, 0xa8, 0xa9,
            0x54, 0xeb, 0xf6, 0xf7, 0x32, 0x39, 0xd4, 0x26, 0x55, 0x95,
            0xad, 0xef, 0xfb, 0xfe, 0x58, 0x86, 0xd7, 0x9e, 0xf4, 0x00,
            0x8d, 0x8c, 0x2a, 0x0c, 0xbd, 0x42, 0x04, 0xce, 0xa7, 0x3f,
            0x04, 0xf6, 0xee, 0x80, 0xf2, 0xaa, 0xef, 0x52, 0xa1, 0x69,
            0x66, 0xda, 0xbe, 0x1a, 0xad, 0x5d, 0xda, 0x2c, 0x66, 0xea,
            0x1a, 0x6b, 0xbb, 0xe5, 0x1a, 0x51, 0x4a, 0x00, 0x2f, 0x48,
            0xc7, 0x98, 0x75, 0xd8, 0xb9, 0x29, 0xc8, 0xee, 0xf8, 0x66,
            0x6d, 0x0a, 0x9c, 0xb3, 0xf3, 0xfc, 0x78, 0x7c, 0xa2, 0xf8,
            0xa3, 0xf2, 0xb5, 0xc3, 0xf3, 0xb9, 0x7a, 0x91, 0xc1, 0xa7,
            0xe6, 0x25, 0x2e, 0x9c, 0xa8, 0xed, 0x12, 0x65, 0x6e, 0x6a,
            0xf6, 0x12, 0x44, 0x53, 0x70, 0x30, 0x95, 0xc3, 0x9c, 0x2b,
            0x58, 0x2b, 0x3d, 0x08, 0x74, 0x4a, 0xf2, 0xbe, 0x51, 0xb0,
            0xbf, 0x87, 0xd0, 0x4c, 0x27, 0x58, 0x6b, 0xb5, 0x35, 0xc5,
            0x9d, 0xaf, 0x17, 0x31, 0xf8, 0x0b, 0x8f, 0xee, 0xad, 0x81,
            0x36, 0x05, 0x89, 0x08, 0x98, 0xcf, 0x3a, 0xaf, 0x25, 0x87,
            0xc0, 0x49, 0xea, 0xa7, 0xfd, 0x67, 0xf7, 0x45, 0x8e, 0x97,
            0xcc, 0x14, 0x39, 0xe2, 0x36, 0x85, 0xb5, 0x7e, 0x1a, 0x37,
            0xfd, 0x16, 0xf6, 0x71, 0x11, 0x9a, 0x74, 0x30, 0x16, 0xfe,
            0x13, 0x94, 0xa3, 0x3f, 0x84, 0x0d, 0x4f,
          // public exponent
          0x02, 0x03,  // an INTEGER of length 3
             0x01, 0x00, 0x01
  };

  // We use the signature verifier to perform four signature verification
  // tests.
  base::SignatureVerifier verifier;
  bool ok;

  // Test 1: feed all of the data to the verifier at once (a single
  // VerifyUpdate call).
  ok = verifier.VerifyInit(signature_algorithm,
                           sizeof(signature_algorithm),
                           signature, sizeof(signature),
                           public_key_info, sizeof(public_key_info));
  EXPECT_TRUE(ok);
  verifier.VerifyUpdate(tbs_certificate, sizeof(tbs_certificate));
  ok = verifier.VerifyFinal();
  EXPECT_TRUE(ok);

  // Test 2: feed the data to the verifier in three parts (three VerifyUpdate
  // calls).
  ok = verifier.VerifyInit(signature_algorithm,
                           sizeof(signature_algorithm),
                           signature, sizeof(signature),
                           public_key_info, sizeof(public_key_info));
  EXPECT_TRUE(ok);
  verifier.VerifyUpdate(tbs_certificate,       256);
  verifier.VerifyUpdate(tbs_certificate + 256, 256);
  verifier.VerifyUpdate(tbs_certificate + 512, sizeof(tbs_certificate) - 512);
  ok = verifier.VerifyFinal();
  EXPECT_TRUE(ok);

  // Test 3: verify the signature with incorrect data.
  uint8 bad_tbs_certificate[sizeof(tbs_certificate)];
  memcpy(bad_tbs_certificate, tbs_certificate, sizeof(tbs_certificate));
  bad_tbs_certificate[10] += 1;  // Corrupt one byte of the data.
  ok = verifier.VerifyInit(signature_algorithm,
                           sizeof(signature_algorithm),
                           signature, sizeof(signature),
                           public_key_info, sizeof(public_key_info));
  EXPECT_TRUE(ok);
  verifier.VerifyUpdate(bad_tbs_certificate, sizeof(bad_tbs_certificate));
  ok = verifier.VerifyFinal();

  // Purify disables digital signature verification, causing the Windows
  // CryptoAPI function CryptVerifySignature to always succeed.  So we can't
  // check the signature verification results of the negative tests when
  // running inside Purify.  See http://crbug.com/10031.
#ifndef PURIFY
  EXPECT_FALSE(ok);
#endif

  // Test 4: verify a bad signature.
  uint8 bad_signature[sizeof(signature)];
  memcpy(bad_signature, signature, sizeof(signature));
  bad_signature[10] += 1;  // Corrupt one byte of the signature.
  ok = verifier.VerifyInit(signature_algorithm,
                           sizeof(signature_algorithm),
                           bad_signature, sizeof(bad_signature),
                           public_key_info, sizeof(public_key_info));

  // A crypto library (e.g., NSS) may detect that the signature is corrupted
  // and cause VerifyInit to return false, so it is fine for 'ok' to be false.
  if (ok) {
    verifier.VerifyUpdate(tbs_certificate, sizeof(tbs_certificate));
    ok = verifier.VerifyFinal();
#ifndef PURIFY
    EXPECT_FALSE(ok);
#endif
  }
}