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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "crypto/hmac.h" | |
| 6 | |
| 7 #include <windows.h> | |
| 8 #include <stddef.h> | |
| 9 | |
| 10 #include <algorithm> | |
| 11 #include <vector> | |
| 12 | |
| 13 #include "base/logging.h" | |
| 14 #include "crypto/scoped_capi_types.h" | |
| 15 #include "crypto/third_party/nss/chromium-blapi.h" | |
| 16 #include "crypto/third_party/nss/chromium-sha256.h" | |
| 17 #include "crypto/wincrypt_shim.h" | |
| 18 | |
| 19 namespace crypto { | |
| 20 | |
| 21 namespace { | |
| 22 | |
| 23 // Implementation of HMAC-SHA-256: | |
| 24 // | |
| 25 // SHA-256 is supported in Windows XP SP3 or later. We still need to support | |
| 26 // Windows XP SP2, so unfortunately we have to implement HMAC-SHA-256 here. | |
| 27 | |
| 28 enum { | |
| 29 SHA256_BLOCK_SIZE = 64 // Block size (in bytes) of the input to SHA-256. | |
| 30 }; | |
| 31 | |
| 32 // NSS doesn't accept size_t for text size, divide the data into smaller | |
| 33 // chunks as needed. | |
| 34 void Wrapped_SHA256_Update(SHA256Context* ctx, const unsigned char* text, | |
| 35 size_t text_len) { | |
| 36 const unsigned int kChunkSize = 1 << 30; | |
| 37 while (text_len > kChunkSize) { | |
| 38 SHA256_Update(ctx, text, kChunkSize); | |
| 39 text += kChunkSize; | |
| 40 text_len -= kChunkSize; | |
| 41 } | |
| 42 SHA256_Update(ctx, text, (unsigned int)text_len); | |
| 43 } | |
| 44 | |
| 45 // See FIPS 198: The Keyed-Hash Message Authentication Code (HMAC). | |
| 46 void ComputeHMACSHA256(const unsigned char* key, size_t key_len, | |
| 47 const unsigned char* text, size_t text_len, | |
| 48 unsigned char* output, size_t output_len) { | |
| 49 SHA256Context ctx; | |
| 50 | |
| 51 // Pre-process the key, if necessary. | |
| 52 unsigned char key0[SHA256_BLOCK_SIZE]; | |
| 53 if (key_len > SHA256_BLOCK_SIZE) { | |
| 54 SHA256_Begin(&ctx); | |
| 55 Wrapped_SHA256_Update(&ctx, key, key_len); | |
| 56 SHA256_End(&ctx, key0, NULL, SHA256_LENGTH); | |
| 57 memset(key0 + SHA256_LENGTH, 0, SHA256_BLOCK_SIZE - SHA256_LENGTH); | |
| 58 } else { | |
| 59 memcpy(key0, key, key_len); | |
| 60 if (key_len < SHA256_BLOCK_SIZE) | |
| 61 memset(key0 + key_len, 0, SHA256_BLOCK_SIZE - key_len); | |
| 62 } | |
| 63 | |
| 64 unsigned char padded_key[SHA256_BLOCK_SIZE]; | |
| 65 unsigned char inner_hash[SHA256_LENGTH]; | |
| 66 | |
| 67 // XOR key0 with ipad. | |
| 68 for (int i = 0; i < SHA256_BLOCK_SIZE; ++i) | |
| 69 padded_key[i] = key0[i] ^ 0x36; | |
| 70 | |
| 71 // Compute the inner hash. | |
| 72 SHA256_Begin(&ctx); | |
| 73 SHA256_Update(&ctx, padded_key, SHA256_BLOCK_SIZE); | |
| 74 Wrapped_SHA256_Update(&ctx, text, text_len); | |
| 75 SHA256_End(&ctx, inner_hash, NULL, SHA256_LENGTH); | |
| 76 | |
| 77 // XOR key0 with opad. | |
| 78 for (int i = 0; i < SHA256_BLOCK_SIZE; ++i) | |
| 79 padded_key[i] = key0[i] ^ 0x5c; | |
| 80 | |
| 81 // Compute the outer hash. | |
| 82 SHA256_Begin(&ctx); | |
| 83 SHA256_Update(&ctx, padded_key, SHA256_BLOCK_SIZE); | |
| 84 SHA256_Update(&ctx, inner_hash, SHA256_LENGTH); | |
| 85 SHA256_End(&ctx, output, NULL, (unsigned int) output_len); | |
| 86 } | |
| 87 | |
| 88 } // namespace | |
| 89 | |
| 90 struct HMACPlatformData { | |
| 91 ~HMACPlatformData() { | |
| 92 if (!raw_key_.empty()) { | |
| 93 SecureZeroMemory(&raw_key_[0], raw_key_.size()); | |
| 94 } | |
| 95 | |
| 96 // Destroy the key before releasing the provider. | |
| 97 key_.reset(); | |
| 98 } | |
| 99 | |
| 100 ScopedHCRYPTPROV provider_; | |
| 101 ScopedHCRYPTKEY key_; | |
| 102 | |
| 103 // For HMAC-SHA-256 only. | |
| 104 std::vector<unsigned char> raw_key_; | |
| 105 }; | |
| 106 | |
| 107 HMAC::HMAC(HashAlgorithm hash_alg) | |
| 108 : hash_alg_(hash_alg), plat_(new HMACPlatformData()) { | |
| 109 // Only SHA-1 and SHA-256 hash algorithms are supported now. | |
| 110 DCHECK(hash_alg_ == SHA1 || hash_alg_ == SHA256); | |
| 111 } | |
| 112 | |
| 113 bool HMAC::Init(const unsigned char* key, size_t key_length) { | |
| 114 if (plat_->provider_ || plat_->key_ || !plat_->raw_key_.empty()) { | |
| 115 // Init must not be called more than once on the same HMAC object. | |
| 116 NOTREACHED(); | |
| 117 return false; | |
| 118 } | |
| 119 | |
| 120 if (hash_alg_ == SHA256) { | |
| 121 plat_->raw_key_.assign(key, key + key_length); | |
| 122 return true; | |
| 123 } | |
| 124 | |
| 125 if (!CryptAcquireContext(plat_->provider_.receive(), NULL, NULL, | |
| 126 PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { | |
| 127 NOTREACHED(); | |
| 128 return false; | |
| 129 } | |
| 130 | |
| 131 // This code doesn't work on Win2k because PLAINTEXTKEYBLOB and | |
| 132 // CRYPT_IPSEC_HMAC_KEY are not supported on Windows 2000. PLAINTEXTKEYBLOB | |
| 133 // allows the import of an unencrypted key. For Win2k support, a cubmbersome | |
| 134 // exponent-of-one key procedure must be used: | |
| 135 // http://support.microsoft.com/kb/228786/en-us | |
| 136 // CRYPT_IPSEC_HMAC_KEY allows keys longer than 16 bytes. | |
| 137 | |
| 138 struct KeyBlob { | |
| 139 BLOBHEADER header; | |
| 140 DWORD key_size; | |
| 141 BYTE key_data[1]; | |
| 142 }; | |
| 143 size_t key_blob_size = std::max(offsetof(KeyBlob, key_data) + key_length, | |
| 144 sizeof(KeyBlob)); | |
| 145 std::vector<BYTE> key_blob_storage = std::vector<BYTE>(key_blob_size); | |
| 146 KeyBlob* key_blob = reinterpret_cast<KeyBlob*>(&key_blob_storage[0]); | |
| 147 key_blob->header.bType = PLAINTEXTKEYBLOB; | |
| 148 key_blob->header.bVersion = CUR_BLOB_VERSION; | |
| 149 key_blob->header.reserved = 0; | |
| 150 key_blob->header.aiKeyAlg = CALG_RC2; | |
| 151 key_blob->key_size = static_cast<DWORD>(key_length); | |
| 152 memcpy(key_blob->key_data, key, key_length); | |
| 153 | |
| 154 if (!CryptImportKey(plat_->provider_, &key_blob_storage[0], | |
| 155 (DWORD)key_blob_storage.size(), 0, | |
| 156 CRYPT_IPSEC_HMAC_KEY, plat_->key_.receive())) { | |
| 157 NOTREACHED(); | |
| 158 return false; | |
| 159 } | |
| 160 | |
| 161 // Destroy the copy of the key. | |
| 162 SecureZeroMemory(key_blob->key_data, key_length); | |
| 163 | |
| 164 return true; | |
| 165 } | |
| 166 | |
| 167 HMAC::~HMAC() { | |
| 168 } | |
| 169 | |
| 170 bool HMAC::Sign(const base::StringPiece& data, | |
| 171 unsigned char* digest, | |
| 172 size_t digest_length) const { | |
| 173 if (hash_alg_ == SHA256) { | |
| 174 if (plat_->raw_key_.empty()) | |
| 175 return false; | |
| 176 ComputeHMACSHA256(&plat_->raw_key_[0], plat_->raw_key_.size(), | |
| 177 reinterpret_cast<const unsigned char*>(data.data()), | |
| 178 data.size(), digest, digest_length); | |
| 179 return true; | |
| 180 } | |
| 181 | |
| 182 if (!plat_->provider_ || !plat_->key_) | |
| 183 return false; | |
| 184 | |
| 185 if (hash_alg_ != SHA1) { | |
| 186 NOTREACHED(); | |
| 187 return false; | |
| 188 } | |
| 189 | |
| 190 ScopedHCRYPTHASH hash; | |
| 191 if (!CryptCreateHash(plat_->provider_, CALG_HMAC, plat_->key_, 0, | |
| 192 hash.receive())) | |
| 193 return false; | |
| 194 | |
| 195 HMAC_INFO hmac_info; | |
| 196 memset(&hmac_info, 0, sizeof(hmac_info)); | |
| 197 hmac_info.HashAlgid = CALG_SHA1; | |
| 198 if (!CryptSetHashParam(hash, HP_HMAC_INFO, | |
| 199 reinterpret_cast<BYTE*>(&hmac_info), 0)) | |
| 200 return false; | |
| 201 | |
| 202 if (!CryptHashData(hash, reinterpret_cast<const BYTE*>(data.data()), | |
| 203 static_cast<DWORD>(data.size()), 0)) | |
| 204 return false; | |
| 205 | |
| 206 DWORD sha1_size = static_cast<DWORD>(digest_length); | |
| 207 return !!CryptGetHashParam(hash, HP_HASHVAL, digest, &sha1_size, 0); | |
| 208 } | |
| 209 | |
| 210 } // namespace crypto | |
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