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1 // Copyright (c) 2010 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 "base/hmac.h" | |
6 | |
7 #include <windows.h> | |
8 #include <wincrypt.h> | |
9 | |
10 #include <algorithm> | |
11 #include <vector> | |
12 | |
13 #include "base/crypto/scoped_capi_types.h" | |
14 #include "base/logging.h" | |
15 #include "base/third_party/nss/blapi.h" | |
16 #include "base/third_party/nss/sha256.h" | |
17 | |
18 namespace base { | |
19 | |
20 namespace { | |
21 | |
22 // Implementation of HMAC-SHA-256: | |
23 // | |
24 // SHA-256 is supported in Windows XP SP3 or later. We still need to support | |
25 // Windows XP SP2, so unfortunately we have to implement HMAC-SHA-256 here. | |
26 | |
27 enum { | |
28 SHA256_BLOCK_SIZE = 64 // Block size (in bytes) of the input to SHA-256. | |
29 }; | |
30 | |
31 // See FIPS 198: The Keyed-Hash Message Authentication Code (HMAC). | |
32 void ComputeHMACSHA256(const unsigned char* key, size_t key_len, | |
33 const unsigned char* text, size_t text_len, | |
34 unsigned char* output, size_t output_len) { | |
35 SHA256Context ctx; | |
36 | |
37 // Pre-process the key, if necessary. | |
38 unsigned char key0[SHA256_BLOCK_SIZE]; | |
39 if (key_len > SHA256_BLOCK_SIZE) { | |
40 SHA256_Begin(&ctx); | |
41 SHA256_Update(&ctx, key, key_len); | |
42 SHA256_End(&ctx, key0, NULL, SHA256_LENGTH); | |
43 memset(key0 + SHA256_LENGTH, 0, SHA256_BLOCK_SIZE - SHA256_LENGTH); | |
44 } else { | |
45 memcpy(key0, key, key_len); | |
46 memset(key0 + key_len, 0, SHA256_BLOCK_SIZE - key_len); | |
47 } | |
48 | |
49 unsigned char padded_key[SHA256_BLOCK_SIZE]; | |
50 unsigned char inner_hash[SHA256_LENGTH]; | |
51 | |
52 // XOR key0 with ipad. | |
53 for (int i = 0; i < SHA256_BLOCK_SIZE; ++i) | |
54 padded_key[i] = key0[i] ^ 0x36; | |
55 | |
56 // Compute the inner hash. | |
57 SHA256_Begin(&ctx); | |
58 SHA256_Update(&ctx, padded_key, SHA256_BLOCK_SIZE); | |
59 SHA256_Update(&ctx, text, text_len); | |
60 SHA256_End(&ctx, inner_hash, NULL, SHA256_LENGTH); | |
61 | |
62 // XOR key0 with opad. | |
63 for (int i = 0; i < SHA256_BLOCK_SIZE; ++i) | |
64 padded_key[i] = key0[i] ^ 0x5c; | |
65 | |
66 // Compute the outer hash. | |
67 SHA256_Begin(&ctx); | |
68 SHA256_Update(&ctx, padded_key, SHA256_BLOCK_SIZE); | |
69 SHA256_Update(&ctx, inner_hash, SHA256_LENGTH); | |
70 SHA256_End(&ctx, output, NULL, output_len); | |
71 } | |
72 | |
73 } // namespace | |
74 | |
75 struct HMACPlatformData { | |
76 ~HMACPlatformData() { | |
77 if (!raw_key_.empty()) { | |
78 SecureZeroMemory(&raw_key_[0], raw_key_.size()); | |
79 } | |
80 | |
81 // Destroy the key before releasing the provider. | |
82 key_.reset(); | |
83 } | |
84 | |
85 ScopedHCRYPTPROV provider_; | |
86 ScopedHCRYPTKEY key_; | |
87 | |
88 // For HMAC-SHA-256 only. | |
89 std::vector<unsigned char> raw_key_; | |
90 }; | |
91 | |
92 HMAC::HMAC(HashAlgorithm hash_alg) | |
93 : hash_alg_(hash_alg), plat_(new HMACPlatformData()) { | |
94 // Only SHA-1 and SHA-256 hash algorithms are supported now. | |
95 DCHECK(hash_alg_ == SHA1 || hash_alg_ == SHA256); | |
96 } | |
97 | |
98 bool HMAC::Init(const unsigned char* key, int key_length) { | |
99 if (plat_->provider_ || plat_->key_ || !plat_->raw_key_.empty()) { | |
100 // Init must not be called more than once on the same HMAC object. | |
101 NOTREACHED(); | |
102 return false; | |
103 } | |
104 | |
105 if (hash_alg_ == SHA256) { | |
106 if (key_length < SHA256_LENGTH / 2) | |
107 return false; // Key is too short. | |
108 plat_->raw_key_.assign(key, key + key_length); | |
109 return true; | |
110 } | |
111 | |
112 if (!CryptAcquireContext(plat_->provider_.receive(), NULL, NULL, | |
113 PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { | |
114 NOTREACHED(); | |
115 return false; | |
116 } | |
117 | |
118 // This code doesn't work on Win2k because PLAINTEXTKEYBLOB and | |
119 // CRYPT_IPSEC_HMAC_KEY are not supported on Windows 2000. PLAINTEXTKEYBLOB | |
120 // allows the import of an unencrypted key. For Win2k support, a cubmbersome | |
121 // exponent-of-one key procedure must be used: | |
122 // http://support.microsoft.com/kb/228786/en-us | |
123 // CRYPT_IPSEC_HMAC_KEY allows keys longer than 16 bytes. | |
124 | |
125 struct KeyBlob { | |
126 BLOBHEADER header; | |
127 DWORD key_size; | |
128 BYTE key_data[1]; | |
129 }; | |
130 size_t key_blob_size = std::max(offsetof(KeyBlob, key_data) + key_length, | |
131 sizeof(KeyBlob)); | |
132 std::vector<BYTE> key_blob_storage = std::vector<BYTE>(key_blob_size); | |
133 KeyBlob* key_blob = reinterpret_cast<KeyBlob*>(&key_blob_storage[0]); | |
134 key_blob->header.bType = PLAINTEXTKEYBLOB; | |
135 key_blob->header.bVersion = CUR_BLOB_VERSION; | |
136 key_blob->header.reserved = 0; | |
137 key_blob->header.aiKeyAlg = CALG_RC2; | |
138 key_blob->key_size = key_length; | |
139 memcpy(key_blob->key_data, key, key_length); | |
140 | |
141 if (!CryptImportKey(plat_->provider_, &key_blob_storage[0], | |
142 key_blob_storage.size(), 0, CRYPT_IPSEC_HMAC_KEY, | |
143 plat_->key_.receive())) { | |
144 NOTREACHED(); | |
145 return false; | |
146 } | |
147 | |
148 // Destroy the copy of the key. | |
149 SecureZeroMemory(key_blob->key_data, key_length); | |
150 | |
151 return true; | |
152 } | |
153 | |
154 HMAC::~HMAC() { | |
155 } | |
156 | |
157 bool HMAC::Sign(const std::string& data, | |
158 unsigned char* digest, | |
159 int digest_length) { | |
160 if (hash_alg_ == SHA256) { | |
161 if (plat_->raw_key_.empty()) | |
162 return false; | |
163 ComputeHMACSHA256(&plat_->raw_key_[0], plat_->raw_key_.size(), | |
164 reinterpret_cast<const unsigned char*>(data.data()), | |
165 data.size(), digest, digest_length); | |
166 return true; | |
167 } | |
168 | |
169 if (!plat_->provider_ || !plat_->key_) | |
170 return false; | |
171 | |
172 if (hash_alg_ != SHA1) { | |
173 NOTREACHED(); | |
174 return false; | |
175 } | |
176 | |
177 ScopedHCRYPTHASH hash; | |
178 if (!CryptCreateHash(plat_->provider_, CALG_HMAC, plat_->key_, 0, | |
179 hash.receive())) | |
180 return false; | |
181 | |
182 HMAC_INFO hmac_info; | |
183 memset(&hmac_info, 0, sizeof(hmac_info)); | |
184 hmac_info.HashAlgid = CALG_SHA1; | |
185 if (!CryptSetHashParam(hash, HP_HMAC_INFO, | |
186 reinterpret_cast<BYTE*>(&hmac_info), 0)) | |
187 return false; | |
188 | |
189 if (!CryptHashData(hash, reinterpret_cast<const BYTE*>(data.data()), | |
190 static_cast<DWORD>(data.size()), 0)) | |
191 return false; | |
192 | |
193 DWORD sha1_size = digest_length; | |
194 return !!CryptGetHashParam(hash, HP_HASHVAL, digest, &sha1_size, 0); | |
195 } | |
196 | |
197 } // namespace base | |
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