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