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// Copyright (c) 2011 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 <wincrypt.h>
#include <algorithm>
#include <vector>
#include "base/logging.h"
#include "crypto/scoped_capi_types.h"
#include "crypto/third_party/nss/blapi.h"
#include "crypto/third_party/nss/sha256.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.
};
// 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);
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);
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);
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, 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, int 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) {
if (key_length < SHA256_LENGTH / 2)
return false; // Key is too short.
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 = key_length;
memcpy(key_blob->key_data, key, key_length);
if (!CryptImportKey(plat_->provider_, &key_blob_storage[0],
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,
int 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 = digest_length;
return !!CryptGetHashParam(hash, HP_HASHVAL, digest, &sha1_size, 0);
}
} // namespace crypto
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