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// Copyright (c) 2006-2008 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/hmac.h"
#include <windows.h>
#include <wincrypt.h>
#include <algorithm>
#include <vector>
#include "base/logging.h"
namespace base {
struct HMACPlatformData {
// Windows Crypt API resources.
HCRYPTPROV provider_;
HCRYPTHASH hash_;
HCRYPTKEY hkey_;
};
HMAC::HMAC(HashAlgorithm hash_alg)
: hash_alg_(hash_alg), plat_(new HMACPlatformData()) {
// Only SHA-1 digest is supported now.
DCHECK(hash_alg_ == SHA1);
}
bool HMAC::Init(const unsigned char *key, int key_length) {
if (plat_->provider_ || plat_->hkey_) {
// Init must not be called more than once on the same HMAC object.
NOTREACHED();
return false;
}
if (!CryptAcquireContext(&plat_->provider_, NULL, NULL,
PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) {
NOTREACHED();
plat_->provider_ = NULL;
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_->hkey_)) {
NOTREACHED();
plat_->hkey_ = NULL;
return false;
}
// Destroy the copy of the key.
SecureZeroMemory(key_blob->key_data, key_length);
return true;
}
HMAC::~HMAC() {
BOOL ok;
if (plat_->hkey_) {
ok = CryptDestroyKey(plat_->hkey_);
DCHECK(ok);
}
if (plat_->hash_) {
ok = CryptDestroyHash(plat_->hash_);
DCHECK(ok);
}
if (plat_->provider_) {
ok = CryptReleaseContext(plat_->provider_, 0);
DCHECK(ok);
}
}
bool HMAC::Sign(const std::string& data,
unsigned char* digest,
int digest_length) {
if (!plat_->provider_ || !plat_->hkey_)
return false;
if (hash_alg_ != SHA1) {
NOTREACHED();
return false;
}
if (!CryptCreateHash(
plat_->provider_, CALG_HMAC, plat_->hkey_, 0, &plat_->hash_))
return false;
HMAC_INFO hmac_info;
memset(&hmac_info, 0, sizeof(hmac_info));
hmac_info.HashAlgid = CALG_SHA1;
if (!CryptSetHashParam(plat_->hash_, HP_HMAC_INFO,
reinterpret_cast<BYTE*>(&hmac_info), 0))
return false;
if (!CryptHashData(plat_->hash_,
reinterpret_cast<const BYTE*>(data.data()),
static_cast<DWORD>(data.size()), 0))
return false;
DWORD sha1_size = digest_length;
if (!CryptGetHashParam(plat_->hash_, HP_HASHVAL, digest, &sha1_size, 0))
return false;
return true;
}
} // namespace base
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