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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/symmetric_key.h"
#include <CommonCrypto/CommonCryptor.h>
#include <CoreFoundation/CFString.h>
#include <Security/cssm.h>
#include "base/logging.h"
#include "crypto/cssm_init.h"
namespace {
CSSM_KEY_TYPE CheckKeyParams(crypto::SymmetricKey::Algorithm algorithm,
size_t key_size_in_bits) {
if (algorithm == crypto::SymmetricKey::AES) {
CHECK(key_size_in_bits == 128 ||
key_size_in_bits == 192 ||
key_size_in_bits == 256)
<< "Invalid key size " << key_size_in_bits << " bits";
return CSSM_ALGID_AES;
} else {
// FIPS 198 Section 3 requires a HMAC-SHA-1 derived keys to be at least
// (HMAC-SHA-1 output size / 2) to be compliant. Since the ouput size of
// HMAC-SHA-1 is 160 bits, we require at least 80 bits here.
CHECK(algorithm == crypto::SymmetricKey::HMAC_SHA1);
CHECK(key_size_in_bits >= 80 && (key_size_in_bits % 8) == 0)
<< "Invalid key size " << key_size_in_bits << " bits";
return CSSM_ALGID_SHA1HMAC_LEGACY;
}
}
uint8_t* CreateRandomBytes(size_t size) {
CSSM_RETURN err;
CSSM_CC_HANDLE ctx;
err = CSSM_CSP_CreateRandomGenContext(crypto::GetSharedCSPHandle(),
CSSM_ALGID_APPLE_YARROW,
NULL,
size, &ctx);
if (err) {
crypto::LogCSSMError("CSSM_CSP_CreateRandomGenContext", err);
return NULL;
}
CSSM_DATA random_data = {};
err = CSSM_GenerateRandom(ctx, &random_data);
if (err) {
crypto::LogCSSMError("CSSM_GenerateRandom", err);
random_data.Data = NULL;
}
CSSM_DeleteContext(ctx);
return random_data.Data; // Caller responsible for freeing this.
}
inline CSSM_DATA StringToData(const std::string& str) {
CSSM_DATA data = {
str.size(),
reinterpret_cast<uint8_t*>(const_cast<char*>(str.data()))
};
return data;
}
} // namespace
namespace crypto {
SymmetricKey::~SymmetricKey() {
std::fill(key_.begin(), key_.end(), 0);
}
// static
SymmetricKey* SymmetricKey::GenerateRandomKey(Algorithm algorithm,
size_t key_size_in_bits) {
CheckKeyParams(algorithm, key_size_in_bits);
size_t key_size_in_bytes = (key_size_in_bits + 7) / 8;
uint8_t* random_bytes = CreateRandomBytes(key_size_in_bytes);
if (!random_bytes)
return NULL;
SymmetricKey *key = new SymmetricKey(random_bytes, key_size_in_bits);
std::fill(random_bytes, random_bytes + key_size_in_bytes, 0);
free(random_bytes);
return key;
}
// static
SymmetricKey* SymmetricKey::DeriveKeyFromPassword(Algorithm algorithm,
const std::string& password,
const std::string& salt,
size_t iterations,
size_t key_size_in_bits) {
// Derived (haha) from cdsaDeriveKey() in Apple's CryptoSample.
CSSM_KEY_TYPE key_type = CheckKeyParams(algorithm, key_size_in_bits);
SymmetricKey* derived_key = NULL;
CSSM_KEY cssm_key = {};
CSSM_CC_HANDLE ctx = 0;
CSSM_ACCESS_CREDENTIALS credentials = {};
CSSM_RETURN err;
CSSM_DATA salt_data = StringToData(salt);
err = CSSM_CSP_CreateDeriveKeyContext(GetSharedCSPHandle(),
CSSM_ALGID_PKCS5_PBKDF2,
key_type, key_size_in_bits,
&credentials,
NULL,
iterations,
&salt_data,
NULL,
&ctx);
if (err) {
LogCSSMError("CSSM_CSP_CreateDeriveKeyContext", err);
return NULL;
}
CSSM_PKCS5_PBKDF2_PARAMS params = {};
params.Passphrase = StringToData(password);
params.PseudoRandomFunction = CSSM_PKCS5_PBKDF2_PRF_HMAC_SHA1;
CSSM_DATA param_data = {sizeof(params), reinterpret_cast<uint8_t*>(¶ms)};
err = CSSM_DeriveKey(ctx,
¶m_data,
CSSM_KEYUSE_ANY,
CSSM_KEYATTR_RETURN_DATA | CSSM_KEYATTR_EXTRACTABLE,
NULL,
NULL,
&cssm_key);
if (err) {
LogCSSMError("CSSM_DeriveKey", err);
goto exit;
}
DCHECK_EQ(cssm_key.KeyData.Length, key_size_in_bits / 8);
derived_key = new SymmetricKey(cssm_key.KeyData.Data, key_size_in_bits);
exit:
CSSM_DeleteContext(ctx);
CSSM_FreeKey(GetSharedCSPHandle(), &credentials, &cssm_key, false);
return derived_key;
}
// static
SymmetricKey* SymmetricKey::Import(Algorithm algorithm,
const std::string& raw_key) {
return new SymmetricKey(raw_key.data(), raw_key.size() * 8);
}
SymmetricKey::SymmetricKey(const void* key_data, size_t key_size_in_bits)
: key_(reinterpret_cast<const char*>(key_data), key_size_in_bits / 8) {
}
bool SymmetricKey::GetRawKey(std::string* raw_key) {
*raw_key = key_;
return true;
}
CSSM_DATA SymmetricKey::cssm_data() const {
return StringToData(key_);
}
} // namespace crypto
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