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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/encryptor.h"
#include <cryptohi.h>
#include <stddef.h>
#include <stdint.h>
#include <vector>
#include "base/logging.h"
#include "crypto/nss_util.h"
#include "crypto/symmetric_key.h"
namespace crypto {
namespace {
inline CK_MECHANISM_TYPE GetMechanism(Encryptor::Mode mode) {
switch (mode) {
case Encryptor::CBC:
return CKM_AES_CBC_PAD;
case Encryptor::CTR:
// AES-CTR encryption uses ECB encryptor as a building block since
// NSS doesn't support CTR encryption mode.
return CKM_AES_ECB;
default:
NOTREACHED() << "Unsupported mode of operation";
break;
}
return static_cast<CK_MECHANISM_TYPE>(-1);
}
} // namespace
Encryptor::Encryptor()
: key_(NULL),
mode_(CBC) {
EnsureNSSInit();
}
Encryptor::~Encryptor() {
}
bool Encryptor::Init(SymmetricKey* key,
Mode mode,
const base::StringPiece& iv) {
DCHECK(key);
DCHECK(CBC == mode || CTR == mode) << "Unsupported mode of operation";
key_ = key;
mode_ = mode;
if (mode == CBC && iv.size() != AES_BLOCK_SIZE)
return false;
switch (mode) {
case CBC:
SECItem iv_item;
iv_item.type = siBuffer;
iv_item.data = reinterpret_cast<unsigned char*>(
const_cast<char *>(iv.data()));
iv_item.len = iv.size();
param_.reset(PK11_ParamFromIV(GetMechanism(mode), &iv_item));
break;
case CTR:
param_.reset(PK11_ParamFromIV(GetMechanism(mode), NULL));
break;
}
return param_ != NULL;
}
bool Encryptor::Encrypt(const base::StringPiece& plaintext,
std::string* ciphertext) {
CHECK(!plaintext.empty() || (mode_ == CBC));
ScopedPK11Context context(PK11_CreateContextBySymKey(GetMechanism(mode_),
CKA_ENCRYPT,
key_->key(),
param_.get()));
if (!context.get())
return false;
return (mode_ == CTR) ?
CryptCTR(context.get(), plaintext, ciphertext) :
Crypt(context.get(), plaintext, ciphertext);
}
bool Encryptor::Decrypt(const base::StringPiece& ciphertext,
std::string* plaintext) {
CHECK(!ciphertext.empty());
ScopedPK11Context context(PK11_CreateContextBySymKey(
GetMechanism(mode_), (mode_ == CTR ? CKA_ENCRYPT : CKA_DECRYPT),
key_->key(), param_.get()));
if (!context.get())
return false;
if (mode_ == CTR)
return CryptCTR(context.get(), ciphertext, plaintext);
if (ciphertext.size() % AES_BLOCK_SIZE != 0) {
// Decryption will fail if the input is not a multiple of the block size.
// PK11_CipherOp has a bug where it will do an invalid memory access before
// the start of the input, so avoid calling it. (NSS bug 922780).
plaintext->clear();
return false;
}
return Crypt(context.get(), ciphertext, plaintext);
}
bool Encryptor::Crypt(PK11Context* context,
const base::StringPiece& input,
std::string* output) {
size_t output_len = input.size() + AES_BLOCK_SIZE;
CHECK_GT(output_len, input.size());
output->resize(output_len);
uint8_t* output_data =
reinterpret_cast<uint8_t*>(const_cast<char*>(output->data()));
int input_len = input.size();
uint8_t* input_data =
reinterpret_cast<uint8_t*>(const_cast<char*>(input.data()));
int op_len;
SECStatus rv = PK11_CipherOp(context,
output_data,
&op_len,
output_len,
input_data,
input_len);
if (SECSuccess != rv) {
output->clear();
return false;
}
unsigned int digest_len;
rv = PK11_DigestFinal(context,
output_data + op_len,
&digest_len,
output_len - op_len);
if (SECSuccess != rv) {
output->clear();
return false;
}
output->resize(op_len + digest_len);
return true;
}
bool Encryptor::CryptCTR(PK11Context* context,
const base::StringPiece& input,
std::string* output) {
if (!counter_.get()) {
LOG(ERROR) << "Counter value not set in CTR mode.";
return false;
}
size_t output_len = ((input.size() + AES_BLOCK_SIZE - 1) / AES_BLOCK_SIZE) *
AES_BLOCK_SIZE;
CHECK_GE(output_len, input.size());
output->resize(output_len);
uint8_t* output_data =
reinterpret_cast<uint8_t*>(const_cast<char*>(output->data()));
size_t mask_len;
bool ret = GenerateCounterMask(input.size(), output_data, &mask_len);
if (!ret)
return false;
CHECK_EQ(mask_len, output_len);
int op_len;
SECStatus rv = PK11_CipherOp(context,
output_data,
&op_len,
output_len,
output_data,
mask_len);
if (SECSuccess != rv)
return false;
CHECK_EQ(static_cast<int>(mask_len), op_len);
unsigned int digest_len;
rv = PK11_DigestFinal(context,
NULL,
&digest_len,
0);
if (SECSuccess != rv)
return false;
CHECK(!digest_len);
// Use |output_data| to mask |input|.
MaskMessage(reinterpret_cast<uint8_t*>(const_cast<char*>(input.data())),
input.length(), output_data, output_data);
output->resize(input.length());
return true;
}
} // namespace crypto
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