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// Copyright (c) 2013 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 "net/quic/crypto/aes_128_gcm_12_decrypter.h"
#include <openssl/evp.h>
#include "base/memory/scoped_ptr.h"
#include "net/quic/crypto/scoped_evp_cipher_ctx.h"
using base::StringPiece;
namespace net {
namespace {
const size_t kKeySize = 16;
const size_t kNoncePrefixSize = 4;
} // namespace
Aes128Gcm12Decrypter::Aes128Gcm12Decrypter() {}
// static
bool Aes128Gcm12Decrypter::IsSupported() { return true; }
bool Aes128Gcm12Decrypter::SetKey(StringPiece key) {
DCHECK_EQ(key.size(), sizeof(key_));
if (key.size() != sizeof(key_)) {
return false;
}
memcpy(key_, key.data(), key.size());
return true;
}
bool Aes128Gcm12Decrypter::SetNoncePrefix(StringPiece nonce_prefix) {
DCHECK_EQ(nonce_prefix.size(), kNoncePrefixSize);
if (nonce_prefix.size() != kNoncePrefixSize) {
return false;
}
memcpy(nonce_, nonce_prefix.data(), nonce_prefix.size());
return true;
}
bool Aes128Gcm12Decrypter::Decrypt(StringPiece nonce,
StringPiece associated_data,
StringPiece ciphertext,
unsigned char* output,
size_t* output_length) {
if (ciphertext.length() < kAuthTagSize ||
nonce.size() != kNoncePrefixSize + sizeof(QuicPacketSequenceNumber)) {
return false;
}
const size_t plaintext_size = ciphertext.length() - kAuthTagSize;
// |len| is passed to an OpenSSL function to receive the output length.
int len;
ScopedEVPCipherCtx ctx;
// Set the cipher type and the key. The IV (nonce) is set below.
if (EVP_DecryptInit_ex(ctx.get(), EVP_aes_128_gcm(), NULL, key_, NULL) == 0) {
return false;
}
// Set the IV (nonce) length.
if (EVP_CIPHER_CTX_ctrl(ctx.get(), EVP_CTRL_GCM_SET_IVLEN, nonce.size(),
NULL) == 0) {
return false;
}
// Set the IV (nonce).
if (EVP_DecryptInit_ex(
ctx.get(), NULL, NULL, NULL,
reinterpret_cast<const unsigned char*>(nonce.data())) == 0) {
return false;
}
// Set the authentication tag.
if (EVP_CIPHER_CTX_ctrl(
ctx.get(), EVP_CTRL_GCM_SET_TAG, kAuthTagSize,
const_cast<char*>(ciphertext.data()) + plaintext_size) == 0) {
return false;
}
// If we pass a NULL, zero-length associated data to OpenSSL then it breaks.
// Thus we only set non-empty associated data.
if (!associated_data.empty()) {
// Set the associated data. The second argument (output buffer) must be
// NULL.
if (EVP_DecryptUpdate(
ctx.get(), NULL, &len,
reinterpret_cast<const unsigned char*>(associated_data.data()),
associated_data.size()) == 0) {
return false;
}
}
if (EVP_DecryptUpdate(
ctx.get(), output, &len,
reinterpret_cast<const unsigned char*>(ciphertext.data()),
plaintext_size) == 0) {
return false;
}
output += len;
if (EVP_DecryptFinal_ex(ctx.get(), output, &len) == 0) {
return false;
}
output += len;
*output_length = plaintext_size;
return true;
}
QuicData* Aes128Gcm12Decrypter::DecryptPacket(
QuicPacketSequenceNumber sequence_number,
StringPiece associated_data,
StringPiece ciphertext) {
COMPILE_ASSERT(sizeof(nonce_) == kNoncePrefixSize + sizeof(sequence_number),
incorrect_nonce_size);
if (ciphertext.length() < kAuthTagSize) {
return NULL;
}
size_t plaintext_size;
scoped_ptr<char[]> plaintext(new char[ciphertext.length()]);
memcpy(nonce_ + kNoncePrefixSize, &sequence_number, sizeof(sequence_number));
if (!Decrypt(StringPiece(reinterpret_cast<char*>(nonce_), sizeof(nonce_)),
associated_data, ciphertext,
reinterpret_cast<unsigned char*>(plaintext.get()),
&plaintext_size)) {
return NULL;
}
return new QuicData(plaintext.release(), plaintext_size, true);
}
StringPiece Aes128Gcm12Decrypter::GetKey() const {
return StringPiece(reinterpret_cast<const char*>(key_), sizeof(key_));
}
StringPiece Aes128Gcm12Decrypter::GetNoncePrefix() const {
return StringPiece(reinterpret_cast<const char*>(nonce_), kNoncePrefixSize);
}
} // namespace net
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