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/* <!-- copyright */
/*
* aria2 - The high speed download utility
*
* Copyright (C) 2010 Tatsuhiro Tsujikawa
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* In addition, as a special exception, the copyright holders give
* permission to link the code of portions of this program with the
* OpenSSL library under certain conditions as described in each
* individual source file, and distribute linked combinations
* including the two.
* You must obey the GNU General Public License in all respects
* for all of the code used other than OpenSSL. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you
* do not wish to do so, delete this exception statement from your
* version. If you delete this exception statement from all source
* files in the program, then also delete it here.
*/
/* copyright --> */
#include "LibgcryptDHKeyExchange.h"
#include "DlAbortEx.h"
#include "fmt.h"
namespace aria2 {
namespace {
void handleError(gcry_error_t err)
{
throw DL_ABORT_EX
(fmt("Exception in libgcrypt routine(DHKeyExchange class): %s",
gcry_strerror(err)));
}
} // namespace
DHKeyExchange::DHKeyExchange()
: keyLength_(0),
prime_(nullptr),
generator_(nullptr),
privateKey_(nullptr),
publicKey_(nullptr)
{}
DHKeyExchange::~DHKeyExchange()
{
gcry_mpi_release(prime_);
gcry_mpi_release(generator_);
gcry_mpi_release(privateKey_);
gcry_mpi_release(publicKey_);
}
void DHKeyExchange::init(const unsigned char* prime, size_t primeBits,
const unsigned char* generator,
size_t privateKeyBits)
{
gcry_mpi_release(prime_);
gcry_mpi_release(generator_);
gcry_mpi_release(privateKey_);
{
gcry_error_t r = gcry_mpi_scan(&prime_, GCRYMPI_FMT_HEX,
prime, 0, nullptr);
if(r) {
handleError(r);
}
}
{
gcry_error_t r = gcry_mpi_scan(&generator_, GCRYMPI_FMT_HEX,
generator, 0, nullptr);
if(r) {
handleError(r);
}
}
privateKey_ = gcry_mpi_new(0);
gcry_mpi_randomize(privateKey_, privateKeyBits, GCRY_STRONG_RANDOM);
keyLength_ = (primeBits+7)/8;
}
void DHKeyExchange::generatePublicKey()
{
gcry_mpi_release(publicKey_);
publicKey_ = gcry_mpi_new(0);
gcry_mpi_powm(publicKey_, generator_, privateKey_, prime_);
}
size_t DHKeyExchange::getPublicKey(unsigned char* out, size_t outLength) const
{
if(outLength < keyLength_) {
throw DL_ABORT_EX
(fmt("Insufficient buffer for public key. expect:%lu, actual:%lu",
static_cast<unsigned long>(keyLength_),
static_cast<unsigned long>(outLength)));
}
memset(out, 0, outLength);
size_t publicKeyBytes = (gcry_mpi_get_nbits(publicKey_)+7)/8;
size_t offset = keyLength_-publicKeyBytes;
size_t nwritten;
gcry_error_t r = gcry_mpi_print(GCRYMPI_FMT_USG, out+offset,
outLength-offset, &nwritten, publicKey_);
if(r) {
handleError(r);
}
return nwritten;
}
void DHKeyExchange::generateNonce(unsigned char* out, size_t outLength) const
{
gcry_create_nonce(out, outLength);
}
size_t DHKeyExchange::computeSecret(unsigned char* out, size_t outLength,
const unsigned char* peerPublicKeyData,
size_t peerPublicKeyLength) const
{
if(outLength < keyLength_) {
throw DL_ABORT_EX
(fmt("Insufficient buffer for secret. expect:%lu, actual:%lu",
static_cast<unsigned long>(keyLength_),
static_cast<unsigned long>(outLength)));
}
gcry_mpi_t peerPublicKey;
{
gcry_error_t r = gcry_mpi_scan(&peerPublicKey,
GCRYMPI_FMT_USG,
peerPublicKeyData,
peerPublicKeyLength,
nullptr);
if(r) {
handleError(r);
}
}
gcry_mpi_t secret = gcry_mpi_new(0);
gcry_mpi_powm(secret, peerPublicKey, privateKey_, prime_);
gcry_mpi_release(peerPublicKey);
memset(out, 0, outLength);
size_t secretBytes = (gcry_mpi_get_nbits(secret)+7)/8;
size_t offset = keyLength_-secretBytes;
size_t nwritten;
{
gcry_error_t r = gcry_mpi_print(GCRYMPI_FMT_USG, out+offset,
outLength-offset, &nwritten, secret);
gcry_mpi_release(secret);
if(r) {
handleError(r);
}
}
return nwritten;
}
} // namespace aria2
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