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/* <!-- copyright */
/*
* aria2 - The high speed download utility
*
* Copyright (C) 2006 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 --> */
#ifndef _D_LIBSSL_DH_KEY_EXCHANGE_H_
#define _D_LIBSSL_DH_KEY_EXCHANGE_H_
#include "common.h"
#include "DlAbortEx.h"
#include "StringFormat.h"
#include <cstring>
#include <openssl/dh.h>
#include <openssl/rand.h>
#include <openssl/err.h>
namespace aria2 {
class DHKeyExchange {
private:
BN_CTX* bnCtx_;
size_t keyLength_;
BIGNUM* prime_;
BIGNUM* generator_;
BIGNUM* privateKey_;
BIGNUM* publicKey_;
void handleError(const std::string& funName) const
{
throw DL_ABORT_EX
(StringFormat("Exception in libssl routine %s(DHKeyExchange class): %s",
funName.c_str(), ERR_error_string(ERR_get_error(), 0)).str());
}
public:
DHKeyExchange():bnCtx_(0),
keyLength_(0),
prime_(0),
generator_(0),
privateKey_(0),
publicKey_(0) {}
~DHKeyExchange()
{
BN_CTX_free(bnCtx_);
BN_free(prime_);
BN_free(generator_);
BN_free(privateKey_);
BN_free(publicKey_);
}
void init(const unsigned char* prime, size_t primeBits,
const unsigned char* generator,
size_t privateKeyBits)
{
BN_CTX_free(bnCtx_);
bnCtx_ = BN_CTX_new();
if(!bnCtx_) {
handleError("BN_CTX_new in init");
}
BN_free(prime_);
prime_ = 0;
BN_free(generator_);
generator_ = 0;
BN_free(privateKey_);
privateKey_ = 0;
if(BN_hex2bn(&prime_, reinterpret_cast<const char*>(prime)) == 0) {
handleError("BN_hex2bn in init");
}
if(BN_hex2bn(&generator_, reinterpret_cast<const char*>(generator)) == 0) {
handleError("BN_hex2bn in init");
}
privateKey_ = BN_new();
if(BN_rand(privateKey_, privateKeyBits, -1, false) == 0) {
handleError("BN_new in init");
}
keyLength_ = (primeBits+7)/8;
}
void generatePublicKey()
{
BN_free(publicKey_);
publicKey_ = BN_new();
BN_mod_exp(publicKey_, generator_, privateKey_, prime_, bnCtx_);
}
size_t getPublicKey(unsigned char* out, size_t outLength) const
{
if(outLength < keyLength_) {
throw DL_ABORT_EX
(StringFormat("Insufficient buffer for public key. expect:%u, actual:%u",
keyLength_, outLength).str());
}
memset(out, 0, outLength);
size_t publicKeyBytes = BN_num_bytes(publicKey_);
size_t offset = keyLength_-publicKeyBytes;
size_t nwritten = BN_bn2bin(publicKey_, out+offset);
if(nwritten != publicKeyBytes) {
throw DL_ABORT_EX
(StringFormat("BN_bn2bin in DHKeyExchange::getPublicKey, %u bytes written, but %u bytes expected.", nwritten, publicKeyBytes).str());
}
return nwritten;
}
void generateNonce(unsigned char* out, size_t outLength) const
{
if(RAND_bytes(out, outLength) != 1) {
handleError("RAND_bytes in generateNonce");
}
}
size_t computeSecret(unsigned char* out, size_t outLength,
const unsigned char* peerPublicKeyData,
size_t peerPublicKeyLength) const
{
if(outLength < keyLength_) {
throw DL_ABORT_EX
(StringFormat("Insufficient buffer for secret. expect:%u, actual:%u",
keyLength_, outLength).str());
}
BIGNUM* peerPublicKey = BN_bin2bn(peerPublicKeyData, peerPublicKeyLength, 0);
if(!peerPublicKey) {
handleError("BN_bin2bn in computeSecret");
}
BIGNUM* secret = BN_new();
BN_mod_exp(secret, peerPublicKey, privateKey_, prime_, bnCtx_);
BN_free(peerPublicKey);
memset(out, 0, outLength);
size_t secretBytes = BN_num_bytes(secret);
size_t offset = keyLength_-secretBytes;
size_t nwritten = BN_bn2bin(secret, out+offset);
BN_free(secret);
if(nwritten != secretBytes) {
throw DL_ABORT_EX
(StringFormat("BN_bn2bin in DHKeyExchange::getPublicKey, %u bytes written, but %u bytes expected.", nwritten, secretBytes).str());
}
return nwritten;
}
};
} // namespace aria2
#endif // _D_LIBSSL_DH_KEY_EXCHANGE_H_
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