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* aria2 - The high speed download utility
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* Copyright (C) 2013 Nils Maier
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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* In addition, as a special exception, the copyright holders give
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* permission to link the code of portions of this program with the
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* OpenSSL library under certain conditions as described in each
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* individual source file, and distribute linked combinations
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* You must obey the GNU General Public License in all respects
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* for all of the code used other than OpenSSL. If you modify
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* file(s) with this exception, you may extend this exception to your
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* version of the file(s), but you are not obligated to do so. If you
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* do not wish to do so, delete this exception statement from your
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* version. If you delete this exception statement from all source
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* files in the program, then also delete it here.
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#include "InternalDHKeyExchange.h"
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#include "DlAbortEx.h"
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#include "LogFactory.h"
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void DHKeyExchange::init(const unsigned char* prime, size_t primeBits,
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const unsigned char* generator, size_t privateKeyBits)
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std::string pr = reinterpret_cast<const char*>(prime);
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if (pr.length() % 2) {
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pr = util::fromHex(pr.begin(), pr.end());
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throw DL_ABORT_EX("No valid prime supplied");
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prime_ = n(pr.c_str(), pr.length());
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std::string gen = reinterpret_cast<const char*>(generator);
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if (gen.length() % 2) {
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gen = util::fromHex(gen.begin(), gen.end());
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throw DL_ABORT_EX("No valid generator supplied");
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generator_ = n(gen.c_str(), gen.length());
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size_t pbytes = (privateKeyBits + 7) / 8;
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unsigned char buf[pbytes];
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util::generateRandomData(buf, pbytes);
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privateKey_ = n(reinterpret_cast<char*>(buf), pbytes);
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keyLength_ = (primeBits + 7) / 8;
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void DHKeyExchange::generatePublicKey()
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publicKey_ = generator_.mul_mod(privateKey_, prime_);
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size_t DHKeyExchange::getPublicKey(unsigned char* out, size_t outLength) const
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if (outLength < keyLength_) {
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throw DL_ABORT_EX(fmt("Insufficient buffer for public key. expect:%lu, actual:%lu",
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static_cast<unsigned long>(keyLength_),
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static_cast<unsigned long>(outLength)));
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publicKey_.binary(reinterpret_cast<char*>(out), outLength);
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void DHKeyExchange::generateNonce(unsigned char* out, size_t outLength) const
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util::generateRandomData(out, outLength);
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size_t DHKeyExchange::computeSecret(unsigned char* out, size_t outLength,
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const unsigned char* peerPublicKeyData,
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size_t peerPublicKeyLength) const
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if (outLength < keyLength_) {
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throw DL_ABORT_EX(fmt("Insufficient buffer for secret. expect:%lu, actual:%lu",
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static_cast<unsigned long>(keyLength_),
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static_cast<unsigned long>(outLength)));
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if (prime_.length() < peerPublicKeyLength) {
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throw DL_ABORT_EX(fmt("peer public key overflows bignum. max:%lu, actual:%lu",
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static_cast<unsigned long>(prime_.length()),
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static_cast<unsigned long>(peerPublicKeyLength)));
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n peerKey(reinterpret_cast<const char*>(peerPublicKeyData), peerPublicKeyLength);
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n secret = peerKey.mul_mod(privateKey_, prime_);
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secret.binary(reinterpret_cast<char*>(out), outLength);