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/*
* Copyright (C) 2022 Dinglan Peng
*
* This 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 software 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 software; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
* USA.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#ifndef HAVE_NETTLE
#error "This header should not be compiled without HAVE_NETTLE defined"
#endif
#include <stdlib.h>
#ifndef WIN32
#include <unistd.h>
#endif
#include <assert.h>
#include <nettle/aes.h>
#include <nettle/md5.h>
#include <nettle/bignum.h>
#include <rfb/CSecurityDH.h>
#include <rfb/CConnection.h>
#include <rdr/InStream.h>
#include <rdr/OutStream.h>
#include <rdr/RandomStream.h>
#include <rfb/Exception.h>
#include <os/os.h>
using namespace rfb;
const int MinKeyLength = 128;
const int MaxKeyLength = 1024;
CSecurityDH::CSecurityDH(CConnection* cc_)
: CSecurity(cc_), keyLength(0)
{
mpz_init(g);
mpz_init(p);
mpz_init(A);
mpz_init(b);
mpz_init(B);
mpz_init(k);
}
CSecurityDH::~CSecurityDH()
{
mpz_clear(g);
mpz_clear(p);
mpz_clear(A);
mpz_clear(b);
mpz_clear(B);
mpz_clear(k);
}
bool CSecurityDH::processMsg()
{
if (readKey()) {
writeCredentials();
return true;
}
return false;
}
bool CSecurityDH::readKey()
{
rdr::InStream* is = cc->getInStream();
if (!is->hasData(4))
return false;
is->setRestorePoint();
uint16_t gen = is->readU16();
keyLength = is->readU16();
if (keyLength < MinKeyLength)
throw Exception("DH key is too short");
if (keyLength > MaxKeyLength)
throw Exception("DH key is too long");
if (!is->hasDataOrRestore(keyLength * 2))
return false;
is->clearRestorePoint();
mpz_set_ui(g, gen);
std::vector<uint8_t> pBytes(keyLength);
std::vector<uint8_t> ABytes(keyLength);
is->readBytes(pBytes.data(), pBytes.size());
is->readBytes(ABytes.data(), ABytes.size());
nettle_mpz_set_str_256_u(p, pBytes.size(), pBytes.data());
nettle_mpz_set_str_256_u(A, ABytes.size(), ABytes.data());
return true;
}
void CSecurityDH::writeCredentials()
{
std::string username;
std::string password;
rdr::RandomStream rs;
(CSecurity::upg)->getUserPasswd(isSecure(), &username, &password);
std::vector<uint8_t> bBytes(keyLength);
if (!rs.hasData(keyLength))
throw Exception("failed to generate DH private key");
rs.readBytes(bBytes.data(), bBytes.size());
nettle_mpz_set_str_256_u(b, bBytes.size(), bBytes.data());
mpz_powm(k, A, b, p);
mpz_powm(B, g, b, p);
std::vector<uint8_t> sharedSecret(keyLength);
std::vector<uint8_t> BBytes(keyLength);
nettle_mpz_get_str_256(sharedSecret.size(), sharedSecret.data(), k);
nettle_mpz_get_str_256(BBytes.size(), BBytes.data(), B);
uint8_t key[16];
struct md5_ctx md5Ctx;
md5_init(&md5Ctx);
md5_update(&md5Ctx, sharedSecret.size(), sharedSecret.data());
md5_digest(&md5Ctx, 16, key);
struct aes128_ctx aesCtx;
aes128_set_encrypt_key(&aesCtx, key);
uint8_t buf[128];
if (!rs.hasData(128))
throw Exception("failed to generate random padding");
rs.readBytes(buf, 128);
if (username.size() >= 64)
throw Exception("username is too long");
memcpy(buf, username.c_str(), username.size() + 1);
if (password.size() >= 64)
throw Exception("password is too long");
memcpy(buf + 64, password.c_str(), password.size() + 1);
aes128_encrypt(&aesCtx, 128, buf, buf);
rdr::OutStream* os = cc->getOutStream();
os->writeBytes(buf, 128);
os->writeBytes(BBytes.data(), BBytes.size());
os->flush();
}
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