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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/des.h>
#include <nettle/cbc.h>
#include <nettle/bignum.h>
#include <rfb/CSecurityMSLogonII.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;
CSecurityMSLogonII::CSecurityMSLogonII(CConnection* cc_)
: CSecurity(cc_)
{
mpz_init(g);
mpz_init(p);
mpz_init(A);
mpz_init(b);
mpz_init(B);
mpz_init(k);
}
CSecurityMSLogonII::~CSecurityMSLogonII()
{
mpz_clear(g);
mpz_clear(p);
mpz_clear(A);
mpz_clear(b);
mpz_clear(B);
mpz_clear(k);
}
bool CSecurityMSLogonII::processMsg()
{
if (readKey()) {
writeCredentials();
return true;
}
return false;
}
bool CSecurityMSLogonII::readKey()
{
rdr::InStream* is = cc->getInStream();
if (!is->hasData(24))
return false;
uint8_t gBytes[8];
uint8_t pBytes[8];
uint8_t ABytes[8];
is->readBytes(gBytes, 8);
is->readBytes(pBytes, 8);
is->readBytes(ABytes, 8);
nettle_mpz_set_str_256_u(g, 8, gBytes);
nettle_mpz_set_str_256_u(p, 8, pBytes);
nettle_mpz_set_str_256_u(A, 8, ABytes);
return true;
}
void CSecurityMSLogonII::writeCredentials()
{
std::string username;
std::string password;
rdr::RandomStream rs;
(CSecurity::upg)->getUserPasswd(isSecure(), &username, &password);
std::vector<uint8_t> bBytes(8);
if (!rs.hasData(8))
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);
uint8_t key[8];
uint8_t reversedKey[8];
uint8_t BBytes[8];
uint8_t user[256];
uint8_t pass[64];
nettle_mpz_get_str_256(8, key, k);
nettle_mpz_get_str_256(8, BBytes, B);
for (int i = 0; i < 8; ++i) {
uint8_t x = 0;
for (int j = 0; j < 8; ++j) {
x |= ((key[i] >> j) & 1) << (7 - j);
}
reversedKey[i] = x;
}
if (!rs.hasData(256 + 64))
throw Exception("failed to generate random padding");
rs.readBytes(user, 256);
rs.readBytes(pass, 64);
if (username.size() >= 256)
throw Exception("username is too long");
memcpy(user, username.c_str(), username.size() + 1);
if (password.size() >= 64)
throw Exception("password is too long");
memcpy(pass, password.c_str(), password.size() + 1);
// DES-CBC with the original key as IV, and the reversed one as the DES key
struct CBC_CTX(struct des_ctx, DES_BLOCK_SIZE) ctx;
des_fix_parity(8, reversedKey, reversedKey);
des_set_key(&ctx.ctx, reversedKey);
CBC_SET_IV(&ctx, key);
CBC_ENCRYPT(&ctx, des_encrypt, 256, user, user);
CBC_SET_IV(&ctx, key);
CBC_ENCRYPT(&ctx, des_encrypt, 64, pass, pass);
rdr::OutStream* os = cc->getOutStream();
os->writeBytes(BBytes, 8);
os->writeBytes(user, 256);
os->writeBytes(pass, 64);
os->flush();
}
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