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/***************************************************************************
* fqterm, a terminal emulator for both BBS and *nix. *
* Copyright (C) 2008 fqterm development group. *
* *
* 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 St, Fifth Floor, Boston, MA 02110-1301 USA. *
***************************************************************************/
#include "fqterm_ssh_kex.h"
#include "fqterm_trace.h"
#include <openssl/md5.h>
namespace FQTerm {
FQTermSSHKex::FQTermSSHKex(const char *V_C, const char *V_S) {
V_C_ = new char[strlen(V_C) + 1];
V_S_ = new char[strlen(V_S) + 1];
strcpy(V_C_, V_C);
strcpy(V_S_, V_S);
}
FQTermSSHKex::~FQTermSSHKex() {
delete[] V_C_;
delete[] V_S_;
}
//==============================================================================
//FQTermSSH1Kex
//==============================================================================
FQTermSSH1Kex::FQTermSSH1Kex(const char *V_C, const char *V_S)
: FQTermSSHKex(V_C, V_S) {
is_first_kex_ = true;
kex_state_ = FQTermSSH1Kex::BEFORE_PUBLICKEY;
}
FQTermSSH1Kex::~FQTermSSH1Kex(){}
void FQTermSSH1Kex::initKex(FQTermSSHPacketReceiver *packetReceiver,
FQTermSSHPacketSender *packetSender) {
packet_receiver_ = packetReceiver;
packet_sender_ = packetSender;
packet_receiver_->disconnect(this);
FQ_VERIFY(connect(packet_receiver_, SIGNAL(packetAvaliable(int)),
this, SLOT(handlePacket(int))));
kex_state_ = FQTermSSH1Kex::BEFORE_PUBLICKEY;
emit reKex();
}
void FQTermSSH1Kex::handlePacket(int type) {
switch (kex_state_) {
case FQTermSSH1Kex::BEFORE_PUBLICKEY:
makeSessionKey();
kex_state_ = FQTermSSH1Kex::SESSIONKEY_SENT;
break;
case FQTermSSH1Kex::SESSIONKEY_SENT:
if (type != SSH1_SMSG_SUCCESS) {
emit kexError(tr("Kex exchange failed!"));
break;
}
emit kexOK();
kex_state_ = FQTermSSH1Kex::KEYEX_OK;
break;
case FQTermSSH1Kex::KEYEX_OK:
break;
}
}
void FQTermSSH1Kex::makeSessionKey() {
int i;
BIGNUM *key = BN_new();
BIGNUM *host_rsa_e = BN_new();
BIGNUM *host_rsa_n = BN_new();
BIGNUM *server_rsa_e = BN_new();
BIGNUM *server_rsa_n = BN_new();
u_int32_t rand_val;
int bits;
int rbits;
if (packet_receiver_->packetType() != SSH1_SMSG_PUBLIC_KEY) {
emit kexError(tr("startKex: First packet is not public key"));
return ;
}
packet_receiver_->getRawData((char*)cookie_, 8);
// Get the public key.
server_key_ = ssh_pubkey_new(SSH_RSA);
bits = packet_receiver_->getInt();
packet_receiver_->getBN(server_rsa_e);
packet_receiver_->getBN(server_rsa_n);
ssh_pubkey_setrsa(server_key_, server_rsa_n, server_rsa_e, NULL);
rbits = BN_num_bits(server_rsa_n);
if (bits != rbits) {
FQ_TRACE("sshkex", 0) << "Warning: Server lies about "
<< "size of server public key: "
<< "actual size: " << rbits
<< " vs. announced: " << bits;
FQ_TRACE("sshkex", 0) << "Warning: This may be due to "
<< "an old implementation of ssh.";
}
// Get the host key.
host_key_ = ssh_pubkey_new(SSH_RSA);
bits = packet_receiver_->getInt();
packet_receiver_->getBN(host_rsa_e);
packet_receiver_->getBN(host_rsa_n);
ssh_pubkey_setrsa(host_key_, host_rsa_n, host_rsa_e, NULL);
rbits = BN_num_bits(host_rsa_n);
if (bits != rbits) {
FQ_TRACE("sshkex", 0) << "Warning: Server lies about "
<< "size of server public key: "
<< "actual size: " << rbits
<< " vs. announced: " << bits;
FQ_TRACE("sshkex", 0) << "Warning: This may be due to "
<< "an old implementation of ssh.";
}
// Get protocol flags.
server_flag_ = packet_receiver_->getInt();
ciphers_ = packet_receiver_->getInt();
auth_ = packet_receiver_->getInt();
if ((ciphers_ &(1 << SSH_CIPHER_3DES)) == 0) {
FQ_VERIFY(false); // server do not support my cipher
}
makeSessionId();
// Generate an encryption key for the session. The key is a 256 bit
// random number, interpreted as a 32-byte key, with the least
// significant 8 bits being the first byte of the key.
for (i = 0; i < 32; i++) {
if (i % 4 == 0) {
rand_val = rand();
}
session_key_[i] = (rand_val &0xff);
rand_val >>= 8;
}
BN_set_word(key, 0);
for (i = 0; i < 32; i++) {
BN_lshift(key, key, 8);
if (i < 16) {
BN_add_word(key, session_key_[i] ^ session_id_[i]);
} else {
BN_add_word(key, session_key_[i]);
}
}
if (BN_cmp(server_rsa_n, host_rsa_n) < 0) {
ssh_pubkey_encrypt(server_key_, key, key);
ssh_pubkey_encrypt(host_key_, key, key);
} else {
ssh_pubkey_encrypt(host_key_, key, key);
ssh_pubkey_encrypt(server_key_, key, key);
}
ssh_pubkey_free(host_key_);
ssh_pubkey_free(server_key_);
packet_sender_->startPacket(SSH1_CMSG_SESSION_KEY);
packet_sender_->putByte(SSH_CIPHER_3DES);
packet_sender_->putRawData((const uint8_t*)cookie_, 8);
packet_sender_->putBN(key);
BN_free(key);
packet_sender_->putInt(1);
packet_sender_->write();
packet_sender_->startEncryption(session_key_, NULL);
packet_receiver_->startEncryption(session_key_, NULL);
}
void FQTermSSH1Kex::makeSessionId() {
u_char *p;
MD5_CTX ctx;
int servlen, hostlen;
const BIGNUM *host_n;
const BIGNUM *server_n;
const BIGNUM *e, *d;
MD5_Init(&ctx);
ssh_pubkey_getrsa(server_key_, &server_n, &e, &d);
ssh_pubkey_getrsa(host_key_, &host_n, &e, &d);
servlen = BN_num_bytes(server_n);
hostlen = BN_num_bytes(host_n);
p = new u_char[servlen + hostlen];
BN_bn2bin(host_n, p);
BN_bn2bin(server_n, p+hostlen);
MD5_Update(&ctx, p, servlen+hostlen);
MD5_Update(&ctx, cookie_, 8);
MD5_Final(session_id_, &ctx);
delete [] p;
}
} // namespace FQTerm
#include "fqterm_ssh_kex.moc"
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