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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_trace.h"
#include "fqterm_ssh2_packet.h"
#include "ssh_endian.h"
#include "buffer.h"
#include "ssh_packet.h"
namespace FQTerm {
//==============================================================================
//FQTermSSH2PacketReceiver
//==============================================================================
void FQTermSSH2PacketReceiver::parseData(buffer *input) {
FQ_TRACE("ssh2packet", 9) << "----------------------------Receive "
<< (cipher->started ? "Encrypted": "plain")
<< " Packet----<<<<<<<";
while (buffer_len(input) > 0) {
// 1. Check the ssh packet
if (buffer_len(input) < 16
|| (cipher->started && buffer_len(input) < cipher->blkSize)
|| buffer_len(input) < last_expected_input_length_
) {
FQ_TRACE("ssh2packet", 3)
<< "Got an incomplete packet. Wait for more data.";
return ;
}
if (last_expected_input_length_ == 0) {
if (cipher->started) {
// decrypte the first block to get the packet_length field.
FQ_VERIFY(cipher->crypt(cipher, buffer_data(input), buffer_data(input), cipher->blkSize)==1);
}
} else {
// last_expected_input_length_ != 0
// indicates an incomplete ssh2 packet received last time,
// the first block of data is already decrypted at that time,
// so it must not be decrypted again.
}
int packet_len = ntohu32(buffer_data(input));
if (packet_len > SSH_BUFFER_MAX) {
emit packetError(tr("parseData: packet too big"));
return ;
}
int expected_input_len = 4 + packet_len + (is_mac_ ? mac->dgstSize : 0);
if (buffer_len(input) < (long)expected_input_len) {
FQ_TRACE("ssh2packet", 3)
<< "The packet is too small. Wait for more data.";
last_expected_input_length_ = expected_input_len;
return ;
} else {
last_expected_input_length_ = 0;
}
// 2. decrypte data.
if (cipher->started) {
// decrypte blocks left.
unsigned char *tmp = buffer_data(input) + cipher->blkSize;
int left_len = expected_input_len - cipher->blkSize - mac->dgstSize;
FQ_VERIFY(cipher->crypt(cipher, tmp, tmp, left_len)==1);
}
// 3. check MAC
if (is_mac_) {
int digest_len = mac->dgstSize;
uint8_t digest[MAX_DGSTLEN];
buffer mbuf;
buffer_init(&mbuf);
buffer_append_be32(&mbuf, sequence_no_);
buffer_append(&mbuf, (const uint8_t*)buffer_data(input),
expected_input_len - digest_len);
mac->getmac(mac, buffer_data(&mbuf), buffer_len(&mbuf), digest);
buffer_deinit(&mbuf);
u_char *received_digest = buffer_data(input) + expected_input_len - digest_len;
if (memcmp(digest, received_digest, digest_len) != 0) {
emit packetError("incorrect MAC.");
return ;
}
}
// 4. get every field of the ssh packet.
packet_len = buffer_get_u32(input);
uint8_t padding_len = buffer_get_u8(input);
real_data_len_ = packet_len - 1 - padding_len;
buffer_clear(&recvbuf);
buffer_append(&recvbuf, buffer_data(input), real_data_len_);
buffer_consume(input, packet_len - 1);
if (is_mac_)
buffer_consume(input, mac->dgstSize);
// 5. notify others a ssh packet is parsed successfully.
packet_type_ = buffer_get_u8(&recvbuf);
real_data_len_ -= 1;
emit packetAvaliable(packet_type_);
++sequence_no_;
}
}
} // namespace FQTerm
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