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/*
* Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
* Please refer to the LICENSE.txt for licensing details.
*/
package ch.ethz.ssh2.transport;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.SecureRandom;
import ch.ethz.ssh2.crypto.cipher.BlockCipher;
import ch.ethz.ssh2.crypto.cipher.CipherInputStream;
import ch.ethz.ssh2.crypto.cipher.CipherOutputStream;
import ch.ethz.ssh2.crypto.cipher.NullCipher;
import ch.ethz.ssh2.crypto.digest.MAC;
import ch.ethz.ssh2.log.Logger;
import ch.ethz.ssh2.packets.Packets;
/**
* TransportConnection.
*
* @author Christian Plattner
* @version $Id: TransportConnection.java 41 2011-06-02 10:36:41Z [email protected] $
*/
public class TransportConnection
{
private static final Logger log = Logger.getLogger(TransportConnection.class);
int send_seq_number = 0;
int recv_seq_number = 0;
CipherInputStream cis;
CipherOutputStream cos;
boolean useRandomPadding = false;
/* Depends on current MAC and CIPHER */
MAC send_mac;
byte[] send_mac_buffer;
int send_padd_blocksize = 8;
MAC recv_mac;
byte[] recv_mac_buffer;
byte[] recv_mac_buffer_cmp;
int recv_padd_blocksize = 8;
/* won't change */
final byte[] send_padding_buffer = new byte[256];
final byte[] send_packet_header_buffer = new byte[5];
final byte[] recv_padding_buffer = new byte[256];
final byte[] recv_packet_header_buffer = new byte[5];
boolean recv_packet_header_present = false;
ClientServerHello csh;
final SecureRandom rnd;
public TransportConnection(InputStream is, OutputStream os, SecureRandom rnd)
{
this.cis = new CipherInputStream(new NullCipher(), is);
this.cos = new CipherOutputStream(new NullCipher(), os);
this.rnd = rnd;
}
public void changeRecvCipher(BlockCipher bc, MAC mac)
{
cis.changeCipher(bc);
recv_mac = mac;
recv_mac_buffer = (mac != null) ? new byte[mac.size()] : null;
recv_mac_buffer_cmp = (mac != null) ? new byte[mac.size()] : null;
recv_padd_blocksize = bc.getBlockSize();
if (recv_padd_blocksize < 8)
recv_padd_blocksize = 8;
}
public void changeSendCipher(BlockCipher bc, MAC mac)
{
if ((bc instanceof NullCipher) == false)
{
/* Only use zero byte padding for the first few packets */
useRandomPadding = true;
/* Once we start encrypting, there is no way back */
}
cos.changeCipher(bc);
send_mac = mac;
send_mac_buffer = (mac != null) ? new byte[mac.size()] : null;
send_padd_blocksize = bc.getBlockSize();
if (send_padd_blocksize < 8)
send_padd_blocksize = 8;
}
public void sendMessage(byte[] message) throws IOException
{
sendMessage(message, 0, message.length, 0);
}
public void sendMessage(byte[] message, int off, int len) throws IOException
{
sendMessage(message, off, len, 0);
}
public int getPacketOverheadEstimate()
{
// return an estimate for the paket overhead (for send operations)
return 5 + 4 + (send_padd_blocksize - 1) + send_mac_buffer.length;
}
public void sendMessage(byte[] message, int off, int len, int padd) throws IOException
{
if (padd < 4)
padd = 4;
else if (padd > 64)
padd = 64;
int packet_len = 5 + len + padd; /* Minimum allowed padding is 4 */
int slack = packet_len % send_padd_blocksize;
if (slack != 0)
{
packet_len += (send_padd_blocksize - slack);
}
if (packet_len < 16)
packet_len = 16;
int padd_len = packet_len - (5 + len);
if (useRandomPadding)
{
for (int i = 0; i < padd_len; i = i + 4)
{
/*
* don't waste calls to rnd.nextInt() (by using only 8bit of the
* output). just believe me: even though we may write here up to 3
* bytes which won't be used, there is no "buffer overflow" (i.e.,
* arrayindexoutofbounds). the padding buffer is big enough =) (256
* bytes, and that is bigger than any current cipher block size + 64).
*/
int r = rnd.nextInt();
send_padding_buffer[i] = (byte) r;
send_padding_buffer[i + 1] = (byte) (r >> 8);
send_padding_buffer[i + 2] = (byte) (r >> 16);
send_padding_buffer[i + 3] = (byte) (r >> 24);
}
}
else
{
/* use zero padding for unencrypted traffic */
for (int i = 0; i < padd_len; i++)
send_padding_buffer[i] = 0;
/* Actually this code is paranoid: we never filled any
* bytes into the padding buffer so far, therefore it should
* consist of zeros only.
*/
}
send_packet_header_buffer[0] = (byte) ((packet_len - 4) >> 24);
send_packet_header_buffer[1] = (byte) ((packet_len - 4) >> 16);
send_packet_header_buffer[2] = (byte) ((packet_len - 4) >> 8);
send_packet_header_buffer[3] = (byte) ((packet_len - 4));
send_packet_header_buffer[4] = (byte) padd_len;
cos.write(send_packet_header_buffer, 0, 5);
cos.write(message, off, len);
cos.write(send_padding_buffer, 0, padd_len);
if (send_mac != null)
{
send_mac.initMac(send_seq_number);
send_mac.update(send_packet_header_buffer, 0, 5);
send_mac.update(message, off, len);
send_mac.update(send_padding_buffer, 0, padd_len);
send_mac.getMac(send_mac_buffer, 0);
cos.writePlain(send_mac_buffer, 0, send_mac_buffer.length);
}
cos.flush();
if (log.isDebugEnabled())
{
log.debug("Sent " + Packets.getMessageName(message[off] & 0xff) + " " + len + " bytes payload");
}
send_seq_number++;
}
public int peekNextMessageLength() throws IOException
{
if (recv_packet_header_present == false)
{
cis.read(recv_packet_header_buffer, 0, 5);
recv_packet_header_present = true;
}
int packet_length = ((recv_packet_header_buffer[0] & 0xff) << 24)
| ((recv_packet_header_buffer[1] & 0xff) << 16) | ((recv_packet_header_buffer[2] & 0xff) << 8)
| ((recv_packet_header_buffer[3] & 0xff));
int padding_length = recv_packet_header_buffer[4] & 0xff;
if (packet_length > 35000 || packet_length < 12)
throw new IOException("Illegal packet size! (" + packet_length + ")");
int payload_length = packet_length - padding_length - 1;
if (payload_length < 0)
throw new IOException("Illegal padding_length in packet from remote (" + padding_length + ")");
return payload_length;
}
public int receiveMessage(byte buffer[], int off, int len) throws IOException
{
if (recv_packet_header_present == false)
{
cis.read(recv_packet_header_buffer, 0, 5);
}
else
recv_packet_header_present = false;
int packet_length = ((recv_packet_header_buffer[0] & 0xff) << 24)
| ((recv_packet_header_buffer[1] & 0xff) << 16) | ((recv_packet_header_buffer[2] & 0xff) << 8)
| ((recv_packet_header_buffer[3] & 0xff));
int padding_length = recv_packet_header_buffer[4] & 0xff;
if (packet_length > 35000 || packet_length < 12)
throw new IOException("Illegal packet size! (" + packet_length + ")");
int payload_length = packet_length - padding_length - 1;
if (payload_length < 0)
throw new IOException("Illegal padding_length in packet from remote (" + padding_length + ")");
if (payload_length >= len)
throw new IOException("Receive buffer too small (" + len + ", need " + payload_length + ")");
cis.read(buffer, off, payload_length);
cis.read(recv_padding_buffer, 0, padding_length);
if (recv_mac != null)
{
cis.readPlain(recv_mac_buffer, 0, recv_mac_buffer.length);
recv_mac.initMac(recv_seq_number);
recv_mac.update(recv_packet_header_buffer, 0, 5);
recv_mac.update(buffer, off, payload_length);
recv_mac.update(recv_padding_buffer, 0, padding_length);
recv_mac.getMac(recv_mac_buffer_cmp, 0);
for (int i = 0; i < recv_mac_buffer.length; i++)
{
if (recv_mac_buffer[i] != recv_mac_buffer_cmp[i])
throw new IOException("Remote sent corrupt MAC.");
}
}
recv_seq_number++;
if (log.isDebugEnabled())
{
log.debug("Received " + Packets.getMessageName(buffer[off] & 0xff) + " " + payload_length
+ " bytes payload");
}
return payload_length;
}
}