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Ganymed SSH 2 » ch » ethz » ssh2 » transport » TransportConnection.java

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, plattner@inf.ethz.ch
 * @version $Id: TransportConnection.java,v 1.8 2006/02/14 19:43:15 cplattne Exp $
 */
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.isEnabled())
    {
      log.log(90, "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.isEnabled())
    {
      log.log(90, "Received " + Packets.getMessageName(buffer[off] & 0xff) + " " + payload_length
          + " bytes payload");
    }

    return payload_length;
  }
}
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