/**
* Copyright (C) 2006-2008 Werner Dittmann
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*
* Authors: Werner Dittmann <Werner.Dittmann@t-online.de>
*/
package net.java.sip.communicator.impl.media.transform.zrtp;
import net.java.sip.communicator.impl.media.transform.*;
import gnu.java.zrtp.packets.*;
import gnu.java.zrtp.utils.*;
/**
* ZRTP packet representation.
*
* This class extends the RawPacket class and adds some methods
* required by the ZRTP transformer.
*
* @author Werner Dittmann <Werner.Dittmann@t-online.de>
*
*/
public class ZrtpRawPacket extends RawPacket
{
/**
* Each ZRTP packet conatins this magic number.
*/
public static byte[] zrtpMagic;
static {
zrtpMagic = new byte[4];
zrtpMagic[0]= 0x5a;
zrtpMagic[1]= 0x52;
zrtpMagic[2]= 0x54;
zrtpMagic[3]= 0x50;
}
/**
* Construct an input ZrtpRawPacket using a received RTP raw packet.
*
* @param pkt a raw RTP packet as received
*/
public ZrtpRawPacket(RawPacket pkt)
{
super (pkt.getBuffer(), pkt.getOffset(), pkt.getLength());
}
/**
* Construct an output ZrtpRawPacket using specified value.
*
* Initialize this packet and set the ZRTP magic value
* to mark it as a ZRTP packet.
*
* @param buf Byte array holding the content of this Packet
* @param off Start offset of packet content inside buffer
* @param len Length of the packet's data
*/
public ZrtpRawPacket(byte[] buf, int off, int len)
{
super (buf, off, len);
buffer[offset] = 0x10;
buffer[offset+1] = 0;
int at = 4;
buffer[offset + at++] = zrtpMagic[0];
buffer[offset + at++] = zrtpMagic[1];
buffer[offset + at++] = zrtpMagic[2];
buffer[offset + at] = zrtpMagic[3];
}
/**
* Check if it could be a ZRTP packet.
*
* The method checks if the first byte of the received data
* matches the defined ZRTP pattern 0x10
*
* @return true if could be a ZRTP packet, false otherwise.
*/
protected boolean isZrtpPacket()
{
if ((buffer[offset] & 0x10) == 0x10)
{
return true;
}
return false;
}
/**
* Check if it is really a ZRTP packet.
*
* The method checks if the packet contains the ZRTP magic
* number.
*
* @return true if packet contains the magic number, false otherwise.
*/
protected boolean hasMagic()
{
if (buffer[offset + 4] == zrtpMagic[0]
&& buffer[offset + 5] == zrtpMagic[1]
&& buffer[offset + 6] == zrtpMagic[2]
&& buffer[offset + 7] == zrtpMagic[3])
{
return true;
}
return false;
}
/**
* Set the sequence number in this packet.
* @param seq
*/
protected void setSeqNum(short seq)
{
int at = 2;
buffer[offset + at++] = (byte)(seq>>8);
buffer[offset + at] = (byte)seq;
}
/**
* Set SSRC in this packet
* @param ssrc
*/
protected void setSSRC(int ssrc)
{
setIntegerAt(ssrc, 8);
}
/**
* Read the SSRC data from packet.
*
* @return SSRC data
*/
protected int getSSRC()
{
return (int)(readUnsignedIntAsLong(8) & 0xffffffff);
}
/**
* Check if the CRC of this packet is ok.
*
* @return true if the CRC is valid, false otherwise
*/
protected boolean checkCrc()
{
int crc = readInt(length-ZrtpPacketBase.CRC_SIZE);
return ZrtpCrc32.zrtpCheckCksum(buffer, offset, length-ZrtpPacketBase.CRC_SIZE, crc);
}
/**
* Set ZRTP CRC in this packet
*/
protected void setCrc()
{
int crc = ZrtpCrc32.zrtpGenerateCksum(buffer, offset,length-ZrtpPacketBase.CRC_SIZE);
// convert and store CRC in crc field of ZRTP packet.
crc = ZrtpCrc32.zrtpEndCksum(crc);
setIntegerAt(crc, length - ZrtpPacketBase.CRC_SIZE);
}
/**
* Get the ZRTP message part from the ZRTP packet.
*
* @return The ZRTP message part.
*/
protected byte[] getMessagePart()
{
return readRegion(ZRTPTransformEngine.ZRTP_PACKET_HEADER, length-ZRTPTransformEngine.ZRTP_PACKET_HEADER);
}
/**
* Set an integer at specified offset in network order.
*
* @param data The integer to store in the packet
* @param at Offset into the buffer
*/
private void setIntegerAt(int data, int at)
{
buffer[offset + at++] = (byte)(data>>24);
buffer[offset + at++] = (byte)(data>>16);
buffer[offset + at++] = (byte)(data>>8);
buffer[offset + at] = (byte)data;
}
public static void main(String argv[])
{
byte[] buf = new byte[30];
ZrtpRawPacket pkt = new ZrtpRawPacket(buf, 0, buf.length);
ZrtpUtils.hexdump("zrtp raw", pkt.buffer, pkt.length);
}
}