public static ZonePacket?TryParse(byte[] rawData, Int32 secureKey)
{
try
{
return(ZonePacket.Parse(ref rawData, secureKey));
}
catch
{
return(null);
}
}
public byte[] GetBytes(Int32 secureKey)
{
var memoryStream = new MemoryStream();
memoryStream.Write(BitConverter.GetBytes(Signature), 0, 4);
memoryStream.Write(BitConverter.GetBytes(UnionType), 0, 4);
memoryStream.Write(BitConverter.GetBytes(SecureKey), 0, 4);
memoryStream.Write(BitConverter.GetBytes(SequenceID), 0, 4);
byte[] packetBytes = memoryStream.ToArray();
ZonePacket.xorBytes(ref packetBytes, ZoneClient.DEFAULT_SECURE_KEY);
return(packetBytes);
}
public static IZonePacket FromMessage(MessageServer message, ZoneClient zoneClientState)
{
Int32 secureKey = zoneClientState.SecureKey;
UInt32 sequenceID = zoneClientState.SequenceID++;
var messageBytes = message.GetBytes();
var newZonePacket = new ZonePacket();
newZonePacket.Signature = ZONE_SIGNATURE;
newZonePacket.Size = messageBytes.Length;
newZonePacket.SequenceID = sequenceID;
newZonePacket.CRC = calculateCRC(messageBytes);
newZonePacket.Data = message.GetBytes();
return(newZonePacket);
}
public CRCMismatchException(ZonePacket ParsedPacket, Int32 ComputedCRC)
{
this.ParsedPacket = ParsedPacket;
this.ComputedCRC = ComputedCRC;
}
public static ZonePacket Parse(ref byte[] rawData, Int32 secureKey)
{
if (rawData.Length < 16)
{
throw new NotEnoughBytesException();
}
xorBytes(ref rawData, secureKey);
var parsedPacket = new ZonePacket();
parsedPacket.Signature = BitConverter.ToInt32(rawData, 0);
parsedPacket.Size = BitConverter.ToInt32(rawData, 4);
parsedPacket.SequenceID = BitConverter.ToUInt32(rawData, 8);
parsedPacket.CRC = BitConverter.ToInt32(rawData, 12);
parsedPacket.Data = new byte[parsedPacket.Size];
if (parsedPacket.Data.Length > rawData.Length - 16)
{
throw new NotEnoughBytesException();
// not enough bytes to parse message. This can happen. What do to?
}
else
{
Array.Copy(rawData, 16, parsedPacket.Data, 0, parsedPacket.Data.Length);
if (rawData.Length - (parsedPacket.Size + 16) > 0)
{
// This means the packets were nagled, and the key was applied to ending bytes unnecessarily
xorBytesFixTail(ref parsedPacket.Data, secureKey);
}
}
// remove from rawData the parsed ZonePacket
Array.Reverse(rawData);
Array.Resize(ref rawData, rawData.Length - (parsedPacket.Size + 16));
Array.Reverse(rawData);
xorBytes(ref rawData, secureKey);
// Check CRC
Int32 computedCRC = calculateCRC(parsedPacket.Data);
if (computedCRC != parsedPacket.CRC)
{
// this might mean the key was applied to the ending bytes unnecessarily. Let's attempt to fix it
xorBytesFixTail(ref parsedPacket.Data, secureKey, 1);
if (calculateCRC(parsedPacket.Data) != parsedPacket.CRC)
{
xorBytesFixTail(ref parsedPacket.Data, secureKey, 1); // unapply xor because it wasn't effective
xorBytesFixTail(ref parsedPacket.Data, secureKey, 2);
if (calculateCRC(parsedPacket.Data) != parsedPacket.CRC)
{
xorBytesFixTail(ref parsedPacket.Data, secureKey, 2);
xorBytesFixTail(ref parsedPacket.Data, secureKey, 3);
if (calculateCRC(parsedPacket.Data) != parsedPacket.CRC)
{
xorBytesFixTail(ref parsedPacket.Data, secureKey, 3);
throw new CRCMismatchException(parsedPacket, computedCRC);
}
}
}
}
return(parsedPacket);
}
