void XteaDecrypt(InputMessage message)
{
int encryptedSize = message.GetUnreadSize();
if (encryptedSize % 8 != 0)
{
throw new Exception("invalid encrypted network message with size: " + (encryptedSize % 8) + ", " + message.GetU16());
}
byte[] unreadBuffer = message.GetUnreadBuffer();
int readPos = 0;
while (readPos < encryptedSize / 4)
{
uint v0 = BitConverter.ToUInt32(unreadBuffer, readPos * 4);
uint v1 = BitConverter.ToUInt32(unreadBuffer, (readPos + 1) * 4);
uint delta = 0x61C88647;
uint sum = 0xC6EF3720;
for (int i = 0; i < 32; i++)
{
v1 -= ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + m_XteaKey[sum >> 11 & 3]);
sum += delta;
v0 -= ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + m_XteaKey[sum & 3]);
}
int tmpReadPos = 0;
byte[] v0Array = BitConverter.GetBytes(v0);
byte[] v1Array = BitConverter.GetBytes(v1);
foreach (byte v in v0Array)
{
unreadBuffer[readPos * 4 + tmpReadPos++] = v;
}
foreach (byte v in v1Array)
{
unreadBuffer[readPos * 4 + tmpReadPos++] = v;
}
readPos = readPos + 2;
}
ushort decryptedSize = (ushort)(BitConverter.ToUInt16(unreadBuffer, 0) + 2);
int sizeDelta = decryptedSize - encryptedSize;
if (sizeDelta > 0 || -sizeDelta > encryptedSize)
{
throw new Exception("invalid decrypted network message with sizeDelta: " + sizeDelta);
}
byte[] newBuffer = new byte[decryptedSize - 2];
Array.Copy(unreadBuffer, 2, newBuffer, 0, decryptedSize - 2);
message.SetBuffer(newBuffer);
}
