public override byte[] ClientUdpPostDecrypt(byte[] plaindata, int datalength, out int outlength)
{
if (datalength <= 8)
{
outlength = 0;
return(plaindata);
}
var md5 = CreateHMAC(user_key);
var md5data = md5.ComputeHash(plaindata, 0, datalength - 1);
if (md5data[0] != plaindata[datalength - 1])
{
outlength = 0;
return(plaindata);
}
md5 = CreateHMAC(Server.key);
md5data = md5.ComputeHash(plaindata, datalength - 8, 7);
var rand_len = UdpGetRandLen(random_server, md5data);
outlength = datalength - rand_len - 8;
encryptor = (StreamEncryptor)EncryptorFactory.GetEncryptor("chacha20", Convert.ToBase64String(user_key) + Convert.ToBase64String(md5data, 0, 16));
{
var iv = new byte[8];
Array.Copy(Server.key, iv, 8);
encryptor.Decrypt(iv, 8, plaindata, out _);
}
encryptor.Decrypt(plaindata, outlength, plaindata, out outlength);
return(plaindata);
}
public override byte[] ClientPostDecrypt(byte[] plaindata, int datalength, out int outlength)
{
var outdata = new byte[recv_buf_len + datalength];
Array.Copy(plaindata, 0, recv_buf, recv_buf_len, datalength);
recv_buf_len += datalength;
outlength = 0;
var key = new byte[user_key.Length + 4];
user_key.CopyTo(key, 0);
while (recv_buf_len > 4)
{
BitConverter.GetBytes(recv_id).CopyTo(key, key.Length - 4);
var md5 = CreateHMAC(key);
var data_len = ((recv_buf[1] ^ last_server_hash[15]) << 8) + (recv_buf[0] ^ last_server_hash[14]);
var rand_len = GetRecvRandLen(data_len, random_server, last_server_hash);
var len = rand_len + data_len;
if (len >= 4096)
{
throw new ObfsException("ClientPostDecrypt data error");
}
if (len + 4 > recv_buf_len)
{
break;
}
var md5data = md5.ComputeHash(recv_buf, 0, len + 2);
if (md5data[0] != recv_buf[len + 2] ||
md5data[1] != recv_buf[len + 3]
)
{
throw new ObfsException("ClientPostDecrypt data uncorrect checksum");
}
{
var pos = 2;
var outlen = data_len;
Util.Utils.SetArrayMinSize2(ref outdata, outlength + outlen);
var data = new byte[outlen];
Array.Copy(recv_buf, pos, data, 0, outlen);
encryptor.Decrypt(data, outlen, data, out outlen);
last_server_hash = md5data;
if (recv_id == 1)
{
Server.tcp_mss = recv_tcp_mss = data[0] | (data[1] << 8);
pos = 2;
outlen -= 2;
send_back_cmd.Add(0xff00);
}
else
{
pos = 0;
}
Array.Copy(data, pos, outdata, outlength, outlen);
outlength += outlen;
recv_buf_len -= len + 4;
Array.Copy(recv_buf, len + 4, recv_buf, 0, recv_buf_len);
++recv_id;
}
}
return(outdata);
}
public void PackAuthData(byte[] data, int datalength, byte[] outdata, out int outlength)
{
const int authhead_len = 4 + 8 + 4 + 16 + 4;
var encrypt = new byte[24];
if (Server.data is AuthDataAesChain authData)
{
lock (authData)
{
if (authData.connectionID > 0xFF000000)
{
authData.clientID = null;
}
if (authData.clientID == null)
{
authData.clientID = new byte[4];
g_random.GetBytes(authData.clientID);
authData.connectionID = (uint)BitConverter.ToInt32(authData.clientID, 0) % 0xFFFFFD;
}
authData.connectionID += 1;
Array.Copy(authData.clientID, 0, encrypt, 4, 4);
Array.Copy(BitConverter.GetBytes(authData.connectionID), 0, encrypt, 8, 4);
}
}
outlength = authhead_len;
var encrypt_data = new byte[32];
var key = new byte[Server.Iv.Length + Server.key.Length];
Server.Iv.CopyTo(key, 0);
Server.key.CopyTo(key, Server.Iv.Length);
var utc_time_second = (ulong)Math.Floor(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds);
var utc_time = (uint)utc_time_second;
Array.Copy(BitConverter.GetBytes(utc_time), 0, encrypt, 0, 4);
encrypt[12] = (byte)Server.overhead;
encrypt[13] = (byte)(Server.overhead >> 8);
send_tcp_mss = 1024; //random.Next(1024) + 400;
recv_tcp_mss = send_tcp_mss;
encrypt[14] = (byte)send_tcp_mss;
encrypt[15] = (byte)(send_tcp_mss >> 8);
// first 12 bytes
{
var rnd = new byte[4];
random.NextBytes(rnd);
rnd.CopyTo(outdata, 0);
var md5 = CreateHMAC(key);
var md5data = md5.ComputeHash(rnd, 0, rnd.Length);
last_client_hash = md5data;
Array.Copy(md5data, 0, outdata, rnd.Length, 8);
}
// uid & 16 bytes auth data
{
var uid = new byte[4];
var index_of_split = Server.param.IndexOf(':');
if (index_of_split > 0)
{
try
{
var user = uint.Parse(Server.param.Substring(0, index_of_split));
user_key = System.Text.Encoding.UTF8.GetBytes(Server.param.Substring(index_of_split + 1));
BitConverter.GetBytes(user).CopyTo(uid, 0);
}
catch (Exception ex)
{
Logging.Log(LogLevel.Warn, $"Faild to parse auth param, fallback to basic mode. {ex}");
}
}
if (user_key == null)
{
random.NextBytes(uid);
user_key = Server.key;
}
for (var i = 0; i < 4; ++i)
{
uid[i] ^= last_client_hash[8 + i];
}
var encrypt_key = user_key;
var streamEncryptor = (StreamEncryptor)EncryptorFactory.GetEncryptor("aes-128-cbc", Convert.ToBase64String(encrypt_key) + SALT);
streamEncryptor.SetIV(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 });
streamEncryptor.Encrypt(encrypt, 16, encrypt_data, out _);
streamEncryptor.Dispose();
Array.Copy(encrypt_data, 0, encrypt, 4, 16);
uid.CopyTo(encrypt, 0);
}
// final HMAC
{
var md5 = CreateHMAC(user_key);
var md5data = md5.ComputeHash(encrypt, 0, 20);
last_server_hash = md5data;
Array.Copy(md5data, 0, encrypt, 20, 4);
}
encrypt.CopyTo(outdata, 12);
encryptor = (StreamEncryptor)EncryptorFactory.GetEncryptor("chacha20", Convert.ToBase64String(user_key) + Convert.ToBase64String(last_client_hash, 0, 16));
{
var iv = new byte[8];
Array.Copy(last_client_hash, iv, 8);
encryptor.SetIV(iv);
}
{
encryptor.Decrypt(last_server_hash, 8, outdata, out _);
}
// combine first chunk
{
var pack_outdata = new byte[outdata.Length];
PackData(data, datalength, pack_outdata, out var pack_outlength);
Array.Copy(pack_outdata, 0, outdata, outlength, pack_outlength);
outlength += pack_outlength;
}
}