public override byte[] ClientUdpPreEncrypt(byte[] plaindata, int datalength, out int outlength)
{
byte[] outdata = new byte[datalength + 1024];
if (user_key == null)
{
user_id = new byte[4];
int index_of_split = Server.param.IndexOf(':');
if (index_of_split > 0)
{
try
{
uint 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(user_id, 0);
}
catch (Exception ex)
{
Logging.Log(LogLevel.Warn, $"Faild to parse auth param, fallback to basic mode. {ex}");
}
}
if (user_key == null)
{
random.NextBytes(user_id);
user_key = Server.key;
}
}
byte[] auth_data = new byte[3];
random.NextBytes(auth_data);
byte[] md5data = MbedTLS.ComputeHash(Server.key, auth_data, 0, auth_data.Length);
int rand_len = UdpGetRandLen(random_client, md5data);
byte[] rand_data = new byte[rand_len];
random.NextBytes(rand_data);
outlength = datalength + rand_len + 8;
encryptor = EncryptorFactory.GetEncryptor("rc4", Convert.ToBase64String(user_key) + Convert.ToBase64String(md5data, 0, 16));
encryptor.Encrypt(plaindata, datalength, outdata, out datalength);
rand_data.CopyTo(outdata, datalength);
auth_data.CopyTo(outdata, outlength - 8);
byte[] uid = new byte[4];
for (int i = 0; i < 4; ++i)
{
uid[i] = (byte)(user_id[i] ^ md5data[i]);
}
uid.CopyTo(outdata, outlength - 5);
md5data = MbedTLS.ComputeHash(user_key, outdata, 0, outlength - 1);
return(outdata);
}
public void PackData(byte[] data, int datalength, byte[] outdata, out int outlength)
{
int rand_len = GetRandLen(datalength);
outlength = rand_len + datalength + 2;
outdata[0] = (byte)(datalength ^ last_client_hash[14]);
outdata[1] = (byte)((datalength >> 8) ^ last_client_hash[15]);
{
byte[] rnd_data = new byte[rand_len];
random.NextBytes(rnd_data);
encryptor.Encrypt(data, datalength, data, out datalength);
if (datalength > 0)
{
if (rand_len > 0)
{
int start_pos = GetRandStartPos(rand_len, random_client);
Array.Copy(data, 0, outdata, 2 + start_pos, datalength);
Array.Copy(rnd_data, 0, outdata, 2, start_pos);
Array.Copy(rnd_data, start_pos, outdata, 2 + start_pos + datalength, rand_len - start_pos);
}
else
{
Array.Copy(data, 0, outdata, 2, datalength);
}
}
else
{
rnd_data.CopyTo(outdata, 2);
}
}
byte[] key = new byte[user_key.Length + 4];
user_key.CopyTo(key, 0);
BitConverter.GetBytes(pack_id).CopyTo(key, key.Length - 4);
++pack_id;
byte[] md5data = MbedTLS.ComputeHash(key, outdata, 0, outlength);
last_client_hash = md5data;
Array.Copy(md5data, 0, outdata, outlength, 2);
outlength += 2;
}
public override byte[] ClientUdpPostDecrypt(byte[] plaindata, int datalength, out int outlength)
{
if (datalength <= 8)
{
outlength = 0;
return(plaindata);
}
byte[] md5data = MbedTLS.ComputeHash(user_key, plaindata, 0, datalength - 1);
if (md5data[0] != plaindata[datalength - 1])
{
outlength = 0;
return(plaindata);
}
md5data = MbedTLS.ComputeHash(Server.key, plaindata, datalength - 8, 7);
int rand_len = UdpGetRandLen(random_server, md5data);
outlength = datalength - rand_len - 8;
encryptor = EncryptorFactory.GetEncryptor("rc4", Convert.ToBase64String(user_key) + Convert.ToBase64String(md5data, 0, 16));
encryptor.Decrypt(plaindata, outlength, plaindata, out outlength);
return(plaindata);
}
public override byte[] ClientPostDecrypt(byte[] plaindata, int datalength, out int outlength)
{
byte[] outdata = new byte[recv_buf_len + datalength];
Array.Copy(plaindata, 0, recv_buf, recv_buf_len, datalength);
recv_buf_len += datalength;
outlength = 0;
byte[] 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);
int data_len = ((recv_buf[1] ^ last_server_hash[15]) << 8) + (recv_buf[0] ^ last_server_hash[14]);
int rand_len = GetRandLen(data_len, random_server, last_server_hash);
int len = rand_len + data_len;
if (len >= 4096)
{
throw new ObfsException("ClientPostDecrypt data error");
}
if (len + 4 > recv_buf_len)
{
break;
}
byte[] md5data = MbedTLS.ComputeHash(key, 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");
}
int pos;
if (data_len > 0 && rand_len > 0)
{
pos = 2 + GetRandStartPos(rand_len, random_server);
}
else
{
pos = 2;
}
int outlen = data_len;
Util.Utils.SetArrayMinSize2(ref outdata, outlength + outlen);
byte[] 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 = data[0] | (data[1] << 8);
pos = 2;
outlen -= 2;
}
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;
byte[] encrypt = new byte[24];
AuthDataAesChain authData = Server.data as AuthDataAesChain;
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 = (UInt32)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;
byte[] encrypt_data = new byte[32];
byte[] key = new byte[Server.iv.Length + Server.key.Length];
Server.iv.CopyTo(key, 0);
Server.key.CopyTo(key, Server.iv.Length);
UInt64 utc_time_second = (UInt64)Math.Floor(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds);
UInt32 utc_time = (UInt32)(utc_time_second);
Array.Copy(BitConverter.GetBytes(utc_time), 0, encrypt, 0, 4);
encrypt[12] = (byte)(Server.overhead);
encrypt[13] = (byte)(Server.overhead >> 8);
// first 12 bytes
{
byte[] rnd = new byte[4];
random.NextBytes(rnd);
rnd.CopyTo(outdata, 0);
byte[] md5data = MbedTLS.ComputeHash(key, rnd, 0, rnd.Length);
last_client_hash = md5data;
Array.Copy(md5data, 0, outdata, rnd.Length, 8);
}
// uid & 16 bytes auth data
{
byte[] uid = new byte[4];
int index_of_split = Server.param.IndexOf(':');
if (index_of_split > 0)
{
try
{
uint 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 (int i = 0; i < 4; ++i)
{
uid[i] ^= last_client_hash[8 + i];
}
byte[] encrypt_key = user_key;
IEncryptor encryptor = EncryptorFactory.GetEncryptor("aes-128-cbc", Convert.ToBase64String(encrypt_key) + SALT);
encryptor.SetIV(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 });
encryptor.Encrypt(encrypt, 16, encrypt_data, out int enc_outlen);
encryptor.Dispose();
Array.Copy(encrypt_data, 16, encrypt, 4, 16);
uid.CopyTo(encrypt, 0);
}
// final HMAC
{
byte[] md5data = MbedTLS.ComputeHash(user_key, encrypt, 0, 20);
last_server_hash = md5data;
Array.Copy(md5data, 0, encrypt, 20, 4);
}
encrypt.CopyTo(outdata, 12);
encryptor = EncryptorFactory.GetEncryptor("rc4", Convert.ToBase64String(user_key) + Convert.ToBase64String(last_client_hash, 0, 16));
// combine first chunk
{
byte[] pack_outdata = new byte[outdata.Length];
PackData(data, datalength, pack_outdata, out int pack_outlength);
Array.Copy(pack_outdata, 0, outdata, outlength, pack_outlength);
outlength += pack_outlength;
}
}