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MTProto 2.0 #23

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15 changes: 13 additions & 2 deletions src/TgSharp.Core/Network/MtProtoSender.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,13 +24,15 @@ public class MtProtoSender

private readonly TcpTransport transport;
private readonly Session session;
private readonly Random random;

public readonly List<ulong> needConfirmation = new List<ulong>();

public MtProtoSender(TcpTransport transport, Session session)
{
this.transport = transport;
this.session = session;
this.random = new Random();
}

private int GenerateSequence(bool confirmed)
Expand Down Expand Up @@ -74,7 +76,12 @@ private int GenerateSequence(bool confirmed)

byte[] msgKey;
byte[] ciphertext;
using (MemoryStream plaintextPacket = makeMemory(8 + 8 + 8 + 4 + 4 + packet.Length))

int size = 8 + 8 + 8 + 4 + 4 + packet.Length;
var randomPaddingLength = random.Next(1024 / 16) * 16 + 16 - size % 16;
size += randomPaddingLength;

using (MemoryStream plaintextPacket = makeMemory(size))
{
using (BinaryWriter plaintextWriter = new BinaryWriter(plaintextPacket))
{
Expand All @@ -85,7 +92,11 @@ private int GenerateSequence(bool confirmed)
plaintextWriter.Write(packet.Length);
plaintextWriter.Write(packet);

msgKey = Helpers.CalcMsgKey(plaintextPacket.GetBuffer());
var padding = new byte[randomPaddingLength];
random.NextBytes(padding);
plaintextWriter.Write(padding);

msgKey = Helpers.CalcMsgKey(session.AuthKey.Data, plaintextPacket.GetBuffer());
ciphertext = AES.EncryptAES(Helpers.CalcKey(session.AuthKey.Data, msgKey, true), plaintextPacket.GetBuffer());
}
}
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65 changes: 21 additions & 44 deletions src/TgSharp.Core/Utils/Helpers.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
using System;
using System.Linq;
using System.Security.Cryptography;
using TgSharp.Core.MTProto.Crypto;

Expand Down Expand Up @@ -27,69 +28,45 @@ public static byte[] GenerateRandomBytes(int num)
return data;
}

public static AESKeyData CalcKey(byte[] sharedKey, byte[] msgKey, bool client)
public static AESKeyData CalcKey(byte[] authKey, byte[] msgKey, bool client)
{
int x = client ? 0 : 8;
byte[] buffer = new byte[48];

Array.Copy(msgKey, 0, buffer, 0, 16); // buffer[0:16] = msgKey
Array.Copy(sharedKey, x, buffer, 16, 32); // buffer[16:48] = authKey[x:x+32]
byte[] sha1a = sha1(buffer); // sha1a = sha1(buffer)
//sha256_a = SHA256 (msg_key + substr (auth_key, x, 36));
var sha256A = SHA256(msgKey.Concat(authKey.Skip(x).Take(36)).ToArray());
//sha256_b = SHA256 (substr (auth_key, 40+x, 36) + msg_key);
var sha256B = SHA256(authKey.Skip(40 + x).Take(36).Concat(msgKey).ToArray());
//aes_key = substr (sha256_a, 0, 8) + substr (sha256_b, 8, 16) + substr (sha256_a, 24, 8);
var key = sha256A.Take(8).Concat(sha256B.Skip(8).Take(16)).Concat(sha256A.Skip(24).Take(8)).ToArray();
//aes_iv = substr (sha256_b, 0, 8) + substr (sha256_a, 8, 16) + substr (sha256_b, 24, 8);
var iv = sha256B.Take(8).Concat(sha256A.Skip(8).Take(16)).Concat(sha256B.Skip(24).Take(8)).ToArray();

Array.Copy(sharedKey, 32 + x, buffer, 0, 16); // buffer[0:16] = authKey[x+32:x+48]
Array.Copy(msgKey, 0, buffer, 16, 16); // buffer[16:32] = msgKey
Array.Copy(sharedKey, 48 + x, buffer, 32, 16); // buffer[32:48] = authKey[x+48:x+64]
byte[] sha1b = sha1(buffer); // sha1b = sha1(buffer)

Array.Copy(sharedKey, 64 + x, buffer, 0, 32); // buffer[0:32] = authKey[x+64:x+96]
Array.Copy(msgKey, 0, buffer, 32, 16); // buffer[32:48] = msgKey
byte[] sha1c = sha1(buffer); // sha1c = sha1(buffer)

Array.Copy(msgKey, 0, buffer, 0, 16); // buffer[0:16] = msgKey
Array.Copy(sharedKey, 96 + x, buffer, 16, 32); // buffer[16:48] = authKey[x+96:x+128]
byte[] sha1d = sha1(buffer); // sha1d = sha1(buffer)

byte[] key = new byte[32]; // key = sha1a[0:8] + sha1b[8:20] + sha1c[4:16]
Array.Copy(sha1a, 0, key, 0, 8);
Array.Copy(sha1b, 8, key, 8, 12);
Array.Copy(sha1c, 4, key, 20, 12);

byte[] iv = new byte[32]; // iv = sha1a[8:20] + sha1b[0:8] + sha1c[16:20] + sha1d[0:8]
Array.Copy(sha1a, 8, iv, 0, 12);
Array.Copy(sha1b, 0, iv, 12, 8);
Array.Copy(sha1c, 16, iv, 20, 4);
Array.Copy(sha1d, 0, iv, 24, 8);

return new AESKeyData(key, iv);
}

public static byte[] CalcMsgKey(byte[] data)
public static byte[] CalcMsgKey(byte[] authKey, byte[] data)
{
byte[] msgKey = new byte[16];
Array.Copy(sha1(data), 4, msgKey, 0, 16);
return msgKey;
}
//msg_key_large = SHA256 (substr (auth_key, 88+0, 32) + plaintext + random_padding);
var msgKeyLarge = SHA256(authKey.Skip(88).Take(32).Concat(data).ToArray());

public static byte[] CalcMsgKey(byte[] data, int offset, int limit)
{
byte[] msgKey = new byte[16];
Array.Copy(sha1(data, offset, limit), 4, msgKey, 0, 16);
return msgKey;
//msg_key = substr (msg_key_large, 8, 16);
return msgKeyLarge.Skip(8).Take(16).ToArray();
}

public static byte[] sha1(byte[] data)
public static byte[] SHA256(byte[] data)
{
using (SHA1 sha1 = new SHA1Managed())
using (SHA256 sha256 = new SHA256Managed())
{
return sha1.ComputeHash(data);
return sha256.ComputeHash(data);
}
}

public static byte[] sha1(byte[] data, int offset, int limit)
public static byte[] SHA256(byte[] data, int offset, int limit)
{
using (SHA1 sha1 = new SHA1Managed())
using (SHA256 sha256 = new SHA256Managed())
{
return sha1.ComputeHash(data, offset, limit);
return sha256.ComputeHash(data, offset, limit);
}
}
}
Expand Down