Habbo2020-Desktop

Work in progress

This repository is a continuation of my research in 2020.
The main intent is to help out Tanji to support the Unity client.

Warning

Never connect to the Habbo server with an invalid client certificate.
If you do this you will get banned for 100 years.

This project has certificate validation built in to prevent this mistake.
Use at your own risk.

Usage

1. Refresh the self-signed SSL certificates in src/MitmServerNet/Certificates/Self.
   openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 3650 -nodes -subj "/C=XX/ST=StateName/L=CityName/O=CompanyName/OU=CompanySectionName/CN=CommonNameOrHostname"
2. Enter Habbo certificate password in src/MitmServerNet/appsettings.json.
3. Patch Unity client. Example code coming soon
4. Play Habbo.

Client Protocol

Describes how the Habbo Unity client connects to the Habbo server.

1. Connect with WebSocket

The client connects to the Habbo server at wss://game-us.habbo.com:30001/websocket.

GET /websocket HTTP/1.1

User-Agent: websocket-sharp/1.0
Upgrade: websocket
Connection: Upgrade
Host: game-us.habbo.com:30001
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Version: 13

2. mTLS Handshake

Client sends StartTLS, server replies with OK.
Afterwards it does the mTLS handshake using the BouncyCastle TlsClientProtocol.cs.

Client receives handshake messages in this order.

- server_hello (2)
- certificate (11)
- server_key_exchange (12) 
- certificate_request (13)
- server_key_exchange (14)
- finished (20)

For the certificate_request the client must send a valid certificate, THIS IS VERY IMPORTANT.
It will work without but you will get a ban for 100 years.

In the Habbo client this certificate is loaded as such:

using System.Security.Cryptography.X509Certificates;

var certificateData = Convert.FromBase64String("MIIQUQIBAzCCEBcG....");
var certificate = new X509Certificate(certificateData, "yai7th....");

Meaning you can reliably dump the certificate if you hook X509Certificate(byte[] rawData, string password).
The certificate subject is CN=Habbo-Client-habbo2020-PROD-1455, OU=Habbo_Client, O=Sulake Oy, L=Helsinki, S=Uusimaa, C=FI.

See the code in Middle.cs#ConnectToHabbo for a working example.

3. Diffie Hellman

Next up is the diffie hellman handshake that is also used in the flash client.
Important packet in order.

Client - ClientHelloMessageComposer [4000]

Contains a 8 byte nonce for the ChaCha20 cipher used later.

var nonce = packet.ReadString();
var nonceHex = string.Empty;

for (var i = 0; i < 8; i++)
{
    nonceHex += nonce.Substring(i * 3, 2);
}

_nonce = Convert.FromHexString(nonceHex);

Client - InitDiffieHandshakeMessageComposer [207]

Prompts the server to start with the handshake.

Server - InitDiffieHandshakeEvent [278]

Sends signed prime and generator, client decrypts with embedded RSA public key.
The embedded RSA public key is loaded using BigInteger.Parse(string value, NumberStyles style) as hex.

Client - CompleteDiffieHandshakeMessageComposer [208]

Client sends encrypted DHPublic to the server, server decrypts with RSA private key and calculates a shared key.

Server - CompleteDiffieHandshakeEvent [279]

Server sends encrypted DHPublic to the client, client decrypts with RSA public key and calculates a shared key.

The client and server both have a shared key (up to 32 bytes) and a nonce (8 bytes). These are used for ChaCha20.
The shared key must be padded with 0x00 bytes up to 32 bytes.

4. Shuffled communication

Using ChaCha20 you must encrypt and decrypt all the packet ids sent to and received from the Unity client.

private static void Process(HabboChaCha20 cipher, Span<byte> header)
{
    Span<byte> headerReverse = stackalloc byte[2];
    
    headerReverse[0] = header[1];
    headerReverse[1] = header[0];
    
    cipher.Process(headerReverse);
    
    header[0] = headerReverse[1];
    header[1] = headerReverse[0];
}

Screenshot