Need help in fixing client connection

[/dev/not/null]

Hello, Mangos Community! I'm trying to developing python core from scratch and using your project as example. Currently my client stucks on 'Connected' and I think problem can be with packet encryption. Can anybody help me with debug or advice ? This is my project.

And this is how packet encrypted:

class HeaderCrypt(object):

    ENCRYPT_HEADER_SIZE = 4
    DECRYPT_HEADER_SIZE = 6

    def __init__(self, session_key):
        self.session_key = session_key
        self.send_i = 0
        self.send_j = 0
        self.recv_i = 0
        self.recv_j = 0

    def encrypt(self, data):
        assert len(data) >= HeaderCrypt.ENCRYPT_HEADER_SIZE
        encrypted_header = [0] * HeaderCrypt.ENCRYPT_HEADER_SIZE

        for index in range(HeaderCrypt.ENCRYPT_HEADER_SIZE):
            enc = (data[index] ^ self.session_key[self.send_i]) + self.send_j
            enc %= 0x100
            encrypted_header[index] = self.send_j = enc
            self.send_i = (self.send_i + 1) % len(self.session_key)

        return bytes(encrypted_header) + data[HeaderCrypt.ENCRYPT_HEADER_SIZE:]

    def decrypt(self, data):
        assert len(data) >= HeaderCrypt.DECRYPT_HEADER_SIZE
        decrypted_header = [0] * HeaderCrypt.DECRYPT_HEADER_SIZE

        for index in range(self.DECRYPT_HEADER_SIZE):
            dec = (data[index] - self.recv_j) ^ self.session_key[self.recv_i]
            dec %= 0x100
            decrypted_header[index] = dec
            self.recv_j = data[index]
            self.recv_i = (self.recv_i + 1) % len(self.session_key)

        return bytes(decrypted_header) + data[HeaderCrypt.DECRYPT_HEADER_SIZE:]

 

[H0zen]

Here is the relevant code from MaNGOS regarding encrypting / decrypting. Translating to Python should be trivial, and I guess you notice where is your issue.

    // encryption
    // _key = session key
    for (size_t t = 0; t < ENCRYPT_HEADER_SIZE; t++)
     {
         _send_i %= _key.size();
         uint8 x = (data[t] ^ _key[_send_i]) + _send_j;
         ++_send_i;
         data[t] = _send_j = x;
     }

    // decryption
    // _key = session key
     for (size_t t = 0; t < DECRYPT_HEADER_SIZE; t++)
     {
         _recv_i %= _key.size();
         uint8 x = (data[t] - _recv_j) ^ _key[_recv_i];
         ++_recv_i;
         _recv_j = data[t];
         data[t] = x;
     }

 

[/dev/not/null]

On 12/4/2018 at 11:28 AM, H0zen said:

Here is the relevant code from MaNGOS regarding encrypting / decrypting. Translating to Python should be trivial, and I guess you notice where is your issue.

    // encryption
    // _key = session key
    for (size_t t = 0; t < ENCRYPT_HEADER_SIZE; t++)
     {
         _send_i %= _key.size();
         uint8 x = (data[t] ^ _key[_send_i]) + _send_j;
         ++_send_i;
         data[t] = _send_j = x;
     }

    // decryption
    // _key = session key
     for (size_t t = 0; t < DECRYPT_HEADER_SIZE; t++)
     {
         _recv_i %= _key.size();
         uint8 x = (data[t] - _recv_j) ^ _key[_recv_i];
         ++_recv_i;
         _recv_j = data[t];
         data[t] = x;
     }

 

Well, as I can see from the mangos code, there are also some key generating exists:

void AuthCrypt::Init(BigNumber* K)
{
    uint8* key = new uint8[SHA_DIGEST_LENGTH];
    uint8 recvSeed[SEED_KEY_SIZE] = { 0x38, 0xA7, 0x83, 0x15, 0xF8, 0x92, 0x25, 0x30, 0x71, 0x98, 0x67, 0xB1, 0x8C, 0x4, 0xE2, 0xAA };
    HMACSHA1 recvHash(SEED_KEY_SIZE, (uint8*)recvSeed);
    recvHash.UpdateBigNumber(K);
    recvHash.Finalize();
    memcpy(key, recvHash.GetDigest(), SHA_DIGEST_LENGTH);
    _key.resize(SHA_DIGEST_LENGTH);
    std::copy(key, key + SHA_DIGEST_LENGTH, _key.begin());
    delete[] key;

    _send_i = _send_j = _recv_i = _recv_j = 0;
    _initialized = true;
}

I tried to implement this in Python, but had no success:

 

    def _generate_key(self, session_key):
        key = bytes(20)
        seed = b'8\xa7\x83\x15\xf8\x92%0q\x98g\xb1\x8c\x04\xe2\xaa'
        hashed = hmac.new(seed, None, sha1)
        return hashed.digest()

Need help with hmac_sha1 python implementation.

[/dev/not/null]

If I understands it correctly - first 16 bytes are same to any hash and only last 4 uses ?

[/dev/not/null]

Solved. I just need to add code to generate key for HeaderCrypt correctly:

    def _generate_key(self, session_key):
        seed = b'8\xa7\x83\x15\xf8\x92%0q\x98g\xb1\x8c\x04\xe2\xaa'
        hashed = hmac.new(seed, session_key, sha1)
        return hashed.digest()