public static AuthKey Deserialize(Bytes key) =>
key.ToArrayUnsafe().Apply(Helpers.Sha1).Apply(BtHelpers.Deserialize(br => {
var auxHash = br.ReadUInt64();
br.ReadBytes(4);
var keyId = br.ReadUInt64();
return(new AuthKey(key, keyId, auxHash));
}));
public async Task Send(byte[] msg)
{
var session = _session.Get();
var plainText = BtHelpers.UsingMemBinWriter(bw =>
{
bw.Write(session.Salt);
bw.Write(session.Id);
bw.Write(msg);
var bs = bw.BaseStream;
var requiredPadding = (16 - (int)bs.Position % 16).Apply(x => x == 16 ? 0 : x);
var randomPadding = (Rnd.NextInt32() & 15) * 16;
var padding = 16 + requiredPadding + randomPadding;
bw.Write(Rnd.NextBytes(padding));
});
var authKey = session.AuthKey.Key.ToArrayUnsafe();
var msgKey = CalcMsgKey(authKey, plainText, true);
var aesKey = CalcAesKey(authKey, msgKey, true);
var cipherText = Aes.EncryptAES(aesKey, plainText);
await BtHelpers.UsingMemBinWriter(bw =>
{
bw.Write(session.AuthKey.KeyId);
bw.Write(msgKey);
bw.Write(cipherText);
}).Apply(_transport.Send);
}
public async Task <BinaryReader> Receive()
{
var plainText = await ReceivePlainText();
return(plainText.Apply(BtHelpers.Deserialize(br =>
{
var remoteSalt = br.ReadUInt64();
var remoteSessionId = br.ReadUInt64();
return br;
})));
}
async Task <byte[]> ReceivePlainText()
{
var body = await _transport.Receive();
return(body.Apply(BtHelpers.Deserialize(br =>
{
var authKeyId = br.ReadUInt64(); // TODO: check auth key id
var msgKey = br.ReadBytes(16); // TODO: check msg_key correctness
var keyData = CalcAesKey(_session.Get().AuthKey.Key.ToArrayUnsafe(), msgKey, false);
var bs = br.BaseStream;
var cipherTextLen = (int)(bs.Length - bs.Position);
var cipherText = br.ReadBytes(cipherTextLen);
var plainText = Aes.DecryptAES(keyData, cipherText);
return plainText;
})));
}
