public EncryptedMessage(byte[] authKey, byte[] plainData)
{
_authKey = authKey;
using (var ms = new MemoryStream(plainData))
{
using (var br = new BinaryReader(ms))
{
AuthKeyId = br.ReadInt64();
MsgKey = new BigInteger(br.ReadBytes(16));
// дешифруем эту дату
byte[] aesKey = CalculateAesKey(8, MsgKey.GetBytes());
byte[] aesIv = CalculateIV(8, MsgKey.GetBytes());
var aesIge = new Aes256IgeManaged(aesKey, aesIv);
Data = new EncryptedData(aesIge.Decrypt(br.ReadBytes(plainData.Length - 8 - 16)));
}
}
}
/// <summary>
/// Обработка DH параметров
/// </summary>
/// <param name="dhparams"></param>
/// <returns></returns>
private Combinator ProcessDhParams(Combinator dhparams)
{
var ea = dhparams.Get<byte[]>("encrypted_answer");
// Обновим server nonce
_serverNonce = dhparams.Get<BigInteger>("server_nonce");
// Расшифровка строки
var aes = new Aes256IgeManaged(CalculateTmpAesKey(_newNonce, _serverNonce),
CalculateTmpAesIV(_newNonce, _serverNonce));
byte[] answerWithHash = aes.Decrypt(ea);
if (answerWithHash.Length % 16 != 0)
throw new ArgumentException("Неверный ответ внутри сообщения");
byte[] answer = answerWithHash.Skip(20).ToArray();
return new Combinator(answer, "Server_DH_inner_data");
}
/// <summary>
/// Генерация клиентского запроса с параметрами Диффи-Хеллмана
/// </summary>
/// <param name="serverDh"></param>
/// <returns></returns>
private Combinator SetClientDhParams(Combinator serverDh)
{
var g = serverDh.Get<int>("g");
var dhPrime = serverDh.Get<byte[]>("dh_prime");
var gA = serverDh.Get<byte[]>("g_a");
var dh = new DiffieHellmanManaged(dhPrime, new BigInteger(g).GetBytes(), 2048);
// generate the public key of the second DH instance
byte[] gB = dh.CreateKeyExchange();
// let the second DH instance compute the shared secret using the first DH public key
_authKey = dh.DecryptKeyExchange(gA);
// Сформируем ответ
// отдаем g_b в BE
var clientDhInnerData = new Combinator("client_DH_inner_data", _nonce, _serverNonce, (long)0, gB);
byte[] s = clientDhInnerData.Serialize();
// Шифрование строки
var aes = new Aes256IgeManaged(CalculateTmpAesKey(_newNonce, _serverNonce)
, CalculateTmpAesIV(_newNonce, _serverNonce));
using (var ms = new MemoryStream())
using (var bw = new BinaryWriter(ms))
{
SHA1 sha1 = SHA1.Create();
bw.Write(sha1.ComputeHash(s));
bw.Write(s);
var r = new Random();
while (bw.BaseStream.Length % 16 != 0)
bw.Write((byte)r.Next());
s = aes.Encrypt(ms.ToArray());
}
// Сформируем ответ
var setClientDhParams = new Combinator("set_client_DH_params", _nonce, _serverNonce, s);
return setClientDhParams;
}
public byte[] Serialize()
{
using (var ms = new MemoryStream())
{
using (var bw = new BinaryWriter(ms))
{
bw.Write(AuthKeyId);
bw.Write(MsgKey.GetBytes());
byte[] aesKey = CalculateAesKey(0, MsgKey.GetBytes());
byte[] aesIV = CalculateIV(0, MsgKey.GetBytes());
var aesIge = new Aes256IgeManaged(aesKey, aesIV);
bw.Write(aesIge.Encrypt(Data.Serialize()));
}
return ms.ToArray();
}
}
