TLSharp/TLSharp.Core/Auth/Step1_PQRequest.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using TLSharp.Core.MTProto;
using TLSharp.Core.MTProto.Crypto;

namespace TLSharp.Core.Auth
{
	public class Step1_Response
	{
		public byte[] Nonce { get; set; }
		public byte[] ServerNonce { get; set; }
		public BigInteger Pq { get; set; }
		public List<byte[]> Fingerprints { get; set; }
	}

	public class Step1_PQRequest
	{
		private byte[] nonce;

		public Step1_PQRequest()
		{
			nonce = new byte[16];
		}

		public byte[] ToBytes()
		{
			new Random().NextBytes(nonce);
			const int constructorNumber = 0x60469778;

			using (var memoryStream = new MemoryStream())
			{
				using (var binaryWriter = new BinaryWriter(memoryStream))
				{
					binaryWriter.Write(constructorNumber);
					binaryWriter.Write(nonce);

					return memoryStream.ToArray();
				}
			}
		}

		public Step1_Response FromBytes(byte[] bytes)
		{
			var fingerprints = new List<byte[]>();

			using (var memoryStream = new MemoryStream(bytes, false))
			{
				using (var binaryReader = new BinaryReader(memoryStream))
				{
					const int responseConstructorNumber = 0x05162463;
					var responseCode = binaryReader.ReadInt32();
					if (responseCode != responseConstructorNumber)
					{
						throw new InvalidOperationException($"invalid response code: {responseCode}");
					}

					var nonceFromServer = binaryReader.ReadBytes(16);
					
					if (!nonceFromServer.SequenceEqual(nonce))
					{
						throw new InvalidOperationException("invalid nonce from server");
					}
					
					var serverNonce = binaryReader.ReadBytes(16);

					byte[] pqbytes = Serializers.Bytes.read(binaryReader);
					var pq = new BigInteger(1, pqbytes);

					var vectorId = binaryReader.ReadInt32();
					const int vectorConstructorNumber = 0x1cb5c415;
					if (vectorId != vectorConstructorNumber)
					{
						throw new InvalidOperationException($"Invalid vector constructor number {vectorId}");
					}

					var fingerprintCount = binaryReader.ReadInt32();
					for (var i = 0; i < fingerprintCount; i++)
					{
						byte[] fingerprint = binaryReader.ReadBytes(8);
						fingerprints.Add(fingerprint);
					}

					return new Step1_Response
					{
						Fingerprints = fingerprints,
						Nonce = nonce,
						Pq = pq,
						ServerNonce = serverNonce
					};
				}
			}
		}
	}
}