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https://github.com/EpinelPS/EpinelPS.git
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This commit is contained in:
Mikhail Thompson
316
nksrv/Utils/PacketDecryption.cs
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316
nksrv/Utils/PacketDecryption.cs
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using EmbedIO;
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using Microsoft.AspNetCore.DataProtection.KeyManagement;
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using nksrv.LobbyServer;
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using Sodium;
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using System;
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using System.Collections.Generic;
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using System.IO.Compression;
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using System.Linq;
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using System.Numerics;
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using System.Text;
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using System.Threading.Tasks;
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namespace nksrv.Utils
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{
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public class PacketDecryption
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{
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public static async Task<PacketDecryptResponse> DecryptOrReturnContentAsync(IHttpContext ctx, bool decompress = false)
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{
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byte[] bin = Array.Empty<byte>();
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using MemoryStream buffer = new MemoryStream();
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var stream = ctx.Request.InputStream;
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var encoding = ctx.Request.Headers[HttpHeaderNames.ContentEncoding]?.Trim();
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Stream decryptedStream;
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switch (encoding)
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{
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case CompressionMethodNames.Gzip:
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decryptedStream = new GZipStream(stream, CompressionMode.Decompress);
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break;
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case CompressionMethodNames.Deflate:
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decryptedStream = new DeflateStream(stream, CompressionMode.Decompress);
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break;
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case CompressionMethodNames.None:
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case null:
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decryptedStream = stream;
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break;
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case "gzip,enc":
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var responseLen = CBorReadItem(stream); // length of header (not including encrypted data)
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stream.ReadByte(); // ignore padding
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stream.ReadByte(); // ignore padding
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var decryptionToken = CBorReadString(stream);
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var nonce = CBorReadByteString(stream);
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MemoryStream encryptedBytes = new MemoryStream();
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stream.CopyTo(encryptedBytes);
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var bytes = encryptedBytes.ToArray();
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var key = LobbyHandler.GetInfo(decryptionToken);
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if (key == null)
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{
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throw HttpException.BadRequest("Invalid decryption token");
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}
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var additionalData = GenerateAdditionalData(decryptionToken, false);
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var x = SecretAeadXChaCha20Poly1305.Decrypt(bytes, nonce, key.Keys.ReadSharedSecret, additionalData.ToArray());
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var ms = new MemoryStream(x);
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// File.WriteAllBytes("fullPkt-decr", ms.ToArray());
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var unkVal1 = ms.ReadByte();
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var pktLen = ms.ReadByte() & 0x1f;
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var seqNumB = ms.ReadByte();
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var seqNum = seqNumB;
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if (seqNumB >= 24)
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{
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var b = ms.ReadByte();
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seqNum = BitConverter.ToUInt16(new byte[] { (byte)b, (byte)seqNumB }, 0);
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// todo support uint32
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}
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var startPos = (int)ms.Position;
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//Console.WriteLine("seg #: " + seqNum + ",actual:" + bytes.Length + "cntlen:" + ctx.Request.ContentLength64);
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var contents = x.Skip(startPos).ToArray();
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if (contents.Length != 0 && contents[0] == 31)
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{
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//File.WriteAllBytes("contentsgzip", contents);
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// gzip compression is used
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using Stream csStream = new GZipStream(new MemoryStream(contents), CompressionMode.Decompress);
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using MemoryStream decoded = new MemoryStream();
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csStream.CopyTo(decoded);
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contents = decoded.ToArray();
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}
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return new PacketDecryptResponse() { Contents = contents, UserId = key.UserId, UsedAuthToken = decryptionToken };
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default:
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throw HttpException.BadRequest($"Unsupported content encoding \"{encoding}\"");
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}
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await stream.CopyToAsync(buffer, 81920, ctx.CancellationToken).ConfigureAwait(continueOnCapturedContext: false);
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return new PacketDecryptResponse() { Contents = buffer.ToArray() };
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}
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public static byte[] EncryptData(byte[] message, string authToken)
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{
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var key = LobbyHandler.GetInfo(authToken);
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if (key == null)
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{
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throw HttpException.BadRequest("Invalid decryption token");
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}
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MemoryStream m = new MemoryStream();
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m.WriteByte(89); // cbor ushort
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// 42bytes of data past header, 3 bytes for auth token bytestring, 2 bytes for nonce prefix, 24 bytes for nonce data
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var headerLen = 2 + 3 + authToken.Length + 2 + 24;
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byte[] headerLenBytes = BitConverter.GetBytes((ushort)headerLen);
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if (BitConverter.IsLittleEndian) headerLenBytes = headerLenBytes.Reverse().ToArray();
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m.Write(headerLenBytes, 0, headerLenBytes.Length);
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// write 2 bytes that i am not sure about
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m.WriteByte(131);
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m.WriteByte(1);
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// write auth token len
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m.WriteByte(89); // cbor ushort
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var authLenBytes = BitConverter.GetBytes((ushort)authToken.Length);
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if (BitConverter.IsLittleEndian) authLenBytes = authLenBytes.Reverse().ToArray();
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m.Write(authLenBytes, 0, authLenBytes.Length);
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// write actual auth token
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var authBytes = Encoding.UTF8.GetBytes(authToken);
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m.Write(authBytes, 0, authBytes.Length);
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// write nonce
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m.WriteByte(88); // cbor byte
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m.WriteByte(24); // nonce length
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// generate it
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byte[] nonce = new byte[24];
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new Random().NextBytes(nonce);
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// write nonce bytes
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m.Write(nonce, 0, nonce.Length);
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// get additional data
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var additionalData = GenerateAdditionalData(authToken, true);
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// prep payload
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MemoryStream msm = new MemoryStream();
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msm.WriteByte(88);
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msm.WriteByte(0);
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msm.Write(message);
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var encryptedBytes = SecretAeadXChaCha20Poly1305.Encrypt(msm.ToArray(), nonce, key.Keys.TransferSharedSecret, additionalData.ToArray());
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// write encrypted data
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m.Write(encryptedBytes);
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byte[] data = m.ToArray();
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//File.WriteAllBytes("our-encryption", data);
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// we are done
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return data;
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}
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private static byte[] GenerateAdditionalData(string authToken, bool encrypting)
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{
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// Generate "additional data" which consists of auth token and its length using cbor.
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// Not sure what the first bytes are but they are always the same. 89 represents start of UShort
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MemoryStream additionalData = new();
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additionalData.WriteByte((byte)(encrypting ? 129 : 130));
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additionalData.WriteByte(1);
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// write auth token len
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if (!encrypting)
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{
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var authLen = BitConverter.GetBytes((ushort)authToken.Length);
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if (BitConverter.IsLittleEndian)
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authLen = authLen.Reverse().ToArray();
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additionalData.WriteByte(89);
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additionalData.Write(authLen, 0, authLen.Length);
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// write our authentication token
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var authBytes = Encoding.UTF8.GetBytes(authToken);
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additionalData.Write(authBytes, 0, authBytes.Length);
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}
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return additionalData.ToArray();
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}
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private static string CBorReadString(Stream s)
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{
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CBorItem item = CBorReadItem(s);
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if (item.MajorType != 2)
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{
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throw new Exception("invalid string");
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}
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string resp = "";
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var len = item.FullValue;
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for (int i = 0; i < len; i++)
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{
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var b = s.ReadByte();
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if (b == -1) throw new EndOfStreamException();
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resp += (char)b;
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}
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return resp;
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}
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private static byte[] CBorReadByteString(Stream s)
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{
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CBorItem item = CBorReadItem(s);
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if (item.MajorType != 2)
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{
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throw new Exception("invalid string");
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}
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var len = item.FullValue;
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byte[] resp = new byte[len];
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for (int i = 0; i < len; i++)
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{
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var b = s.ReadByte();
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if (b == -1) throw new EndOfStreamException();
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resp[i] = (byte)b;
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}
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return resp;
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}
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private static CBorItem CBorReadItem(Stream s)
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{
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var b = s.ReadByte();
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var type = b & 0x1f;
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var res = new CBorItem();
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res.MajorType = (b >> 5) & 7;
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switch (type)
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{
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case 24:
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// byte
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res.ByteValue = new byte[] { (byte)s.ReadByte() };
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res.type = CBorItemType.Byte;
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res.FullValue = (int)res.ByteValue[0];
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break;
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case 25:
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byte[] arr = new byte[2];
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ReadToBuff(s, arr);
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if (BitConverter.IsLittleEndian)
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Array.Reverse(arr);
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res.ByteValue = arr;
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res.type = CBorItemType.UShort;
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res.UShortValue = BitConverter.ToUInt16(arr, 0);
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res.FullValue = res.UShortValue;
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break;
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default:
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// throw new NotImplementedException();
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break;
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}
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return res;
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}
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private static void ReadToBuff(Stream s, byte[] buf)
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{
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int i = 0;
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while (i != buf.Length)
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{
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if (i > buf.Length)
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throw new ArgumentOutOfRangeException();
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var pos = buf.Length - i;
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var read = s.Read(buf, i, buf.Length - i);
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if (read == 0)
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break;
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i += read;
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}
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if (i < buf.Length)
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{
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throw new EndOfStreamException();
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}
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}
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}
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public class PacketDecryptResponse
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{
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public ulong UserId;
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public string UsedAuthToken;
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public byte[] Contents;
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}
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public class CBorItem
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{
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public CBorItemType type;
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public byte[] ByteValue;
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public ushort UShortValue;
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public int MajorType;
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public int FullValue;
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}
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public enum CBorItemType
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{
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Byte,
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UShort,
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ByteString,
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}
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}
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