133 lines
4.7 KiB
C#
133 lines
4.7 KiB
C#
using System.Buffers.Binary;
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using System.Security.Cryptography;
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using Fleet.Core;
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namespace MoShiro.Protocol;
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/// <summary>
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/// 数据面的 TCP 连接（Fleet 之外的线格式）。连接都由 Probe 发起；TLS 是可选的（ClientHello 以 0x16 开头，
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/// 明文首帧以 "MN" 开头，所以同一个端口可以区分）。首帧：
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/// <c>"MN"(2) version(1) session_id(8) stream_id(4) nonce(16) mac(16)</c>，认证失败直接关闭连接；
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/// 之后是 <c>VarInt 长度 | 正文</c> 的消息，回显类消息的正文是 <c>seq(u32) send_ts_us(i64) | padding</c>。
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/// </summary>
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public static class TcpWire
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{
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public const int AuthBytes = 2 + 1 + 8 + 4 + 16 + 16;
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public const int NonceBytes = 16;
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public const int MinEchoBody = 12;
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public const int MaxMessageBytes = 1 << 20;
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public static void WriteAuth(Span<byte> destination, long sessionId, uint streamId, ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> key)
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{
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BinaryPrimitives.WriteUInt16LittleEndian(destination, MeasurementDatagram.Magic);
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destination[2] = MeasurementDatagram.Version;
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BinaryPrimitives.WriteInt64LittleEndian(destination[3..], sessionId);
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BinaryPrimitives.WriteUInt32LittleEndian(destination[11..], streamId);
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nonce[..NonceBytes].CopyTo(destination[15..]);
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Span<byte> full = stackalloc byte[32];
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HMACSHA256.HashData(key, destination[..(AuthBytes - 16)], full);
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full[..16].CopyTo(destination[(AuthBytes - 16)..]);
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}
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/// <summary>解析首帧（MAC 要在查到会话密钥之后用 <see cref="VerifyAuth"/> 校验）。</summary>
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public static bool TryParseAuth(ReadOnlySpan<byte> frame, out long sessionId, out uint streamId, out ReadOnlySpan<byte> nonce)
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{
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sessionId = 0;
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streamId = 0;
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nonce = default;
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if (frame.Length != AuthBytes || BinaryPrimitives.ReadUInt16LittleEndian(frame) != MeasurementDatagram.Magic || frame[2] != MeasurementDatagram.Version)
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{
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return false;
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}
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sessionId = BinaryPrimitives.ReadInt64LittleEndian(frame[3..]);
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streamId = BinaryPrimitives.ReadUInt32LittleEndian(frame[11..]);
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nonce = frame.Slice(15, NonceBytes);
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return true;
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}
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public static bool VerifyAuth(ReadOnlySpan<byte> frame, ReadOnlySpan<byte> key)
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{
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Span<byte> full = stackalloc byte[32];
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HMACSHA256.HashData(key, frame[..(AuthBytes - 16)], full);
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return CryptographicOperations.FixedTimeEquals(full[..16], frame[(AuthBytes - 16)..]);
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}
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/// <summary>回显消息正文：<c>seq | send_ts_us | padding</c>，总长度 <paramref name="size"/>。</summary>
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public static void WriteEchoBody(Span<byte> destination, uint seq, long sendTsUs)
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{
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destination.Clear();
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BinaryPrimitives.WriteUInt32LittleEndian(destination, seq);
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BinaryPrimitives.WriteInt64LittleEndian(destination[4..], sendTsUs);
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}
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public static bool TryReadEchoBody(ReadOnlySpan<byte> body, out uint seq, out long sendTsUs)
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{
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seq = 0;
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sendTsUs = 0;
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if (body.Length < MinEchoBody)
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{
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return false;
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}
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seq = BinaryPrimitives.ReadUInt32LittleEndian(body);
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sendTsUs = BinaryPrimitives.ReadInt64LittleEndian(body[4..]);
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return true;
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}
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/// <summary>读取一条 <c>VarInt 长度 | 正文</c> 消息；连接结束或长度非法时返回 null。</summary>
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public static async ValueTask<byte[]?> ReadMessageAsync(Stream stream, CancellationToken ct)
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{
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ulong length = 0;
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int shift = 0;
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byte[] one = new byte[1];
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for (int i = 0; i < VarInt.MaxBytes; i++)
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{
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if (await stream.ReadAsync(one, ct) == 0)
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{
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return null;
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}
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length |= (ulong)(one[0] & 0x7F) << shift;
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if ((one[0] & 0x80) == 0)
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{
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break;
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}
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shift += 7;
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if (i == VarInt.MaxBytes - 1)
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{
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return null;
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}
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}
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if (length > MaxMessageBytes)
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{
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return null;
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}
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byte[] body = new byte[length];
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int read = 0;
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while (read < body.Length)
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{
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int n = await stream.ReadAsync(body.AsMemory(read), ct);
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if (n == 0)
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{
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return null;
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}
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read += n;
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}
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return body;
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}
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public static async ValueTask WriteMessageAsync(Stream stream, ReadOnlyMemory<byte> body, CancellationToken ct)
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{
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byte[] prefix = new byte[VarInt.MaxBytes];
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int n = VarInt.Write(prefix, (ulong)body.Length);
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await stream.WriteAsync(prefix.AsMemory(0, n), ct);
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await stream.WriteAsync(body, ct);
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}
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}
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