justme
83e5120377
Namespaces, assemblies, projects and directories, the solution, binaries, images, systemd units, config paths, environment variables, protocol method names, the media type and the raw chunk magic all move to MoShiro/moshiro. Existing data and deployments are not compatible and must be recreated. Also fix the architecture tests after the solution layout change and make the update tests independent of their order.
92 lines
3.7 KiB
C#
92 lines
3.7 KiB
C#
using System.Buffers.Binary;
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using System.Security.Cryptography;
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namespace MoShiro.Protocol;
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public enum UdpPacketType : byte
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{
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EchoRequest = 1,
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EchoReply = 2,
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/// <summary>单向数据（udp_train），以及 Probe 为了保持 NAT 映射和让 Agent 学到源地址而发的探活包。</summary>
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Data = 3,
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}
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public readonly record struct UdpHeader(UdpPacketType Type, long SessionId, uint StreamId, uint Seq, long SendTsUs);
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/// <summary>
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/// 数据面的 UDP 包（Fleet 之外的线格式）：
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/// <c>magic(2) version(1) type(1) session_id(8) stream_id(4) seq(4) send_ts_us(8) | padding | mac(16)</c>，
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/// mac = HMAC-SHA256(session_key, 前面全部字节) 截断到 16 字节。所有整数小端。
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/// 接收方对不合法的包静默丢弃并计数，不回复（防放大）。
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/// </summary>
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public static class UdpPacket
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{
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public const ushort Magic = 0x4D4E; // "MN"
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public const byte Version = 1;
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public const int HeaderBytes = 28;
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public const int MacBytes = 16;
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public const int MinBytes = HeaderBytes + MacBytes;
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public const int MaxBytes = 1472;
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/// <summary>检查长度、magic、version、type 并解析头部（不校验 MAC）。</summary>
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public static bool TryParseHeader(ReadOnlySpan<byte> packet, out UdpHeader header)
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{
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header = default;
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if (packet.Length is < MinBytes or > MaxBytes
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|| BinaryPrimitives.ReadUInt16LittleEndian(packet) != Magic
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|| packet[2] != Version
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|| packet[3] is < (byte)UdpPacketType.EchoRequest or > (byte)UdpPacketType.Data)
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{
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return false;
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}
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header = new UdpHeader(
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(UdpPacketType)packet[3],
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BinaryPrimitives.ReadInt64LittleEndian(packet[4..]),
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BinaryPrimitives.ReadUInt32LittleEndian(packet[12..]),
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BinaryPrimitives.ReadUInt32LittleEndian(packet[16..]),
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BinaryPrimitives.ReadInt64LittleEndian(packet[20..]));
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return true;
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}
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/// <summary>写入整个包（长度就是 <paramref name="destination"/> 的长度），填充为零，末尾是 MAC。</summary>
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public static void Write(Span<byte> destination, in UdpHeader header, ReadOnlySpan<byte> key)
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{
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if (destination.Length is < MinBytes or > MaxBytes)
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{
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throw new ArgumentOutOfRangeException(nameof(destination), "packet size must be between 44 and 1472 bytes");
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}
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destination.Clear();
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BinaryPrimitives.WriteUInt16LittleEndian(destination, Magic);
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destination[2] = Version;
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destination[3] = (byte)header.Type;
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BinaryPrimitives.WriteInt64LittleEndian(destination[4..], header.SessionId);
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BinaryPrimitives.WriteUInt32LittleEndian(destination[12..], header.StreamId);
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BinaryPrimitives.WriteUInt32LittleEndian(destination[16..], header.Seq);
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BinaryPrimitives.WriteInt64LittleEndian(destination[20..], header.SendTsUs);
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Seal(destination, key);
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}
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/// <summary>重新计算并写入末尾的 MAC（回复包复用请求包的缓冲区时使用）。</summary>
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public static void Seal(Span<byte> packet, ReadOnlySpan<byte> key)
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{
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Span<byte> full = stackalloc byte[32];
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HMACSHA256.HashData(key, packet[..^MacBytes], full);
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full[..MacBytes].CopyTo(packet[^MacBytes..]);
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}
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public static bool VerifyMac(ReadOnlySpan<byte> packet, ReadOnlySpan<byte> key)
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{
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if (packet.Length < MinBytes)
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{
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return false;
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}
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Span<byte> full = stackalloc byte[32];
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HMACSHA256.HashData(key, packet[..^MacBytes], full);
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return CryptographicOperations.FixedTimeEquals(full[..MacBytes], packet[^MacBytes..]);
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}
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}
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