justme
2e146d4da7
ci/woodpecker/push/main-amd64-build Pipeline was successful
Namespaces, assemblies, solution, binaries, images, systemd units, config paths, environment variables, protocol methods and the Linux user are all renamed. Breaking: existing databases, node identities and installed units must be recreated.
92 lines
3.7 KiB
C#
92 lines
3.7 KiB
C#
using System.Buffers.Binary;
|
||
using System.Security.Cryptography;
|
||
|
||
namespace MoShiro.Protocol;
|
||
|
||
public enum UdpPacketType : byte
|
||
{
|
||
EchoRequest = 1,
|
||
EchoReply = 2,
|
||
|
||
/// <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>
|
||
Data = 3,
|
||
}
|
||
|
||
public readonly record struct UdpHeader(UdpPacketType Type, long SessionId, uint StreamId, uint Seq, long SendTsUs);
|
||
|
||
/// <summary>
|
||
/// 数据面的 UDP 包（Fleet 之外的线格式）：
|
||
/// <c>magic(2) version(1) type(1) session_id(8) stream_id(4) seq(4) send_ts_us(8) | padding | mac(16)</c>，
|
||
/// mac = HMAC-SHA256(session_key, 前面全部字节) 截断到 16 字节。所有整数小端。
|
||
/// 接收方对不合法的包静默丢弃并计数，不回复（防放大）。
|
||
/// </summary>
|
||
public static class UdpPacket
|
||
{
|
||
public const ushort Magic = 0x4D4E; // "MN"
|
||
public const byte Version = 1;
|
||
public const int HeaderBytes = 28;
|
||
public const int MacBytes = 16;
|
||
public const int MinBytes = HeaderBytes + MacBytes;
|
||
public const int MaxBytes = 1472;
|
||
|
||
/// <summary>检查长度、magic、version、type 并解析头部（不校验 MAC）。</summary>
|
||
public static bool TryParseHeader(ReadOnlySpan<byte> packet, out UdpHeader header)
|
||
{
|
||
header = default;
|
||
if (packet.Length is < MinBytes or > MaxBytes
|
||
|| BinaryPrimitives.ReadUInt16LittleEndian(packet) != Magic
|
||
|| packet[2] != Version
|
||
|| packet[3] is < (byte)UdpPacketType.EchoRequest or > (byte)UdpPacketType.Data)
|
||
{
|
||
return false;
|
||
}
|
||
|
||
header = new UdpHeader(
|
||
(UdpPacketType)packet[3],
|
||
BinaryPrimitives.ReadInt64LittleEndian(packet[4..]),
|
||
BinaryPrimitives.ReadUInt32LittleEndian(packet[12..]),
|
||
BinaryPrimitives.ReadUInt32LittleEndian(packet[16..]),
|
||
BinaryPrimitives.ReadInt64LittleEndian(packet[20..]));
|
||
return true;
|
||
}
|
||
|
||
/// <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>
|
||
public static void Write(Span<byte> destination, in UdpHeader header, ReadOnlySpan<byte> key)
|
||
{
|
||
if (destination.Length is < MinBytes or > MaxBytes)
|
||
{
|
||
throw new ArgumentOutOfRangeException(nameof(destination), "packet size must be between 44 and 1472 bytes");
|
||
}
|
||
|
||
destination.Clear();
|
||
BinaryPrimitives.WriteUInt16LittleEndian(destination, Magic);
|
||
destination[2] = Version;
|
||
destination[3] = (byte)header.Type;
|
||
BinaryPrimitives.WriteInt64LittleEndian(destination[4..], header.SessionId);
|
||
BinaryPrimitives.WriteUInt32LittleEndian(destination[12..], header.StreamId);
|
||
BinaryPrimitives.WriteUInt32LittleEndian(destination[16..], header.Seq);
|
||
BinaryPrimitives.WriteInt64LittleEndian(destination[20..], header.SendTsUs);
|
||
Seal(destination, key);
|
||
}
|
||
|
||
/// <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>
|
||
public static void Seal(Span<byte> packet, ReadOnlySpan<byte> key)
|
||
{
|
||
Span<byte> full = stackalloc byte[32];
|
||
HMACSHA256.HashData(key, packet[..^MacBytes], full);
|
||
full[..MacBytes].CopyTo(packet[^MacBytes..]);
|
||
}
|
||
|
||
public static bool VerifyMac(ReadOnlySpan<byte> packet, ReadOnlySpan<byte> key)
|
||
{
|
||
if (packet.Length < MinBytes)
|
||
{
|
||
return false;
|
||
}
|
||
|
||
Span<byte> full = stackalloc byte[32];
|
||
HMACSHA256.HashData(key, packet[..^MacBytes], full);
|
||
return CryptographicOperations.FixedTimeEquals(full[..MacBytes], packet[^MacBytes..]);
|
||
}
|
||
}
|