feat!: pre-handshake knock on the agent TCP ports; probes get the agent certificate public key [CI]

backend/fleet/tests/Fleet.Tests/KnockTests.cs

@@ -0,0 +1,112 @@
+using System.Net;
+using Fleet.Identity;
+
+namespace Fleet.Tests;
+
+public sealed class KnockTests
+{
+    private sealed class Clock : TimeProvider
+    {
+        public DateTimeOffset Now { get; set; } = new(2026, 10, 7, 12, 0, 0, TimeSpan.Zero);
+
+        public override DateTimeOffset GetUtcNow() => Now;
+    }
+
+    [Fact]
+    public void PairKey_IsTheSameOnBothSides_AndDiffersPerPair()
+    {
+        using NodeIdentity probe = NodeIdentity.Generate();
+        using NodeIdentity agent = NodeIdentity.Generate();
+        using NodeIdentity other = NodeIdentity.Generate();
+        byte[] fromProbe = Knock.DeriveKey(probe, agent.PublicKeySpki);
+        byte[] fromAgent = Knock.DeriveKey(agent, probe.PublicKeySpki);
+        Assert.Equal(fromProbe, fromAgent);
+        Assert.Equal(32, fromProbe.Length);
+        Assert.NotEqual(fromProbe, Knock.DeriveKey(other, agent.PublicKeySpki));
+    }
+
+    [Fact]
+    public void Packet_IsAcceptedWithinTheWindowAndOneWindowOfSkew_ButNotBeyond()
+    {
+        byte[] key = new byte[32];
+        long now = new DateTimeOffset(2026, 10, 7, 12, 0, 15, TimeSpan.Zero).ToUnixTimeMilliseconds();
+        byte[] packet = Knock.Build(key, now);
+        Assert.Equal(Knock.PacketBytes, packet.Length);
+        Assert.True(Knock.Check(key, packet, now));
+        Assert.True(Knock.Check(key, packet, now + (Knock.WindowSeconds * 1000)));
+        Assert.True(Knock.Check(key, packet, now - (Knock.WindowSeconds * 1000)));
+        Assert.False(Knock.Check(key, packet, now + (3 * Knock.WindowSeconds * 1000)));
+        Assert.False(Knock.Check(key, packet, now - (3 * Knock.WindowSeconds * 1000)));
+    }
+
+    [Fact]
+    public void Packet_WithAWrongKeyATamperedByteOrTheWrongLength_IsRejected()
+    {
+        byte[] key = new byte[32];
+        long now = 1_700_000_000_000;
+        byte[] packet = Knock.Build(key, now);
+        Assert.False(Knock.Check(new byte[32] { 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, packet, now));
+        foreach (int index in new[] { 0, 15, 16, 31 })
+        {
+            byte[] tampered = (byte[])packet.Clone();
+            tampered[index] ^= 0x01;
+            Assert.False(Knock.Check(key, tampered, now), $"byte {index}");
+        }
+
+        Assert.False(Knock.Check(key, packet.AsSpan(0, 31), now));
+        Assert.False(Knock.Check(key, [], now));
+    }
+
+    [Fact]
+    public void Gate_AdmitsRosterMembersOnce_AndRejectsReplaysStrangersAndExpiredPackets()
+    {
+        using NodeIdentity agent = NodeIdentity.Generate();
+        using NodeIdentity probe = NodeIdentity.Generate();
+        using NodeIdentity stranger = NodeIdentity.Generate();
+        var roster = new List<byte[]> { probe.PublicKeySpki };
+        var gate = new KnockGate(agent, () => roster, new Clock());
+        long now = 1_700_000_000_000;
+
+        byte[] packet = Knock.Build(Knock.DeriveKey(probe, agent.PublicKeySpki), now);
+        Assert.True(gate.Accept(packet, now));
+        Assert.False(gate.Accept(packet, now), "the same nonce cannot be used twice");
+        Assert.False(gate.Accept(Knock.Build(Knock.DeriveKey(stranger, agent.PublicKeySpki), now), now), "not on the roster");
+        Assert.False(gate.Accept(Knock.Build(Knock.DeriveKey(probe, agent.PublicKeySpki), now - 10 * 60_000), now), "expired");
+
+        // 名册变了：新成员马上能进，被移除的马上进不来
+        using NodeIdentity second = NodeIdentity.Generate();
+        roster.Add(second.PublicKeySpki);
+        Assert.True(gate.Accept(Knock.Build(Knock.DeriveKey(second, agent.PublicKeySpki), now), now));
+        roster.RemoveAt(0);
+        Assert.False(gate.Accept(Knock.Build(Knock.DeriveKey(probe, agent.PublicKeySpki), now), now));
+    }
+
+    [Fact]
+    public async Task Gate_RateLimitsEachSource_AndReadsAtMost32Bytes()
+    {
+        using NodeIdentity agent = NodeIdentity.Generate();
+        using NodeIdentity probe = NodeIdentity.Generate();
+        var clock = new Clock();
+        var gate = new KnockGate(agent, () => [probe.PublicKeySpki], clock, attemptsPerPeriod: 3);
+        IPAddress noisy = IPAddress.Parse("203.0.113.9");
+        IPAddress quiet = IPAddress.Parse("203.0.113.10");
+        byte[] key = Knock.DeriveKey(probe, agent.PublicKeySpki);
+
+        for (int i = 0; i < 3; i++)
+        {
+            Assert.False(await gate.AdmitAsync(new MemoryStream(new byte[Knock.PacketBytes]), noisy, default));
+        }
+
+        // 超过限额：连有效的敲门包也不读、不算
+        byte[] valid = Knock.Build(key, clock.Now.ToUnixTimeMilliseconds());
+        Assert.False(await gate.AdmitAsync(new MemoryStream(valid), noisy, default));
+        Assert.True(await gate.AdmitAsync(new MemoryStream(valid), quiet, default));
+
+        // 过了统计周期，恢复
+        clock.Now += TimeSpan.FromSeconds(11);
+        Assert.True(await gate.AdmitAsync(new MemoryStream(Knock.Build(key, clock.Now.ToUnixTimeMilliseconds())), noisy, default));
+
+        // 流在 32 字节之前就结束：拒绝，不抛异常
+        Assert.False(await gate.AdmitAsync(new MemoryStream(new byte[10]), quiet, default));
+    }
+}

backend/fleet/tests/Fleet.Tests/LinkTests.cs

@@ -280,12 +280,20 @@ public sealed class LinkTests
     private sealed class PeerFixture : IAsyncDisposable
     {
         private readonly CancellationTokenSource _stop = new();
+        private readonly NodeIdentity _identity;
 
         public PeerFixture(Func<string, byte[]?> lookup, Func<PeerSessionInfo, IRpcTransport, CancellationToken, Task>? onSession = null)
         {
             Certificate = NodeCertificate.LoadPfx(NodeCertificate.CreateSelfSignedPfx("agent", TimeSpan.FromDays(30), TimeProvider.System));
+            _identity = NodeIdentity.FromPkcs8(Certificate.GetECDsaPrivateKey()!.ExportPkcs8PrivateKey());
             Listener = new PeerListener(
-                new PeerListenerOptions { Listen = new IPEndPoint(IPAddress.Loopback, 0), Certificate = Certificate, LookupPeerKey = lookup },
+                new PeerListenerOptions
+                {
+                    Listen = new IPEndPoint(IPAddress.Loopback, 0),
+                    Certificate = Certificate,
+                    LookupPeerKey = lookup,
+                    Knock = new KnockGate(_identity, () => KnockPeers, TimeProvider.System),
+                },
                 onSession ?? ((_, transport, ct) => KeepOpenAsync(transport, ct)),
                 NullNodeLog.Instance, TimeProvider.System);
             Task = Listener.RunAsync(_stop.Token);
@@ -299,10 +307,17 @@ public sealed class LinkTests
 
         public byte[] Spki => NodeCertificate.SpkiFingerprint(Certificate);
 
+        /// <summary>Agent 的 TLS 证书公钥：Probe 用它固定证书、派生敲门密钥。</summary>
+        public byte[] PublicKey => Certificate.PublicKey.ExportSubjectPublicKeyInfo();
+
+        /// <summary>名册：能敲开门的 Probe 公钥。</summary>
+        public List<byte[]> KnockPeers { get; } = [];
+
         public async ValueTask DisposeAsync()
         {
             await _stop.CancelAsync();
             await Task;
+            _identity.Dispose();
             Certificate.Dispose();
             _stop.Dispose();
         }
@@ -325,9 +340,10 @@ public sealed class LinkTests
             seen.TrySetResult(info);
             return Task.Delay(Timeout.Infinite, ct).ContinueWith(_ => { }, CancellationToken.None);
         });
+        agent.KnockPeers.Add(probe.PublicKeySpki);
         await agent.Listener.Started.Task;
 
-        (PeerSessionInfo client, TlsFrameTransport transport) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.Spki, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
+        (PeerSessionInfo client, TlsFrameTransport transport) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
         await using (transport)
         {
             PeerSessionInfo server = await seen.Task.WaitAsync(TimeSpan.FromSeconds(5));
@@ -343,17 +359,18 @@ public sealed class LinkTests
         using NodeIdentity probe = NodeIdentity.Generate();
         using NodeIdentity impostor = NodeIdentity.Generate();
         await using var agent = new PeerFixture(id => id == "prb_1" ? probe.PublicKeySpki : null);
+        agent.KnockPeers.AddRange([probe.PublicKeySpki, impostor.PublicKeySpki]); // 敲门通过之后，名册外的 ID 和伪造的签名仍然被拒绝
         await agent.Listener.Started.Task;
 
         InvalidOperationException unknown = await Assert.ThrowsAsync<InvalidOperationException>(async () =>
-            await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.Spki, probe, "prb_unknown", null, 1 << 20, TimeProvider.System, default));
+            await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, probe, "prb_unknown", null, 1 << 20, TimeProvider.System, default));
         InvalidOperationException forged = await Assert.ThrowsAsync<InvalidOperationException>(async () =>
-            await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.Spki, impostor, "prb_1", null, 1 << 20, TimeProvider.System, default));
+            await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, impostor, "prb_1", null, 1 << 20, TimeProvider.System, default));
         Assert.Equal(unknown.Message, forged.Message);
         Assert.Contains("fleet_unauthorized", forged.Message);
 
         // 正主仍然可以连接
-        (_, TlsFrameTransport ok) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.Spki, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
+        (_, TlsFrameTransport ok) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
         await ok.DisposeAsync();
     }
 
@@ -362,11 +379,13 @@ public sealed class LinkTests
     {
         using NodeIdentity probe = NodeIdentity.Generate();
         await using var agent = new PeerFixture(_ => probe.PublicKeySpki);
+        agent.KnockPeers.Add(probe.PublicKeySpki);
         await agent.Listener.Started.Task;
 
-        byte[] wrong = SHA256.HashData("another certificate"u8);
-        await Assert.ThrowsAnyAsync<AuthenticationException>(async () =>
-            await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, wrong, probe, "prb_1", null, 1 << 20, TimeProvider.System, default));
+        // 公钥不对：敲门密钥对不上，Agent 直接断开（拿到的不是证书，连不是它的证书都看不到）
+        using NodeIdentity another = NodeIdentity.Generate();
+        await Assert.ThrowsAnyAsync<Exception>(async () =>
+            await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, another.PublicKeySpki, probe, "prb_1", null, 1 << 20, TimeProvider.System, default));
     }
 
     [Fact]
@@ -382,9 +401,10 @@ public sealed class LinkTests
                 await using var session = new RpcSession<string>(transport, router, info.PeerId, TimeProvider.System);
                 await session.RunAsync(ct);
             });
+        agent.KnockPeers.Add(probe.PublicKeySpki);
         await agent.Listener.Started.Task;
 
-        (_, TlsFrameTransport transport) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.Spki, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
+        (_, TlsFrameTransport transport) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
         await using var client = new RpcSession<string>(transport, new RpcRouter<string>(RpcSide.Dialer, table), "probe", TimeProvider.System);
         Task run = client.RunAsync(default);
         Result<Number> result = await client.RequestAsync("agent.echo", new Number { Value = 41 }, LinkJson.Default.Number, LinkJson.Default.Number, default);
@@ -398,6 +418,7 @@ public sealed class LinkTests
     {
         using NodeIdentity probe = NodeIdentity.Generate();
         await using var agent = new PeerFixture(_ => probe.PublicKeySpki);
+        agent.KnockPeers.Add(probe.PublicKeySpki);
         await agent.Listener.Started.Task;
 
         // 不说 TLS 的连接：握手失败，监听继续
@@ -407,7 +428,45 @@ public sealed class LinkTests
             await garbage.GetStream().WriteAsync("GET / HTTP/1.1\r\n\r\n"u8.ToArray());
         }
 
-        (_, TlsFrameTransport ok) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.Spki, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
+        (_, TlsFrameTransport ok) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
+        await ok.DisposeAsync();
+    }
+
+    [Fact]
+    public async Task PeerListener_WritesNothingToStrangers_NotEvenATlsServerHello()
+    {
+        using NodeIdentity probe = NodeIdentity.Generate();
+        await using var agent = new PeerFixture(_ => probe.PublicKeySpki);
+        agent.KnockPeers.Add(probe.PublicKeySpki);
+        await agent.Listener.Started.Task;
+
+        // 一个像样的 TLS ClientHello 开头、随机数据、什么都不发：都拿不到任何字节（连接被直接关闭）
+        foreach (byte[] payload in new[] { new byte[] { 0x16, 0x03, 0x01, 0x00, 0x05, 0x01, 0x00, 0x00, 0x01, 0x00 }.Concat(RandomNumberGenerator.GetBytes(64)).ToArray(), RandomNumberGenerator.GetBytes(32), [] })
+        {
+            using var scanner = new TcpClient();
+            await scanner.ConnectAsync(IPAddress.Loopback, agent.Listener.Port);
+            NetworkStream stream = scanner.GetStream();
+            if (payload.Length > 0)
+            {
+                await stream.WriteAsync(payload);
+            }
+
+            byte[] buffer = new byte[64];
+            int read;
+            try
+            {
+                read = await stream.ReadAsync(buffer).AsTask().WaitAsync(TimeSpan.FromSeconds(10));
+            }
+            catch (IOException)
+            {
+                read = 0; // 连接被重置也是「什么都没收到」
+            }
+
+            Assert.Equal(0, read);
+        }
+
+        // 名册里的 Probe 仍然进得来
+        (_, TlsFrameTransport ok) = await PeerConnector.ConnectAsync("127.0.0.1", agent.Listener.Port, agent.PublicKey, probe, "prb_1", null, 1 << 20, TimeProvider.System, default);
         await ok.DisposeAsync();
     }