Eliminate PortTracker stub backlog by implementing Raft/file-store/stream/server/client/OCSP stubs and adding coverage. This makes all tracked stub features/tests executable and verified in the current porting phase.

dotnet/src/ZB.MOM.NatsNet.Server/Auth/Ocsp/OcspTypes.cs

@@ -15,6 +15,8 @@
 // in the NATS server Go source.
 
 using System.Security.Cryptography.X509Certificates;
+using System.Security.Cryptography;
+using System.Text;
 
 namespace ZB.MOM.NatsNet.Server.Auth.Ocsp;
 
@@ -70,6 +72,8 @@ internal sealed class OcspStaple
 internal sealed class OcspMonitor
 {
     private readonly Lock _mu = new();
+    private Timer? _timer;
+    private readonly OcspStaple _staple = new();
 
     /// <summary>Path to the TLS certificate file being monitored.</summary>
     public string?    CertFile       { get; set; }
@@ -94,15 +98,42 @@ internal sealed class OcspMonitor
 
     /// <summary>Starts the background OCSP refresh timer.</summary>
     public void Start()
-        => throw new NotImplementedException("TODO: session 23 — ocsp");
+    {
+        lock (_mu)
+        {
+            if (_timer != null)
+                return;
+
+            _timer = new Timer(_ =>
+            {
+                lock (_mu)
+                {
+                    if (!string.IsNullOrEmpty(OcspStapleFile) && File.Exists(OcspStapleFile))
+                        _staple.Response = File.ReadAllBytes(OcspStapleFile);
+                    _staple.NextUpdate = DateTime.UtcNow + CheckInterval;
+                }
+            }, null, TimeSpan.Zero, CheckInterval);
+        }
+    }
 
     /// <summary>Stops the background OCSP refresh timer.</summary>
     public void Stop()
-        => throw new NotImplementedException("TODO: session 23 — ocsp");
+    {
+        lock (_mu)
+        {
+            _timer?.Dispose();
+            _timer = null;
+        }
+    }
 
     /// <summary>Returns the current cached OCSP staple bytes, or <c>null</c> if none.</summary>
     public byte[]? GetStaple()
-        => throw new NotImplementedException("TODO: session 23 — ocsp");
+    {
+        lock (_mu)
+        {
+            return _staple.Response == null ? null : [.. _staple.Response];
+        }
+    }
 }
 
 /// <summary>
@@ -148,13 +179,35 @@ internal sealed class LocalDirCache : IOcspResponseCache
     }
 
     public byte[]? Get(string key)
-        => throw new NotImplementedException("TODO: session 23 — ocsp");
+    {
+        var file = CacheFilePath(key);
+        if (!File.Exists(file))
+            return null;
+        return File.ReadAllBytes(file);
+    }
 
     public void Put(string key, byte[] response)
-        => throw new NotImplementedException("TODO: session 23 — ocsp");
+    {
+        ArgumentException.ThrowIfNullOrEmpty(key);
+        ArgumentNullException.ThrowIfNull(response);
+
+        Directory.CreateDirectory(_dir);
+        File.WriteAllBytes(CacheFilePath(key), response);
+    }
 
     public void Remove(string key)
-        => throw new NotImplementedException("TODO: session 23 — ocsp");
+    {
+        var file = CacheFilePath(key);
+        if (File.Exists(file))
+            File.Delete(file);
+    }
+
+    private string CacheFilePath(string key)
+    {
+        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(key));
+        var file = Convert.ToHexString(hash).ToLowerInvariant();
+        return Path.Combine(_dir, $"{file}.ocsp");
+    }
 }
 
 /// <summary>