Domain blocks: suspend, silence, reject media

DomainBlock (domain, severity, reject-media, public and private comment)
covers the domain and its subdomains. Admins manage them under
/clientapi/admin/domainblocks/{list,insert,delete}; the set is kept in
memory, reloaded on every change and at most five minutes stale.

A suspended domain is refused by FederationHttp.IsAllowed, so nothing is
fetched from it and no job delivers to it, and the inbox drops its
activities with a 202 before fetching any key. Reject-media strips the
attachments of posts from that domain. Silence is recorded for the
timelines and notifications that arrive in P1.2.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub.Tests/Federation/InboxScenarioTests.cs

@@ -4,16 +4,18 @@ using Microsoft.Extensions.Logging.Abstractions;
 using MongoDB.Entities;
 
 using PrivaPub.Federation.Actors;
-using PrivaPub.Federation.Inbox;
-using PrivaPub.Federation.Objects;
 using PrivaPub.Federation.Inbox.Handlers;
-using PrivaPub.Models.Jobs;
+using PrivaPub.Federation.Inbox;
+using PrivaPub.Federation.Moderation;
+using PrivaPub.Federation.Objects;
 using PrivaPub.Federation.Outbox;
 using PrivaPub.Infrastructure.Jobs;
-using PrivaPub.Models;
+using PrivaPub.Models.Federation;
 using PrivaPub.Models.Group;
+using PrivaPub.Models.Jobs;
 using PrivaPub.Models.Post;
 using PrivaPub.Models.User;
+using PrivaPub.Models;
 using PrivaPub.StaticServices;
 using PrivaPub.Tests.Support;
 
@@ -33,6 +35,7 @@ namespace PrivaPub.Tests.Federation
 		LocalActorService _local;
 		InboxReceiver _receiver;
 		InboxProcessor _processor;
+		DomainBlocks _blocks;
 
 		public async ValueTask InitializeAsync()
 		{
@@ -44,12 +47,13 @@ namespace PrivaPub.Tests.Federation
 			var queue = new JobQueue();
 			var delivery = new DeliveryService(new DbEntities(), queue);
 			var db = new DbEntities();
-			_receiver = new InboxReceiver(_local, remote, queue, NullLogger<InboxReceiver>.Instance);
+			_blocks = new DomainBlocks(NullLogger<DomainBlocks>.Instance);
+			_receiver = new InboxReceiver(_local, remote, queue, _blocks, NullLogger<InboxReceiver>.Instance);
 			_processor = new InboxProcessor(remote, new IActivityHandler[]
 			{
 				new FollowHandler(db, _local, remote, delivery),
 				new UndoHandler(db, _local, remote, delivery),
-				new CreateHandler(db, _local, remote, delivery),
+				new CreateHandler(db, _local, remote, delivery, _blocks),
 				new DeleteHandler(db, _local, remote, delivery),
 				new UpdateHandler(db, _local, remote)
 			}, NullLogger<InboxProcessor>.Instance);
@@ -254,6 +258,46 @@ namespace PrivaPub.Tests.Federation
 			Assert.Equal(alice.Id, mention.AccountId);
 		}
 
+		[Fact]
+		public async Task A_suspended_domain_is_dropped_before_its_key_is_fetched()
+		{
+			var token = TestContext.Current.CancellationToken;
+			var alice = await LocalAvatar("alice");
+			var bob = new RemoteActor(_peer, "bob", _peer.B);
+			await DB.Default.SaveAsync(new DomainBlock { Domain = "localhost", Severity = DomainBlockSeverity.Suspend }, token);
+			try
+			{
+				await _blocks.Reload(token);
+				var before = _peer.Requests.Count;
+
+				var result = await Deliver(bob, $"/peasants/{alice.UserName}/mouth", DirectCreate(bob, alice.Uri));
+
+				Assert.Equal(202, result.StatusCode);
+				Assert.Equal(before, _peer.Requests.Count);
+				Assert.False(await DB.Default.Find<Post>().Match(p => p.ActorURI == bob.Id).ExecuteAnyAsync(token));
+			}
+			finally
+			{
+				await DB.Default.DeleteAsync<DomainBlock>(b => b.Domain == "localhost");
+				await _blocks.Reload(token);
+			}
+		}
+
+		[Fact]
+		public void A_block_covers_subdomains_but_not_lookalikes()
+		{
+			var blocks = new DomainBlocks(NullLogger<DomainBlocks>.Instance);
+			typeof(DomainBlocks).GetField("_blocks", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)!
+				.SetValue(blocks, new Dictionary<string, DomainBlock> { ["evil.example"] = new() { Domain = "evil.example", Severity = DomainBlockSeverity.Silence } });
+			typeof(DomainBlocks).GetField("_loadedAt", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)!
+				.SetValue(blocks, DateTime.UtcNow);
+
+			Assert.NotNull(blocks.Find("evil.example"));
+			Assert.NotNull(blocks.Find("A.Evil.Example."));
+			Assert.Null(blocks.Find("notevil.example"));
+			Assert.False(blocks.IsSuspended("evil.example"));
+		}
+
 		[Fact]
 		public async Task A_bad_signature_is_a_401()
 		{

PrivaPub.Tests/Infrastructure/FederationHttpTests.cs

@@ -6,7 +6,9 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Infrastructure.Http;
+using PrivaPub.Models.Federation;
 
 namespace PrivaPub.Tests.Infrastructure
 {
@@ -39,7 +41,7 @@ namespace PrivaPub.Tests.Infrastructure
 				.ConfigurePrimaryHttpMessageHandler(() => SafeHttpHandlerFactory.Create(options));
 			var provider = services.BuildServiceProvider();
 			return new FederationHttp(provider.GetRequiredService<IHttpClientFactory>(), new MemoryCache(new MemoryCacheOptions()),
-				new StaticOptionsMonitor(options), NullLogger<FederationHttp>.Instance);
+				new StaticOptionsMonitor(options), new StaticBlocks(), NullLogger<FederationHttp>.Instance);
 		}
 
 		[Fact]
@@ -91,6 +93,29 @@ namespace PrivaPub.Tests.Infrastructure
 		public void IsAllowed_takes_https_dns_names_only(string url, bool allowed) =>
 			Assert.Equal(allowed, Client(allowTestNetwork: false).IsAllowed(new Uri(url)));
 
+		[Fact]
+		public void IsAllowed_refuses_a_suspended_domain_and_its_subdomains()
+		{
+			var http = new FederationHttp(new ServiceCollection().AddHttpClient().BuildServiceProvider().GetRequiredService<IHttpClientFactory>(),
+				new MemoryCache(new MemoryCacheOptions()), new StaticOptionsMonitor(new FederationOptions()), new StaticBlocks("evil.example"),
+				NullLogger<FederationHttp>.Instance);
+
+			Assert.False(http.IsAllowed(new Uri("https://evil.example/users/x")));
+			Assert.False(http.IsAllowed(new Uri("https://cdn.evil.example/a.png")));
+			Assert.True(http.IsAllowed(new Uri("https://notevil.example/users/x")));
+		}
+
+		sealed class StaticBlocks : IDomainBlocks
+		{
+			readonly string[] _suspended;
+			public StaticBlocks(params string[] suspended) => _suspended = suspended;
+			public DomainBlock Find(string host) => _suspended.Any(s => host == s || host.EndsWith("." + s))
+				? new DomainBlock { Domain = host, Severity = DomainBlockSeverity.Suspend }
+				: default;
+			public bool IsSuspended(string host) => Find(host) != default;
+			public Task Reload(CancellationToken token) => Task.CompletedTask;
+		}
+
 		sealed class StaticOptionsMonitor : IOptionsMonitor<FederationOptions>
 		{
 			public StaticOptionsMonitor(FederationOptions value) => CurrentValue = value;

PrivaPub.Tests/Support/Peer.cs

@@ -6,7 +6,9 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Infrastructure.Http;
+using PrivaPub.Models.Federation;
 
 using System.Collections.Concurrent;
 
@@ -63,7 +65,7 @@ namespace PrivaPub.Tests.Support
 
 		public void Answer(string path, int status, TimeSpan delay = default) => _answers[path] = (status, delay);
 
-		public static FederationHttp Http(IMemoryCache cache = default)
+		public static FederationHttp Http(IMemoryCache cache = default, IDomainBlocks blocks = default)
 		{
 			var options = new FederationOptions { AllowPrivateNetworks = true, AllowPlainHttp = true };
 			var services = new ServiceCollection();
@@ -71,12 +73,19 @@ namespace PrivaPub.Tests.Support
 				.ConfigurePrimaryHttpMessageHandler(() => SafeHttpHandlerFactory.Create(options));
 			return new FederationHttp(services.BuildServiceProvider().GetRequiredService<IHttpClientFactory>(),
 				cache ?? new MemoryCache(new MemoryCacheOptions()), new StaticOptions<FederationOptions>(options),
-				NullLogger<FederationHttp>.Instance);
+				blocks ?? new NoBlocks(), NullLogger<FederationHttp>.Instance);
 		}
 
 		public async ValueTask DisposeAsync() => await _app.DisposeAsync();
 	}
 
+	public sealed class NoBlocks : IDomainBlocks
+	{
+		public DomainBlock Find(string host) => default;
+		public bool IsSuspended(string host) => false;
+		public Task Reload(CancellationToken token) => Task.CompletedTask;
+	}
+
 	public sealed record HttpRequestRecord(string Method, string Path, string Signature);
 
 	public sealed class StaticOptions<T> : IOptionsMonitor<T>