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/Controllers/ClientToServer/DomainBlockController.cs

@@ -0,0 +1,74 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Localization;
+
+using MongoDB.Entities;
+
+using PrivaPub.ClientModels;
+using PrivaPub.ClientModels.Admin;
+using PrivaPub.Federation.Moderation;
+using PrivaPub.Models.Federation;
+using PrivaPub.Resources;
+
+namespace PrivaPub.Controllers.ClientToServer
+{
+	[ApiController,
+		Route("clientapi/admin/domainblocks"),
+		Authorize(Policy = Policies.IsAdmin)]
+	public class DomainBlockController : ControllerBase
+	{
+		readonly IDomainBlocks _domainBlocks;
+		readonly IStringLocalizer _localizer;
+
+		public DomainBlockController(IDomainBlocks domainBlocks, IStringLocalizer<GenericRes> localizer)
+		{
+			_domainBlocks = domainBlocks;
+			_localizer = localizer;
+		}
+
+		[HttpGet, Route("/clientapi/admin/domainblocks/list")]
+		public async Task<IActionResult> List(CancellationToken token) =>
+			Ok((await DB.Default.Find<DomainBlock>().Sort(b => b.Domain, Order.Ascending).ExecuteAsync(token)).Select(ToView).ToList());
+
+		[HttpPost, Route("/clientapi/admin/domainblocks/insert")]
+		public async Task<IActionResult> Insert(DomainBlockForm form, CancellationToken token)
+		{
+			var domain = DomainBlocks.Normalise(form.Domain);
+			if (!ModelState.IsValid || Uri.CheckHostName(domain) != UriHostNameType.Dns)
+				return BadRequest(new WebResult().Invalidate(_localizer["Invalid model."]));
+
+			var block = await DB.Default.UpdateAndGet<DomainBlock>()
+				.Match(b => b.Domain == domain)
+				.Modify(b => b.Domain, domain)
+				.Modify(b => b.Severity, form.Suspend ? DomainBlockSeverity.Suspend : DomainBlockSeverity.Silence)
+				.Modify(b => b.RejectMedia, form.RejectMedia)
+				.Modify(b => b.PublicComment, form.PublicComment)
+				.Modify(b => b.PrivateComment, form.PrivateComment)
+				.Modify(b => b.SetOnInsert(x => x.CreatedAt, DateTime.UtcNow))
+				.Option(o => o.IsUpsert = true)
+				.ExecuteAsync(token);
+			await _domainBlocks.Reload(token);
+			return Ok(ToView(block));
+		}
+
+		[HttpPost, Route("/clientapi/admin/domainblocks/delete")]
+		public async Task<IActionResult> Delete([FromQuery] string domain, CancellationToken token)
+		{
+			domain = DomainBlocks.Normalise(domain);
+			await DB.Default.DeleteAsync<DomainBlock>(b => b.Domain == domain);
+			await _domainBlocks.Reload(token);
+			return Ok();
+		}
+
+		static ViewDomainBlock ToView(DomainBlock block) => new()
+		{
+			Id = block.ID,
+			Domain = block.Domain,
+			Severity = block.Severity.ToString(),
+			RejectMedia = block.RejectMedia,
+			PublicComment = block.PublicComment,
+			PrivateComment = block.PrivateComment,
+			CreatedAt = block.CreatedAt
+		};
+	}
+}

PrivaPub/Federation/Inbox/Handlers/CreateHandler.cs

@@ -2,6 +2,7 @@ using MongoDB.Driver;
 using MongoDB.Entities;
 
 using PrivaPub.Federation.Actors;
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Federation.Objects;
 using PrivaPub.Federation.Outbox;
 using PrivaPub.Federation.Rendering;
@@ -26,13 +27,16 @@ namespace PrivaPub.Federation.Inbox.Handlers
 		readonly ILocalActorService _localActors;
 		readonly IRemoteActorService _remoteActors;
 		readonly IDeliveryService _delivery;
+		readonly IDomainBlocks _domainBlocks;
 
-		public CreateHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery)
+		public CreateHandler(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDeliveryService delivery,
+			IDomainBlocks domainBlocks)
 		{
 			_dbEntities = dbEntities;
 			_localActors = localActors;
 			_remoteActors = remoteActors;
 			_delivery = delivery;
+			_domainBlocks = domainBlocks;
 		}
 
 		public string Type => "Create";
@@ -130,7 +134,7 @@ namespace PrivaPub.Federation.Inbox.Handlers
 				Language = note.Language,
 				Mentions = mentions,
 				Tags = note.Tags.ToList(),
-				Media = note.Attachments.ToList(),
+				Media = _domainBlocks.Find(new Uri(author.ActorURI).Host)?.RejectMedia == true ? new() : note.Attachments.ToList(),
 				InReplyToURI = note.InReplyTo,
 				AnsweringToPostId = parent?.ID,
 				InReplyToAccountId = parent?.AuthorAccountId ?? parent?.GroupUserId,

PrivaPub/Federation/Inbox/InboxReceiver.cs

@@ -1,4 +1,5 @@
 using PrivaPub.Federation.Actors;
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Federation.Objects;
 using PrivaPub.Federation.Signing;
 using PrivaPub.Infrastructure.Jobs;
@@ -28,13 +29,16 @@ namespace PrivaPub.Federation.Inbox
 		readonly ILocalActorService _localActors;
 		readonly IRemoteActorService _remoteActors;
 		readonly IJobQueue _queue;
+		readonly IDomainBlocks _domainBlocks;
 		readonly ILogger<InboxReceiver> _logger;
 
-		public InboxReceiver(ILocalActorService localActors, IRemoteActorService remoteActors, IJobQueue queue, ILogger<InboxReceiver> logger)
+		public InboxReceiver(ILocalActorService localActors, IRemoteActorService remoteActors, IJobQueue queue, IDomainBlocks domainBlocks,
+			ILogger<InboxReceiver> logger)
 		{
 			_localActors = localActors;
 			_remoteActors = remoteActors;
 			_queue = queue;
+			_domainBlocks = domainBlocks;
 			_logger = logger;
 		}
 
@@ -69,6 +73,8 @@ namespace PrivaPub.Federation.Inbox
 			var parameters = HttpSignatures.Parse(request.Headers["Signature"].ToString());
 			if (parameters == default)
 				return new(StatusCodes.Status401Unauthorized, "missing or unreadable Signature header");
+			if (_domainBlocks.IsSuspended(HostOf(parameters.KeyId)) || _domainBlocks.IsSuspended(HostOf(actorUri)))
+				return new(StatusCodes.Status202Accepted);
 
 			var requestProblem = HttpSignatures.CheckRequest(request, parameters, body);
 			if (requestProblem != default)
@@ -99,6 +105,8 @@ namespace PrivaPub.Federation.Inbox
 			return new(StatusCodes.Status202Accepted);
 		}
 
+		static string HostOf(string uri) => Uri.TryCreate(uri, UriKind.Absolute, out var parsed) ? parsed.Host : default;
+
 		async Task<InboxResult> ShapeProblem(string type, JsonNode activity, string actorUri, CancellationToken token)
 		{
 			var activityId = Id(activity);

PrivaPub/Federation/Moderation/DomainBlocks.cs

@@ -0,0 +1,77 @@
+using MongoDB.Entities;
+
+using PrivaPub.Models.Federation;
+
+namespace PrivaPub.Federation.Moderation
+{
+	public interface IDomainBlocks
+	{
+		DomainBlock Find(string host);
+		bool IsSuspended(string host);
+		Task Reload(CancellationToken token);
+	}
+
+	public class DomainBlocks : IDomainBlocks
+	{
+		static readonly TimeSpan Staleness = TimeSpan.FromMinutes(5);
+
+		readonly ILogger<DomainBlocks> _logger;
+		IReadOnlyDictionary<string, DomainBlock> _blocks = new Dictionary<string, DomainBlock>();
+		DateTime _loadedAt = DateTime.MinValue;
+		int _reloading;
+
+		public DomainBlocks(ILogger<DomainBlocks> logger)
+		{
+			_logger = logger;
+		}
+
+		public static string Normalise(string domain) => domain?.Trim().Trim('.').ToLowerInvariant();
+
+		public DomainBlock Find(string host)
+		{
+			RefreshIfStale();
+			host = Normalise(host);
+			var blocks = _blocks;
+			while (!string.IsNullOrEmpty(host))
+			{
+				if (blocks.TryGetValue(host, out var block))
+					return block;
+				var dot = host.IndexOf('.');
+				host = dot < 0 ? default : host[(dot + 1)..];
+			}
+			return default;
+		}
+
+		public bool IsSuspended(string host) => Find(host)?.Severity == DomainBlockSeverity.Suspend;
+
+		public async Task Reload(CancellationToken token)
+		{
+			var blocks = await DB.Default.Find<DomainBlock>().ExecuteAsync(token);
+			_blocks = blocks.Where(b => !string.IsNullOrEmpty(b.Domain))
+				.GroupBy(b => Normalise(b.Domain))
+				.ToDictionary(g => g.Key, g => g.First());
+			_loadedAt = DateTime.UtcNow;
+		}
+
+		void RefreshIfStale()
+		{
+			if (DateTime.UtcNow - _loadedAt < Staleness || Interlocked.Exchange(ref _reloading, 1) == 1)
+				return;
+			_ = Task.Run(async () =>
+			{
+				try
+				{
+					await Reload(CancellationToken.None);
+				}
+				catch (Exception ex)
+				{
+					_logger.LogWarning(ex, "Domain blocks could not be reloaded");
+				}
+				finally
+				{
+					Interlocked.Exchange(ref _reloading, 0);
+				}
+			});
+		}
+	}
+}

PrivaPub/Infrastructure/Data/Indexes.cs

@@ -59,6 +59,7 @@ namespace PrivaPub.Infrastructure.Data
 				.Key(j => j.FinishedAt, KeyType.Ascending)
 				.Option(o => o.ExpireAfter = TimeSpan.FromDays(7))
 				.CreateAsync(token);
+			await Unique<DomainBlock>(b => b.Domain, Builders<DomainBlock>.Filter.Type(b => b.Domain, BsonType.String), token);
 			await Unique<RemoteInstance>(i => i.Host, Builders<RemoteInstance>.Filter.Type(i => i.Host, BsonType.String), token);
 		}
 

PrivaPub/Infrastructure/Http/FederationHttp.cs

@@ -1,6 +1,8 @@
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Options;
 
+using PrivaPub.Federation.Moderation;
+
 using System.Net;
 using System.Text.Json;
 
@@ -41,14 +43,16 @@ namespace PrivaPub.Infrastructure.Http
 		readonly IHttpClientFactory _httpClientFactory;
 		readonly IMemoryCache _cache;
 		readonly IOptionsMonitor<FederationOptions> _options;
+		readonly IDomainBlocks _domainBlocks;
 		readonly ILogger<FederationHttp> _logger;
 
 		public FederationHttp(IHttpClientFactory httpClientFactory, IMemoryCache cache, IOptionsMonitor<FederationOptions> options,
-			ILogger<FederationHttp> logger)
+			IDomainBlocks domainBlocks, ILogger<FederationHttp> logger)
 		{
 			_httpClientFactory = httpClientFactory;
 			_cache = cache;
 			_options = options;
+			_domainBlocks = domainBlocks;
 			_logger = logger;
 		}
 
@@ -56,6 +60,8 @@ namespace PrivaPub.Infrastructure.Http
 		{
 			if (target is not { IsAbsoluteUri: true } || !string.IsNullOrEmpty(target.UserInfo))
 				return false;
+			if (_domainBlocks?.IsSuspended(target.Host) == true)
+				return false;
 			var options = _options.CurrentValue;
 			if (target.Scheme != Uri.UriSchemeHttps && !(options.AllowPlainHttp && target.Scheme == Uri.UriSchemeHttp))
 				return false;

PrivaPub/Middleware/SocialPubConfigurations.cs

@@ -14,6 +14,7 @@ using PrivaPub.Services.ClientToServer.Public;
 using PrivaPub.Federation.Actors;
 using PrivaPub.Federation.Outbox;
 using PrivaPub.Federation.Inbox;
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Federation.Inbox.Handlers;
 using PrivaPub.Domain.Content;
 using PrivaPub.Infrastructure.Http;
@@ -50,6 +51,7 @@ namespace PrivaPub.Middleware
 					SafeHttpHandlerFactory.Create(provider.GetRequiredService<IOptions<FederationOptions>>().Value));
 			return service
 				.AddSingleton<IFederationHttp, FederationHttp>()
+				.AddSingleton<IDomainBlocks, DomainBlocks>()
 				.AddSingleton<IContentRenderer, ContentRenderer>()
 				.AddSingleton<ILocalActorService, LocalActorService>()
 				.AddSingleton<IRemoteActorService, RemoteActorService>()

PrivaPub/Models/Federation/DomainBlock.cs

@@ -0,0 +1,21 @@
+using MongoDB.Entities;
+
+namespace PrivaPub.Models.Federation
+{
+	public class DomainBlock : Entity
+	{
+		public string Domain { get; set; }
+		public DomainBlockSeverity Severity { get; set; }
+		public bool RejectMedia { get; set; }
+		public string PublicComment { get; set; }
+		public string PrivateComment { get; set; }
+		public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+	}
+
+	public enum DomainBlockSeverity
+	{
+		None,
+		Silence,
+		Suspend
+	}
+}

PrivaPub/Program.cs

@@ -154,6 +154,7 @@ try
 		var dbClient = app.Services.GetService(typeof(DbEntities)) as DbEntities;
 		var passwordHasher = app.Services.GetService(typeof(IPasswordHasher)) as IPasswordHasher;
 		await dbClient.Init(passwordHasher);
+		await app.Services.GetRequiredService<PrivaPub.Federation.Moderation.IDomainBlocks>().Reload(CancellationToken.None);
 	}
 	catch (Exception ex)
 	{