A remote handle on its own domain, once that domain's WebFinger agrees (FEP-2c59)

An account on a server whose handles are not its host's (Mastodon's LOCAL_DOMAIN apart from WEB_DOMAIN) showed as
user@host. The actor's `webfinger` names the handle; its domain is kept once WebFinger there points back to the actor,
and asked again when the name changes. A persona's blocked servers match a handle's domain as well as the actor's host,
as the lists Mastodon exports name handles' domains.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Api/Mastodon/Controllers/AccountsController.cs

@@ -392,7 +392,8 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			var blockedBy = local != default
 				? await DB.Default.Find<Block>().Match(b => b.AvatarId == local.Id && b.TargetActorURI == Me.Uri).ExecuteAnyAsync(token)
 				: remote != default && await DB.Default.Find<BlockedBy>().Match(b => b.AvatarId == MyId && b.ActorURI == remote.ActorURI).ExecuteAnyAsync(token);
-			var domainBlocked = remote != default && await DB.Default.Find<AccountDomainBlock>().Match(b => b.AvatarId == MyId && b.Domain == remote.Domain).ExecuteAnyAsync(token);
+			var domainBlocked = remote != default && (await DB.Default.Find<AccountDomainBlock>().Match(b => b.AvatarId == MyId).ExecuteAsync(token))
+				.Any(b => Hidden.Blocks(b.Domain, remote.ActorURI, remote.Domain));
 			return new Relationship
 			{
 				Id = id,

PrivaPub/Domain/Relationships/RelationshipService.cs

@@ -7,6 +7,7 @@ using PrivaPub.Federation.Outbox;
 using PrivaPub.Federation.Rendering;
 using PrivaPub.Models.Federation;
 using PrivaPub.Models.Social;
+using PrivaPub.Models.User;
 using PrivaPub.StaticServices;
 
 using System.Text.Json.Nodes;
@@ -141,11 +142,14 @@ namespace PrivaPub.Domain.Relationships
 			catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
 			{
 			}
-			foreach (var following in await _dbEntities.Followings.Match(f => f.AvatarId == me.Id && !f.TargetIsLocal).ExecuteAsync(token))
-				if (Hidden.HostMatches(following.TargetActorURI, domain))
+			var followings = await _dbEntities.Followings.Match(f => f.AvatarId == me.Id && !f.TargetIsLocal).ExecuteAsync(token);
+			var followers = await _dbEntities.Followers.Match(f => f.LocalActorId == me.Id).ExecuteAsync(token);
+			var handles = await Hidden.HandleDomains(followings.Select(f => f.TargetActorURI).Concat(followers.Select(f => f.ActorURI)).ToList(), token);
+			foreach (var following in followings)
+				if (Hidden.Blocks(domain, following.TargetActorURI, handles.GetValueOrDefault(following.TargetActorURI)))
 					await _follows.UnfollowAs(me, following.TargetActorURI, token);
-			foreach (var follower in await _dbEntities.Followers.Match(f => f.LocalActorId == me.Id).ExecuteAsync(token))
-				if (Hidden.HostMatches(follower.ActorURI, domain))
+			foreach (var follower in followers)
+				if (Hidden.Blocks(domain, follower.ActorURI, handles.GetValueOrDefault(follower.ActorURI)))
 					await DB.Default.DeleteAsync<Follower>(follower.ID);
 		}
 
@@ -167,8 +171,23 @@ namespace PrivaPub.Domain.Relationships
 	public static class Hidden
 	{
 		public static bool HostMatches(string actorUri, string domain) =>
-			Uri.TryCreate(actorUri, UriKind.Absolute, out var uri)
-			&& (uri.Host.Equals(domain, StringComparison.OrdinalIgnoreCase) || uri.Host.EndsWith("." + domain, StringComparison.OrdinalIgnoreCase));
+			Uri.TryCreate(actorUri, UriKind.Absolute, out var uri) && IsOn(uri.Host, domain);
+
+		static bool IsOn(string host, string domain) =>
+			host.Equals(domain, StringComparison.OrdinalIgnoreCase) || host.EndsWith("." + domain, StringComparison.OrdinalIgnoreCase);
+
+		// a server blocked by a persona hides an account whose actor is on it, or whose handle is (its domain apart from its
+		// actor's host, FEP-2c59: the servers Mastodon lists as blocked are its handles' domains)
+		public static bool Blocks(string domain, string actorUri, string handleDomain) =>
+			HostMatches(actorUri, domain) || (!string.IsNullOrEmpty(handleDomain) && IsOn(handleDomain.Split(':')[0], domain));
+
+		// the domains of these accounts' handles, for those known
+		public static async Task<Dictionary<string, string>> HandleDomains(List<string> actorUris, CancellationToken token) =>
+			actorUris.Count == 0
+				? []
+				: (await DB.Default.Find<ForeignAvatar>().Match(a => actorUris.Contains(a.ActorURI))
+					.Project(a => new ForeignAvatar { ActorURI = a.ActorURI, Domain = a.Domain }).ExecuteAsync(token))
+					.GroupBy(a => a.ActorURI).ToDictionary(g => g.Key, g => g.First().Domain);
 
 		public static async Task<HashSet<string>> AuthorsHiddenFrom(string avatarId, IEnumerable<string> actorUris, bool forNotifications, CancellationToken token)
 		{
@@ -186,8 +205,11 @@ namespace PrivaPub.Domain.Relationships
 				if ((mute.ExpiresAt == null || mute.ExpiresAt > now) && (!forNotifications || mute.HideNotifications))
 					hidden.Add(mute.TargetActorURI);
 			var domains = await DB.Default.Find<AccountDomainBlock>().Match(b => b.AvatarId == avatarId).ExecuteAsync(token);
+			if (domains.Count == 0)
+				return hidden;
+			var handles = await HandleDomains(uris, token);
 			foreach (var uri in uris)
-				if (domains.Any(d => HostMatches(uri, d.Domain)))
+				if (domains.Any(d => Blocks(d.Domain, uri, handles.GetValueOrDefault(uri))))
 					hidden.Add(uri);
 			return hidden;
 		}
@@ -206,8 +228,12 @@ namespace PrivaPub.Domain.Relationships
 			foreach (var mute in await DB.Default.Find<Mute>().Match(m => ids.Contains(m.AvatarId) && m.TargetActorURI == actorUri).ExecuteAsync(token))
 				if (mute.ExpiresAt == null || mute.ExpiresAt > now)
 					hiding.Add(mute.AvatarId);
-			foreach (var block in await DB.Default.Find<AccountDomainBlock>().Match(b => ids.Contains(b.AvatarId)).ExecuteAsync(token))
-				if (HostMatches(actorUri, block.Domain))
+			var domains = await DB.Default.Find<AccountDomainBlock>().Match(b => ids.Contains(b.AvatarId)).ExecuteAsync(token);
+			if (domains.Count == 0)
+				return hiding;
+			var handle = (await HandleDomains([actorUri], token)).GetValueOrDefault(actorUri);
+			foreach (var block in domains)
+				if (Blocks(block.Domain, actorUri, handle))
 					hiding.Add(block.AvatarId);
 			return hiding;
 		}

PrivaPub/Federation/Actors/ActorDocument.cs

@@ -25,6 +25,7 @@ namespace PrivaPub.Federation.Actors
 		public string Following { get; init; }
 		public string Featured { get; init; }
 		public string Wall { get; init; }
+		public string WebFinger { get; init; }//FEP-2c59: its handle, user@domain, where the domain is not its host's
 		public string SharedInbox { get; init; }
 		public string Icon { get; init; }
 		public bool Discoverable { get; init; } = true;
@@ -78,6 +79,7 @@ namespace PrivaPub.Federation.Actors
 				Following = RemoteActorService.Text(root, "following"),
 				Featured = RemoteActorService.Text(root, "featured"),
 				Wall = RemoteActorService.Text(root, "wall") ?? RemoteActorService.Text(root, "sm:wall"),
+				WebFinger = RemoteActorService.Text(root, "webfinger")?.Replace("acct:", "", StringComparison.OrdinalIgnoreCase).TrimStart('@'),
 				SharedInbox = root.TryGetProperty("endpoints", out var endpoints) ? RemoteActorService.Text(endpoints, "sharedInbox") : default,
 				Icon = root.TryGetProperty("icon", out var icon) ? RemoteActorService.Text(icon, "url") : default,
 				Discoverable = !root.TryGetProperty("discoverable", out var discoverable) || discoverable.ValueKind != JsonValueKind.False,

PrivaPub/Federation/Actors/RemoteActorService.cs

@@ -190,8 +190,25 @@ namespace PrivaPub.Federation.Actors
 			return true;
 		}
 
-		static async Task<ForeignAvatar> Upsert(ActorDocument actor, ActorKey key, CancellationToken token)
+		// the domain of its handle: its own host, or the one its `webfinger` names (FEP-2c59; a server whose handles are not
+		// its host's, as Mastodon's LOCAL_DOMAIN) once that domain's WebFinger says the handle is this actor. Asked again
+		// only when the handle changes, a rename among them.
+		async Task<string> HandleDomain(ActorDocument actor, CancellationToken token)
 		{
+			var host = new Uri(actor.Id).Authority;
+			var named = actor.WebFinger?.Split('@');
+			if (named is not { Length: 2 } || named[0].Length == 0 || named[1].Length == 0 || named[1].Equals(host, StringComparison.OrdinalIgnoreCase))
+				return host;
+			var domain = named[1].ToLowerInvariant();
+			var stored = await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == actor.Id).ExecuteFirstAsync(token);
+			if (stored?.Domain == domain && stored.UserName == actor.PreferredUsername)
+				return domain;
+			return await ResolveHandle($"{named[0]}@{domain}", token) == actor.Id ? domain : host;
+		}
+
+		async Task<ForeignAvatar> Upsert(ActorDocument actor, ActorKey key, CancellationToken token)
+		{
+			var domain = await HandleDomain(actor, token);
 			var now = DateTime.UtcNow;
 			return await DB.Default.UpdateAndGet<ForeignAvatar>()
 				.Match(a => a.ActorURI == actor.Id)
@@ -199,7 +216,7 @@ namespace PrivaPub.Federation.Actors
 				.Modify(a => a.Name, actor.Name)
 				.Modify(a => a.Biography, ContentSanitizer.Html(actor.Summary))
 				.Modify(a => a.Url, actor.Url)
-				.Modify(a => a.Domain, new Uri(actor.Id).Authority)
+				.Modify(a => a.Domain, domain)
 				.Modify(a => a.InboxURL, actor.Inbox)
 				.Modify(a => a.OutboxURL, actor.Outbox)
 				.Modify(a => a.FollowersURL, actor.Followers)