Everything on, phase 3: sign-in and recovery tell nothing, recovered passwords end sessions, deleted roots are gone everywhere

Owner decision 2026-10-04: fix the account privacy findings.

- Sign-in. Every failure answers "That username and password do not match." after the same work: an unknown login
  is hashed against a decoy, and the comparison is constant-time. "Banned" is told only to someone who gave the right
  password. This covers /clientapi/user/login, /invitation/login and /oauth/login.
- Recovery.
  - Every request answers the same sentence and queues a SendRecovery job, whether or not the account exists or has an
    email. The lookup, the code and SMTP move to RecoveryJob, so neither the answer nor its timing says anything.
  - Codes are kept only as a SHA-256 hash, for one hour. Migration _011 drops the plaintext ones, which never expired.
  - A recovered password ends every session of the root. RootSessions sets CredentialsChangedAt, which JwtEvents
    checks against the JWT's issue time, now stamped as nbf, and revokes each persona's OAuth tokens and authorizations.
- Deleting a root (RootRemoval: the admin route, or the restored self-delete at /clientapi/user/delete, which asks for
  the password).
  - Its sessions end.
  - Each persona and each group it owns sends Delete{Actor} to its followers, its members and the accounts it follows.
  - The personas' posts are emptied.
  - /peasants/{name} answers 410 with a Tombstone (formerType Person or Group), as do its inbox and WebFinger, through
    LocalActorService.Gone. The names stay reserved.
  - The root keeps only a unique `deleted-{id}` name; the second deletion on an instance used to collide on
    "Deleted user".

Also, from phase 2's pasture: GoToSocial files a circle post like a DM and shows it only to accounts it mentions. Each
member's copy, and a member's refetch, now also mentions that member silently. The GoToSocial scenario checks circle
posts in conversations, like DMs, and they pass there now, as on Mastodon.

657 tests pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

PrivaPub/Controllers/ClientToServer/RootUserController.cs

@@ -361,7 +361,7 @@ namespace PrivaPub.Controllers.ClientToServer
 				if (!result.IsValid)
 					return StatusCode(result.StatusCode, result);
 
-				return Ok(result);
+				return Ok(result.Data);//the same sentence for everyone
 			}
 			catch (Exception ex)
 			{
@@ -414,26 +414,23 @@ namespace PrivaPub.Controllers.ClientToServer
 			}
 		}
 
-		//[HttpDelete, Route("delete"), Authorize(Policy = Policies.IsUser)]
-		//public async Task<IActionResult> RemoveSelf()
-		//{
-		//	var result = new WebResult();
-		//	try
-		//	{
-		//		//result = await UsersService.RemoveUserAsync(User.GetUserId());
-		//		if (!result.IsValid)
-		//			return StatusCode(result.StatusCode, result);
-
-		//		await HttpContext.SignOutAsync();
-
-		//		return Ok();
-		//	}
-		//	catch (Exception ex)
-		//	{
-		//		Logger.LogError(ex, $"{nameof(User)}.{nameof(RemoveSelf)}()");
-		//		return BadRequest(result.Invalidate(Localizer["Something went wrong."]));
-		//	}
-		//}
+		[HttpPost, Route("/clientapi/user/delete"), EnableRateLimiting(RateLimiting.Accounts), Authorize(Policy = Policies.IsUser)]
+		public async Task<IActionResult> RemoveSelf(RemoveSelfForm form)
+		{
+			var result = new WebResult();
+			if (!ModelState.IsValid)
+				return BadRequest(result.Invalidate(Localizer["Invalid model."]));
+			try
+			{
+				result = await UsersService.RemoveSelfAsync(User.GetUserId(), form.Password);
+				return result.IsValid ? Ok() : StatusCode(result.StatusCode, result);
+			}
+			catch (Exception ex)
+			{
+				Logger.LogError(ex, $"{nameof(User)}.{nameof(RemoveSelf)}()");
+				return BadRequest(result.Invalidate(Localizer["Something went wrong."]));
+			}
+		}
 
 		#endregion User endpoints
 

PrivaPub/Federation/Actors/LocalActorService.cs

@@ -62,6 +62,7 @@ namespace PrivaPub.Federation.Actors
 	{
 		string BaseAddress { get; }
 		Task<LocalActor> FindByUserName(string userName, CancellationToken token);
+		Task<GoneActor> Gone(string userName, CancellationToken token);
 		Task<LocalActor> FindById(LocalActorKind kind, string id, CancellationToken token);
 		Task<LocalActor> FindByUri(string actorUri, CancellationToken token);
 		Task<LocalActor> GetInstanceActor(CancellationToken token);
@@ -71,6 +72,9 @@ namespace PrivaPub.Federation.Actors
 		LocalActor FromGroup(GroupEntity group);
 	}
 
+	// a persona or group that was deleted: its name stays reserved, and its documents answer 410 with this
+	public sealed record GoneActor(string Uri, string FormerType, DateTime DeletedAt);
+
 	public class LocalActorService : ILocalActorService
 	{
 		public const string InstanceUserName = "privapub";
@@ -113,6 +117,18 @@ namespace PrivaPub.Federation.Actors
 			return group == default ? default : FromGroup(group);
 		}
 
+		public async Task<GoneActor> Gone(string userName, CancellationToken token)
+		{
+			if (string.IsNullOrEmpty(userName))
+				return default;
+			userName = userName.ToLowerInvariant();
+			var avatar = await _dbEntities.Avatars.Match(a => a.UserName == userName && a.DeletionAt.HasValue).ExecuteFirstAsync(token);
+			if (avatar != default)
+				return new GoneActor($"{BaseAddress}/peasants/{avatar.UserName}", "Person", avatar.DeletionAt.Value);
+			var group = await _dbEntities.Groups.Match(g => g.UserName == userName && g.DeletionAt.HasValue).ExecuteFirstAsync(token);
+			return group == default ? default : new GoneActor($"{BaseAddress}/peasants/{group.UserName}", "Group", group.DeletionAt.Value);
+		}
+
 		public async Task<LocalActor> FindById(LocalActorKind kind, string id, CancellationToken token)
 		{
 			switch (kind)

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -53,6 +53,20 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> GetActor(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
+			if (local == default && await _localActors.Gone(actor, token) is { } gone)
+				return new ContentResult
+				{
+					Content = new JsonObject
+					{
+						["@context"] = ActivityPubRenderer.ActivityStreams,
+						["id"] = gone.Uri,
+						["type"] = "Tombstone",
+						["formerType"] = gone.FormerType,
+						["deleted"] = ActivityPubRenderer.Timestamp(gone.DeletedAt)
+					}.ToJsonString(),
+					ContentType = ActivityContentType,
+					StatusCode = StatusCodes.Status410Gone
+				};
 			if (local is not { IsFederated: true })
 				return NotFound();
 			if (WantsHtml() && local.Kind != LocalActorKind.Application)
@@ -282,6 +296,8 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> Inbox(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
+			if (local == default && await _localActors.Gone(actor, token) != default)
+				return StatusCode(StatusCodes.Status410Gone);
 			if (local is not { IsFederated: true })
 				return Answer(_inbox.NoSuchRecipient(Request));
 			return Answer(await _inbox.Receive(Request, local, token));
@@ -328,7 +344,9 @@ namespace PrivaPub.Federation.Controllers
 			{
 				var circle = await _dbEntities.Groups.MatchID(post.GroupId).ExecuteFirstAsync(token);
 				var note = ActivityPubRenderer.Note(post, local, _localActors.FromGroup(circle), post.InReplyToURI);
-				return (local, post, OutboxPublisher.Naming(note, SignedFetchAuthorizer.CircleReaders(circle, requester)));
+				var readers = SignedFetchAuthorizer.CircleReaders(circle, requester);
+				var named = readers.Count == 0 ? new List<Models.User.ForeignAvatar>() : await _dbEntities.ForeignAvatars.Match(a => readers.Contains(a.ActorURI)).ExecuteAsync(token);
+				return (local, post, OutboxPublisher.Naming(note, named));
 			}
 			var rendered = post.Visibility == PostVisibility.Direct
 				? ActivityPubRenderer.DirectNote(post, local, Array.Empty<(string, string)>(), post.ContextURI)

PrivaPub/Federation/Controllers/WellKnownController.cs

@@ -49,6 +49,8 @@ namespace PrivaPub.Federation.Controllers
 				if (parts.Length != 2 || !parts[1].Equals(domain, StringComparison.OrdinalIgnoreCase))
 					return NotFound();
 				actor = await _localActors.FindByUserName(parts[0], token);
+				if (actor == default && await _localActors.Gone(parts[0], token) != default)
+					return StatusCode(StatusCodes.Status410Gone);
 			}
 			else
 				actor = await _localActors.FindByUri(resource, token);

PrivaPub/Federation/Outbox/OutboxPublisher.cs

@@ -2,6 +2,7 @@ using PrivaPub.Federation.Actors;
 using PrivaPub.Federation.Rendering;
 using PrivaPub.Models.Federation;
 using PrivaPub.Models.Post;
+using PrivaPub.Models.User;
 using PrivaPub.StaticServices;
 
 using System.Text.Json.Nodes;
@@ -75,19 +76,18 @@ namespace PrivaPub.Federation.Outbox
 		}
 
 		async Task<IReadOnlyList<string>> CircleMembers(string groupId, CancellationToken token) =>
-			(await CircleRecipients(groupId, token)).Select(r => r.Inbox).Distinct(StringComparer.Ordinal).ToList();
+			(await CircleRecipients(groupId, token)).Select(r => r.InboxURL).Distinct(StringComparer.Ordinal).ToList();
 
-		async Task<IReadOnlyList<(string Member, string Inbox)>> CircleRecipients(string groupId, CancellationToken token)
+		async Task<IReadOnlyList<ForeignAvatar>> CircleRecipients(string groupId, CancellationToken token)
 		{
 			var circle = string.IsNullOrEmpty(groupId) ? default : await _dbEntities.Groups.MatchID(groupId).ExecuteFirstAsync(token);
 			if (circle == default)
-				return Array.Empty<(string, string)>();
+				return Array.Empty<ForeignAvatar>();
 			var remote = circle.Members.Where(m => m.IsForeign).Select(m => m.AvatarId).ToList();
 			if (remote.Count == 0)
-				return Array.Empty<(string, string)>();
+				return Array.Empty<ForeignAvatar>();
 			return (await _dbEntities.ForeignAvatars.Match(a => remote.Contains(a.ActorURI)).ExecuteAsync(token))
 				.Where(a => !string.IsNullOrEmpty(a.InboxURL))
-				.Select(a => (a.ActorURI, a.InboxURL))
 				.ToList();
 		}
 
@@ -95,8 +95,8 @@ namespace PrivaPub.Federation.Outbox
 		{
 			if (post.Visibility == PostVisibility.Circle)
 			{
-				foreach (var (member, inbox) in await CircleRecipients(post.GroupId, token))
-					await _delivery.Enqueue(author, new[] { inbox }, Naming(activity, new[] { member }), token);
+				foreach (var member in await CircleRecipients(post.GroupId, token))
+					await _delivery.Enqueue(author, new[] { member.InboxURL }, Naming(activity, new[] { member }), token);
 				return;
 			}
 			var inboxes = await Audience(author, post, token);
@@ -110,27 +110,44 @@ namespace PrivaPub.Federation.Outbox
 			await Publish(author, post, ActivityPubRenderer.UpdateOf(post, author, group, reason), token);
 		}
 
-		// Mastodon and GoToSocial keep a post only when it names one of their own accounts, and a circle post names only the
-		// circle. So each member's copy, or a member's refetch, also names that member in cc (owner decision 2026-10-04):
-		// it tells each member nothing but that they are in the circle.
-		public static JsonObject Naming(JsonObject activityOrObject, IEnumerable<string> members)
+		// Mastodon keeps a post only when it names one of its own accounts, and GoToSocial shows a post that is neither
+		// public nor for followers only to the accounts it mentions; a circle post names only the circle. So each member's
+		// copy, or a member's refetch, also names that member in cc and mentions them, silently, in its tags (owner decision
+		// 2026-10-04): it tells each member nothing but that they are in the circle.
+		public static JsonObject Naming(JsonObject activityOrObject, IEnumerable<ForeignAvatar> members)
 		{
+			var named = members.ToList();
 			var copy = (JsonObject)activityOrObject.DeepClone();
-			Name(copy, members);
-			if (copy["object"] is JsonObject inner && inner.ContainsKey("to"))
-				Name(inner, members);
+			if (copy["object"] is JsonObject inner)
+			{
+				Name(copy, named, mention: false);
+				if (inner.ContainsKey("to"))
+					Name(inner, named, mention: true);
+			}
+			else
+				Name(copy, named, mention: copy.ContainsKey("attributedTo"));
 			return copy;
 		}
 
-		static void Name(JsonObject node, IEnumerable<string> members)
+		static void Name(JsonObject node, IReadOnlyList<ForeignAvatar> members, bool mention)
 		{
 			var cc = node["cc"] as JsonArray ?? new JsonArray();
+			var tags = node["tag"] as JsonArray ?? new JsonArray();
 			foreach (var member in members)
-				if (!cc.Any(c => c?.GetValue<string>() == member))
-					cc.Add(member);
+			{
+				if (!cc.Any(c => c?.GetValue<string>() == member.ActorURI))
+					cc.Add(member.ActorURI);
+				if (mention && !tags.Any(t => t?["href"]?.GetValue<string>() == member.ActorURI))
+					tags.Add(new JsonObject { ["type"] = "Mention", ["href"] = member.ActorURI, ["name"] = Handle(member) });
+			}
 			node["cc"] = cc;
+			if (mention)
+				node["tag"] = tags;
 		}
 
+		static string Handle(ForeignAvatar member) =>
+			string.IsNullOrEmpty(member.UserName) ? member.ActorURI : $"@{member.UserName}@{new Uri(member.ActorURI).Authority}";
+
 		public async Task PublishProfile(LocalActor actor, CancellationToken token)
 		{
 			var document = ActivityPubRenderer.Actor(actor);

PrivaPub/Infrastructure/Data/Migrations/_011_recovery_codes_are_hashed.cs

@@ -0,0 +1,14 @@
+using MongoDB.Entities;
+
+using PrivaPub.Models.User;
+
+namespace PrivaPub.Infrastructure.Data.Migrations
+{
+	// Recovery codes were stored in plain text and never expired; from now on only a hash with a one-hour expiry is kept.
+	// The old codes are dropped: anyone mid-recovery asks again.
+	public class _011_recovery_codes_are_hashed : IMigration
+	{
+		public async Task UpgradeAsync() =>
+			await DB.Default.DeleteAsync<EmailRecovery>(r => r.CodeHash == null);
+	}
+}

PrivaPub/Middleware/SocialPubConfigurations.cs

@@ -99,6 +99,7 @@ namespace PrivaPub.Middleware
 				.AddSingleton<IPollService, PollService>()
 				.AddSingleton<IQuoteService, QuoteService>()
 				.AddSingleton<IJobHandler, PollRefreshJob>()
+				.AddSingleton<IJobHandler, RecoveryJob>()
 				.AddSingleton<IJobHandler, PollCloseJob>()
 				.AddSingleton<InstanceDescriber>()
 				.AddSingleton<IJobHandler>(services => services.GetRequiredService<InstanceDescriber>())
@@ -182,6 +183,8 @@ namespace PrivaPub.Middleware
 			return service
 				.AddTransient<IDataService, DataService>()
 				.AddTransient<IRootUsersService, RootUsersService>()
+				.AddScoped<IRootSessions, RootSessions>()
+				.AddScoped<IRootRemoval, RootRemoval>()
 				.AddTransient<IPublicAvatarUsersService, PublicAvatarUsersService>()
 				.AddTransient<IPrivateAvatarUsersService, PrivateAvatarUsersService>()
 				.AddTransient<IGroupUsersService, GroupUsersService>()

PrivaPub/Models/Jobs/Job.cs

@@ -29,7 +29,8 @@ namespace PrivaPub.Models.Jobs
 		FetchPreview,
 		RollupDay,
 		CrawlPlan,
-		CrawlInstance
+		CrawlInstance,
+		SendRecovery
 	}
 
 	public enum JobState

PrivaPub/Models/User/EmailRecovery.cs

@@ -5,7 +5,9 @@ namespace PrivaPub.Models.User
 	public class EmailRecovery : Entity
 	{
 		public string RootUserId { get; set; }
-		public string RecoveryCode { get; set; }
+		public string RecoveryCode { get; set; }//plaintext codes before 2026-10-04; migration _011 removed them, never written now
+		public string CodeHash { get; set; }//sha-256 of the code, hex; the code itself exists only in the email
+		public DateTime ExpiresAt { get; set; }
 		public string RequestIP { get; set; }
 		public DateTime CreationDate { get; set; } = DateTime.UtcNow;
 	}

PrivaPub/Models/User/RootUser.cs

@@ -23,6 +23,7 @@ namespace PrivaPub.Models.User
 		public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 		public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
 		public DateTime? DeletedAt { get; set; }
+		public DateTime? CredentialsChangedAt { get; set; }//a /clientapi token issued before this is refused (JwtEvents)
 	}
 
 	public class ContactItem

PrivaPub/Services/IRootUsersService.cs

@@ -16,6 +16,7 @@ namespace PrivaPub.Services
 		Task<WebResult> UnbanUserAsync(UsersIds usersIds);
 
 		Task<WebResult> RemoveUserAsync(UsersIds usersIds);
+		Task<WebResult> RemoveSelfAsync(string rootId, string password);
 
 		Task<WebResult> UpdateUserAsync(UserForm userEmailForm, string userId);
 

PrivaPub/Services/JwtEvents.cs

@@ -33,6 +33,12 @@ namespace PrivaPub.Services
 				context.Fail("The account can no longer be used.");
 				return;
 			}
+			// a password recovery ends every session made before it (RootSessions)
+			if (root.CredentialsChangedAt is { } changed && context.SecurityToken.ValidFrom < changed.AddSeconds(-1))
+			{
+				context.Fail("The account's password was changed.");
+				return;
+			}
 			if (context.Principal.Identity is not ClaimsIdentity identity)
 				return;
 			foreach (var policy in PolicyClaims)

PrivaPub/Services/RecoveryJob.cs

@@ -0,0 +1,88 @@
+using MailKit.Net.Smtp;
+
+using Microsoft.Extensions.Localization;
+
+using MimeKit;
+
+using MongoDB.Entities;
+
+using PrivaPub.Infrastructure.Jobs;
+using PrivaPub.Models.Jobs;
+using PrivaPub.Models.User;
+using PrivaPub.Resources;
+
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+
+namespace PrivaPub.Services
+{
+	public sealed record RecoveryPayload(string RootUserId, string Host);
+
+	// Sends a password recovery link. Every request queues one of these, for an account that exists or not, so the answer
+	// to the request and its timing say nothing; SMTP's slowness and failures happen here, where nobody waits on them.
+	// The code exists only in the email: the database keeps its hash, for an hour.
+	public class RecoveryJob : IJobHandler
+	{
+		public const string Host = "recovery";
+		public static readonly TimeSpan CodeLifetime = TimeSpan.FromHours(1);
+
+		readonly AppConfigurationService _app;
+		readonly IStringLocalizer<GenericRes> _localizer;
+		readonly ILogger<RecoveryJob> _logger;
+
+		public RecoveryJob(AppConfigurationService app, IStringLocalizer<GenericRes> localizer, ILogger<RecoveryJob> logger)
+		{
+			_app = app;
+			_localizer = localizer;
+			_logger = logger;
+		}
+
+		public JobKind Kind => JobKind.SendRecovery;
+		public int Concurrency => 1;
+		public int MaxAttempts => 3;
+		public int PerHostLimit => 1;
+
+		public static string Hash(string code) => Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes(code ?? string.Empty)));
+
+		public async Task<JobOutcome> Handle(Job job, CancellationToken token)
+		{
+			var payload = JsonSerializer.Deserialize<RecoveryPayload>(job.Payload);
+			if (string.IsNullOrEmpty(payload?.RootUserId))
+				return JobOutcome.Done;//asked for an account that does not exist: there is nobody to write to
+			var user = await DB.Default.Find<RootUser>().MatchID(payload.RootUserId).ExecuteFirstAsync(token);
+			if (user is not { DeletedAt: null, IsBanned: false } || string.IsNullOrEmpty(user.Email))
+				return JobOutcome.Done;
+
+			var code = Convert.ToHexStringLower(RandomNumberGenerator.GetBytes(32));
+			await DB.Default.DeleteAsync<EmailRecovery>(r => r.RootUserId == user.ID);
+			await DB.Default.SaveAsync(new EmailRecovery { RootUserId = user.ID, CodeHash = Hash(code), ExpiresAt = DateTime.UtcNow + CodeLifetime }, token);
+
+			var email = _app.AppConfiguration.EmailConfiguration;
+			var message = new MimeMessage();
+			message.From.Add(new MailboxAddress("PrivaPub", email.SmtpUsername));
+			message.To.Add(MailboxAddress.Parse(user.Email));
+			message.Subject = _localizer["PrivaPub - Password recovery link"];
+			message.Body = new TextPart("plain")
+			{
+				Text = string.Format(_localizer[
+					"Hello,\n\nSomeone asked to reset the password of the PrivaPub login {0}. If it was you, open this link within an hour:\n{1}\n\nIf it was not you, ignore this email: nothing changes."],
+					user.UserName, $"{payload.Host}/password-recovery?rc={code}")
+			};
+			try
+			{
+				using var smtp = new SmtpClient();
+				await smtp.ConnectAsync(email.SmtpServer, email.SmtpPort, email.UseSSL, token);
+				await smtp.AuthenticateAsync(email.SmtpUsername, email.SmtpPassword, token);
+				await smtp.SendAsync(message, token);
+				await smtp.DisconnectAsync(quit: true, token);
+				return JobOutcome.Done;
+			}
+			catch (Exception ex) when (ex is not OperationCanceledException || !token.IsCancellationRequested)
+			{
+				_logger.LogWarning(ex, "The recovery email could not be sent");
+				return JobOutcome.Retry("smtp");
+			}
+		}
+	}
+}

PrivaPub/Services/RootRemoval.cs

@@ -0,0 +1,119 @@
+using MongoDB.Entities;
+
+using PrivaPub.Federation.Actors;
+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;
+
+using GroupEntity = PrivaPub.Models.Group.Group;
+using PostEntity = PrivaPub.Models.Post.Post;
+
+namespace PrivaPub.Services
+{
+	public interface IRootRemoval
+	{
+		Task<bool> Remove(string rootId, CancellationToken token);
+	}
+
+	// Deleting a root deletes everything public it had (owner decision 2026-10-04): each persona, and each group a persona
+	// owns, is announced deleted with a Delete of the actor to everyone who follows it, every member and everyone it
+	// follows; their posts are emptied; their names stay reserved, and their documents answer 410 from then on. The root's
+	// sessions end first, so nothing acts as it while it goes.
+	public class RootRemoval : IRootRemoval
+	{
+		readonly DbEntities _dbEntities;
+		readonly ILocalActorService _localActors;
+		readonly IDeliveryService _delivery;
+		readonly IRootSessions _sessions;
+
+		public RootRemoval(DbEntities dbEntities, ILocalActorService localActors, IDeliveryService delivery, IRootSessions sessions)
+		{
+			_dbEntities = dbEntities;
+			_localActors = localActors;
+			_delivery = delivery;
+			_sessions = sessions;
+		}
+
+		public async Task<bool> Remove(string rootId, CancellationToken token)
+		{
+			var root = await _dbEntities.RootUsers.MatchID(rootId).Match(u => u.DeletedAt == null).ExecuteFirstAsync(token);
+			if (root == default)
+				return false;
+			await _sessions.Revoke(root.ID, token);
+			var now = DateTime.UtcNow;
+
+			var avatarIds = (await _dbEntities.RootToAvatars.Match(ra => ra.RootId == root.ID).ExecuteAsync(token)).Select(ra => ra.AvatarId).ToList();
+			var avatars = await _dbEntities.Avatars.Match(a => avatarIds.Contains(a.ID) && !a.DeletionAt.HasValue).ExecuteAsync(token);
+			foreach (var avatar in avatars)
+			{
+				foreach (var group in await _dbEntities.Groups.Match(g => g.OwnerAvatarId == avatar.ID && !g.DeletionAt.HasValue).ExecuteAsync(token))
+				{
+					await Announce(_localActors.FromGroup(group), group.Members.Where(m => m.IsForeign).Select(m => m.AvatarId), token);
+					await DB.Default.Update<GroupEntity>().MatchID(group.ID).Modify(g => g.DeletionAt, now).ExecuteAsync(token);
+				}
+				var persona = _localActors.FromAvatar(avatar);
+				var followed = (await _dbEntities.Followings.Match(f => f.AvatarId == avatar.ID && !f.TargetIsLocal).ExecuteAsync(token))
+					.Select(f => f.TargetActorURI);
+				await Announce(persona, followed, token);
+				await DB.Default.Update<Avatar>().MatchID(avatar.ID).Modify(a => a.DeletionAt, now).ExecuteAsync(token);
+				await Empty(avatar.ID, now, token);
+			}
+
+			await DB.Default.Update<RootUser>().MatchID(root.ID)
+				.Modify(u => u.UserName, $"deleted-{root.ID}")//unique, so a second deletion never collides with the first
+				.Modify(u => u.Email, null)
+				.Modify(u => u.HashedPassword, null)
+				.Modify(u => u.Policies, new List<string>())
+				.Modify(u => u.IsBanned, false)
+				.Modify(u => u.IsEmailValidated, false)
+				.Modify(u => u.DeletedAt, now)
+				.ExecuteAsync(token);
+			await DB.Default.DeleteAsync<EmailRecovery>(r => r.RootUserId == root.ID);
+			return true;
+		}
+
+		// Delete{Actor}: to its followers' (shared) inboxes, and to the inboxes of the other accounts named
+		async Task Announce(LocalActor actor, IEnumerable<string> others, CancellationToken token)
+		{
+			var inboxes = (await _delivery.FollowerInboxes(actor, token)).ToList();
+			var named = others.Where(uri => !string.IsNullOrEmpty(uri)).Distinct().ToList();
+			if (named.Count > 0)
+				inboxes.AddRange((await _dbEntities.ForeignAvatars.Match(a => named.Contains(a.ActorURI)).ExecuteAsync(token))
+					.Select(a => string.IsNullOrEmpty(a.SharedInboxURL) ? a.InboxURL : a.SharedInboxURL));
+			await _delivery.Enqueue(actor, inboxes.Where(i => !string.IsNullOrEmpty(i)).Distinct(), new JsonObject
+			{
+				["@context"] = ActivityPubRenderer.Context(),
+				["id"] = actor.ActivityUri("delete-actor"),
+				["type"] = "Delete",
+				["actor"] = actor.Uri,
+				["object"] = actor.Uri,
+				["to"] = new JsonArray(ActivityPubRenderer.Public),
+				["cc"] = new JsonArray(actor.Followers)
+			}, token);
+		}
+
+		// a persona's posts keep their ids and lose their content, like a single deleted post; a group writes none of its own
+		static async Task Empty(string avatarId, DateTime now, CancellationToken token)
+		{
+			var postIds = (await DB.Default.Find<PostEntity>().Match(p => p.GroupUserId == avatarId && !p.IsFederatedCopy && !p.DeletedAt.HasValue)
+				.Project(p => p.Include(x => x.ID)).ExecuteAsync(token)).Select(p => p.ID).ToList();
+			if (postIds.Count == 0)
+				return;
+			await DB.Default.Update<PostEntity>().Match(p => postIds.Contains(p.ID))
+				.Modify(p => p.DeletedAt, now)
+				.Modify(p => p.Text, null)
+				.Modify(p => p.ContentHtml, null)
+				.Modify(p => p.Title, null)
+				.Modify(p => p.SpoilerText, null)
+				.Modify(p => p.Media, new List<Models.Post.PostMedia>())
+				.Modify(p => p.Revisions, new List<Models.Post.PostRevision>())
+				.ExecuteAsync(token);
+			await DB.Default.DeleteAsync<TimelineEntry>(e => postIds.Contains(e.PostId) || postIds.Contains(e.ReblogOfPostId));
+		}
+	}
+}

PrivaPub/Services/RootSessions.cs

@@ -0,0 +1,41 @@
+using MongoDB.Entities;
+
+using OpenIddict.Abstractions;
+
+using PrivaPub.Models.User;
+using PrivaPub.StaticServices;
+
+namespace PrivaPub.Services
+{
+	public interface IRootSessions
+	{
+		Task Revoke(string rootId, CancellationToken token);
+	}
+
+	// Ends everything a root is signed in with: its /clientapi tokens, through CredentialsChangedAt (checked by JwtEvents),
+	// and the Mastodon API tokens and authorizations of each of its personas. Used when its password is recovered and when
+	// it is deleted.
+	public class RootSessions : IRootSessions
+	{
+		readonly DbEntities _dbEntities;
+		readonly IOpenIddictTokenManager _tokens;
+		readonly IOpenIddictAuthorizationManager _authorizations;
+
+		public RootSessions(DbEntities dbEntities, IOpenIddictTokenManager tokens, IOpenIddictAuthorizationManager authorizations)
+		{
+			_dbEntities = dbEntities;
+			_tokens = tokens;
+			_authorizations = authorizations;
+		}
+
+		public async Task Revoke(string rootId, CancellationToken token)
+		{
+			await DB.Default.Update<RootUser>().MatchID(rootId).Modify(u => u.CredentialsChangedAt, DateTime.UtcNow).ExecuteAsync(token);
+			foreach (var link in await _dbEntities.RootToAvatars.Match(ra => ra.RootId == rootId).ExecuteAsync(token))
+			{
+				await _tokens.RevokeBySubjectAsync(link.AvatarId, token);
+				await _authorizations.RevokeBySubjectAsync(link.AvatarId, token);
+			}
+		}
+	}
+}

PrivaPub/Services/RootUsersService.cs

@@ -14,9 +14,12 @@ using PrivaPub.ClientModels.User;
 using PrivaPub.Models;
 using PrivaPub.Models.User;
 using PrivaPub.Resources;
+using PrivaPub.Infrastructure.Jobs;
+using PrivaPub.Models.Jobs;
 using PrivaPub.StaticServices;
 
 using System.Globalization;
+using System.Text.Json;
 
 #pragma warning disable 8603
 #pragma warning disable 8625
@@ -31,8 +34,14 @@ namespace PrivaPub.Services
 		readonly ILogger<RootUsersService> Logger;
 		readonly AppConfigurationService AppConfigurationService;
 		readonly AuthTokenManager AuthTokenManager;
+		readonly IJobQueue Jobs;
+		readonly IRootSessions Sessions;
+		readonly IRootRemoval Removal;
 
 		public RootUsersService(
+			IJobQueue jobs,
+			IRootSessions sessions,
+			IRootRemoval removal,
 			IStringLocalizer<GenericRes> localizer,
 			ILogger<RootUsersService> logger,
 			IPasswordHasher passwordHasher,
@@ -40,6 +49,9 @@ namespace PrivaPub.Services
 			AppConfigurationService appConfigurationService,
 			AuthTokenManager authTokenManager)
 		{
+			Jobs = jobs;
+			Sessions = sessions;
+			Removal = removal;
 			DbEntities = dbEntities;
 			AuthTokenManager = authTokenManager;
 			PasswordHasher = passwordHasher;
@@ -48,6 +60,12 @@ namespace PrivaPub.Services
 			AppConfigurationService = appConfigurationService;
 		}
 
+		public const string NoMatch = "That username and password do not match.";
+		static string _decoy;
+
+		// a hash nobody's password matches, so an unknown login costs the same hashing as a wrong password
+		string Decoy => _decoy ??= PasswordHasher.Hash(Convert.ToHexString(System.Security.Cryptography.RandomNumberGenerator.GetBytes(16)));
+
 		public async Task<WebResult> SignUpAsync(LoginForm signUpForm, string invitationCode = default,
 			bool isPasswordRequired = false)
 		{
@@ -114,20 +132,16 @@ namespace PrivaPub.Services
 			var result = new WebResult();
 			try
 			{
+				// One answer, after the same work, whether the login is unknown, deleted or the password wrong: sign-in must not
+				// tell anyone which logins exist. Only someone who knows the password learns the login is banned.
 				loginForm.UserName = loginForm.UserName.ToLower();
-				if (!await DbEntities.RootUsers.Match(u => u.UserName == loginForm.UserName && u.DeletedAt == null)
-							.ExecuteAnyAsync())
-					return result.Invalidate(Localizer["Username '{0}' not found.", loginForm.UserName]);
-
-				var user = await DbEntities.RootUsers.Match(u => u.UserName == loginForm.UserName).ExecuteFirstAsync();
+				var user = await DbEntities.RootUsers.Match(u => u.UserName == loginForm.UserName && u.DeletedAt == null).ExecuteFirstAsync();
+				var (verified, needsUpgrade) = PasswordHasher.Check(user?.HashedPassword ?? Decoy, loginForm.Password);
+				if (user?.HashedPassword == default || !verified)
+					return result.Invalidate(Localizer[NoMatch]);
 				if (user.IsBanned)
 					return result.Invalidate(Localizer["User '{0}' banned.", user.UserName]);
 
-				var (verified, needsUpgrade) = PasswordHasher.Check(user.HashedPassword, loginForm.Password);
-
-				if (!verified)
-					return result.Invalidate(Localizer["Wrong password."]);
-
 				if (needsUpgrade)
 					result.ErrorMessage = Localizer["Needs upgrade!"];
 
@@ -261,24 +275,12 @@ namespace PrivaPub.Services
 			var result = new WebResult();
 			try
 			{
-				var users = await DbEntities.RootUsers.Match(u => usersIds.UserIdList.Contains(u.ID) && u.DeletedAt == default).ExecuteAsync();
-				if (users == null || users.Count == 0)
+				var removed = 0;
+				foreach (var id in usersIds.UserIdList.Distinct())
+					if (await Removal.Remove(id, CancellationToken.None))
+						removed++;
+				if (removed == 0)
 					return result.Invalidate(Localizer["User already deleted."]);
-
-				foreach (var user in users)
-				{
-					user.Email = Localizer["Deleted user"];
-					user.HashedPassword = null;
-					user.Policies.Clear();
-					user.IsBanned = false;
-					user.IsEmailValidated = false;
-					//user.TempSecret = null;
-					user.UserName = Localizer["Deleted user"];
-					user.DeletedAt = DateTime.UtcNow;
-
-					await DB.Default.SaveAsync(user);
-				}
-
 				return result;
 			}
 			catch (Exception ex)
@@ -288,6 +290,26 @@ namespace PrivaPub.Services
 			}
 		}
 
+		// A root deletes itself only with its password, so a stolen session cannot.
+		public async Task<WebResult> RemoveSelfAsync(string rootId, string password)
+		{
+			var result = new WebResult();
+			try
+			{
+				var user = await DbEntities.RootUsers.MatchID(rootId).Match(u => u.DeletedAt == null).ExecuteFirstAsync();
+				var (verified, _) = PasswordHasher.Check(user?.HashedPassword ?? Decoy, password ?? string.Empty);
+				if (user?.HashedPassword == default || !verified)
+					return result.Invalidate(Localizer[NoMatch], StatusCodes.Status403Forbidden);
+				await Removal.Remove(user.ID, CancellationToken.None);
+				return result;
+			}
+			catch (Exception ex)
+			{
+				Logger.LogError(ex, $"{nameof(RootUsersService)}.{nameof(RemoveSelfAsync)}()");
+				return result.Invalidate(Localizer["Something went wrong."], exception: ex);
+			}
+		}
+
 		public async Task<WebResult> BanUserAsync(UsersIds usersIds)
 		{
 			var result = new WebResult();
@@ -354,141 +376,22 @@ namespace PrivaPub.Services
 			}
 		}
 
+		public const string RecoverySent = "If that account has an email address, a recovery link is on its way. It works for one hour.";
+
+		// The same answer, after the same work, whether the account exists, has an email or can be written to: recovery must
+		// not tell anyone which logins or addresses exist. RecoveryJob does the rest, out of the request.
 		public async Task<WebResult> SetupAndSendRecoveryEmail(PasswordRecoveryForm passwordRecoveryForm, string host)
 		{
 			var result = new WebResult();
 			try
 			{
-				var usernameExists = false;
-				if (passwordRecoveryForm.IsEmailDisabled)
-				{
-					if (!await DbEntities.RootUsers.Match(u => u.UserName == passwordRecoveryForm.UserName && u.DeletedAt == null)
-								.ExecuteAnyAsync())
-						return result.Invalidate(Localizer["Username '{0}' not found.", passwordRecoveryForm.UserName],
-							StatusCodes.Status404NotFound);
-					usernameExists = true;
-				}
-				else
-				{
-					if (!await DbEntities.RootUsers.Match(u => u.Email == passwordRecoveryForm.Email && u.DeletedAt == null)
-								.ExecuteAnyAsync())
-						return result.Invalidate(Localizer["Username '{0}' not found.", passwordRecoveryForm.UserName],
-							StatusCodes.Status404NotFound);
-				}
-
-				var user = default(RootUser);
-				if (usernameExists)
-					user = await DbEntities.RootUsers.Match(u => u.UserName == passwordRecoveryForm.UserName).ExecuteFirstAsync();
-				else
-					user = await DbEntities.RootUsers.Match(u => u.Email == passwordRecoveryForm.Email).ExecuteFirstAsync();
-
-				if (string.IsNullOrEmpty(user.Email))
-					return result.Invalidate(Localizer["This User doesn't have an email, no way to recover."],
-						StatusCodes.Status423Locked);
-
-				var emailRecovery = await DbEntities.EmailRecoveries
-					.Match(er => er.RootUserId == user.ID).ExecuteFirstAsync();
-
-				if (emailRecovery is null)
-				{
-					emailRecovery = new()
-					{
-						RootUserId = user.ID
-					};
-					await DB.Default.SaveAsync(emailRecovery);
-				}
-
-				using var recoveryCodeGenerator = new Password(true, true, true, false, 127);
-				emailRecovery.RecoveryCode = recoveryCodeGenerator.Next();
-				await DB.Default.SaveAsync(emailRecovery);
-
-				using (var smtpClient = new SmtpClient())
-				{
-					try
-					{
-						await smtpClient.ConnectAsync(AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpServer, AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpPort,
-							AppConfigurationService.AppConfiguration.EmailConfiguration.UseSSL);
-						if (!smtpClient.IsConnected)
-						{
-							Logger.LogError($"Failed to connect to the SMTP server({AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpServer}).");
-							return result.Invalidate(Localizer["Failed to send email."], StatusCodes.Status503ServiceUnavailable);
-						}
-					}
-					catch (Exception ex)
-					{
-						Logger.LogError(ex, $"Error at connection to the SMTP server({AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpServer}).");
-						return result.Invalidate(Localizer["Failed to send email."], StatusCodes.Status503ServiceUnavailable, exception: ex);
-					}
-
-					try
-					{
-						await smtpClient.AuthenticateAsync(AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername, AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpPassword);
-						if (!smtpClient.IsAuthenticated)
-						{
-							Logger.LogError($"Failed SMTP authentication of {AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername}.");
-							return result.Invalidate(Localizer["Failed to send email."],
-								StatusCodes.Status503ServiceUnavailable);
-						}
-					}
-					catch (Exception ex)
-					{
-						Logger.LogError(ex, $"Failed SMTP authentication of {AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername}.");
-						return result.Invalidate(Localizer["Failed to send email."],
-							StatusCodes.Status503ServiceUnavailable, exception: ex);
-					}
-
-					try
-					{
-						var toParsed = await smtpClient.VerifyAsync(user.Email);
-						if (toParsed == null)
-							return result.Invalidate(Localizer["Invalid email."], StatusCodes.Status400BadRequest);
-					}
-					catch (OperationCanceledException ex)
-					{
-						Logger.LogWarning(
-							"SMTP operation canceled at email verification: {Error}", ex.Message);
-					}
-					catch (SmtpCommandException ex)
-					{
-						Logger.LogWarning(
-							"SMTP command exception at email verification: {Error}", ex.Message);
-					}
-					catch (SmtpProtocolException ex)
-					{
-						Logger.LogWarning(
-							"SMTP protocol exception at email verification: {Error}", ex.Message);
-					}
-					catch (Exception ex)
-					{
-						Logger.LogWarning("Exception at email verification: {Error}", ex.Message);
-					}
-
-					var message = new MimeMessage();
-					message.From.Add(new MailboxAddress("PrivaPub", AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername));
-					message.To.Add(MailboxAddress.Parse(user.Email));
-					message.Subject = Localizer["PrivaPub - Password recovery link"];
-					message.Body = new TextPart("plain")
-					{
-						Text = string.Format(Localizer[@"Hey {0},
-
-Eugene from collAnon, following is the password recovery link:
-{1}
-
--- Eugene"], user.UserName, $"{host}/password-recovery?rc={emailRecovery.RecoveryCode}")
-					};
-					try
-					{
-						await smtpClient.SendAsync(message);
-					}
-					catch (Exception ex)
-					{
-						Logger.LogError(ex, $"Error at email sending to {user.Email} from {AppConfigurationService.AppConfiguration.EmailConfiguration.SmtpUsername}.");
-						return result.Invalidate(Localizer["Failed to send email."], StatusCodes.Status503ServiceUnavailable, exception: ex);
-					}
-
-					await smtpClient.DisconnectAsync(quit: true);
-				}
-
+				var userName = passwordRecoveryForm.UserName?.ToLowerInvariant();
+				var user = passwordRecoveryForm.IsEmailDisabled
+					? await DbEntities.RootUsers.Match(u => u.UserName == userName && u.DeletedAt == null).ExecuteFirstAsync()
+					: await DbEntities.RootUsers.Match(u => u.Email == passwordRecoveryForm.Email && u.DeletedAt == null).ExecuteFirstAsync();
+				await Jobs.Enqueue(JobKind.SendRecovery, JsonSerializer.Serialize(new RecoveryPayload(user?.ID, host)), RecoveryJob.Host,
+					dedupeKey: default, CancellationToken.None);
+				result.Data = Localizer[RecoverySent].Value;
 				return result;
 			}
 			catch (Exception ex)
@@ -498,16 +401,19 @@ Eugene from collAnon, following is the password recovery link:
 			}
 		}
 
+		Task<EmailRecovery> LiveRecovery(string recoveryCode)
+		{
+			var hash = RecoveryJob.Hash(recoveryCode);
+			var now = DateTime.UtcNow;
+			return DbEntities.EmailRecoveries.Match(er => er.CodeHash == hash && er.ExpiresAt > now).ExecuteFirstAsync();
+		}
+
 		public async Task<WebResult> IsValidRecoveryCode(string recoveryCode)
 		{
 			var result = new WebResult();
 			try
 			{
-				var isValidRecoveryCode = await DbEntities.EmailRecoveries
-					.Match(er => er.RecoveryCode == recoveryCode).ExecuteAnyAsync();
-
-				result.Data = isValidRecoveryCode;
-
+				result.Data = await LiveRecovery(recoveryCode) != default;
 				return result;
 			}
 			catch (Exception ex)
@@ -516,33 +422,24 @@ Eugene from collAnon, following is the password recovery link:
 			}
 		}
 
+		// A recovered password ends every session the root had: whoever had them may be why it was recovered.
 		public async Task<WebResult> ChangePassword(NewPasswordForm newPasswordForm)
 		{
 			var result = new WebResult();
 			try
 			{
-				var isValidRecoveryCode = await DbEntities.EmailRecoveries
-					.Match(er => er.RecoveryCode == newPasswordForm.RecoveryCode).ExecuteAnyAsync();
-				if (!isValidRecoveryCode)
+				var recovery = await LiveRecovery(newPasswordForm.RecoveryCode);
+				var user = recovery == default ? default
+					: await DbEntities.RootUsers.MatchID(recovery.RootUserId).Match(u => u.DeletedAt == null && !u.IsBanned).ExecuteFirstAsync();
+				if (user == default)
 					return result.Invalidate(Localizer["Invalid recovery code."], StatusCodes.Status404NotFound);
 
-				var emailRecovery = await DbEntities.EmailRecoveries
-					.Match(er => er.RecoveryCode == newPasswordForm.RecoveryCode)
-					.Project(er => er.Include(nameof(EmailRecovery.RootUserId)))
-					.ExecuteFirstAsync();
-
-				if (emailRecovery is null || emailRecovery.RootUserId is null)
-					return result.Invalidate(Localizer["User not found."]);
-
-				var newHashedPassword = PasswordHasher.Hash(newPasswordForm.NewPassword);
-
-				_ = await DB.Default.Update<RootUser>()
-					.Match(u => u.ID == emailRecovery.RootUserId && u.DeletedAt == null)
-					.Modify(u => u.HashedPassword, newHashedPassword)
+				await DB.Default.Update<RootUser>().MatchID(user.ID)
+					.Modify(u => u.HashedPassword, PasswordHasher.Hash(newPasswordForm.NewPassword))
+					.Modify(u => u.UpdatedAt, DateTime.UtcNow)
 					.ExecuteAsync();
-
-				_ = await DB.Default.DeleteAsync<EmailRecovery>(er => er.RecoveryCode == newPasswordForm.RecoveryCode);
-
+				await DB.Default.DeleteAsync<EmailRecovery>(er => er.RootUserId == user.ID);
+				await Sessions.Revoke(user.ID, CancellationToken.None);
 				return result;
 			}
 			catch (Exception ex)

PrivaPub/StaticServices/AuthTokenManager.cs

@@ -44,6 +44,7 @@ namespace PrivaPub.StaticServices
 
 			var token = new JwtSecurityToken(issuer: Configuration["AppConfiguration:Jwt:Issuer"], audience: Configuration["AppConfiguration:Jwt:Audience"],
 					claims: claims,
+					notBefore: DateTime.UtcNow,//its issue time, which JwtEvents compares with RootUser.CredentialsChangedAt
 					expires: expiration,
 					signingCredentials: new(securityKey, SecurityAlgorithms.HmacSha512)
 			);

PrivaPub/StaticServices/PasswordHasher.cs

@@ -31,7 +31,7 @@ namespace PrivaPub.StaticServices
 			using (var algorithm = new Rfc2898DeriveBytes(password, salt, iterations, HashAlgorithmName.SHA512))
 			{
 				var keyToCheck = algorithm.GetBytes(KeySize);
-				var verified = keyToCheck.SequenceEqual(key);
+				var verified = CryptographicOperations.FixedTimeEquals(keyToCheck, key);
 				return (verified, needsUpgrade);
 			}
 		}