Spam Filter before creating user / drive files

packages/backend/src/core/CoreModule.ts

@@ -153,6 +153,7 @@ import { VmimiRelayTimelineService } from './VmimiRelayTimelineService.js';
 import { QueueModule } from './QueueModule.js';
 import { QueueService } from './QueueService.js';
 import { LoggerService } from './LoggerService.js';
+import { SpamFilterService } from './SpamFilterService.js';
 import type { Provider } from '@nestjs/common';
 
 //#region 文字列ベースでのinjection用(循環参照対応のため)
@@ -454,6 +455,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		ApPersonService,
 		ApQuestionService,
 		QueueService,
+		SpamFilterService,
 
 		//#region 文字列ベースでのinjection用(循環参照対応のため)
 		$VmimiRelayTimelineService,
@@ -750,6 +752,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		ApPersonService,
 		ApQuestionService,
 		QueueService,
+		SpamFilterService,
 
 		//#region 文字列ベースでのinjection用(循環参照対応のため)
 		$VmimiRelayTimelineService,

packages/backend/src/core/NoteCreateService.ts

@@ -57,6 +57,7 @@ import { isReply } from '@/misc/is-reply.js';
 import { trackPromise } from '@/misc/promise-tracker.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
 import { CollapsedQueue } from '@/misc/collapsed-queue.js';
+import { SpamFilterService } from '@/core/SpamFilterService.js';
 
 type NotificationType = 'reply' | 'renote' | 'quote' | 'mention';
 
@@ -219,6 +220,7 @@ export class NoteCreateService implements OnApplicationShutdown {
 		private instanceChart: InstanceChart,
 		private utilityService: UtilityService,
 		private userBlockingService: UserBlockingService,
+		private spamFilterService: SpamFilterService,
 	) {
 		this.updateNotesCountQueue = new CollapsedQueue(process.env.NODE_ENV !== 'test' ? 60 * 1000 * 5 : 0, this.collapseNotesCount, this.performUpdateNotesCount);
 	}
@@ -368,15 +370,15 @@ export class NoteCreateService implements OnApplicationShutdown {
 		// if the host is media-silenced, custom emojis are not allowed
 		if (this.utilityService.isMediaSilencedHost(this.meta.mediaSilencedHosts, user.host)) emojis = [];
 
-		const willCauseNotification = mentionedUsers.some(u => u.host === null)
-			|| (data.visibility === 'specified' && data.visibleUsers?.some(u => u.host === null))
-			|| data.reply?.userHost === null || (this.isRenote(data) && this.isQuote(data) && data.renote.userHost === null) || false;
-
-		if (process.env.MISSKEY_BLOCK_MENTIONS_FROM_UNFAMILIAR_REMOTE_USERS === 'true' && user.host !== null && willCauseNotification) {
-			const userEntity = await this.usersRepository.findOneBy({ id: user.id });
-			if ((userEntity?.followersCount ?? 0) === 0) {
-				throw new IdentifiableError('e11b3a16-f543-4885-8eb1-66cad131dbfd', 'Notes including mentions, replies, or renotes from remote users are not allowed until user has at least one local follower.');
-			}
+		if (await this.spamFilterService.isSpam({
+			mentionedUsers,
+			visibility: data.visibility,
+			visibleUsers: data.visibleUsers ?? [],
+			reply: data.reply ?? null,
+			quote: this.isRenote(data) && this.isQuote(data) ? data.renote : null,
+			user: user,
+		})) {
+			throw new IdentifiableError('e11b3a16-f543-4885-8eb1-66cad131dbfd', 'Notes including mentions, replies, or renotes from remote users are not allowed until user has at least one local follower.');
 		}
 
 		tags = tags.filter(tag => Array.from(tag).length <= 128).splice(0, 32);

packages/backend/src/core/SpamFilterService.ts

@@ -0,0 +1,94 @@
+/*
+ * SPDX-FileCopyrightText: anatawa12
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { DI } from '@/di-symbols.js';
+import type { MiMeta, MiNote, MiUser, UsersRepository } from '@/models/_.js';
+import { bindThis } from '@/decorators.js';
+
+type MinimumUser = {
+	id: MiUser['id'];
+	host: MiUser['host'];
+	username: MiUser['username'];
+	uri: MiUser['uri'];
+};
+
+type AuthorUser = {
+	id: MiUser['id'];
+	username: MiUser['username'];
+	host: MiUser['host'];
+};
+
+@Injectable()
+export class SpamFilterService {
+	constructor(
+		@Inject(DI.meta)
+		private meta: MiMeta,
+
+		@Inject(DI.usersRepository)
+		private usersRepository: UsersRepository,
+	) {
+	}
+
+	@bindThis
+	public async isSpam(
+		{
+			mentionedUsers,
+			visibility,
+			visibleUsers,
+			reply,
+			quote,
+			user,
+		}: {
+			mentionedUsers: readonly MinimumUser[],
+			visibility: MiNote['visibility'] | string,
+			visibleUsers: readonly MinimumUser[],
+			reply: MiNote | null,
+			quote: MiNote | null,
+			// null if new remote user
+			user: AuthorUser | null,
+		},
+	) {
+		// spam filter is enabled
+		if (process.env.MISSKEY_BLOCK_MENTIONS_FROM_UNFAMILIAR_REMOTE_USERS !== 'true') return false;
+		// do not check for local user
+		if (user != null && user.host === null) return false;
+
+		// get list of users that will create notification
+		const targetUserIds: string[] = [
+			...mentionedUsers.filter(x => x.host == null).map(x => x.id),
+			...(visibility === 'specified' ? visibleUsers.filter(x => x.host == null).map(x => x.id) : []),
+			...(reply != null && reply.userHost == null ? [reply.userId] : []),
+			...(quote != null && quote.userHost === null ? [quote.userId] : []),
+		];
+
+		// if notification is created only for allowed users, it's not a spam or harmful
+		// if no notification is created, it's not a spam or harmful
+		const allowedIds = new Set<string>([]);
+		if (targetUserIds.every(id => allowedIds.has(id))) return false;
+
+		// if someone follows the user, it's not a spam
+		if (await this.hasFollower(user)) return false;
+
+		// all conditions are met, it's a spam
+		return true;
+	}
+
+	private async hasFollower(user: AuthorUser | null): Promise<boolean> {
+		// the user is new user so no one follows the user
+		if (user == null) return false;
+
+		// if the user looks like MiUser, check followersCount
+		if ('followersCount' in user && typeof user.followersCount === 'number') {
+			return user.followersCount > 0;
+		}
+
+		const userEntity = await this.usersRepository.findOneBy({ id: user.id });
+		// user not found
+		if (userEntity == null) return false;
+
+		return userEntity.followersCount > 0;
+	}
+}

packages/backend/src/core/activitypub/ApAudienceService.ts

@@ -31,7 +31,7 @@ export class ApAudienceService {
 	}
 
 	@bindThis
-	public async parseAudience(actor: MiRemoteUser, to?: ApObject, cc?: ApObject, resolver?: Resolver): Promise<AudienceInfo> {
+	public async parseAudience(actor: MiRemoteUser | null, to?: ApObject, cc?: ApObject, resolver?: Resolver): Promise<AudienceInfo> {
 		const toGroups = this.groupingAudience(getApIds(to), actor);
 		const ccGroups = this.groupingAudience(getApIds(cc), actor);
 
@@ -74,7 +74,7 @@ export class ApAudienceService {
 	}
 
 	@bindThis
-	private groupingAudience(ids: string[], actor: MiRemoteUser): GroupedAudience {
+	private groupingAudience(ids: string[], actor: MiRemoteUser | null): GroupedAudience {
 		const groups: GroupedAudience = {
 			public: [],
 			followers: [],
@@ -106,7 +106,8 @@ export class ApAudienceService {
 	}
 
 	@bindThis
-	private isFollowers(id: string, actor: MiRemoteUser): boolean {
+	private isFollowers(id: string, actor: MiRemoteUser | null): boolean {
+		if (actor == null) return false;
 		return id === (actor.followersUri ?? `${actor.uri}/followers`);
 	}
 }

packages/backend/src/core/activitypub/models/ApNoteService.ts

@@ -23,6 +23,7 @@ import { UtilityService } from '@/core/UtilityService.js';
 import { bindThis } from '@/decorators.js';
 import { checkHttps } from '@/misc/check-https.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
+import { SpamFilterService } from '@/core/SpamFilterService.js';
 import { getOneApId, getApId, getOneApHrefNullable, validPost, isEmoji, getApType } from '../type.js';
 import { ApLoggerService } from '../ApLoggerService.js';
 import { ApMfmService } from '../ApMfmService.js';
@@ -72,6 +73,7 @@ export class ApNoteService {
 		private noteCreateService: NoteCreateService,
 		private apDbResolverService: ApDbResolverService,
 		private apLoggerService: ApLoggerService,
+		private spamFilterService: SpamFilterService,
 	) {
 		this.logger = this.apLoggerService.logger;
 	}
@@ -156,7 +158,7 @@ export class ApNoteService {
 		const uri = getOneApId(note.attributedTo);
 
 		// ローカルで投稿者を検索し、もし凍結されていたらスキップ
-		const cachedActor = await this.apPersonService.fetchPerson(uri) as MiRemoteUser;
+		const cachedActor = await this.apPersonService.fetchPerson(uri) as MiRemoteUser | null;
 		if (cachedActor && cachedActor.isSuspended) {
 			throw new IdentifiableError('85ab9bd7-3a41-4530-959d-f07073900109', 'actor has been suspended');
 		}
@@ -189,6 +191,44 @@ export class ApNoteService {
 		}
 		//#endregion
 
+		// spam check
+		{
+			// fetch audience information.
+			// this logic may treat followers as direct audience, but it's not a problem for spam check.
+			const noteAudience = await this.apAudienceService.parseAudience(cachedActor, note.to, note.cc, resolver);
+			let visibility = noteAudience.visibility;
+			const visibleUsers = noteAudience.visibleUsers;
+
+			// Audience (to, cc) が指定されてなかった場合
+			if (visibility === 'specified' && visibleUsers.length === 0) {
+				if (typeof value === 'string') {	// 入力がstringならばresolverでGETが発生している
+					// こちらから匿名GET出来たものならばpublic
+					visibility = 'public';
+				}
+			}
+
+			// for spam check, we only want to know if the reply / quote target is local user or not.
+			// so we don't have to resolve the note, we just fetch from DB.
+			// reply
+			const reply: MiNote | null = note.inReplyTo ? await this.fetchNote(getApId(note.inReplyTo)) : null;
+
+			// 引用
+			const quoteUris = unique([note._misskey_quote, note.quoteUrl].filter(x => x != null));
+			const quoteFetchResults = await Promise.all(quoteUris.map(uri => this.fetchNote(getApId(uri))));
+			const quote = quoteFetchResults.filter((x) => x != null).at(0) ?? null;
+
+			if (await this.spamFilterService.isSpam({
+				mentionedUsers: apMentions,
+				visibility,
+				visibleUsers,
+				reply: reply,
+				quote: quote,
+				user: cachedActor,
+			})) {
+				throw new IdentifiableError('e11b3a16-f543-4885-8eb1-66cad131dbfd', 'Notes including mentions, replies, or renotes from remote users are not allowed until user has at least one local follower.');
+			}
+		}
+
 		const actor = cachedActor ?? await this.apPersonService.resolvePerson(uri, resolver) as MiRemoteUser;
 
 		// 解決した投稿者が凍結されていたらスキップ