refactoring

Resolve #7779
2021-11-12 02:02:25 +09:00 · 2021-11-12 02:02:25 +09:00 · 0e4a111f81
commit 0e4a111f81
parent 037837b551
1714 changed files with 20803 additions and 11751 deletions
--- a/packages/backend/src/remote/activitypub/ap-request.ts
+++ b/packages/backend/src/remote/activitypub/ap-request.ts
@ -0,0 +1,104 @@
+import * as crypto from 'crypto';
+import { URL } from 'url';
+
+type Request = {
+	url: string;
+	method: string;
+	headers: Record<string, string>;
+};
+
+type PrivateKey = {
+	privateKeyPem: string;
+	keyId: string;
+};
+
+export function createSignedPost(args: { key: PrivateKey, url: string, body: string, additionalHeaders: Record<string, string> }) {
+	const u = new URL(args.url);
+	const digestHeader = `SHA-256=${crypto.createHash('sha256').update(args.body).digest('base64')}`;
+
+	const request: Request = {
+		url: u.href,
+		method: 'POST',
+		headers:  objectAssignWithLcKey({
+			'Date': new Date().toUTCString(),
+			'Host': u.hostname,
+			'Content-Type': 'application/activity+json',
+			'Digest': digestHeader,
+		}, args.additionalHeaders),
+	};
+
+	const result = signToRequest(request, args.key, ['(request-target)', 'date', 'host', 'digest']);
+
+	return {
+		request,
+		signingString: result.signingString,
+		signature: result.signature,
+		signatureHeader: result.signatureHeader,
+	};
+}
+
+export function createSignedGet(args: { key: PrivateKey, url: string, additionalHeaders: Record<string, string> }) {
+	const u = new URL(args.url);
+
+	const request: Request = {
+		url: u.href,
+		method: 'GET',
+		headers:  objectAssignWithLcKey({
+			'Accept': 'application/activity+json, application/ld+json',
+			'Date': new Date().toUTCString(),
+			'Host': new URL(args.url).hostname,
+		}, args.additionalHeaders),
+	};
+
+	const result = signToRequest(request, args.key, ['(request-target)', 'date', 'host', 'accept']);
+
+	return {
+		request,
+		signingString: result.signingString,
+		signature: result.signature,
+		signatureHeader: result.signatureHeader,
+	};
+}
+
+function signToRequest(request: Request, key: PrivateKey, includeHeaders: string[]) {
+	const signingString = genSigningString(request, includeHeaders);
+	const signature = crypto.sign('sha256', Buffer.from(signingString), key.privateKeyPem).toString('base64');
+	const signatureHeader = `keyId="${key.keyId}",algorithm="rsa-sha256",headers="${includeHeaders.join(' ')}",signature="${signature}"`;
+
+	request.headers = objectAssignWithLcKey(request.headers, {
+		Signature: signatureHeader
+	});
+
+	return {
+		request,
+		signingString,
+		signature,
+		signatureHeader,
+	};
+}
+
+function genSigningString(request: Request, includeHeaders: string[]) {
+	request.headers = lcObjectKey(request.headers);
+
+	const results: string[] = [];
+
+	for (const key of includeHeaders.map(x => x.toLowerCase())) {
+		if (key === '(request-target)') {
+			results.push(`(request-target): ${request.method.toLowerCase()} ${new URL(request.url).pathname}`);
+		} else {
+			results.push(`${key}: ${request.headers[key]}`);
+		}
+	}
+
+	return results.join('\n');
+}
+
+function lcObjectKey(src: Record<string, string>) {
+	const dst: Record<string, string> = {};
+	for (const key of Object.keys(src).filter(x => x != '__proto__' && typeof src[x] === 'string')) dst[key.toLowerCase()] = src[key];
+	return dst;
+}
+
+function objectAssignWithLcKey(a: Record<string, string>, b: Record<string, string>) {
+	return Object.assign(lcObjectKey(a), lcObjectKey(b));
+}
--- a/packages/backend/src/remote/activitypub/audience.ts
+++ b/packages/backend/src/remote/activitypub/audience.ts
@ -0,0 +1,92 @@
+import { ApObject, getApIds } from './type';
+import Resolver from './resolver';
+import { resolvePerson } from './models/person';
+import { unique, concat } from '@/prelude/array';
+import * as promiseLimit from 'promise-limit';
+import { User, IRemoteUser } from '@/models/entities/user';
+
+type Visibility = 'public' | 'home' | 'followers' | 'specified';
+
+type AudienceInfo = {
+	visibility: Visibility,
+	mentionedUsers: User[],
+	visibleUsers: User[],
+};
+
+export async function parseAudience(actor: IRemoteUser, to?: ApObject, cc?: ApObject, resolver?: Resolver): Promise<AudienceInfo> {
+	const toGroups = groupingAudience(getApIds(to), actor);
+	const ccGroups = groupingAudience(getApIds(cc), actor);
+
+	const others = unique(concat([toGroups.other, ccGroups.other]));
+
+	const limit = promiseLimit<User | null>(2);
+	const mentionedUsers = (await Promise.all(
+		others.map(id => limit(() => resolvePerson(id, resolver).catch(() => null)))
+	)).filter((x): x is User => x != null);
+
+	if (toGroups.public.length > 0) {
+		return {
+			visibility: 'public',
+			mentionedUsers,
+			visibleUsers: []
+		};
+	}
+
+	if (ccGroups.public.length > 0) {
+		return {
+			visibility: 'home',
+			mentionedUsers,
+			visibleUsers: []
+		};
+	}
+
+	if (toGroups.followers.length > 0) {
+		return {
+			visibility: 'followers',
+			mentionedUsers,
+			visibleUsers: []
+		};
+	}
+
+	return {
+		visibility: 'specified',
+		mentionedUsers,
+		visibleUsers: mentionedUsers
+	};
+}
+
+function groupingAudience(ids: string[], actor: IRemoteUser) {
+	const groups = {
+		public: [] as string[],
+		followers: [] as string[],
+		other: [] as string[],
+	};
+
+	for (const id of ids) {
+		if (isPublic(id)) {
+			groups.public.push(id);
+		} else if (isFollowers(id, actor)) {
+			groups.followers.push(id);
+		} else {
+			groups.other.push(id);
+		}
+	}
+
+	groups.other = unique(groups.other);
+
+	return groups;
+}
+
+function isPublic(id: string) {
+	return [
+		'https://www.w3.org/ns/activitystreams#Public',
+		'as#Public',
+		'Public',
+	].includes(id);
+}
+
+function isFollowers(id: string, actor: IRemoteUser) {
+	return (
+		id === (actor.followersUri || `${actor.uri}/followers`)
+	);
+}
--- a/packages/backend/src/remote/activitypub/db-resolver.ts
+++ b/packages/backend/src/remote/activitypub/db-resolver.ts
@ -0,0 +1,140 @@
+import config from '@/config/index';
+import { Note } from '@/models/entities/note';
+import { User, IRemoteUser } from '@/models/entities/user';
+import { UserPublickey } from '@/models/entities/user-publickey';
+import { MessagingMessage } from '@/models/entities/messaging-message';
+import { Notes, Users, UserPublickeys, MessagingMessages } from '@/models/index';
+import { IObject, getApId } from './type';
+import { resolvePerson } from './models/person';
+import escapeRegexp = require('escape-regexp');
+
+export default class DbResolver {
+	constructor() {
+	}
+
+	/**
+	 * AP Note => Misskey Note in DB
+	 */
+	public async getNoteFromApId(value: string | IObject): Promise<Note | null> {
+		const parsed = this.parseUri(value);
+
+		if (parsed.id) {
+			return (await Notes.findOne({
+				id: parsed.id
+			})) || null;
+		}
+
+		if (parsed.uri) {
+			return (await Notes.findOne({
+				uri: parsed.uri
+			})) || null;
+		}
+
+		return null;
+	}
+
+	public async getMessageFromApId(value: string | IObject): Promise<MessagingMessage | null> {
+		const parsed = this.parseUri(value);
+
+		if (parsed.id) {
+			return (await MessagingMessages.findOne({
+				id: parsed.id
+			})) || null;
+		}
+
+		if (parsed.uri) {
+			return (await MessagingMessages.findOne({
+				uri: parsed.uri
+			})) || null;
+		}
+
+		return null;
+	}
+
+	/**
+	 * AP Person => Misskey User in DB
+	 */
+	public async getUserFromApId(value: string | IObject): Promise<User | null> {
+		const parsed = this.parseUri(value);
+
+		if (parsed.id) {
+			return (await Users.findOne({
+				id: parsed.id
+			})) || null;
+		}
+
+		if (parsed.uri) {
+			return (await Users.findOne({
+				uri: parsed.uri
+			})) || null;
+		}
+
+		return null;
+	}
+
+	/**
+	 * AP KeyId => Misskey User and Key
+	 */
+	public async getAuthUserFromKeyId(keyId: string): Promise<AuthUser | null> {
+		const key = await UserPublickeys.findOne({
+			keyId
+		});
+
+		if (key == null) return null;
+
+		const user = await Users.findOne(key.userId) as IRemoteUser;
+
+		return {
+			user,
+			key
+		};
+	}
+
+	/**
+	 * AP Actor id => Misskey User and Key
+	 */
+	public async getAuthUserFromApId(uri: string): Promise<AuthUser | null> {
+		const user = await resolvePerson(uri) as IRemoteUser;
+
+		if (user == null) return null;
+
+		const key = await UserPublickeys.findOne(user.id);
+
+		return {
+			user,
+			key
+		};
+	}
+
+	public parseUri(value: string | IObject): UriParseResult {
+		const uri = getApId(value);
+
+		const localRegex = new RegExp('^' + escapeRegexp(config.url) + '/' + '(\\w+)' + '/' + '(\\w+)');
+		const matchLocal = uri.match(localRegex);
+
+		if (matchLocal) {
+			return {
+				type: matchLocal[1],
+				id: matchLocal[2]
+			};
+		} else {
+			return {
+				uri
+			};
+		}
+	}
+}
+
+export type AuthUser = {
+	user: IRemoteUser;
+	key?: UserPublickey;
+};
+
+type UriParseResult = {
+	/** id in DB (local object only) */
+	id?: string;
+	/** uri in DB (remote object only) */
+	uri?: string;
+	/** hint of type (local object only, ex: notes, users) */
+	type?: string
+};
--- a/packages/backend/src/remote/activitypub/deliver-manager.ts
+++ b/packages/backend/src/remote/activitypub/deliver-manager.ts
@ -0,0 +1,131 @@
+import { Users, Followings } from '@/models/index';
+import { ILocalUser, IRemoteUser, User } from '@/models/entities/user';
+import { deliver } from '@/queue/index';
+
+//#region types
+interface IRecipe {
+	type: string;
+}
+
+interface IFollowersRecipe extends IRecipe {
+	type: 'Followers';
+}
+
+interface IDirectRecipe extends IRecipe {
+	type: 'Direct';
+	to: IRemoteUser;
+}
+
+const isFollowers = (recipe: any): recipe is IFollowersRecipe =>
+	recipe.type === 'Followers';
+
+const isDirect = (recipe: any): recipe is IDirectRecipe =>
+	recipe.type === 'Direct';
+//#endregion
+
+export default class DeliverManager {
+	private actor: { id: User['id']; host: null; };
+	private activity: any;
+	private recipes: IRecipe[] = [];
+
+	/**
+	 * Constructor
+	 * @param actor Actor
+	 * @param activity Activity to deliver
+	 */
+	constructor(actor: { id: User['id']; host: null; }, activity: any) {
+		this.actor = actor;
+		this.activity = activity;
+	}
+
+	/**
+	 * Add recipe for followers deliver
+	 */
+	public addFollowersRecipe() {
+		const deliver = {
+			type: 'Followers'
+		} as IFollowersRecipe;
+
+		this.addRecipe(deliver);
+	}
+
+	/**
+	 * Add recipe for direct deliver
+	 * @param to To
+	 */
+	public addDirectRecipe(to: IRemoteUser) {
+		const recipe = {
+			type: 'Direct',
+			to
+		} as IDirectRecipe;
+
+		this.addRecipe(recipe);
+	}
+
+	/**
+	 * Add recipe
+	 * @param recipe Recipe
+	 */
+	public addRecipe(recipe: IRecipe) {
+		this.recipes.push(recipe);
+	}
+
+	/**
+	 * Execute delivers
+	 */
+	public async execute() {
+		if (!Users.isLocalUser(this.actor)) return;
+
+		const inboxes = new Set<string>();
+
+		// build inbox list
+		for (const recipe of this.recipes) {
+			if (isFollowers(recipe)) {
+				// followers deliver
+				const followers = await Followings.find({
+					followeeId: this.actor.id
+				});
+
+				for (const following of followers) {
+					if (Followings.isRemoteFollower(following)) {
+						const inbox = following.followerSharedInbox || following.followerInbox;
+						inboxes.add(inbox);
+					}
+				}
+			} else if (isDirect(recipe)) {
+				// direct deliver
+				const inbox = recipe.to.inbox;
+				if (inbox) inboxes.add(inbox);
+			}
+		}
+
+		// deliver
+		for (const inbox of inboxes) {
+			deliver(this.actor, this.activity, inbox);
+		}
+	}
+}
+
+//#region Utilities
+/**
+ * Deliver activity to followers
+ * @param activity Activity
+ * @param from Followee
+ */
+export async function deliverToFollowers(actor: ILocalUser, activity: any) {
+	const manager = new DeliverManager(actor, activity);
+	manager.addFollowersRecipe();
+	await manager.execute();
+}
+
+/**
+ * Deliver activity to user
+ * @param activity Activity
+ * @param to Target user
+ */
+export async function deliverToUser(actor: ILocalUser, activity: any, to: IRemoteUser) {
+	const manager = new DeliverManager(actor, activity);
+	manager.addDirectRecipe(to);
+	await manager.execute();
+}
+//#endregion
--- a/packages/backend/src/remote/activitypub/kernel/accept/follow.ts
+++ b/packages/backend/src/remote/activitypub/kernel/accept/follow.ts
@ -0,0 +1,29 @@
+import { IRemoteUser } from '@/models/entities/user';
+import accept from '@/services/following/requests/accept';
+import { IFollow } from '../../type';
+import DbResolver from '../../db-resolver';
+import { relayAccepted } from '@/services/relay';
+
+export default async (actor: IRemoteUser, activity: IFollow): Promise<string> => {
+	// ※ activityはこっちから投げたフォローリクエストなので、activity.actorは存在するローカルユーザーである必要がある
+
+	const dbResolver = new DbResolver();
+	const follower = await dbResolver.getUserFromApId(activity.actor);
+
+	if (follower == null) {
+		return `skip: follower not found`;
+	}
+
+	if (follower.host != null) {
+		return `skip: follower is not a local user`;
+	}
+
+	// relay
+	const match = activity.id?.match(/follow-relay\/(\w+)/);
+	if (match) {
+		return await relayAccepted(match[1]);
+	}
+
+	await accept(actor, follower);
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/accept/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/accept/index.ts
@ -0,0 +1,24 @@
+import Resolver from '../../resolver';
+import { IRemoteUser } from '@/models/entities/user';
+import acceptFollow from './follow';
+import { IAccept, isFollow, getApType } from '../../type';
+import { apLogger } from '../../logger';
+
+const logger = apLogger;
+
+export default async (actor: IRemoteUser, activity: IAccept): Promise<string> => {
+	const uri = activity.id || activity;
+
+	logger.info(`Accept: ${uri}`);
+
+	const resolver = new Resolver();
+
+	const object = await resolver.resolve(activity.object).catch(e => {
+		logger.error(`Resolution failed: ${e}`);
+		throw e;
+	});
+
+	if (isFollow(object)) return await acceptFollow(actor, object);
+
+	return `skip: Unknown Accept type: ${getApType(object)}`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/add/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/add/index.ts
@ -0,0 +1,23 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { IAdd } from '../../type';
+import { resolveNote } from '../../models/note';
+import { addPinned } from '@/services/i/pin';
+
+export default async (actor: IRemoteUser, activity: IAdd): Promise<void> => {
+	if ('actor' in activity && actor.uri !== activity.actor) {
+		throw new Error('invalid actor');
+	}
+
+	if (activity.target == null) {
+		throw new Error('target is null');
+	}
+
+	if (activity.target === actor.featured) {
+		const note = await resolveNote(activity.object);
+		if (note == null) throw new Error('note not found');
+		await addPinned(actor, note.id);
+		return;
+	}
+
+	throw new Error(`unknown target: ${activity.target}`);
+};
--- a/packages/backend/src/remote/activitypub/kernel/announce/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/announce/index.ts
@ -0,0 +1,19 @@
+import Resolver from '../../resolver';
+import { IRemoteUser } from '@/models/entities/user';
+import announceNote from './note';
+import { IAnnounce, getApId } from '../../type';
+import { apLogger } from '../../logger';
+
+const logger = apLogger;
+
+export default async (actor: IRemoteUser, activity: IAnnounce): Promise<void> => {
+	const uri = getApId(activity);
+
+	logger.info(`Announce: ${uri}`);
+
+	const resolver = new Resolver();
+
+	const targetUri = getApId(activity.object);
+
+	announceNote(resolver, actor, activity, targetUri);
+};
--- a/packages/backend/src/remote/activitypub/kernel/announce/note.ts
+++ b/packages/backend/src/remote/activitypub/kernel/announce/note.ts
@ -0,0 +1,67 @@
+import Resolver from '../../resolver';
+import post from '@/services/note/create';
+import { IRemoteUser } from '@/models/entities/user';
+import { IAnnounce, getApId } from '../../type';
+import { fetchNote, resolveNote } from '../../models/note';
+import { apLogger } from '../../logger';
+import { extractDbHost } from '@/misc/convert-host';
+import { fetchMeta } from '@/misc/fetch-meta';
+import { getApLock } from '@/misc/app-lock';
+import { parseAudience } from '../../audience';
+import { StatusError } from '@/misc/fetch';
+
+const logger = apLogger;
+
+/**
+ * アナウンスアクティビティを捌きます
+ */
+export default async function(resolver: Resolver, actor: IRemoteUser, activity: IAnnounce, targetUri: string): Promise<void> {
+	const uri = getApId(activity);
+
+	// アナウンサーが凍結されていたらスキップ
+	if (actor.isSuspended) {
+		return;
+	}
+
+	// アナウンス先をブロックしてたら中断
+	const meta = await fetchMeta();
+	if (meta.blockedHosts.includes(extractDbHost(uri))) return;
+
+	const unlock = await getApLock(uri);
+
+	try {
+		// 既に同じURIを持つものが登録されていないかチェック
+		const exist = await fetchNote(uri);
+		if (exist) {
+			return;
+		}
+
+		// Announce対象をresolve
+		let renote;
+		try {
+			renote = await resolveNote(targetUri);
+		} catch (e) {
+			// 対象が4xxならスキップ
+			if (e instanceof StatusError && e.isClientError) {
+				logger.warn(`Ignored announce target ${targetUri} - ${e.statusCode}`);
+				return;
+			}
+			logger.warn(`Error in announce target ${targetUri} - ${e.statusCode || e}`);
+			throw e;
+		}
+
+		logger.info(`Creating the (Re)Note: ${uri}`);
+
+		const activityAudience = await parseAudience(actor, activity.to, activity.cc);
+
+		await post(actor, {
+			createdAt: activity.published ? new Date(activity.published) : null,
+			renote,
+			visibility: activityAudience.visibility,
+			visibleUsers: activityAudience.visibleUsers,
+			uri
+		});
+	} finally {
+		unlock();
+	}
+}
--- a/packages/backend/src/remote/activitypub/kernel/block/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/block/index.ts
@ -0,0 +1,22 @@
+import { IBlock } from '../../type';
+import block from '@/services/blocking/create';
+import { IRemoteUser } from '@/models/entities/user';
+import DbResolver from '../../db-resolver';
+
+export default async (actor: IRemoteUser, activity: IBlock): Promise<string> => {
+	// ※ activity.objectにブロック対象があり、それは存在するローカルユーザーのはず
+
+	const dbResolver = new DbResolver();
+	const blockee = await dbResolver.getUserFromApId(activity.object);
+
+	if (blockee == null) {
+		return `skip: blockee not found`;
+	}
+
+	if (blockee.host != null) {
+		return `skip: ブロックしようとしているユーザーはローカルユーザーではありません`;
+	}
+
+	await block(actor, blockee);
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/create/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/create/index.ts
@ -0,0 +1,43 @@
+import Resolver from '../../resolver';
+import { IRemoteUser } from '@/models/entities/user';
+import createNote from './note';
+import { ICreate, getApId, isPost, getApType } from '../../type';
+import { apLogger } from '../../logger';
+import { toArray, concat, unique } from '@/prelude/array';
+
+const logger = apLogger;
+
+export default async (actor: IRemoteUser, activity: ICreate): Promise<void> => {
+	const uri = getApId(activity);
+
+	logger.info(`Create: ${uri}`);
+
+	// copy audiences between activity <=> object.
+	if (typeof activity.object === 'object') {
+		const to = unique(concat([toArray(activity.to), toArray(activity.object.to)]));
+		const cc = unique(concat([toArray(activity.cc), toArray(activity.object.cc)]));
+
+		activity.to = to;
+		activity.cc = cc;
+		activity.object.to = to;
+		activity.object.cc = cc;
+	}
+
+	// If there is no attributedTo, use Activity actor.
+	if (typeof activity.object === 'object' && !activity.object.attributedTo) {
+		activity.object.attributedTo = activity.actor;
+	}
+
+	const resolver = new Resolver();
+
+	const object = await resolver.resolve(activity.object).catch(e => {
+		logger.error(`Resolution failed: ${e}`);
+		throw e;
+	});
+
+	if (isPost(object)) {
+		createNote(resolver, actor, object, false, activity);
+	} else {
+		logger.warn(`Unknown type: ${getApType(object)}`);
+	}
+};
--- a/packages/backend/src/remote/activitypub/kernel/create/note.ts
+++ b/packages/backend/src/remote/activitypub/kernel/create/note.ts
@ -0,0 +1,44 @@
+import Resolver from '../../resolver';
+import { IRemoteUser } from '@/models/entities/user';
+import { createNote, fetchNote } from '../../models/note';
+import { getApId, IObject, ICreate } from '../../type';
+import { getApLock } from '@/misc/app-lock';
+import { extractDbHost } from '@/misc/convert-host';
+import { StatusError } from '@/misc/fetch';
+
+/**
+ * 投稿作成アクティビティを捌きます
+ */
+export default async function(resolver: Resolver, actor: IRemoteUser, note: IObject, silent = false, activity?: ICreate): Promise<string> {
+	const uri = getApId(note);
+
+	if (typeof note === 'object') {
+		if (actor.uri !== note.attributedTo) {
+			return `skip: actor.uri !== note.attributedTo`;
+		}
+
+		if (typeof note.id === 'string') {
+			if (extractDbHost(actor.uri) !== extractDbHost(note.id)) {
+				return `skip: host in actor.uri !== note.id`;
+			}
+		}
+	}
+
+	const unlock = await getApLock(uri);
+
+	try {
+		const exist = await fetchNote(note);
+		if (exist) return 'skip: note exists';
+
+		await createNote(note, resolver, silent);
+		return 'ok';
+	} catch (e) {
+		if (e instanceof StatusError && e.isClientError) {
+			return `skip ${e.statusCode}`;
+		} else {
+			throw e;
+		}
+	} finally {
+		unlock();
+	}
+}
--- a/packages/backend/src/remote/activitypub/kernel/delete/actor.ts
+++ b/packages/backend/src/remote/activitypub/kernel/delete/actor.ts
@ -0,0 +1,26 @@
+import { apLogger } from '../../logger';
+import { createDeleteAccountJob } from '@/queue';
+import { IRemoteUser } from '@/models/entities/user';
+import { Users } from '@/models/index';
+
+const logger = apLogger;
+
+export async function deleteActor(actor: IRemoteUser, uri: string): Promise<string> {
+	logger.info(`Deleting the Actor: ${uri}`);
+
+	if (actor.uri !== uri) {
+		return `skip: delete actor ${actor.uri} !== ${uri}`;
+	}
+
+	if (actor.isDeleted) {
+		logger.info(`skip: already deleted`);
+	}
+
+	const job = await createDeleteAccountJob(actor);
+
+	await Users.update(actor.id, {
+		isDeleted: true,
+	});
+
+	return `ok: queued ${job.name} ${job.id}`;
+}
--- a/packages/backend/src/remote/activitypub/kernel/delete/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/delete/index.ts
@ -0,0 +1,49 @@
+import deleteNote from './note';
+import { IRemoteUser } from '@/models/entities/user';
+import { IDelete, getApId, isTombstone, IObject, validPost, validActor } from '../../type';
+import { toSingle } from '@/prelude/array';
+import { deleteActor } from './actor';
+
+/**
+ * 削除アクティビティを捌きます
+ */
+export default async (actor: IRemoteUser, activity: IDelete): Promise<string> => {
+	if ('actor' in activity && actor.uri !== activity.actor) {
+		throw new Error('invalid actor');
+	}
+
+	// 削除対象objectのtype
+	let formarType: string | undefined;
+
+	if (typeof activity.object === 'string') {
+		// typeが不明だけど、どうせ消えてるのでremote resolveしない
+		formarType = undefined;
+	} else {
+		const object = activity.object as IObject;
+		if (isTombstone(object)) {
+			formarType = toSingle(object.formerType);
+		} else {
+			formarType = toSingle(object.type);
+		}
+	}
+
+	const uri = getApId(activity.object);
+
+	// type不明でもactorとobjectが同じならばそれはPersonに違いない
+	if (!formarType && actor.uri === uri) {
+		formarType = 'Person';
+	}
+
+	// それでもなかったらおそらくNote
+	if (!formarType) {
+		formarType = 'Note';
+	}
+
+	if (validPost.includes(formarType)) {
+		return await deleteNote(actor, uri);
+	} else if (validActor.includes(formarType)) {
+		return await deleteActor(actor, uri);
+	} else {
+		return `Unknown type ${formarType}`;
+	}
+};
--- a/packages/backend/src/remote/activitypub/kernel/delete/note.ts
+++ b/packages/backend/src/remote/activitypub/kernel/delete/note.ts
@ -0,0 +1,41 @@
+import { IRemoteUser } from '@/models/entities/user';
+import deleteNode from '@/services/note/delete';
+import { apLogger } from '../../logger';
+import DbResolver from '../../db-resolver';
+import { getApLock } from '@/misc/app-lock';
+import { deleteMessage } from '@/services/messages/delete';
+
+const logger = apLogger;
+
+export default async function(actor: IRemoteUser, uri: string): Promise<string> {
+	logger.info(`Deleting the Note: ${uri}`);
+
+	const unlock = await getApLock(uri);
+
+	try {
+		const dbResolver = new DbResolver();
+		const note = await dbResolver.getNoteFromApId(uri);
+
+		if (note == null) {
+			const message = await dbResolver.getMessageFromApId(uri);
+			if (message == null) return 'message not found';
+
+			if (message.userId !== actor.id) {
+				return '投稿を削除しようとしているユーザーは投稿の作成者ではありません';
+			}
+
+			await deleteMessage(message);
+
+			return 'ok: message deleted';
+		}
+
+		if (note.userId !== actor.id) {
+			return '投稿を削除しようとしているユーザーは投稿の作成者ではありません';
+		}
+
+		await deleteNode(actor, note);
+		return 'ok: note deleted';
+	} finally {
+		unlock();
+	}
+}
--- a/packages/backend/src/remote/activitypub/kernel/flag/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/flag/index.ts
@ -0,0 +1,30 @@
+import { IRemoteUser } from '@/models/entities/user';
+import config from '@/config/index';
+import { IFlag, getApIds } from '../../type';
+import { AbuseUserReports, Users } from '@/models/index';
+import { In } from 'typeorm';
+import { genId } from '@/misc/gen-id';
+
+export default async (actor: IRemoteUser, activity: IFlag): Promise<string> => {
+	// objectは `(User|Note) | (User|Note)[]` だけど、全パターンDBスキーマと対応させられないので
+	// 対象ユーザーは一番最初のユーザー として あとはコメントとして格納する
+	const uris = getApIds(activity.object);
+
+	const userIds = uris.filter(uri => uri.startsWith(config.url + '/users/')).map(uri => uri.split('/').pop());
+	const users = await Users.find({
+		id: In(userIds)
+	});
+	if (users.length < 1) return `skip`;
+
+	await AbuseUserReports.insert({
+		id: genId(),
+		createdAt: new Date(),
+		targetUserId: users[0].id,
+		targetUserHost: users[0].host,
+		reporterId: actor.id,
+		reporterHost: actor.host,
+		comment: `${activity.content}\n${JSON.stringify(uris, null, 2)}`
+	});
+
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/follow.ts
+++ b/packages/backend/src/remote/activitypub/kernel/follow.ts
@ -0,0 +1,20 @@
+import { IRemoteUser } from '@/models/entities/user';
+import follow from '@/services/following/create';
+import { IFollow } from '../type';
+import DbResolver from '../db-resolver';
+
+export default async (actor: IRemoteUser, activity: IFollow): Promise<string> => {
+	const dbResolver = new DbResolver();
+	const followee = await dbResolver.getUserFromApId(activity.object);
+
+	if (followee == null) {
+		return `skip: followee not found`;
+	}
+
+	if (followee.host != null) {
+		return `skip: フォローしようとしているユーザーはローカルユーザーではありません`;
+	}
+
+	await follow(actor, followee, activity.id);
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/index.ts
@ -0,0 +1,71 @@
+import { IObject, isCreate, isDelete, isUpdate, isRead, isFollow, isAccept, isReject, isAdd, isRemove, isAnnounce, isLike, isUndo, isBlock, isCollectionOrOrderedCollection, isCollection, isFlag } from '../type';
+import { IRemoteUser } from '@/models/entities/user';
+import create from './create/index';
+import performDeleteActivity from './delete/index';
+import performUpdateActivity from './update/index';
+import { performReadActivity } from './read';
+import follow from './follow';
+import undo from './undo/index';
+import like from './like';
+import announce from './announce/index';
+import accept from './accept/index';
+import reject from './reject/index';
+import add from './add/index';
+import remove from './remove/index';
+import block from './block/index';
+import flag from './flag/index';
+import { apLogger } from '../logger';
+import Resolver from '../resolver';
+import { toArray } from '@/prelude/array';
+
+export async function performActivity(actor: IRemoteUser, activity: IObject) {
+	if (isCollectionOrOrderedCollection(activity)) {
+		const resolver = new Resolver();
+		for (const item of toArray(isCollection(activity) ? activity.items : activity.orderedItems)) {
+			const act = await resolver.resolve(item);
+			try {
+				await performOneActivity(actor, act);
+			} catch (e) {
+				apLogger.error(e);
+			}
+		}
+	} else {
+		await performOneActivity(actor, activity);
+	}
+}
+
+async function performOneActivity(actor: IRemoteUser, activity: IObject): Promise<void> {
+	if (actor.isSuspended) return;
+
+	if (isCreate(activity)) {
+		await create(actor, activity);
+	} else if (isDelete(activity)) {
+		await performDeleteActivity(actor, activity);
+	} else if (isUpdate(activity)) {
+		await performUpdateActivity(actor, activity);
+	} else if (isRead(activity)) {
+		await performReadActivity(actor, activity);
+	} else if (isFollow(activity)) {
+		await follow(actor, activity);
+	} else if (isAccept(activity)) {
+		await accept(actor, activity);
+	} else if (isReject(activity)) {
+		await reject(actor, activity);
+	} else if (isAdd(activity)) {
+		await add(actor, activity).catch(err => apLogger.error(err));
+	} else if (isRemove(activity)) {
+		await remove(actor, activity).catch(err => apLogger.error(err));
+	} else if (isAnnounce(activity)) {
+		await announce(actor, activity);
+	} else if (isLike(activity)) {
+		await like(actor, activity);
+	} else if (isUndo(activity)) {
+		await undo(actor, activity);
+	} else if (isBlock(activity)) {
+		await block(actor, activity);
+	} else if (isFlag(activity)) {
+		await flag(actor, activity);
+	} else {
+		apLogger.warn(`unrecognized activity type: ${(activity as any).type}`);
+	}
+}
--- a/packages/backend/src/remote/activitypub/kernel/like.ts
+++ b/packages/backend/src/remote/activitypub/kernel/like.ts
@ -0,0 +1,21 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { ILike, getApId } from '../type';
+import create from '@/services/note/reaction/create';
+import { fetchNote, extractEmojis } from '../models/note';
+
+export default async (actor: IRemoteUser, activity: ILike) => {
+	const targetUri = getApId(activity.object);
+
+	const note = await fetchNote(targetUri);
+	if (!note) return `skip: target note not found ${targetUri}`;
+
+	await extractEmojis(activity.tag || [], actor.host).catch(() => null);
+
+	return await create(actor, note, activity._misskey_reaction || activity.content || activity.name).catch(e => {
+		if (e.id === '51c42bb4-931a-456b-bff7-e5a8a70dd298') {
+			return 'skip: already reacted';
+		} else {
+			throw e;
+		}
+	}).then(() => 'ok');
+};
--- a/packages/backend/src/remote/activitypub/kernel/move/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/move/index.ts
--- a/packages/backend/src/remote/activitypub/kernel/read.ts
+++ b/packages/backend/src/remote/activitypub/kernel/read.ts
@ -0,0 +1,27 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { IRead, getApId } from '../type';
+import { isSelfHost, extractDbHost } from '@/misc/convert-host';
+import { MessagingMessages } from '@/models/index';
+import { readUserMessagingMessage } from '../../../server/api/common/read-messaging-message';
+
+export const performReadActivity = async (actor: IRemoteUser, activity: IRead): Promise<string> => {
+	const id = await getApId(activity.object);
+
+	if (!isSelfHost(extractDbHost(id))) {
+		return `skip: Read to foreign host (${id})`;
+	}
+
+	const messageId = id.split('/').pop();
+
+	const message = await MessagingMessages.findOne(messageId);
+	if (message == null) {
+		return `skip: message not found`;
+	}
+
+	if (actor.id != message.recipientId) {
+		return `skip: actor is not a message recipient`;
+	}
+
+	await readUserMessagingMessage(message.recipientId!, message.userId, [message.id]);
+	return `ok: mark as read (${message.userId} => ${message.recipientId} ${message.id})`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/reject/follow.ts
+++ b/packages/backend/src/remote/activitypub/kernel/reject/follow.ts
@ -0,0 +1,29 @@
+import { IRemoteUser } from '@/models/entities/user';
+import reject from '@/services/following/requests/reject';
+import { IFollow } from '../../type';
+import DbResolver from '../../db-resolver';
+import { relayRejected } from '@/services/relay';
+
+export default async (actor: IRemoteUser, activity: IFollow): Promise<string> => {
+	// ※ activityはこっちから投げたフォローリクエストなので、activity.actorは存在するローカルユーザーである必要がある
+
+	const dbResolver = new DbResolver();
+	const follower = await dbResolver.getUserFromApId(activity.actor);
+
+	if (follower == null) {
+		return `skip: follower not found`;
+	}
+
+	if (follower.host != null) {
+		return `skip: follower is not a local user`;
+	}
+
+	// relay
+	const match = activity.id?.match(/follow-relay\/(\w+)/);
+	if (match) {
+		return await relayRejected(match[1]);
+	}
+
+	await reject(actor, follower);
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/reject/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/reject/index.ts
@ -0,0 +1,24 @@
+import Resolver from '../../resolver';
+import { IRemoteUser } from '@/models/entities/user';
+import rejectFollow from './follow';
+import { IReject, isFollow, getApType } from '../../type';
+import { apLogger } from '../../logger';
+
+const logger = apLogger;
+
+export default async (actor: IRemoteUser, activity: IReject): Promise<string> => {
+	const uri = activity.id || activity;
+
+	logger.info(`Reject: ${uri}`);
+
+	const resolver = new Resolver();
+
+	const object = await resolver.resolve(activity.object).catch(e => {
+		logger.error(`Resolution failed: ${e}`);
+		throw e;
+	});
+
+	if (isFollow(object)) return await rejectFollow(actor, object);
+
+	return `skip: Unknown Reject type: ${getApType(object)}`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/remove/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/remove/index.ts
@ -0,0 +1,23 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { IRemove } from '../../type';
+import { resolveNote } from '../../models/note';
+import { removePinned } from '@/services/i/pin';
+
+export default async (actor: IRemoteUser, activity: IRemove): Promise<void> => {
+	if ('actor' in activity && actor.uri !== activity.actor) {
+		throw new Error('invalid actor');
+	}
+
+	if (activity.target == null) {
+		throw new Error('target is null');
+	}
+
+	if (activity.target === actor.featured) {
+		const note = await resolveNote(activity.object);
+		if (note == null) throw new Error('note not found');
+		await removePinned(actor, note.id);
+		return;
+	}
+
+	throw new Error(`unknown target: ${activity.target}`);
+};
--- a/packages/backend/src/remote/activitypub/kernel/undo/announce.ts
+++ b/packages/backend/src/remote/activitypub/kernel/undo/announce.ts
@ -0,0 +1,17 @@
+import { Notes } from '@/models/index';
+import { IRemoteUser } from '@/models/entities/user';
+import { IAnnounce, getApId } from '../../type';
+import deleteNote from '@/services/note/delete';
+
+export const undoAnnounce = async (actor: IRemoteUser, activity: IAnnounce): Promise<string> => {
+	const uri = getApId(activity);
+
+	const note = await Notes.findOne({
+		uri
+	});
+
+	if (!note) return 'skip: no such Announce';
+
+	await deleteNote(actor, note);
+	return 'ok: deleted';
+};
--- a/packages/backend/src/remote/activitypub/kernel/undo/block.ts
+++ b/packages/backend/src/remote/activitypub/kernel/undo/block.ts
@ -0,0 +1,20 @@
+import { IBlock } from '../../type';
+import unblock from '@/services/blocking/delete';
+import { IRemoteUser } from '@/models/entities/user';
+import DbResolver from '../../db-resolver';
+
+export default async (actor: IRemoteUser, activity: IBlock): Promise<string> => {
+	const dbResolver = new DbResolver();
+	const blockee = await dbResolver.getUserFromApId(activity.object);
+
+	if (blockee == null) {
+		return `skip: blockee not found`;
+	}
+
+	if (blockee.host != null) {
+		return `skip: ブロック解除しようとしているユーザーはローカルユーザーではありません`;
+	}
+
+	await unblock(actor, blockee);
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/undo/follow.ts
+++ b/packages/backend/src/remote/activitypub/kernel/undo/follow.ts
@ -0,0 +1,41 @@
+import unfollow from '@/services/following/delete';
+import cancelRequest from '@/services/following/requests/cancel';
+import { IFollow } from '../../type';
+import { IRemoteUser } from '@/models/entities/user';
+import { FollowRequests, Followings } from '@/models/index';
+import DbResolver from '../../db-resolver';
+
+export default async (actor: IRemoteUser, activity: IFollow): Promise<string> => {
+	const dbResolver = new DbResolver();
+
+	const followee = await dbResolver.getUserFromApId(activity.object);
+	if (followee == null) {
+		return `skip: followee not found`;
+	}
+
+	if (followee.host != null) {
+		return `skip: フォロー解除しようとしているユーザーはローカルユーザーではありません`;
+	}
+
+	const req = await FollowRequests.findOne({
+		followerId: actor.id,
+		followeeId: followee.id
+	});
+
+	const following = await Followings.findOne({
+		followerId: actor.id,
+		followeeId: followee.id
+	});
+
+	if (req) {
+		await cancelRequest(followee, actor);
+		return `ok: follow request canceled`;
+	}
+
+	if (following) {
+		await unfollow(actor, followee);
+		return `ok: unfollowed`;
+	}
+
+	return `skip: リクエストもフォローもされていない`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/undo/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/undo/index.ts
@ -0,0 +1,34 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { IUndo, isFollow, isBlock, isLike, isAnnounce, getApType } from '../../type';
+import unfollow from './follow';
+import unblock from './block';
+import undoLike from './like';
+import { undoAnnounce } from './announce';
+import Resolver from '../../resolver';
+import { apLogger } from '../../logger';
+
+const logger = apLogger;
+
+export default async (actor: IRemoteUser, activity: IUndo): Promise<string> => {
+	if ('actor' in activity && actor.uri !== activity.actor) {
+		throw new Error('invalid actor');
+	}
+
+	const uri = activity.id || activity;
+
+	logger.info(`Undo: ${uri}`);
+
+	const resolver = new Resolver();
+
+	const object = await resolver.resolve(activity.object).catch(e => {
+		logger.error(`Resolution failed: ${e}`);
+		throw e;
+	});
+
+	if (isFollow(object)) return await unfollow(actor, object);
+	if (isBlock(object)) return await unblock(actor, object);
+	if (isLike(object)) return await undoLike(actor, object);
+	if (isAnnounce(object)) return await undoAnnounce(actor, object);
+
+	return `skip: unknown object type ${getApType(object)}`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/undo/like.ts
+++ b/packages/backend/src/remote/activitypub/kernel/undo/like.ts
@ -0,0 +1,21 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { ILike, getApId } from '../../type';
+import deleteReaction from '@/services/note/reaction/delete';
+import { fetchNote } from '../../models/note';
+
+/**
+ * Process Undo.Like activity
+ */
+export default async (actor: IRemoteUser, activity: ILike) => {
+	const targetUri = getApId(activity.object);
+
+	const note = await fetchNote(targetUri);
+	if (!note) return `skip: target note not found ${targetUri}`;
+
+	await deleteReaction(actor, note).catch(e => {
+		if (e.id === '60527ec9-b4cb-4a88-a6bd-32d3ad26817d') return;
+		throw e;
+	});
+
+	return `ok`;
+};
--- a/packages/backend/src/remote/activitypub/kernel/update/index.ts
+++ b/packages/backend/src/remote/activitypub/kernel/update/index.ts
@ -0,0 +1,34 @@
+import { IRemoteUser } from '@/models/entities/user';
+import { getApType, IUpdate, isActor } from '../../type';
+import { apLogger } from '../../logger';
+import { updateQuestion } from '../../models/question';
+import Resolver from '../../resolver';
+import { updatePerson } from '../../models/person';
+
+/**
+ * Updateアクティビティを捌きます
+ */
+export default async (actor: IRemoteUser, activity: IUpdate): Promise<string> => {
+	if ('actor' in activity && actor.uri !== activity.actor) {
+		return `skip: invalid actor`;
+	}
+
+	apLogger.debug('Update');
+
+	const resolver = new Resolver();
+
+	const object = await resolver.resolve(activity.object).catch(e => {
+		apLogger.error(`Resolution failed: ${e}`);
+		throw e;
+	});
+
+	if (isActor(object)) {
+		await updatePerson(actor.uri!, resolver, object);
+		return `ok: Person updated`;
+	} else if (getApType(object) === 'Question') {
+		await updateQuestion(object).catch(e => console.log(e));
+		return `ok: Question updated`;
+	} else {
+		return `skip: Unknown type: ${getApType(object)}`;
+	}
+};
--- a/packages/backend/src/remote/activitypub/logger.ts
+++ b/packages/backend/src/remote/activitypub/logger.ts
@ -0,0 +1,3 @@
+import { remoteLogger } from '../logger';
+
+export const apLogger = remoteLogger.createSubLogger('ap', 'magenta');
--- a/packages/backend/src/remote/activitypub/misc/contexts.ts
+++ b/packages/backend/src/remote/activitypub/misc/contexts.ts
@ -0,0 +1,526 @@
+/* tslint:disable:quotemark indent */
+const id_v1 = {
+  "@context": {
+    "id": "@id",
+    "type": "@type",
+
+    "cred": "https://w3id.org/credentials#",
+    "dc": "http://purl.org/dc/terms/",
+    "identity": "https://w3id.org/identity#",
+    "perm": "https://w3id.org/permissions#",
+    "ps": "https://w3id.org/payswarm#",
+    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+    "rdfs": "http://www.w3.org/2000/01/rdf-schema#",
+    "sec": "https://w3id.org/security#",
+    "schema": "http://schema.org/",
+    "xsd": "http://www.w3.org/2001/XMLSchema#",
+
+    "Group": "https://www.w3.org/ns/activitystreams#Group",
+
+    "claim": {"@id": "cred:claim", "@type": "@id"},
+    "credential": {"@id": "cred:credential", "@type": "@id"},
+    "issued": {"@id": "cred:issued", "@type": "xsd:dateTime"},
+    "issuer": {"@id": "cred:issuer", "@type": "@id"},
+    "recipient": {"@id": "cred:recipient", "@type": "@id"},
+    "Credential": "cred:Credential",
+    "CryptographicKeyCredential": "cred:CryptographicKeyCredential",
+
+    "about": {"@id": "schema:about", "@type": "@id"},
+    "address": {"@id": "schema:address", "@type": "@id"},
+    "addressCountry": "schema:addressCountry",
+    "addressLocality": "schema:addressLocality",
+    "addressRegion": "schema:addressRegion",
+    "comment": "rdfs:comment",
+    "created": {"@id": "dc:created", "@type": "xsd:dateTime"},
+    "creator": {"@id": "dc:creator", "@type": "@id"},
+    "description": "schema:description",
+    "email": "schema:email",
+    "familyName": "schema:familyName",
+    "givenName": "schema:givenName",
+    "image": {"@id": "schema:image", "@type": "@id"},
+    "label": "rdfs:label",
+    "name": "schema:name",
+    "postalCode": "schema:postalCode",
+    "streetAddress": "schema:streetAddress",
+    "title": "dc:title",
+    "url": {"@id": "schema:url", "@type": "@id"},
+    "Person": "schema:Person",
+    "PostalAddress": "schema:PostalAddress",
+    "Organization": "schema:Organization",
+
+    "identityService": {"@id": "identity:identityService", "@type": "@id"},
+    "idp": {"@id": "identity:idp", "@type": "@id"},
+    "Identity": "identity:Identity",
+
+    "paymentProcessor": "ps:processor",
+    "preferences": {"@id": "ps:preferences", "@type": "@vocab"},
+
+    "cipherAlgorithm": "sec:cipherAlgorithm",
+    "cipherData": "sec:cipherData",
+    "cipherKey": "sec:cipherKey",
+    "digestAlgorithm": "sec:digestAlgorithm",
+    "digestValue": "sec:digestValue",
+    "domain": "sec:domain",
+    "expires": {"@id": "sec:expiration", "@type": "xsd:dateTime"},
+    "initializationVector": "sec:initializationVector",
+    "member": {"@id": "schema:member", "@type": "@id"},
+    "memberOf": {"@id": "schema:memberOf", "@type": "@id"},
+    "nonce": "sec:nonce",
+    "normalizationAlgorithm": "sec:normalizationAlgorithm",
+    "owner": {"@id": "sec:owner", "@type": "@id"},
+    "password": "sec:password",
+    "privateKey": {"@id": "sec:privateKey", "@type": "@id"},
+    "privateKeyPem": "sec:privateKeyPem",
+    "publicKey": {"@id": "sec:publicKey", "@type": "@id"},
+    "publicKeyPem": "sec:publicKeyPem",
+    "publicKeyService": {"@id": "sec:publicKeyService", "@type": "@id"},
+    "revoked": {"@id": "sec:revoked", "@type": "xsd:dateTime"},
+    "signature": "sec:signature",
+    "signatureAlgorithm": "sec:signatureAlgorithm",
+    "signatureValue": "sec:signatureValue",
+    "CryptographicKey": "sec:Key",
+    "EncryptedMessage": "sec:EncryptedMessage",
+    "GraphSignature2012": "sec:GraphSignature2012",
+    "LinkedDataSignature2015": "sec:LinkedDataSignature2015",
+
+    "accessControl": {"@id": "perm:accessControl", "@type": "@id"},
+    "writePermission": {"@id": "perm:writePermission", "@type": "@id"}
+  }
+};
+
+const security_v1 = {
+  "@context": {
+    "id": "@id",
+    "type": "@type",
+
+    "dc": "http://purl.org/dc/terms/",
+    "sec": "https://w3id.org/security#",
+    "xsd": "http://www.w3.org/2001/XMLSchema#",
+
+    "EcdsaKoblitzSignature2016": "sec:EcdsaKoblitzSignature2016",
+    "Ed25519Signature2018": "sec:Ed25519Signature2018",
+    "EncryptedMessage": "sec:EncryptedMessage",
+    "GraphSignature2012": "sec:GraphSignature2012",
+    "LinkedDataSignature2015": "sec:LinkedDataSignature2015",
+    "LinkedDataSignature2016": "sec:LinkedDataSignature2016",
+    "CryptographicKey": "sec:Key",
+
+    "authenticationTag": "sec:authenticationTag",
+    "canonicalizationAlgorithm": "sec:canonicalizationAlgorithm",
+    "cipherAlgorithm": "sec:cipherAlgorithm",
+    "cipherData": "sec:cipherData",
+    "cipherKey": "sec:cipherKey",
+    "created": {"@id": "dc:created", "@type": "xsd:dateTime"},
+    "creator": {"@id": "dc:creator", "@type": "@id"},
+    "digestAlgorithm": "sec:digestAlgorithm",
+    "digestValue": "sec:digestValue",
+    "domain": "sec:domain",
+    "encryptionKey": "sec:encryptionKey",
+    "expiration": {"@id": "sec:expiration", "@type": "xsd:dateTime"},
+    "expires": {"@id": "sec:expiration", "@type": "xsd:dateTime"},
+    "initializationVector": "sec:initializationVector",
+    "iterationCount": "sec:iterationCount",
+    "nonce": "sec:nonce",
+    "normalizationAlgorithm": "sec:normalizationAlgorithm",
+    "owner": {"@id": "sec:owner", "@type": "@id"},
+    "password": "sec:password",
+    "privateKey": {"@id": "sec:privateKey", "@type": "@id"},
+    "privateKeyPem": "sec:privateKeyPem",
+    "publicKey": {"@id": "sec:publicKey", "@type": "@id"},
+    "publicKeyBase58": "sec:publicKeyBase58",
+    "publicKeyPem": "sec:publicKeyPem",
+    "publicKeyWif": "sec:publicKeyWif",
+    "publicKeyService": {"@id": "sec:publicKeyService", "@type": "@id"},
+    "revoked": {"@id": "sec:revoked", "@type": "xsd:dateTime"},
+    "salt": "sec:salt",
+    "signature": "sec:signature",
+    "signatureAlgorithm": "sec:signingAlgorithm",
+    "signatureValue": "sec:signatureValue"
+  }
+};
+
+const activitystreams = {
+  "@context": {
+    "@vocab": "_:",
+    "xsd": "http://www.w3.org/2001/XMLSchema#",
+    "as": "https://www.w3.org/ns/activitystreams#",
+    "ldp": "http://www.w3.org/ns/ldp#",
+    "vcard": "http://www.w3.org/2006/vcard/ns#",
+    "id": "@id",
+    "type": "@type",
+    "Accept": "as:Accept",
+    "Activity": "as:Activity",
+    "IntransitiveActivity": "as:IntransitiveActivity",
+    "Add": "as:Add",
+    "Announce": "as:Announce",
+    "Application": "as:Application",
+    "Arrive": "as:Arrive",
+    "Article": "as:Article",
+    "Audio": "as:Audio",
+    "Block": "as:Block",
+    "Collection": "as:Collection",
+    "CollectionPage": "as:CollectionPage",
+    "Relationship": "as:Relationship",
+    "Create": "as:Create",
+    "Delete": "as:Delete",
+    "Dislike": "as:Dislike",
+    "Document": "as:Document",
+    "Event": "as:Event",
+    "Follow": "as:Follow",
+    "Flag": "as:Flag",
+    "Group": "as:Group",
+    "Ignore": "as:Ignore",
+    "Image": "as:Image",
+    "Invite": "as:Invite",
+    "Join": "as:Join",
+    "Leave": "as:Leave",
+    "Like": "as:Like",
+    "Link": "as:Link",
+    "Mention": "as:Mention",
+    "Note": "as:Note",
+    "Object": "as:Object",
+    "Offer": "as:Offer",
+    "OrderedCollection": "as:OrderedCollection",
+    "OrderedCollectionPage": "as:OrderedCollectionPage",
+    "Organization": "as:Organization",
+    "Page": "as:Page",
+    "Person": "as:Person",
+    "Place": "as:Place",
+    "Profile": "as:Profile",
+    "Question": "as:Question",
+    "Reject": "as:Reject",
+    "Remove": "as:Remove",
+    "Service": "as:Service",
+    "TentativeAccept": "as:TentativeAccept",
+    "TentativeReject": "as:TentativeReject",
+    "Tombstone": "as:Tombstone",
+    "Undo": "as:Undo",
+    "Update": "as:Update",
+    "Video": "as:Video",
+    "View": "as:View",
+    "Listen": "as:Listen",
+    "Read": "as:Read",
+    "Move": "as:Move",
+    "Travel": "as:Travel",
+    "IsFollowing": "as:IsFollowing",
+    "IsFollowedBy": "as:IsFollowedBy",
+    "IsContact": "as:IsContact",
+    "IsMember": "as:IsMember",
+    "subject": {
+      "@id": "as:subject",
+      "@type": "@id"
+    },
+    "relationship": {
+      "@id": "as:relationship",
+      "@type": "@id"
+    },
+    "actor": {
+      "@id": "as:actor",
+      "@type": "@id"
+    },
+    "attributedTo": {
+      "@id": "as:attributedTo",
+      "@type": "@id"
+    },
+    "attachment": {
+      "@id": "as:attachment",
+      "@type": "@id"
+    },
+    "bcc": {
+      "@id": "as:bcc",
+      "@type": "@id"
+    },
+    "bto": {
+      "@id": "as:bto",
+      "@type": "@id"
+    },
+    "cc": {
+      "@id": "as:cc",
+      "@type": "@id"
+    },
+    "context": {
+      "@id": "as:context",
+      "@type": "@id"
+    },
+    "current": {
+      "@id": "as:current",
+      "@type": "@id"
+    },
+    "first": {
+      "@id": "as:first",
+      "@type": "@id"
+    },
+    "generator": {
+      "@id": "as:generator",
+      "@type": "@id"
+    },
+    "icon": {
+      "@id": "as:icon",
+      "@type": "@id"
+    },
+    "image": {
+      "@id": "as:image",
+      "@type": "@id"
+    },
+    "inReplyTo": {
+      "@id": "as:inReplyTo",
+      "@type": "@id"
+    },
+    "items": {
+      "@id": "as:items",
+      "@type": "@id"
+    },
+    "instrument": {
+      "@id": "as:instrument",
+      "@type": "@id"
+    },
+    "orderedItems": {
+      "@id": "as:items",
+      "@type": "@id",
+      "@container": "@list"
+    },
+    "last": {
+      "@id": "as:last",
+      "@type": "@id"
+    },
+    "location": {
+      "@id": "as:location",
+      "@type": "@id"
+    },
+    "next": {
+      "@id": "as:next",
+      "@type": "@id"
+    },
+    "object": {
+      "@id": "as:object",
+      "@type": "@id"
+    },
+    "oneOf": {
+      "@id": "as:oneOf",
+      "@type": "@id"
+    },
+    "anyOf": {
+      "@id": "as:anyOf",
+      "@type": "@id"
+    },
+    "closed": {
+      "@id": "as:closed",
+      "@type": "xsd:dateTime"
+    },
+    "origin": {
+      "@id": "as:origin",
+      "@type": "@id"
+    },
+    "accuracy": {
+      "@id": "as:accuracy",
+      "@type": "xsd:float"
+    },
+    "prev": {
+      "@id": "as:prev",
+      "@type": "@id"
+    },
+    "preview": {
+      "@id": "as:preview",
+      "@type": "@id"
+    },
+    "replies": {
+      "@id": "as:replies",
+      "@type": "@id"
+    },
+    "result": {
+      "@id": "as:result",
+      "@type": "@id"
+    },
+    "audience": {
+      "@id": "as:audience",
+      "@type": "@id"
+    },
+    "partOf": {
+      "@id": "as:partOf",
+      "@type": "@id"
+    },
+    "tag": {
+      "@id": "as:tag",
+      "@type": "@id"
+    },
+    "target": {
+      "@id": "as:target",
+      "@type": "@id"
+    },
+    "to": {
+      "@id": "as:to",
+      "@type": "@id"
+    },
+    "url": {
+      "@id": "as:url",
+      "@type": "@id"
+    },
+    "altitude": {
+      "@id": "as:altitude",
+      "@type": "xsd:float"
+    },
+    "content": "as:content",
+    "contentMap": {
+      "@id": "as:content",
+      "@container": "@language"
+    },
+    "name": "as:name",
+    "nameMap": {
+      "@id": "as:name",
+      "@container": "@language"
+    },
+    "duration": {
+      "@id": "as:duration",
+      "@type": "xsd:duration"
+    },
+    "endTime": {
+      "@id": "as:endTime",
+      "@type": "xsd:dateTime"
+    },
+    "height": {
+      "@id": "as:height",
+      "@type": "xsd:nonNegativeInteger"
+    },
+    "href": {
+      "@id": "as:href",
+      "@type": "@id"
+    },
+    "hreflang": "as:hreflang",
+    "latitude": {
+      "@id": "as:latitude",
+      "@type": "xsd:float"
+    },
+    "longitude": {
+      "@id": "as:longitude",
+      "@type": "xsd:float"
+    },
+    "mediaType": "as:mediaType",
+    "published": {
+      "@id": "as:published",
+      "@type": "xsd:dateTime"
+    },
+    "radius": {
+      "@id": "as:radius",
+      "@type": "xsd:float"
+    },
+    "rel": "as:rel",
+    "startIndex": {
+      "@id": "as:startIndex",
+      "@type": "xsd:nonNegativeInteger"
+    },
+    "startTime": {
+      "@id": "as:startTime",
+      "@type": "xsd:dateTime"
+    },
+    "summary": "as:summary",
+    "summaryMap": {
+      "@id": "as:summary",
+      "@container": "@language"
+    },
+    "totalItems": {
+      "@id": "as:totalItems",
+      "@type": "xsd:nonNegativeInteger"
+    },
+    "units": "as:units",
+    "updated": {
+      "@id": "as:updated",
+      "@type": "xsd:dateTime"
+    },
+    "width": {
+      "@id": "as:width",
+      "@type": "xsd:nonNegativeInteger"
+    },
+    "describes": {
+      "@id": "as:describes",
+      "@type": "@id"
+    },
+    "formerType": {
+      "@id": "as:formerType",
+      "@type": "@id"
+    },
+    "deleted": {
+      "@id": "as:deleted",
+      "@type": "xsd:dateTime"
+    },
+    "inbox": {
+      "@id": "ldp:inbox",
+      "@type": "@id"
+    },
+    "outbox": {
+      "@id": "as:outbox",
+      "@type": "@id"
+    },
+    "following": {
+      "@id": "as:following",
+      "@type": "@id"
+    },
+    "followers": {
+      "@id": "as:followers",
+      "@type": "@id"
+    },
+    "streams": {
+      "@id": "as:streams",
+      "@type": "@id"
+    },
+    "preferredUsername": "as:preferredUsername",
+    "endpoints": {
+      "@id": "as:endpoints",
+      "@type": "@id"
+    },
+    "uploadMedia": {
+      "@id": "as:uploadMedia",
+      "@type": "@id"
+    },
+    "proxyUrl": {
+      "@id": "as:proxyUrl",
+      "@type": "@id"
+    },
+    "liked": {
+      "@id": "as:liked",
+      "@type": "@id"
+    },
+    "oauthAuthorizationEndpoint": {
+      "@id": "as:oauthAuthorizationEndpoint",
+      "@type": "@id"
+    },
+    "oauthTokenEndpoint": {
+      "@id": "as:oauthTokenEndpoint",
+      "@type": "@id"
+    },
+    "provideClientKey": {
+      "@id": "as:provideClientKey",
+      "@type": "@id"
+    },
+    "signClientKey": {
+      "@id": "as:signClientKey",
+      "@type": "@id"
+    },
+    "sharedInbox": {
+      "@id": "as:sharedInbox",
+      "@type": "@id"
+    },
+    "Public": {
+      "@id": "as:Public",
+      "@type": "@id"
+    },
+    "source": "as:source",
+    "likes": {
+      "@id": "as:likes",
+      "@type": "@id"
+    },
+    "shares": {
+      "@id": "as:shares",
+      "@type": "@id"
+    },
+    "alsoKnownAs": {
+      "@id": "as:alsoKnownAs",
+      "@type": "@id"
+    }
+  }
+};
+
+export const CONTEXTS: Record<string, any> = {
+  "https://w3id.org/identity/v1": id_v1,
+  "https://w3id.org/security/v1": security_v1,
+  "https://www.w3.org/ns/activitystreams": activitystreams,
+};
--- a/packages/backend/src/remote/activitypub/misc/get-note-html.ts
+++ b/packages/backend/src/remote/activitypub/misc/get-note-html.ts
@ -0,0 +1,10 @@
+import * as mfm from 'mfm-js';
+import { Note } from '@/models/entities/note';
+import { toHtml } from '../../../mfm/to-html';
+
+export default function(note: Note) {
+	let html = note.text ? toHtml(mfm.parse(note.text), JSON.parse(note.mentionedRemoteUsers)) : null;
+	if (html == null) html = '<p>.</p>';
+
+	return html;
+}
--- a/packages/backend/src/remote/activitypub/misc/html-to-mfm.ts
+++ b/packages/backend/src/remote/activitypub/misc/html-to-mfm.ts
@ -0,0 +1,9 @@
+import { IObject } from '../type';
+import { extractApHashtagObjects } from '../models/tag';
+import { fromHtml } from '../../../mfm/from-html';
+
+export function htmlToMfm(html: string, tag?: IObject | IObject[]) {
+	const hashtagNames = extractApHashtagObjects(tag).map(x => x.name).filter((x): x is string => x != null);
+
+	return fromHtml(html, hashtagNames);
+}
--- a/packages/backend/src/remote/activitypub/misc/ld-signature.ts
+++ b/packages/backend/src/remote/activitypub/misc/ld-signature.ts
@ -0,0 +1,134 @@
+import * as crypto from 'crypto';
+import * as jsonld from 'jsonld';
+import { CONTEXTS } from './contexts';
+import fetch from 'node-fetch';
+import { httpAgent, httpsAgent } from '@/misc/fetch';
+
+// RsaSignature2017 based from https://github.com/transmute-industries/RsaSignature2017
+
+export class LdSignature {
+	public debug = false;
+	public preLoad = true;
+	public loderTimeout = 10 * 1000;
+
+	constructor() {
+	}
+
+	public async signRsaSignature2017(data: any, privateKey: string, creator: string, domain?: string, created?: Date): Promise<any> {
+		const options = {
+			type: 'RsaSignature2017',
+			creator,
+			domain,
+			nonce: crypto.randomBytes(16).toString('hex'),
+			created: (created || new Date()).toISOString()
+		} as {
+			type: string;
+			creator: string;
+			domain: string;
+			nonce: string;
+			created: string;
+		};
+
+		if (!domain) {
+			delete options.domain;
+		}
+
+		const toBeSigned = await this.createVerifyData(data, options);
+
+		const signer = crypto.createSign('sha256');
+		signer.update(toBeSigned);
+		signer.end();
+
+		const signature = signer.sign(privateKey);
+
+		return {
+			...data,
+			signature: {
+				...options,
+				signatureValue: signature.toString('base64')
+			}
+		};
+	}
+
+	public async verifyRsaSignature2017(data: any, publicKey: string): Promise<boolean> {
+		const toBeSigned = await this.createVerifyData(data, data.signature);
+		const verifier = crypto.createVerify('sha256');
+		verifier.update(toBeSigned);
+		return verifier.verify(publicKey, data.signature.signatureValue, 'base64');
+	}
+
+	public async createVerifyData(data: any, options: any) {
+		const transformedOptions = {
+			...options,
+			'@context': 'https://w3id.org/identity/v1'
+		};
+		delete transformedOptions['type'];
+		delete transformedOptions['id'];
+		delete transformedOptions['signatureValue'];
+		const canonizedOptions = await this.normalize(transformedOptions);
+		const optionsHash = this.sha256(canonizedOptions);
+		const transformedData = { ...data };
+		delete transformedData['signature'];
+		const cannonidedData = await this.normalize(transformedData);
+		if (this.debug) console.debug(`cannonidedData: ${cannonidedData}`);
+		const documentHash = this.sha256(cannonidedData);
+		const verifyData = `${optionsHash}${documentHash}`;
+		return verifyData;
+	}
+
+	public async normalize(data: any) {
+		const customLoader = this.getLoader();
+		return await jsonld.normalize(data, {
+			documentLoader: customLoader
+		});
+	}
+
+	private getLoader() {
+		return async (url: string): Promise<any> => {
+			if (!url.match('^https?\:\/\/')) throw `Invalid URL ${url}`;
+
+			if (this.preLoad) {
+				if (url in CONTEXTS) {
+					if (this.debug) console.debug(`HIT: ${url}`);
+					return {
+						contextUrl: null,
+						document: CONTEXTS[url],
+						documentUrl: url
+					};
+				}
+			}
+
+			if (this.debug) console.debug(`MISS: ${url}`);
+			const document = await this.fetchDocument(url);
+			return {
+				contextUrl: null,
+				document: document,
+				documentUrl: url
+			};
+		};
+	}
+
+	private async fetchDocument(url: string) {
+		const json = await fetch(url, {
+			headers: {
+				Accept: 'application/ld+json, application/json',
+			},
+			timeout: this.loderTimeout,
+			agent: u => u.protocol == 'http:' ? httpAgent : httpsAgent,
+		}).then(res => {
+			if (!res.ok) {
+				throw `${res.status} ${res.statusText}`;
+			} else {
+				return res.json();
+			}
+		});
+
+		return json;
+	}
+
+	public sha256(data: string): string {
+		const hash = crypto.createHash('sha256');
+		hash.update(data);
+		return hash.digest('hex');
+	}
+}
--- a/packages/backend/src/remote/activitypub/models/icon.ts
+++ b/packages/backend/src/remote/activitypub/models/icon.ts
@ -0,0 +1,5 @@
+export type IIcon = {
+	type: string;
+	mediaType?: string;
+	url?: string;
+};
--- a/packages/backend/src/remote/activitypub/models/identifier.ts
+++ b/packages/backend/src/remote/activitypub/models/identifier.ts
@ -0,0 +1,5 @@
+export type IIdentifier = {
+	type: string;
+	name: string;
+	value: string;
+};
--- a/packages/backend/src/remote/activitypub/models/image.ts
+++ b/packages/backend/src/remote/activitypub/models/image.ts
@ -0,0 +1,62 @@
+import uploadFromUrl from '@/services/drive/upload-from-url';
+import { IRemoteUser } from '@/models/entities/user';
+import Resolver from '../resolver';
+import { fetchMeta } from '@/misc/fetch-meta';
+import { apLogger } from '../logger';
+import { DriveFile } from '@/models/entities/drive-file';
+import { DriveFiles } from '@/models/index';
+import { truncate } from '@/misc/truncate';
+import { DB_MAX_IMAGE_COMMENT_LENGTH } from '@/misc/hard-limits';
+
+const logger = apLogger;
+
+/**
+ * Imageを作成します。
+ */
+export async function createImage(actor: IRemoteUser, value: any): Promise<DriveFile> {
+	// 投稿者が凍結されていたらスキップ
+	if (actor.isSuspended) {
+		throw new Error('actor has been suspended');
+	}
+
+	const image = await new Resolver().resolve(value) as any;
+
+	if (image.url == null) {
+		throw new Error('invalid image: url not privided');
+	}
+
+	logger.info(`Creating the Image: ${image.url}`);
+
+	const instance = await fetchMeta();
+	const cache = instance.cacheRemoteFiles;
+
+	let file = await uploadFromUrl(image.url, actor, null, image.url, image.sensitive, false, !cache, truncate(image.name, DB_MAX_IMAGE_COMMENT_LENGTH));
+
+	if (file.isLink) {
+		// URLが異なっている場合、同じ画像が以前に異なるURLで登録されていたということなので、
+		// URLを更新する
+		if (file.url !== image.url) {
+			await DriveFiles.update({ id: file.id }, {
+				url: image.url,
+				uri: image.url
+			});
+
+			file = await DriveFiles.findOneOrFail(file.id);
+		}
+	}
+
+	return file;
+}
+
+/**
+ * Imageを解決します。
+ *
+ * Misskeyに対象のImageが登録されていればそれを返し、そうでなければ
+ * リモートサーバーからフェッチしてMisskeyに登録しそれを返します。
+ */
+export async function resolveImage(actor: IRemoteUser, value: any): Promise<DriveFile> {
+	// TODO
+
+	// リモートサーバーからフェッチしてきて登録
+	return await createImage(actor, value);
+}
--- a/packages/backend/src/remote/activitypub/models/mention.ts
+++ b/packages/backend/src/remote/activitypub/models/mention.ts
@ -0,0 +1,24 @@
+import { toArray, unique } from '@/prelude/array';
+import { IObject, isMention, IApMention } from '../type';
+import { resolvePerson } from './person';
+import * as promiseLimit from 'promise-limit';
+import Resolver from '../resolver';
+import { User } from '@/models/entities/user';
+
+export async function extractApMentions(tags: IObject | IObject[] | null | undefined) {
+	const hrefs = unique(extractApMentionObjects(tags).map(x => x.href as string));
+
+	const resolver = new Resolver();
+
+	const limit = promiseLimit<User | null>(2);
+	const mentionedUsers = (await Promise.all(
+		hrefs.map(x => limit(() => resolvePerson(x, resolver).catch(() => null)))
+	)).filter((x): x is User => x != null);
+
+	return mentionedUsers;
+}
+
+export function extractApMentionObjects(tags: IObject | IObject[] | null | undefined): IApMention[] {
+	if (tags == null) return [];
+	return toArray(tags).filter(isMention);
+}
--- a/packages/backend/src/remote/activitypub/models/note.ts
+++ b/packages/backend/src/remote/activitypub/models/note.ts
@ -0,0 +1,356 @@
+import * as promiseLimit from 'promise-limit';
+
+import config from '@/config/index';
+import Resolver from '../resolver';
+import post from '@/services/note/create';
+import { resolvePerson, updatePerson } from './person';
+import { resolveImage } from './image';
+import { IRemoteUser } from '@/models/entities/user';
+import { htmlToMfm } from '../misc/html-to-mfm';
+import { extractApHashtags } from './tag';
+import { unique, toArray, toSingle } from '@/prelude/array';
+import { extractPollFromQuestion } from './question';
+import vote from '@/services/note/polls/vote';
+import { apLogger } from '../logger';
+import { DriveFile } from '@/models/entities/drive-file';
+import { deliverQuestionUpdate } from '@/services/note/polls/update';
+import { extractDbHost, toPuny } from '@/misc/convert-host';
+import { Emojis, Polls, MessagingMessages } from '@/models/index';
+import { Note } from '@/models/entities/note';
+import { IObject, getOneApId, getApId, getOneApHrefNullable, validPost, IPost, isEmoji, getApType } from '../type';
+import { Emoji } from '@/models/entities/emoji';
+import { genId } from '@/misc/gen-id';
+import { fetchMeta } from '@/misc/fetch-meta';
+import { getApLock } from '@/misc/app-lock';
+import { createMessage } from '@/services/messages/create';
+import { parseAudience } from '../audience';
+import { extractApMentions } from './mention';
+import DbResolver from '../db-resolver';
+import { StatusError } from '@/misc/fetch';
+
+const logger = apLogger;
+
+export function validateNote(object: any, uri: string) {
+	const expectHost = extractDbHost(uri);
+
+	if (object == null) {
+		return new Error('invalid Note: object is null');
+	}
+
+	if (!validPost.includes(getApType(object))) {
+		return new Error(`invalid Note: invalid object type ${getApType(object)}`);
+	}
+
+	if (object.id && extractDbHost(object.id) !== expectHost) {
+		return new Error(`invalid Note: id has different host. expected: ${expectHost}, actual: ${extractDbHost(object.id)}`);
+	}
+
+	if (object.attributedTo && extractDbHost(getOneApId(object.attributedTo)) !== expectHost) {
+		return new Error(`invalid Note: attributedTo has different host. expected: ${expectHost}, actual: ${extractDbHost(object.attributedTo)}`);
+	}
+
+	return null;
+}
+
+/**
+ * Noteをフェッチします。
+ *
+ * Misskeyに対象のNoteが登録されていればそれを返します。
+ */
+export async function fetchNote(object: string | IObject): Promise<Note | null> {
+	const dbResolver = new DbResolver();
+	return await dbResolver.getNoteFromApId(object);
+}
+
+/**
+ * Noteを作成します。
+ */
+export async function createNote(value: string | IObject, resolver?: Resolver, silent = false): Promise<Note | null> {
+	if (resolver == null) resolver = new Resolver();
+
+	const object: any = await resolver.resolve(value);
+
+	const entryUri = getApId(value);
+	const err = validateNote(object, entryUri);
+	if (err) {
+		logger.error(`${err.message}`, {
+			resolver: {
+				history: resolver.getHistory()
+			},
+			value: value,
+			object: object
+		});
+		throw new Error('invalid note');
+	}
+
+	const note: IPost = object;
+
+	logger.debug(`Note fetched: ${JSON.stringify(note, null, 2)}`);
+
+	logger.info(`Creating the Note: ${note.id}`);
+
+	// 投稿者をフェッチ
+	const actor = await resolvePerson(getOneApId(note.attributedTo), resolver) as IRemoteUser;
+
+	// 投稿者が凍結されていたらスキップ
+	if (actor.isSuspended) {
+		throw new Error('actor has been suspended');
+	}
+
+	const noteAudience = await parseAudience(actor, note.to, note.cc);
+	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';
+		}
+	}
+
+	let isTalk = note._misskey_talk && visibility === 'specified';
+
+	const apMentions = await extractApMentions(note.tag);
+	const apHashtags = await extractApHashtags(note.tag);
+
+	// 添付ファイル
+	// TODO: attachmentは必ずしもImageではない
+	// TODO: attachmentは必ずしも配列ではない
+	// Noteがsensitiveなら添付もsensitiveにする
+	const limit = promiseLimit(2);
+
+	note.attachment = Array.isArray(note.attachment) ? note.attachment : note.attachment ? [note.attachment] : [];
+	const files = note.attachment
+		.map(attach => attach.sensitive = note.sensitive)
+		? (await Promise.all(note.attachment.map(x => limit(() => resolveImage(actor, x)) as Promise<DriveFile>)))
+			.filter(image => image != null)
+		: [];
+
+	// リプライ
+	const reply: Note | null = note.inReplyTo
+		? await resolveNote(note.inReplyTo, resolver).then(x => {
+			if (x == null) {
+				logger.warn(`Specified inReplyTo, but nout found`);
+				throw new Error('inReplyTo not found');
+			} else {
+				return x;
+			}
+		}).catch(async e => {
+			// トークだったらinReplyToのエラーは無視
+			const uri = getApId(note.inReplyTo);
+			if (uri.startsWith(config.url + '/')) {
+				const id = uri.split('/').pop();
+				const talk = await MessagingMessages.findOne(id);
+				if (talk) {
+					isTalk = true;
+					return null;
+				}
+			}
+
+			logger.warn(`Error in inReplyTo ${note.inReplyTo} - ${e.statusCode || e}`);
+			throw e;
+		})
+		: null;
+
+	// 引用
+	let quote: Note | undefined | null;
+
+	if (note._misskey_quote || note.quoteUrl) {
+		const tryResolveNote = async (uri: string): Promise<{
+			status: 'ok';
+			res: Note | null;
+		} | {
+			status: 'permerror' | 'temperror';
+		}> => {
+			if (typeof uri !== 'string' || !uri.match(/^https?:/)) return { status: 'permerror' };
+			try {
+				const res = await resolveNote(uri);
+				if (res) {
+					return {
+						status: 'ok',
+						res
+					};
+				} else {
+					return {
+						status: 'permerror'
+					};
+				}
+			} catch (e) {
+				return {
+					status: (e instanceof StatusError && e.isClientError) ? 'permerror' : 'temperror'
+				};
+			}
+		};
+
+		const uris = unique([note._misskey_quote, note.quoteUrl].filter((x): x is string => typeof x === 'string'));
+		const results = await Promise.all(uris.map(uri => tryResolveNote(uri)));
+
+		quote = results.filter((x): x is { status: 'ok', res: Note | null } => x.status === 'ok').map(x => x.res).find(x => x);
+		if (!quote) {
+			if (results.some(x => x.status === 'temperror')) {
+				throw 'quote resolve failed';
+			}
+		}
+	}
+
+	const cw = note.summary === '' ? null : note.summary;
+
+	// テキストのパース
+	const text = note._misskey_content || (note.content ? htmlToMfm(note.content, note.tag) : null);
+
+	// vote
+	if (reply && reply.hasPoll) {
+		const poll = await Polls.findOneOrFail(reply.id);
+
+		const tryCreateVote = async (name: string, index: number): Promise<null> => {
+			if (poll.expiresAt && Date.now() > new Date(poll.expiresAt).getTime()) {
+				logger.warn(`vote to expired poll from AP: actor=${actor.username}@${actor.host}, note=${note.id}, choice=${name}`);
+			} else if (index >= 0) {
+				logger.info(`vote from AP: actor=${actor.username}@${actor.host}, note=${note.id}, choice=${name}`);
+				await vote(actor, reply, index);
+
+				// リモートフォロワーにUpdate配信
+				deliverQuestionUpdate(reply.id);
+			}
+			return null;
+		};
+
+		if (note.name) {
+			return await tryCreateVote(note.name, poll.choices.findIndex(x => x === note.name));
+		}
+	}
+
+	const emojis = await extractEmojis(note.tag || [], actor.host).catch(e => {
+		logger.info(`extractEmojis: ${e}`);
+		return [] as Emoji[];
+	});
+
+	const apEmojis = emojis.map(emoji => emoji.name);
+
+	const poll = await extractPollFromQuestion(note, resolver).catch(() => undefined);
+
+	// ユーザーの情報が古かったらついでに更新しておく
+	if (actor.lastFetchedAt == null || Date.now() - actor.lastFetchedAt.getTime() > 1000 * 60 * 60 * 24) {
+		if (actor.uri) updatePerson(actor.uri);
+	}
+
+	if (isTalk) {
+		for (const recipient of visibleUsers) {
+			await createMessage(actor, recipient, undefined, text || undefined, (files && files.length > 0) ? files[0] : null, object.id);
+			return null;
+		}
+	}
+
+	return await post(actor, {
+		createdAt: note.published ? new Date(note.published) : null,
+		files,
+		reply,
+		renote: quote,
+		name: note.name,
+		cw,
+		text,
+		viaMobile: false,
+		localOnly: false,
+		visibility,
+		visibleUsers,
+		apMentions,
+		apHashtags,
+		apEmojis,
+		poll,
+		uri: note.id,
+		url: getOneApHrefNullable(note.url),
+	}, silent);
+}
+
+/**
+ * Noteを解決します。
+ *
+ * Misskeyに対象のNoteが登録されていればそれを返し、そうでなければ
+ * リモートサーバーからフェッチしてMisskeyに登録しそれを返します。
+ */
+export async function resolveNote(value: string | IObject, resolver?: Resolver): Promise<Note | null> {
+	const uri = typeof value === 'string' ? value : value.id;
+	if (uri == null) throw new Error('missing uri');
+
+	// ブロックしてたら中断
+	const meta = await fetchMeta();
+	if (meta.blockedHosts.includes(extractDbHost(uri))) throw { statusCode: 451 };
+
+	const unlock = await getApLock(uri);
+
+	try {
+		//#region このサーバーに既に登録されていたらそれを返す
+		const exist = await fetchNote(uri);
+
+		if (exist) {
+			return exist;
+		}
+		//#endregion
+
+		if (uri.startsWith(config.url)) {
+			throw new StatusError('cannot resolve local note', 400, 'cannot resolve local note');
+		}
+
+		// リモートサーバーからフェッチしてきて登録
+		// ここでuriの代わりに添付されてきたNote Objectが指定されていると、サーバーフェッチを経ずにノートが生成されるが
+		// 添付されてきたNote Objectは偽装されている可能性があるため、常にuriを指定してサーバーフェッチを行う。
+		return await createNote(uri, resolver, true);
+	} finally {
+		unlock();
+	}
+}
+
+export async function extractEmojis(tags: IObject | IObject[], host: string): Promise<Emoji[]> {
+	host = toPuny(host);
+
+	if (!tags) return [];
+
+	const eomjiTags = toArray(tags).filter(isEmoji);
+
+	return await Promise.all(eomjiTags.map(async tag => {
+		const name = tag.name!.replace(/^:/, '').replace(/:$/, '');
+		tag.icon = toSingle(tag.icon);
+
+		const exists = await Emojis.findOne({
+			host,
+			name
+		});
+
+		if (exists) {
+			if ((tag.updated != null && exists.updatedAt == null)
+				|| (tag.id != null && exists.uri == null)
+				|| (tag.updated != null && exists.updatedAt != null && new Date(tag.updated) > exists.updatedAt)
+				|| (tag.icon!.url !== exists.url)
+			) {
+				await Emojis.update({
+					host,
+					name,
+				}, {
+					uri: tag.id,
+					url: tag.icon!.url,
+					updatedAt: new Date(),
+				});
+
+				return await Emojis.findOne({
+					host,
+					name
+				}) as Emoji;
+			}
+
+			return exists;
+		}
+
+		logger.info(`register emoji host=${host}, name=${name}`);
+
+		return await Emojis.save({
+			id: genId(),
+			host,
+			name,
+			uri: tag.id,
+			url: tag.icon!.url,
+			updatedAt: new Date(),
+			aliases: []
+		} as Partial<Emoji>);
+	}));
+}
--- a/packages/backend/src/remote/activitypub/models/person.ts
+++ b/packages/backend/src/remote/activitypub/models/person.ts
@ -0,0 +1,494 @@
+import { URL } from 'url';
+import * as promiseLimit from 'promise-limit';
+
+import $, { Context } from 'cafy';
+import config from '@/config/index';
+import Resolver from '../resolver';
+import { resolveImage } from './image';
+import { isCollectionOrOrderedCollection, isCollection, IActor, getApId, getOneApHrefNullable, IObject, isPropertyValue, IApPropertyValue, getApType, isActor } from '../type';
+import { fromHtml } from '../../../mfm/from-html';
+import { htmlToMfm } from '../misc/html-to-mfm';
+import { resolveNote, extractEmojis } from './note';
+import { registerOrFetchInstanceDoc } from '@/services/register-or-fetch-instance-doc';
+import { extractApHashtags } from './tag';
+import { apLogger } from '../logger';
+import { Note } from '@/models/entities/note';
+import { updateUsertags } from '@/services/update-hashtag';
+import { Users, Instances, DriveFiles, Followings, UserProfiles, UserPublickeys } from '@/models/index';
+import { User, IRemoteUser } from '@/models/entities/user';
+import { Emoji } from '@/models/entities/emoji';
+import { UserNotePining } from '@/models/entities/user-note-pining';
+import { genId } from '@/misc/gen-id';
+import { instanceChart, usersChart } from '@/services/chart/index';
+import { UserPublickey } from '@/models/entities/user-publickey';
+import { isDuplicateKeyValueError } from '@/misc/is-duplicate-key-value-error';
+import { toPuny } from '@/misc/convert-host';
+import { UserProfile } from '@/models/entities/user-profile';
+import { getConnection } from 'typeorm';
+import { toArray } from '@/prelude/array';
+import { fetchInstanceMetadata } from '@/services/fetch-instance-metadata';
+import { normalizeForSearch } from '@/misc/normalize-for-search';
+import { truncate } from '@/misc/truncate';
+import { StatusError } from '@/misc/fetch';
+
+const logger = apLogger;
+
+const nameLength = 128;
+const summaryLength = 2048;
+
+/**
+ * Validate and convert to actor object
+ * @param x Fetched object
+ * @param uri Fetch target URI
+ */
+function validateActor(x: IObject, uri: string): IActor {
+	const expectHost = toPuny(new URL(uri).hostname);
+
+	if (x == null) {
+		throw new Error('invalid Actor: object is null');
+	}
+
+	if (!isActor(x)) {
+		throw new Error(`invalid Actor type '${x.type}'`);
+	}
+
+	const validate = (name: string, value: any, validater: Context) => {
+		const e = validater.test(value);
+		if (e) throw new Error(`invalid Actor: ${name} ${e.message}`);
+	};
+
+	validate('id', x.id, $.str.min(1));
+	validate('inbox', x.inbox, $.str.min(1));
+	validate('preferredUsername', x.preferredUsername, $.str.min(1).max(128).match(/^\w([\w-.]*\w)?$/));
+
+	// These fields are only informational, and some AP software allows these
+	// fields to be very long. If they are too long, we cut them off. This way
+	// we can at least see these users and their activities.
+	validate('name', truncate(x.name, nameLength), $.optional.nullable.str);
+	validate('summary', truncate(x.summary, summaryLength), $.optional.nullable.str);
+
+	const idHost = toPuny(new URL(x.id!).hostname);
+	if (idHost !== expectHost) {
+		throw new Error('invalid Actor: id has different host');
+	}
+
+	if (x.publicKey) {
+		if (typeof x.publicKey.id !== 'string') {
+			throw new Error('invalid Actor: publicKey.id is not a string');
+		}
+
+		const publicKeyIdHost = toPuny(new URL(x.publicKey.id).hostname);
+		if (publicKeyIdHost !== expectHost) {
+			throw new Error('invalid Actor: publicKey.id has different host');
+		}
+	}
+
+	return x;
+}
+
+/**
+ * Personをフェッチします。
+ *
+ * Misskeyに対象のPersonが登録されていればそれを返します。
+ */
+export async function fetchPerson(uri: string, resolver?: Resolver): Promise<User | null> {
+	if (typeof uri !== 'string') throw new Error('uri is not string');
+
+	// URIがこのサーバーを指しているならデータベースからフェッチ
+	if (uri.startsWith(config.url + '/')) {
+		const id = uri.split('/').pop();
+		return await Users.findOne(id).then(x => x || null);
+	}
+
+	//#region このサーバーに既に登録されていたらそれを返す
+	const exist = await Users.findOne({ uri });
+
+	if (exist) {
+		return exist;
+	}
+	//#endregion
+
+	return null;
+}
+
+/**
+ * Personを作成します。
+ */
+export async function createPerson(uri: string, resolver?: Resolver): Promise<User> {
+	if (typeof uri !== 'string') throw new Error('uri is not string');
+
+	if (uri.startsWith(config.url)) {
+		throw new StatusError('cannot resolve local user', 400, 'cannot resolve local user');
+	}
+
+	if (resolver == null) resolver = new Resolver();
+
+	const object = await resolver.resolve(uri) as any;
+
+	const person = validateActor(object, uri);
+
+	logger.info(`Creating the Person: ${person.id}`);
+
+	const host = toPuny(new URL(object.id).hostname);
+
+	const { fields } = analyzeAttachments(person.attachment || []);
+
+	const tags = extractApHashtags(person.tag).map(tag => normalizeForSearch(tag)).splice(0, 32);
+
+	const isBot = getApType(object) === 'Service';
+
+	const bday = person['vcard:bday']?.match(/^\d{4}-\d{2}-\d{2}/);
+
+	// Create user
+	let user: IRemoteUser;
+	try {
+		// Start transaction
+		await getConnection().transaction(async transactionalEntityManager => {
+			user = await transactionalEntityManager.save(new User({
+				id: genId(),
+				avatarId: null,
+				bannerId: null,
+				createdAt: new Date(),
+				lastFetchedAt: new Date(),
+				name: truncate(person.name, nameLength),
+				isLocked: !!person.manuallyApprovesFollowers,
+				isExplorable: !!person.discoverable,
+				username: person.preferredUsername,
+				usernameLower: person.preferredUsername!.toLowerCase(),
+				host,
+				inbox: person.inbox,
+				sharedInbox: person.sharedInbox || (person.endpoints ? person.endpoints.sharedInbox : undefined),
+				followersUri: person.followers ? getApId(person.followers) : undefined,
+				featured: person.featured ? getApId(person.featured) : undefined,
+				uri: person.id,
+				tags,
+				isBot,
+				isCat: (person as any).isCat === true
+			})) as IRemoteUser;
+
+			await transactionalEntityManager.save(new UserProfile({
+				userId: user.id,
+				description: person.summary ? htmlToMfm(truncate(person.summary, summaryLength), person.tag) : null,
+				url: getOneApHrefNullable(person.url),
+				fields,
+				birthday: bday ? bday[0] : null,
+				location: person['vcard:Address'] || null,
+				userHost: host
+			}));
+
+			if (person.publicKey) {
+				await transactionalEntityManager.save(new UserPublickey({
+					userId: user.id,
+					keyId: person.publicKey.id,
+					keyPem: person.publicKey.publicKeyPem
+				}));
+			}
+		});
+	} catch (e) {
+		// duplicate key error
+		if (isDuplicateKeyValueError(e)) {
+			// /users/@a => /users/:id のように入力がaliasなときにエラーになることがあるのを対応
+			const u = await Users.findOne({
+				uri: person.id
+			});
+
+			if (u) {
+				user = u as IRemoteUser;
+			} else {
+				throw new Error('already registered');
+			}
+		} else {
+			logger.error(e);
+			throw e;
+		}
+	}
+
+	// Register host
+	registerOrFetchInstanceDoc(host).then(i => {
+		Instances.increment({ id: i.id }, 'usersCount', 1);
+		instanceChart.newUser(i.host);
+		fetchInstanceMetadata(i);
+	});
+
+	usersChart.update(user!, true);
+
+	// ハッシュタグ更新
+	updateUsertags(user!, tags);
+
+	//#region アバターとヘッダー画像をフェッチ
+	const [avatar, banner] = await Promise.all([
+		person.icon,
+		person.image
+	].map(img =>
+		img == null
+			? Promise.resolve(null)
+			: resolveImage(user!, img).catch(() => null)
+	));
+
+	const avatarId = avatar ? avatar.id : null;
+	const bannerId = banner ? banner.id : null;
+	const avatarUrl = avatar ? DriveFiles.getPublicUrl(avatar, true) : null;
+	const bannerUrl = banner ? DriveFiles.getPublicUrl(banner) : null;
+	const avatarBlurhash = avatar ? avatar.blurhash : null;
+	const bannerBlurhash = banner ? banner.blurhash : null;
+
+	await Users.update(user!.id, {
+		avatarId,
+		bannerId,
+		avatarUrl,
+		bannerUrl,
+		avatarBlurhash,
+		bannerBlurhash
+	});
+
+	user!.avatarId = avatarId;
+	user!.bannerId = bannerId;
+	user!.avatarUrl = avatarUrl;
+	user!.bannerUrl = bannerUrl;
+	user!.avatarBlurhash = avatarBlurhash;
+	user!.bannerBlurhash = bannerBlurhash;
+	//#endregion
+
+	//#region カスタム絵文字取得
+	const emojis = await extractEmojis(person.tag || [], host).catch(e => {
+		logger.info(`extractEmojis: ${e}`);
+		return [] as Emoji[];
+	});
+
+	const emojiNames = emojis.map(emoji => emoji.name);
+
+	await Users.update(user!.id, {
+		emojis: emojiNames
+	});
+	//#endregion
+
+	await updateFeatured(user!.id).catch(err => logger.error(err));
+
+	return user!;
+}
+
+/**
+ * Personの情報を更新します。
+ * Misskeyに対象のPersonが登録されていなければ無視します。
+ * @param uri URI of Person
+ * @param resolver Resolver
+ * @param hint Hint of Person object (この値が正当なPersonの場合、Remote resolveをせずに更新に利用します)
+ */
+export async function updatePerson(uri: string, resolver?: Resolver | null, hint?: object): Promise<void> {
+	if (typeof uri !== 'string') throw new Error('uri is not string');
+
+	// URIがこのサーバーを指しているならスキップ
+	if (uri.startsWith(config.url + '/')) {
+		return;
+	}
+
+	//#region このサーバーに既に登録されているか
+	const exist = await Users.findOne({ uri }) as IRemoteUser;
+
+	if (exist == null) {
+		return;
+	}
+	//#endregion
+
+	if (resolver == null) resolver = new Resolver();
+
+	const object = hint || await resolver.resolve(uri) as any;
+
+	const person = validateActor(object, uri);
+
+	logger.info(`Updating the Person: ${person.id}`);
+
+	// アバターとヘッダー画像をフェッチ
+	const [avatar, banner] = await Promise.all([
+		person.icon,
+		person.image
+	].map(img =>
+		img == null
+			? Promise.resolve(null)
+			: resolveImage(exist, img).catch(() => null)
+	));
+
+	// カスタム絵文字取得
+	const emojis = await extractEmojis(person.tag || [], exist.host).catch(e => {
+		logger.info(`extractEmojis: ${e}`);
+		return [] as Emoji[];
+	});
+
+	const emojiNames = emojis.map(emoji => emoji.name);
+
+	const { fields } = analyzeAttachments(person.attachment || []);
+
+	const tags = extractApHashtags(person.tag).map(tag => normalizeForSearch(tag)).splice(0, 32);
+
+	const bday = person['vcard:bday']?.match(/^\d{4}-\d{2}-\d{2}/);
+
+	const updates = {
+		lastFetchedAt: new Date(),
+		inbox: person.inbox,
+		sharedInbox: person.sharedInbox || (person.endpoints ? person.endpoints.sharedInbox : undefined),
+		followersUri: person.followers ? getApId(person.followers) : undefined,
+		featured: person.featured,
+		emojis: emojiNames,
+		name: truncate(person.name, nameLength),
+		tags,
+		isBot: getApType(object) === 'Service',
+		isCat: (person as any).isCat === true,
+		isLocked: !!person.manuallyApprovesFollowers,
+		isExplorable: !!person.discoverable,
+	} as Partial<User>;
+
+	if (avatar) {
+		updates.avatarId = avatar.id;
+		updates.avatarUrl = DriveFiles.getPublicUrl(avatar, true);
+		updates.avatarBlurhash = avatar.blurhash;
+	}
+
+	if (banner) {
+		updates.bannerId = banner.id;
+		updates.bannerUrl = DriveFiles.getPublicUrl(banner);
+		updates.bannerBlurhash = banner.blurhash;
+	}
+
+	// Update user
+	await Users.update(exist.id, updates);
+
+	if (person.publicKey) {
+		await UserPublickeys.update({ userId: exist.id }, {
+			keyId: person.publicKey.id,
+			keyPem: person.publicKey.publicKeyPem
+		});
+	}
+
+	await UserProfiles.update({ userId: exist.id }, {
+		url: getOneApHrefNullable(person.url),
+		fields,
+		description: person.summary ? htmlToMfm(truncate(person.summary, summaryLength), person.tag) : null,
+		birthday: bday ? bday[0] : null,
+		location: person['vcard:Address'] || null,
+	});
+
+	// ハッシュタグ更新
+	updateUsertags(exist, tags);
+
+	// 該当ユーザーが既にフォロワーになっていた場合はFollowingもアップデートする
+	await Followings.update({
+		followerId: exist.id
+	}, {
+		followerSharedInbox: person.sharedInbox || (person.endpoints ? person.endpoints.sharedInbox : undefined)
+	});
+
+	await updateFeatured(exist.id).catch(err => logger.error(err));
+}
+
+/**
+ * Personを解決します。
+ *
+ * Misskeyに対象のPersonが登録されていればそれを返し、そうでなければ
+ * リモートサーバーからフェッチしてMisskeyに登録しそれを返します。
+ */
+export async function resolvePerson(uri: string, resolver?: Resolver): Promise<User> {
+	if (typeof uri !== 'string') throw new Error('uri is not string');
+
+	//#region このサーバーに既に登録されていたらそれを返す
+	const exist = await fetchPerson(uri);
+
+	if (exist) {
+		return exist;
+	}
+	//#endregion
+
+	// リモートサーバーからフェッチしてきて登録
+	if (resolver == null) resolver = new Resolver();
+	return await createPerson(uri, resolver);
+}
+
+const services: {
+		[x: string]: (id: string, username: string) => any
+	} = {
+	'misskey:authentication:twitter': (userId, screenName) => ({ userId, screenName }),
+	'misskey:authentication:github': (id, login) => ({ id, login }),
+	'misskey:authentication:discord': (id, name) => $discord(id, name)
+};
+
+const $discord = (id: string, name: string) => {
+	if (typeof name !== 'string')
+		name = 'unknown#0000';
+	const [username, discriminator] = name.split('#');
+	return { id, username, discriminator };
+};
+
+function addService(target: { [x: string]: any }, source: IApPropertyValue) {
+	const service = services[source.name];
+
+	if (typeof source.value !== 'string')
+		source.value = 'unknown';
+
+	const [id, username] = source.value.split('@');
+
+	if (service)
+		target[source.name.split(':')[2]] = service(id, username);
+}
+
+export function analyzeAttachments(attachments: IObject | IObject[] | undefined) {
+	const fields: {
+		name: string,
+		value: string
+	}[] = [];
+	const services: { [x: string]: any } = {};
+
+	if (Array.isArray(attachments)) {
+		for (const attachment of attachments.filter(isPropertyValue)) {
+			if (isPropertyValue(attachment.identifier)) {
+				addService(services, attachment.identifier);
+			} else {
+				fields.push({
+					name: attachment.name,
+					value: fromHtml(attachment.value)
+				});
+			}
+		}
+	}
+
+	return { fields, services };
+}
+
+export async function updateFeatured(userId: User['id']) {
+	const user = await Users.findOneOrFail(userId);
+	if (!Users.isRemoteUser(user)) return;
+	if (!user.featured) return;
+
+	logger.info(`Updating the featured: ${user.uri}`);
+
+	const resolver = new Resolver();
+
+	// Resolve to (Ordered)Collection Object
+	const collection = await resolver.resolveCollection(user.featured);
+	if (!isCollectionOrOrderedCollection(collection)) throw new Error(`Object is not Collection or OrderedCollection`);
+
+	// Resolve to Object(may be Note) arrays
+	const unresolvedItems = isCollection(collection) ? collection.items : collection.orderedItems;
+	const items = await Promise.all(toArray(unresolvedItems).map(x => resolver.resolve(x)));
+
+	// Resolve and regist Notes
+	const limit = promiseLimit<Note | null>(2);
+	const featuredNotes = await Promise.all(items
+		.filter(item => getApType(item) === 'Note')	// TODO: Noteでなくてもいいかも
+		.slice(0, 5)
+		.map(item => limit(() => resolveNote(item, resolver))));
+
+	await getConnection().transaction(async transactionalEntityManager => {
+		await transactionalEntityManager.delete(UserNotePining, { userId: user.id });
+
+		// とりあえずidを別の時間で生成して順番を維持
+		let td = 0;
+		for (const note of featuredNotes.filter(note => note != null)) {
+			td -= 1000;
+			transactionalEntityManager.insert(UserNotePining, {
+				id: genId(new Date(Date.now() + td)),
+				createdAt: new Date(),
+				userId: user.id,
+				noteId: note!.id
+			});
+		}
+	});
+}
--- a/packages/backend/src/remote/activitypub/models/question.ts
+++ b/packages/backend/src/remote/activitypub/models/question.ts
@ -0,0 +1,83 @@
+import config from '@/config/index';
+import Resolver from '../resolver';
+import { IObject, IQuestion, isQuestion,  } from '../type';
+import { apLogger } from '../logger';
+import { Notes, Polls } from '@/models/index';
+import { IPoll } from '@/models/entities/poll';
+
+export async function extractPollFromQuestion(source: string | IObject, resolver?: Resolver): Promise<IPoll> {
+	if (resolver == null) resolver = new Resolver();
+
+	const question = await resolver.resolve(source);
+
+	if (!isQuestion(question)) {
+		throw new Error('invalid type');
+	}
+
+	const multiple = !question.oneOf;
+	const expiresAt = question.endTime ? new Date(question.endTime) : question.closed ? new Date(question.closed) : null;
+
+	if (multiple && !question.anyOf) {
+		throw new Error('invalid question');
+	}
+
+	const choices = question[multiple ? 'anyOf' : 'oneOf']!
+		.map((x, i) => x.name!);
+
+	const votes = question[multiple ? 'anyOf' : 'oneOf']!
+		.map((x, i) => x.replies && x.replies.totalItems || x._misskey_votes || 0);
+
+	return {
+		choices,
+		votes,
+		multiple,
+		expiresAt
+	};
+}
+
+/**
+ * Update votes of Question
+ * @param uri URI of AP Question object
+ * @returns true if updated
+ */
+export async function updateQuestion(value: any) {
+	const uri = typeof value === 'string' ? value : value.id;
+
+	// URIがこのサーバーを指しているならスキップ
+	if (uri.startsWith(config.url + '/')) throw new Error('uri points local');
+
+	//#region このサーバーに既に登録されているか
+	const note = await Notes.findOne({ uri });
+	if (note == null) throw new Error('Question is not registed');
+
+	const poll = await Polls.findOne({ noteId: note.id });
+	if (poll == null) throw new Error('Question is not registed');
+	//#endregion
+
+	// resolve new Question object
+	const resolver = new Resolver();
+	const question = await resolver.resolve(value) as IQuestion;
+	apLogger.debug(`fetched question: ${JSON.stringify(question, null, 2)}`);
+
+	if (question.type !== 'Question') throw new Error('object is not a Question');
+
+	const apChoices = question.oneOf || question.anyOf;
+
+	let changed = false;
+
+	for (const choice of poll.choices) {
+		const oldCount = poll.votes[poll.choices.indexOf(choice)];
+		const newCount = apChoices!.filter(ap => ap.name === choice)[0].replies!.totalItems;
+
+		if (oldCount != newCount) {
+			changed = true;
+			poll.votes[poll.choices.indexOf(choice)] = newCount;
+		}
+	}
+
+	await Polls.update({ noteId: note.id }, {
+		votes: poll.votes
+	});
+
+	return changed;
+}
--- a/packages/backend/src/remote/activitypub/models/tag.ts
+++ b/packages/backend/src/remote/activitypub/models/tag.ts
@ -0,0 +1,18 @@
+import { toArray } from '@/prelude/array';
+import { IObject, isHashtag, IApHashtag } from '../type';
+
+export function extractApHashtags(tags: IObject | IObject[] | null | undefined) {
+	if (tags == null) return [];
+
+	const hashtags = extractApHashtagObjects(tags);
+
+	return hashtags.map(tag => {
+		const m = tag.name.match(/^#(.+)/);
+		return m ? m[1] : null;
+	}).filter((x): x is string => x != null);
+}
+
+export function extractApHashtagObjects(tags: IObject | IObject[] | null | undefined): IApHashtag[] {
+	if (tags == null) return [];
+	return toArray(tags).filter(isHashtag);
+}
--- a/packages/backend/src/remote/activitypub/perform.ts
+++ b/packages/backend/src/remote/activitypub/perform.ts
@ -0,0 +1,7 @@
+import { IObject } from './type';
+import { IRemoteUser } from '@/models/entities/user';
+import { performActivity } from './kernel/index';
+
+export default async (actor: IRemoteUser, activity: IObject): Promise<void> => {
+	await performActivity(actor, activity);
+};
--- a/packages/backend/src/remote/activitypub/renderer/accept.ts
+++ b/packages/backend/src/remote/activitypub/renderer/accept.ts
@ -0,0 +1,8 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+
+export default (object: any, user: { id: User['id']; host: null }) => ({
+	type: 'Accept',
+	actor: `${config.url}/users/${user.id}`,
+	object
+});
--- a/packages/backend/src/remote/activitypub/renderer/add.ts
+++ b/packages/backend/src/remote/activitypub/renderer/add.ts
@ -0,0 +1,9 @@
+import config from '@/config/index';
+import { ILocalUser } from '@/models/entities/user';
+
+export default (user: ILocalUser, target: any, object: any) => ({
+	type: 'Add',
+	actor: `${config.url}/users/${user.id}`,
+	target,
+	object
+});
--- a/packages/backend/src/remote/activitypub/renderer/announce.ts
+++ b/packages/backend/src/remote/activitypub/renderer/announce.ts
@ -0,0 +1,29 @@
+import config from '@/config/index';
+import { Note } from '@/models/entities/note';
+
+export default (object: any, note: Note) => {
+	const attributedTo = `${config.url}/users/${note.userId}`;
+
+	let to: string[] = [];
+	let cc: string[] = [];
+
+	if (note.visibility === 'public') {
+		to = ['https://www.w3.org/ns/activitystreams#Public'];
+		cc = [`${attributedTo}/followers`];
+	} else if (note.visibility === 'home') {
+		to = [`${attributedTo}/followers`];
+		cc = ['https://www.w3.org/ns/activitystreams#Public'];
+	} else {
+		return null;
+	}
+
+	return {
+		id: `${config.url}/notes/${note.id}/activity`,
+		actor: `${config.url}/users/${note.userId}`,
+		type: 'Announce',
+		published: note.createdAt.toISOString(),
+		to,
+		cc,
+		object
+	};
+};
--- a/packages/backend/src/remote/activitypub/renderer/block.ts
+++ b/packages/backend/src/remote/activitypub/renderer/block.ts
@ -0,0 +1,8 @@
+import config from '@/config/index';
+import { ILocalUser, IRemoteUser } from '@/models/entities/user';
+
+export default (blocker: ILocalUser, blockee: IRemoteUser) => ({
+	type: 'Block',
+	actor: `${config.url}/users/${blocker.id}`,
+	object: blockee.uri
+});
--- a/packages/backend/src/remote/activitypub/renderer/create.ts
+++ b/packages/backend/src/remote/activitypub/renderer/create.ts
@ -0,0 +1,17 @@
+import config from '@/config/index';
+import { Note } from '@/models/entities/note';
+
+export default (object: any, note: Note) => {
+	const activity = {
+		id: `${config.url}/notes/${note.id}/activity`,
+		actor: `${config.url}/users/${note.userId}`,
+		type: 'Create',
+		published: note.createdAt.toISOString(),
+		object
+	} as any;
+
+	if (object.to) activity.to = object.to;
+	if (object.cc) activity.cc = object.cc;
+
+	return activity;
+};
--- a/packages/backend/src/remote/activitypub/renderer/delete.ts
+++ b/packages/backend/src/remote/activitypub/renderer/delete.ts
@ -0,0 +1,9 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+
+export default (object: any, user: { id: User['id']; host: null }) => ({
+	type: 'Delete',
+	actor: `${config.url}/users/${user.id}`,
+	object,
+	published: new Date().toISOString(),
+});
--- a/packages/backend/src/remote/activitypub/renderer/document.ts
+++ b/packages/backend/src/remote/activitypub/renderer/document.ts
@ -0,0 +1,9 @@
+import { DriveFile } from '@/models/entities/drive-file';
+import { DriveFiles } from '@/models/index';
+
+export default (file: DriveFile) => ({
+	type: 'Document',
+	mediaType: file.type,
+	url: DriveFiles.getPublicUrl(file),
+	name: file.comment,
+});
--- a/packages/backend/src/remote/activitypub/renderer/emoji.ts
+++ b/packages/backend/src/remote/activitypub/renderer/emoji.ts
@ -0,0 +1,14 @@
+import config from '@/config/index';
+import { Emoji } from '@/models/entities/emoji';
+
+export default (emoji: Emoji) => ({
+	id: `${config.url}/emojis/${emoji.name}`,
+	type: 'Emoji',
+	name: `:${emoji.name}:`,
+	updated: emoji.updatedAt != null ? emoji.updatedAt.toISOString() : new Date().toISOString,
+	icon: {
+		type: 'Image',
+		mediaType: emoji.type || 'image/png',
+		url: emoji.url
+	}
+});
--- a/packages/backend/src/remote/activitypub/renderer/follow-relay.ts
+++ b/packages/backend/src/remote/activitypub/renderer/follow-relay.ts
@ -0,0 +1,14 @@
+import config from '@/config/index';
+import { Relay } from '@/models/entities/relay';
+import { ILocalUser } from '@/models/entities/user';
+
+export function renderFollowRelay(relay: Relay, relayActor: ILocalUser) {
+	const follow = {
+		id: `${config.url}/activities/follow-relay/${relay.id}`,
+		type: 'Follow',
+		actor: `${config.url}/users/${relayActor.id}`,
+		object: 'https://www.w3.org/ns/activitystreams#Public'
+	};
+
+	return follow;
+}
--- a/packages/backend/src/remote/activitypub/renderer/follow-user.ts
+++ b/packages/backend/src/remote/activitypub/renderer/follow-user.ts
@ -0,0 +1,12 @@
+import config from '@/config/index';
+import { Users } from '@/models/index';
+import { User } from '@/models/entities/user';
+
+/**
+ * Convert (local|remote)(Follower|Followee)ID to URL
+ * @param id Follower|Followee ID
+ */
+export default async function renderFollowUser(id: User['id']): Promise<any> {
+	const user = await Users.findOneOrFail(id);
+	return Users.isLocalUser(user) ? `${config.url}/users/${user.id}` : user.uri;
+}
--- a/packages/backend/src/remote/activitypub/renderer/follow.ts
+++ b/packages/backend/src/remote/activitypub/renderer/follow.ts
@ -0,0 +1,15 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+import { Users } from '@/models/index';
+
+export default (follower: { id: User['id']; host: User['host']; uri: User['host'] }, followee: { id: User['id']; host: User['host']; uri: User['host'] }, requestId?: string) => {
+	const follow = {
+		type: 'Follow',
+		actor: Users.isLocalUser(follower) ? `${config.url}/users/${follower.id}` : follower.uri,
+		object: Users.isLocalUser(followee) ? `${config.url}/users/${followee.id}` : followee.uri
+	} as any;
+
+	if (requestId) follow.id = requestId;
+
+	return follow;
+};
--- a/packages/backend/src/remote/activitypub/renderer/hashtag.ts
+++ b/packages/backend/src/remote/activitypub/renderer/hashtag.ts
@ -0,0 +1,7 @@
+import config from '@/config/index';
+
+export default (tag: string) => ({
+	type: 'Hashtag',
+	href: `${config.url}/tags/${encodeURIComponent(tag)}`,
+	name: `#${tag}`
+});
--- a/packages/backend/src/remote/activitypub/renderer/image.ts
+++ b/packages/backend/src/remote/activitypub/renderer/image.ts
@ -0,0 +1,9 @@
+import { DriveFile } from '@/models/entities/drive-file';
+import { DriveFiles } from '@/models/index';
+
+export default (file: DriveFile) => ({
+	type: 'Image',
+	url: DriveFiles.getPublicUrl(file),
+	sensitive: file.isSensitive,
+	name: file.comment
+});
--- a/packages/backend/src/remote/activitypub/renderer/index.ts
+++ b/packages/backend/src/remote/activitypub/renderer/index.ts
@ -0,0 +1,59 @@
+import config from '@/config/index';
+import { v4 as uuid } from 'uuid';
+import { IActivity } from '../type';
+import { LdSignature } from '../misc/ld-signature';
+import { getUserKeypair } from '@/misc/keypair-store';
+import { User } from '@/models/entities/user';
+
+export const renderActivity = (x: any): IActivity | null => {
+	if (x == null) return null;
+
+	if (x !== null && typeof x === 'object' && x.id == null) {
+		x.id = `${config.url}/${uuid()}`;
+	}
+
+	return Object.assign({
+		'@context': [
+			'https://www.w3.org/ns/activitystreams',
+			'https://w3id.org/security/v1',
+			{
+				// as non-standards
+				manuallyApprovesFollowers: 'as:manuallyApprovesFollowers',
+				sensitive: 'as:sensitive',
+				Hashtag: 'as:Hashtag',
+				quoteUrl: 'as:quoteUrl',
+				// Mastodon
+				toot: 'http://joinmastodon.org/ns#',
+				Emoji: 'toot:Emoji',
+				featured: 'toot:featured',
+				discoverable: 'toot:discoverable',
+				// schema
+				schema: 'http://schema.org#',
+				PropertyValue: 'schema:PropertyValue',
+				value: 'schema:value',
+				// Misskey
+				misskey: `${config.url}/ns#`,
+				'_misskey_content': 'misskey:_misskey_content',
+				'_misskey_quote': 'misskey:_misskey_quote',
+				'_misskey_reaction': 'misskey:_misskey_reaction',
+				'_misskey_votes': 'misskey:_misskey_votes',
+				'_misskey_talk': 'misskey:_misskey_talk',
+				'isCat': 'misskey:isCat',
+				// vcard
+				vcard: 'http://www.w3.org/2006/vcard/ns#',
+			}
+		]
+	}, x);
+};
+
+export const attachLdSignature = async (activity: any, user: { id: User['id']; host: null; }): Promise<IActivity | null> => {
+	if (activity == null) return null;
+
+	const keypair = await getUserKeypair(user.id);
+
+	const ldSignature = new LdSignature();
+	ldSignature.debug = false;
+	activity = await ldSignature.signRsaSignature2017(activity, keypair.privateKey, `${config.url}/users/${user.id}#main-key`);
+
+	return activity;
+};
--- a/packages/backend/src/remote/activitypub/renderer/key.ts
+++ b/packages/backend/src/remote/activitypub/renderer/key.ts
@ -0,0 +1,14 @@
+import config from '@/config/index';
+import { ILocalUser } from '@/models/entities/user';
+import { UserKeypair } from '@/models/entities/user-keypair';
+import { createPublicKey } from 'crypto';
+
+export default (user: ILocalUser, key: UserKeypair, postfix?: string) => ({
+	id: `${config.url}/users/${user.id}${postfix || '/publickey'}`,
+	type: 'Key',
+	owner: `${config.url}/users/${user.id}`,
+	publicKeyPem: createPublicKey(key.publicKey).export({
+		type: 'spki',
+		format: 'pem'
+	})
+});
--- a/packages/backend/src/remote/activitypub/renderer/like.ts
+++ b/packages/backend/src/remote/activitypub/renderer/like.ts
@ -0,0 +1,30 @@
+import config from '@/config/index';
+import { NoteReaction } from '@/models/entities/note-reaction';
+import { Note } from '@/models/entities/note';
+import { Emojis } from '@/models/index';
+import renderEmoji from './emoji';
+
+export const renderLike = async (noteReaction: NoteReaction, note: Note) => {
+	const reaction = noteReaction.reaction;
+
+	const object =  {
+		type: 'Like',
+		id: `${config.url}/likes/${noteReaction.id}`,
+		actor: `${config.url}/users/${noteReaction.userId}`,
+		object: note.uri ? note.uri : `${config.url}/notes/${noteReaction.noteId}`,
+		content: reaction,
+		_misskey_reaction: reaction
+	} as any;
+
+	if (reaction.startsWith(':')) {
+		const name = reaction.replace(/:/g, '');
+		const emoji = await Emojis.findOne({
+			name,
+			host: null
+		});
+
+		if (emoji) object.tag = [ renderEmoji(emoji) ];
+	}
+
+	return object;
+};
--- a/packages/backend/src/remote/activitypub/renderer/mention.ts
+++ b/packages/backend/src/remote/activitypub/renderer/mention.ts
@ -0,0 +1,9 @@
+import config from '@/config/index';
+import { User, ILocalUser } from '@/models/entities/user';
+import { Users } from '@/models/index';
+
+export default (mention: User) => ({
+	type: 'Mention',
+	href: Users.isRemoteUser(mention) ? mention.uri : `${config.url}/users/${(mention as ILocalUser).id}`,
+	name: Users.isRemoteUser(mention) ? `@${mention.username}@${mention.host}` : `@${(mention as ILocalUser).username}`,
+});
--- a/packages/backend/src/remote/activitypub/renderer/note.ts
+++ b/packages/backend/src/remote/activitypub/renderer/note.ts
@ -0,0 +1,168 @@
+import renderDocument from './document';
+import renderHashtag from './hashtag';
+import renderMention from './mention';
+import renderEmoji from './emoji';
+import config from '@/config/index';
+import toHtml from '../misc/get-note-html';
+import { Note, IMentionedRemoteUsers } from '@/models/entities/note';
+import { DriveFile } from '@/models/entities/drive-file';
+import { DriveFiles, Notes, Users, Emojis, Polls } from '@/models/index';
+import { In } from 'typeorm';
+import { Emoji } from '@/models/entities/emoji';
+import { Poll } from '@/models/entities/poll';
+
+export default async function renderNote(note: Note, dive = true, isTalk = false): Promise<any> {
+	const getPromisedFiles = async (ids: string[]) => {
+		if (!ids || ids.length === 0) return [];
+		const items = await DriveFiles.find({ id: In(ids) });
+		return ids.map(id => items.find(item => item.id === id)).filter(item => item != null) as DriveFile[];
+	};
+
+	let inReplyTo;
+	let inReplyToNote: Note | undefined;
+
+	if (note.replyId) {
+		inReplyToNote = await Notes.findOne(note.replyId);
+
+		if (inReplyToNote != null) {
+			const inReplyToUser = await Users.findOne(inReplyToNote.userId);
+
+			if (inReplyToUser != null) {
+				if (inReplyToNote.uri) {
+					inReplyTo = inReplyToNote.uri;
+				} else {
+					if (dive) {
+						inReplyTo = await renderNote(inReplyToNote, false);
+					} else {
+						inReplyTo = `${config.url}/notes/${inReplyToNote.id}`;
+					}
+				}
+			}
+		}
+	} else {
+		inReplyTo = null;
+	}
+
+	let quote;
+
+	if (note.renoteId) {
+		const renote = await Notes.findOne(note.renoteId);
+
+		if (renote) {
+			quote = renote.uri ? renote.uri : `${config.url}/notes/${renote.id}`;
+		}
+	}
+
+	const user = await Users.findOneOrFail(note.userId);
+
+	const attributedTo = `${config.url}/users/${user.id}`;
+
+	const mentions = (JSON.parse(note.mentionedRemoteUsers) as IMentionedRemoteUsers).map(x => x.uri);
+
+	let to: string[] = [];
+	let cc: string[] = [];
+
+	if (note.visibility === 'public') {
+		to = ['https://www.w3.org/ns/activitystreams#Public'];
+		cc = [`${attributedTo}/followers`].concat(mentions);
+	} else if (note.visibility === 'home') {
+		to = [`${attributedTo}/followers`];
+		cc = ['https://www.w3.org/ns/activitystreams#Public'].concat(mentions);
+	} else if (note.visibility === 'followers') {
+		to = [`${attributedTo}/followers`];
+		cc = mentions;
+	} else {
+		to = mentions;
+	}
+
+	const mentionedUsers = note.mentions.length > 0 ? await Users.find({
+		id: In(note.mentions)
+	}) : [];
+
+	const hashtagTags = (note.tags || []).map(tag => renderHashtag(tag));
+	const mentionTags = mentionedUsers.map(u => renderMention(u));
+
+	const files = await getPromisedFiles(note.fileIds);
+
+	const text = note.text;
+	let poll: Poll | undefined;
+
+	if (note.hasPoll) {
+		poll = await Polls.findOne({ noteId: note.id });
+	}
+
+	let apText = text;
+	if (apText == null) apText = '';
+
+	if (quote) {
+		apText += `\n\nRE: ${quote}`;
+	}
+
+	const summary = note.cw === '' ? String.fromCharCode(0x200B) : note.cw;
+
+	const content = toHtml(Object.assign({}, note, {
+		text: apText
+	}));
+
+	const emojis = await getEmojis(note.emojis);
+	const apemojis = emojis.map(emoji => renderEmoji(emoji));
+
+	const tag = [
+		...hashtagTags,
+		...mentionTags,
+		...apemojis,
+	];
+
+	const asPoll = poll ? {
+		type: 'Question',
+		content: toHtml(Object.assign({}, note, {
+			text: text
+		})),
+		[poll.expiresAt && poll.expiresAt < new Date() ? 'closed' : 'endTime']: poll.expiresAt,
+		[poll.multiple ? 'anyOf' : 'oneOf']: poll.choices.map((text, i) => ({
+			type: 'Note',
+			name: text,
+			replies: {
+				type: 'Collection',
+				totalItems: poll!.votes[i]
+			}
+		}))
+	} : {};
+
+	const asTalk = isTalk ? {
+		_misskey_talk: true
+	} : {};
+
+	return {
+		id: `${config.url}/notes/${note.id}`,
+		type: 'Note',
+		attributedTo,
+		summary,
+		content,
+		_misskey_content: text,
+		_misskey_quote: quote,
+		quoteUrl: quote,
+		published: note.createdAt.toISOString(),
+		to,
+		cc,
+		inReplyTo,
+		attachment: files.map(renderDocument),
+		sensitive: note.cw != null || files.some(file => file.isSensitive),
+		tag,
+		...asPoll,
+		...asTalk
+	};
+}
+
+export async function getEmojis(names: string[]): Promise<Emoji[]> {
+	if (names == null || names.length === 0) return [];
+
+	const emojis = await Promise.all(
+		names.map(name => Emojis.findOne({
+			name,
+			host: null
+		}))
+	);
+
+	return emojis.filter(emoji => emoji != null) as Emoji[];
+}
--- a/packages/backend/src/remote/activitypub/renderer/ordered-collection-page.ts
+++ b/packages/backend/src/remote/activitypub/renderer/ordered-collection-page.ts
@ -0,0 +1,23 @@
+/**
+ * Render OrderedCollectionPage
+ * @param id URL of self
+ * @param totalItems Number of total items
+ * @param orderedItems Items
+ * @param partOf URL of base
+ * @param prev URL of prev page (optional)
+ * @param next URL of next page (optional)
+ */
+export default function(id: string, totalItems: any, orderedItems: any, partOf: string, prev?: string, next?: string) {
+	const page = {
+		id,
+		partOf,
+		type: 'OrderedCollectionPage',
+		totalItems,
+		orderedItems
+	} as any;
+
+	if (prev) page.prev = prev;
+	if (next) page.next = next;
+
+	return page;
+}
--- a/packages/backend/src/remote/activitypub/renderer/ordered-collection.ts
+++ b/packages/backend/src/remote/activitypub/renderer/ordered-collection.ts
@ -0,0 +1,21 @@
+/**
+ * Render OrderedCollection
+ * @param id URL of self
+ * @param totalItems Total number of items
+ * @param first URL of first page (optional)
+ * @param last URL of last page (optional)
+ * @param orderedItems attached objects (optional)
+ */
+export default function(id: string | null, totalItems: any, first?: string, last?: string, orderedItems?: object) {
+	const page: any = {
+		id,
+		type: 'OrderedCollection',
+		totalItems,
+	};
+
+	if (first) page.first = first;
+	if (last) page.last = last;
+	if (orderedItems) page.orderedItems = orderedItems;
+
+	return page;
+}
--- a/packages/backend/src/remote/activitypub/renderer/person.ts
+++ b/packages/backend/src/remote/activitypub/renderer/person.ts
@ -0,0 +1,89 @@
+import { URL } from 'url';
+import * as mfm from 'mfm-js';
+import renderImage from './image';
+import renderKey from './key';
+import config from '@/config/index';
+import { ILocalUser } from '@/models/entities/user';
+import { toHtml } from '../../../mfm/to-html';
+import { getEmojis } from './note';
+import renderEmoji from './emoji';
+import { IIdentifier } from '../models/identifier';
+import renderHashtag from './hashtag';
+import { DriveFiles, UserProfiles } from '@/models/index';
+import { getUserKeypair } from '@/misc/keypair-store';
+
+export async function renderPerson(user: ILocalUser) {
+	const id = `${config.url}/users/${user.id}`;
+	const isSystem = !!user.username.match(/\./);
+
+	const [avatar, banner, profile] = await Promise.all([
+		user.avatarId ? DriveFiles.findOne(user.avatarId) : Promise.resolve(undefined),
+		user.bannerId ? DriveFiles.findOne(user.bannerId) : Promise.resolve(undefined),
+		UserProfiles.findOneOrFail(user.id)
+	]);
+
+	const attachment: {
+		type: 'PropertyValue',
+		name: string,
+		value: string,
+		identifier?: IIdentifier
+	}[] = [];
+
+	if (profile.fields) {
+		for (const field of profile.fields) {
+			attachment.push({
+				type: 'PropertyValue',
+				name: field.name,
+				value: (field.value != null && field.value.match(/^https?:/))
+					? `<a href="${new URL(field.value).href}" rel="me nofollow noopener" target="_blank">${new URL(field.value).href}</a>`
+					: field.value
+			});
+		}
+	}
+
+	const emojis = await getEmojis(user.emojis);
+	const apemojis = emojis.map(emoji => renderEmoji(emoji));
+
+	const hashtagTags = (user.tags || []).map(tag => renderHashtag(tag));
+
+	const tag = [
+		...apemojis,
+		...hashtagTags,
+	];
+
+	const keypair = await getUserKeypair(user.id);
+
+	const person = {
+		type: isSystem ? 'Application' : user.isBot ? 'Service' : 'Person',
+		id,
+		inbox: `${id}/inbox`,
+		outbox: `${id}/outbox`,
+		followers: `${id}/followers`,
+		following: `${id}/following`,
+		featured: `${id}/collections/featured`,
+		sharedInbox: `${config.url}/inbox`,
+		endpoints: { sharedInbox: `${config.url}/inbox` },
+		url: `${config.url}/@${user.username}`,
+		preferredUsername: user.username,
+		name: user.name,
+		summary: profile.description ? toHtml(mfm.parse(profile.description)) : null,
+		icon: avatar ? renderImage(avatar) : null,
+		image: banner ? renderImage(banner) : null,
+		tag,
+		manuallyApprovesFollowers: user.isLocked,
+		discoverable: !!user.isExplorable,
+		publicKey: renderKey(user, keypair, `#main-key`),
+		isCat: user.isCat,
+		attachment: attachment.length ? attachment : undefined
+	} as any;
+
+	if (profile?.birthday) {
+		person['vcard:bday'] = profile.birthday;
+	}
+
+	if (profile?.location) {
+		person['vcard:Address'] = profile.location;
+	}
+
+	return person;
+}
--- a/packages/backend/src/remote/activitypub/renderer/question.ts
+++ b/packages/backend/src/remote/activitypub/renderer/question.ts
@ -0,0 +1,23 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+import { Note } from '@/models/entities/note';
+import { Poll } from '@/models/entities/poll';
+
+export default async function renderQuestion(user: { id: User['id'] }, note: Note, poll: Poll) {
+	const question = {
+		type: 'Question',
+		id: `${config.url}/questions/${note.id}`,
+		actor: `${config.url}/users/${user.id}`,
+		content:  note.text || '',
+		[poll.multiple ? 'anyOf' : 'oneOf']: poll.choices.map((text, i) => ({
+			name: text,
+			_misskey_votes: poll.votes[i],
+			replies: {
+				type: 'Collection',
+				totalItems: poll.votes[i]
+			}
+		}))
+	};
+
+	return question;
+}
--- a/packages/backend/src/remote/activitypub/renderer/read.ts
+++ b/packages/backend/src/remote/activitypub/renderer/read.ts
@ -0,0 +1,9 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+import { MessagingMessage } from '@/models/entities/messaging-message';
+
+export const renderReadActivity = (user: { id: User['id'] }, message: MessagingMessage) => ({
+	type: 'Read',
+	actor: `${config.url}/users/${user.id}`,
+	object: message.uri
+});
--- a/packages/backend/src/remote/activitypub/renderer/reject.ts
+++ b/packages/backend/src/remote/activitypub/renderer/reject.ts
@ -0,0 +1,8 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+
+export default (object: any, user: { id: User['id'] }) => ({
+	type: 'Reject',
+	actor: `${config.url}/users/${user.id}`,
+	object
+});
--- a/packages/backend/src/remote/activitypub/renderer/remove.ts
+++ b/packages/backend/src/remote/activitypub/renderer/remove.ts
@ -0,0 +1,9 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+
+export default (user: { id: User['id'] }, target: any, object: any) => ({
+	type: 'Remove',
+	actor: `${config.url}/users/${user.id}`,
+	target,
+	object
+});
--- a/packages/backend/src/remote/activitypub/renderer/tombstone.ts
+++ b/packages/backend/src/remote/activitypub/renderer/tombstone.ts
@ -0,0 +1,4 @@
+export default (id: string) => ({
+	id,
+	type: 'Tombstone'
+});
--- a/packages/backend/src/remote/activitypub/renderer/undo.ts
+++ b/packages/backend/src/remote/activitypub/renderer/undo.ts
@ -0,0 +1,13 @@
+import config from '@/config/index';
+import { ILocalUser, User } from '@/models/entities/user';
+
+export default (object: any, user: { id: User['id'] }) => {
+	if (object == null) return null;
+
+	return {
+		type: 'Undo',
+		actor: `${config.url}/users/${user.id}`,
+		object,
+		published: new Date().toISOString(),
+	};
+};
--- a/packages/backend/src/remote/activitypub/renderer/update.ts
+++ b/packages/backend/src/remote/activitypub/renderer/update.ts
@ -0,0 +1,15 @@
+import config from '@/config/index';
+import { User } from '@/models/entities/user';
+
+export default (object: any, user: { id: User['id'] }) => {
+	const activity = {
+		id: `${config.url}/users/${user.id}#updates/${new Date().getTime()}`,
+		actor: `${config.url}/users/${user.id}`,
+		type: 'Update',
+		to: [ 'https://www.w3.org/ns/activitystreams#Public' ],
+		object,
+		published: new Date().toISOString(),
+	} as any;
+
+	return activity;
+};
--- a/packages/backend/src/remote/activitypub/renderer/vote.ts
+++ b/packages/backend/src/remote/activitypub/renderer/vote.ts
@ -0,0 +1,23 @@
+import config from '@/config/index';
+import { Note } from '@/models/entities/note';
+import { IRemoteUser, User } from '@/models/entities/user';
+import { PollVote } from '@/models/entities/poll-vote';
+import { Poll } from '@/models/entities/poll';
+
+export default async function renderVote(user: { id: User['id'] }, vote: PollVote, note: Note, poll: Poll, pollOwner: IRemoteUser): Promise<any> {
+	return {
+		id: `${config.url}/users/${user.id}#votes/${vote.id}/activity`,
+		actor: `${config.url}/users/${user.id}`,
+		type: 'Create',
+		to: [pollOwner.uri],
+		published: new Date().toISOString(),
+		object: {
+			id: `${config.url}/users/${user.id}#votes/${vote.id}`,
+			type: 'Note',
+			attributedTo: `${config.url}/users/${user.id}`,
+			to: [pollOwner.uri],
+			inReplyTo: note.uri,
+			name: poll.choices[vote.choice]
+		}
+	};
+}
--- a/packages/backend/src/remote/activitypub/request.ts
+++ b/packages/backend/src/remote/activitypub/request.ts
@ -0,0 +1,58 @@
+import config from '@/config/index';
+import { getUserKeypair } from '@/misc/keypair-store';
+import { User } from '@/models/entities/user';
+import { getResponse } from '../../misc/fetch';
+import { createSignedPost, createSignedGet } from './ap-request';
+
+export default async (user: { id: User['id'] }, url: string, object: any) => {
+	const body = JSON.stringify(object);
+
+	const keypair = await getUserKeypair(user.id);
+
+	const req = createSignedPost({
+		key: {
+			privateKeyPem: keypair.privateKey,
+			keyId: `${config.url}/users/${user.id}#main-key`
+		},
+		url,
+		body,
+		additionalHeaders: {
+			'User-Agent': config.userAgent,
+		}
+	});
+
+	await getResponse({
+		url,
+		method: req.request.method,
+		headers: req.request.headers,
+		body,
+	});
+};
+
+/**
+ * Get AP object with http-signature
+ * @param user http-signature user
+ * @param url URL to fetch
+ */
+export async function signedGet(url: string, user: { id: User['id'] }) {
+	const keypair = await getUserKeypair(user.id);
+
+	const req = createSignedGet({
+		key: {
+			privateKeyPem: keypair.privateKey,
+			keyId: `${config.url}/users/${user.id}#main-key`
+		},
+		url,
+		additionalHeaders: {
+			'User-Agent': config.userAgent,
+		}
+	});
+
+	const res = await getResponse({
+		url,
+		method: req.request.method,
+		headers: req.request.headers
+	});
+
+	return await res.json();
+}
--- a/packages/backend/src/remote/activitypub/resolver.ts
+++ b/packages/backend/src/remote/activitypub/resolver.ts
@ -0,0 +1,73 @@
+import config from '@/config/index';
+import { getJson } from '@/misc/fetch';
+import { ILocalUser } from '@/models/entities/user';
+import { getInstanceActor } from '@/services/instance-actor';
+import { signedGet } from './request';
+import { IObject, isCollectionOrOrderedCollection, ICollection, IOrderedCollection } from './type';
+import { fetchMeta } from '@/misc/fetch-meta';
+import { extractDbHost } from '@/misc/convert-host';
+
+export default class Resolver {
+	private history: Set<string>;
+	private user?: ILocalUser;
+
+	constructor() {
+		this.history = new Set();
+	}
+
+	public getHistory(): string[] {
+		return Array.from(this.history);
+	}
+
+	public async resolveCollection(value: string | IObject): Promise<ICollection | IOrderedCollection> {
+		const collection = typeof value === 'string'
+			? await this.resolve(value)
+			: value;
+
+		if (isCollectionOrOrderedCollection(collection)) {
+			return collection;
+		} else {
+			throw new Error(`unrecognized collection type: ${collection.type}`);
+		}
+	}
+
+	public async resolve(value: string | IObject): Promise<IObject> {
+		if (value == null) {
+			throw new Error('resolvee is null (or undefined)');
+		}
+
+		if (typeof value !== 'string') {
+			return value;
+		}
+
+		if (this.history.has(value)) {
+			throw new Error('cannot resolve already resolved one');
+		}
+
+		this.history.add(value);
+
+		const meta = await fetchMeta();
+		const host = extractDbHost(value);
+		if (meta.blockedHosts.includes(host)) {
+			throw new Error('Instance is blocked');
+		}
+
+		if (config.signToActivityPubGet && !this.user) {
+			this.user = await getInstanceActor();
+		}
+
+		const object = this.user
+			? await signedGet(value, this.user)
+			: await getJson(value, 'application/activity+json, application/ld+json');
+
+		if (object == null || (
+			Array.isArray(object['@context']) ?
+				!object['@context'].includes('https://www.w3.org/ns/activitystreams') :
+				object['@context'] !== 'https://www.w3.org/ns/activitystreams'
+		)) {
+			throw new Error('invalid response');
+		}
+
+		return object;
+	}
+}
--- a/packages/backend/src/remote/activitypub/type.ts
+++ b/packages/backend/src/remote/activitypub/type.ts
@ -0,0 +1,289 @@
+export type obj = { [x: string]: any };
+export type ApObject = IObject | string | (IObject | string)[];
+
+export interface IObject {
+	'@context': string | obj | obj[];
+	type: string | string[];
+	id?: string;
+	summary?: string;
+	published?: string;
+	cc?: ApObject;
+	to?: ApObject;
+	attributedTo: ApObject;
+	attachment?: any[];
+	inReplyTo?: any;
+	replies?: ICollection;
+	content?: string;
+	name?: string;
+	startTime?: Date;
+	endTime?: Date;
+	icon?: any;
+	image?: any;
+	url?: ApObject;
+	href?: string;
+	tag?: IObject | IObject[];
+	sensitive?: boolean;
+}
+
+/**
+ * Get array of ActivityStreams Objects id
+ */
+export function getApIds(value: ApObject | undefined): string[] {
+	if (value == null) return [];
+	const array = Array.isArray(value) ? value : [value];
+	return array.map(x => getApId(x));
+}
+
+/**
+ * Get first ActivityStreams Object id
+ */
+export function getOneApId(value: ApObject): string {
+	const firstOne = Array.isArray(value) ? value[0] : value;
+	return getApId(firstOne);
+}
+
+/**
+ * Get ActivityStreams Object id
+ */
+export function getApId(value: string | IObject): string {
+	if (typeof value === 'string') return value;
+	if (typeof value.id === 'string') return value.id;
+	throw new Error(`cannot detemine id`);
+}
+
+/**
+ * Get ActivityStreams Object type
+ */
+export function getApType(value: IObject): string {
+	if (typeof value.type === 'string') return value.type;
+	if (Array.isArray(value.type) && typeof value.type[0] === 'string') return value.type[0];
+	throw new Error(`cannot detect type`);
+}
+
+export function getOneApHrefNullable(value: ApObject | undefined): string | undefined {
+	const firstOne = Array.isArray(value) ? value[0] : value;
+	return getApHrefNullable(firstOne);
+}
+
+export function getApHrefNullable(value: string | IObject | undefined): string | undefined {
+	if (typeof value === 'string') return value;
+	if (typeof value?.href === 'string') return value.href;
+	return undefined;
+}
+
+export interface IActivity extends IObject {
+	//type: 'Activity';
+	actor: IObject | string;
+	object: IObject | string;
+	target?: IObject | string;
+	/** LD-Signature */
+	signature?: {
+		type: string;
+		created: Date;
+		creator: string;
+		domain?: string;
+		nonce?: string;
+		signatureValue: string;
+	};
+}
+
+export interface ICollection extends IObject {
+	type: 'Collection';
+	totalItems: number;
+	items: ApObject;
+}
+
+export interface IOrderedCollection extends IObject {
+	type: 'OrderedCollection';
+	totalItems: number;
+	orderedItems: ApObject;
+}
+
+export const validPost = ['Note', 'Question', 'Article', 'Audio', 'Document', 'Image', 'Page', 'Video', 'Event'];
+
+export const isPost = (object: IObject): object is IPost =>
+	validPost.includes(getApType(object));
+
+export interface IPost extends IObject {
+	type: 'Note' | 'Question' | 'Article' | 'Audio' | 'Document' | 'Image' | 'Page' | 'Video' | 'Event';
+	_misskey_content?: string;
+	_misskey_quote?: string;
+	quoteUrl?: string;
+	_misskey_talk: boolean;
+}
+
+export interface IQuestion extends IObject {
+	type: 'Note' | 'Question';
+	_misskey_content?: string;
+	_misskey_quote?: string;
+	quoteUrl?: string;
+	oneOf?: IQuestionChoice[];
+	anyOf?: IQuestionChoice[];
+	endTime?: Date;
+	closed?: Date;
+}
+
+export const isQuestion = (object: IObject): object is IQuestion =>
+	getApType(object) === 'Note' || getApType(object) === 'Question';
+
+interface IQuestionChoice {
+	name?: string;
+	replies?: ICollection;
+	_misskey_votes?: number;
+}
+export interface ITombstone extends IObject {
+	type: 'Tombstone';
+	formerType?: string;
+	deleted?: Date;
+}
+
+export const isTombstone = (object: IObject): object is ITombstone =>
+	getApType(object) === 'Tombstone';
+
+export const validActor = ['Person', 'Service', 'Group', 'Organization', 'Application'];
+
+export const isActor = (object: IObject): object is IActor =>
+	validActor.includes(getApType(object));
+
+export interface IActor extends IObject {
+	type: 'Person' | 'Service' | 'Organization' | 'Group' | 'Application';
+	name?: string;
+	preferredUsername?: string;
+	manuallyApprovesFollowers?: boolean;
+	discoverable?: boolean;
+	inbox: string;
+	sharedInbox?: string;	// 後方互換性のため
+	publicKey?: {
+		id: string;
+		publicKeyPem: string;
+	};
+	followers?: string | ICollection | IOrderedCollection;
+	following?: string | ICollection | IOrderedCollection;
+	featured?: string | IOrderedCollection;
+	outbox: string | IOrderedCollection;
+	endpoints?: {
+		sharedInbox?: string;
+	};
+	'vcard:bday'?: string;
+	'vcard:Address'?: string;
+}
+
+export const isCollection = (object: IObject): object is ICollection =>
+	getApType(object) === 'Collection';
+
+export const isOrderedCollection = (object: IObject): object is IOrderedCollection =>
+	getApType(object) === 'OrderedCollection';
+
+export const isCollectionOrOrderedCollection = (object: IObject): object is ICollection | IOrderedCollection =>
+	isCollection(object) || isOrderedCollection(object);
+
+export interface IApPropertyValue extends IObject {
+	type: 'PropertyValue';
+	identifier: IApPropertyValue;
+	name: string;
+	value: string;
+}
+
+export const isPropertyValue = (object: IObject): object is IApPropertyValue =>
+	object &&
+	getApType(object) === 'PropertyValue' &&
+	typeof object.name === 'string' &&
+	typeof (object as any).value === 'string';
+
+export interface IApMention extends IObject {
+	type: 'Mention';
+	href: string;
+}
+
+export const isMention = (object: IObject): object is IApMention=>
+	getApType(object) === 'Mention' &&
+	typeof object.href === 'string';
+
+export interface IApHashtag extends IObject {
+	type: 'Hashtag';
+	name: string;
+}
+
+export const isHashtag = (object: IObject): object is IApHashtag =>
+	getApType(object) === 'Hashtag' &&
+	typeof object.name === 'string';
+
+export interface IApEmoji extends IObject {
+	type: 'Emoji';
+	updated: Date;
+}
+
+export const isEmoji = (object: IObject): object is IApEmoji =>
+	getApType(object) === 'Emoji' && !Array.isArray(object.icon) && object.icon.url != null;
+
+export interface ICreate extends IActivity {
+	type: 'Create';
+}
+
+export interface IDelete extends IActivity {
+	type: 'Delete';
+}
+
+export interface IUpdate extends IActivity {
+	type: 'Update';
+}
+
+export interface IRead extends IActivity {
+	type: 'Read';
+}
+
+export interface IUndo extends IActivity {
+	type: 'Undo';
+}
+
+export interface IFollow extends IActivity {
+	type: 'Follow';
+}
+
+export interface IAccept extends IActivity {
+	type: 'Accept';
+}
+
+export interface IReject extends IActivity {
+	type: 'Reject';
+}
+
+export interface IAdd extends IActivity {
+	type: 'Add';
+}
+
+export interface IRemove extends IActivity {
+	type: 'Remove';
+}
+
+export interface ILike extends IActivity {
+	type: 'Like' | 'EmojiReaction' | 'EmojiReact';
+	_misskey_reaction?: string;
+}
+
+export interface IAnnounce extends IActivity {
+	type: 'Announce';
+}
+
+export interface IBlock extends IActivity {
+	type: 'Block';
+}
+
+export interface IFlag extends IActivity {
+	type: 'Flag';
+}
+
+export const isCreate = (object: IObject): object is ICreate => getApType(object) === 'Create';
+export const isDelete = (object: IObject): object is IDelete => getApType(object) === 'Delete';
+export const isUpdate = (object: IObject): object is IUpdate => getApType(object) === 'Update';
+export const isRead = (object: IObject): object is IRead => getApType(object) === 'Read';
+export const isUndo = (object: IObject): object is IUndo => getApType(object) === 'Undo';
+export const isFollow = (object: IObject): object is IFollow => getApType(object) === 'Follow';
+export const isAccept = (object: IObject): object is IAccept => getApType(object) === 'Accept';
+export const isReject = (object: IObject): object is IReject => getApType(object) === 'Reject';
+export const isAdd = (object: IObject): object is IAdd => getApType(object) === 'Add';
+export const isRemove = (object: IObject): object is IRemove => getApType(object) === 'Remove';
+export const isLike = (object: IObject): object is ILike => getApType(object) === 'Like' || getApType(object) === 'EmojiReaction' || getApType(object) === 'EmojiReact';
+export const isAnnounce = (object: IObject): object is IAnnounce => getApType(object) === 'Announce';
+export const isBlock = (object: IObject): object is IBlock => getApType(object) === 'Block';
+export const isFlag = (object: IObject): object is IFlag => getApType(object) === 'Flag';
--- a/packages/backend/src/remote/logger.ts
+++ b/packages/backend/src/remote/logger.ts
@ -0,0 +1,3 @@
+import Logger from '@/services/logger';
+
+export const remoteLogger = new Logger('remote', 'cyan');
--- a/packages/backend/src/remote/resolve-user.ts
+++ b/packages/backend/src/remote/resolve-user.ts
@ -0,0 +1,110 @@
+import { URL } from 'url';
+import webFinger from './webfinger';
+import config from '@/config/index';
+import { createPerson, updatePerson } from './activitypub/models/person';
+import { remoteLogger } from './logger';
+import * as chalk from 'chalk';
+import { User, IRemoteUser } from '@/models/entities/user';
+import { Users } from '@/models/index';
+import { toPuny } from '@/misc/convert-host';
+
+const logger = remoteLogger.createSubLogger('resolve-user');
+
+export async function resolveUser(username: string, host: string | null, option?: any, resync = false): Promise<User> {
+	const usernameLower = username.toLowerCase();
+
+	if (host == null) {
+		logger.info(`return local user: ${usernameLower}`);
+		return await Users.findOne({ usernameLower, host: null }).then(u => {
+			if (u == null) {
+				throw new Error('user not found');
+			} else {
+				return u;
+			}
+		});
+	}
+
+	host = toPuny(host);
+
+	if (config.host == host) {
+		logger.info(`return local user: ${usernameLower}`);
+		return await Users.findOne({ usernameLower, host: null }).then(u => {
+			if (u == null) {
+				throw new Error('user not found');
+			} else {
+				return u;
+			}
+		});
+	}
+
+	const user = await Users.findOne({ usernameLower, host }, option) as IRemoteUser;
+
+	const acctLower = `${usernameLower}@${host}`;
+
+	if (user == null) {
+		const self = await resolveSelf(acctLower);
+
+		logger.succ(`return new remote user: ${chalk.magenta(acctLower)}`);
+		return await createPerson(self.href);
+	}
+
+	// resyncオプション OR ユーザー情報が古い場合は、WebFilgerからやりなおして返す
+	if (resync || user.lastFetchedAt == null || Date.now() - user.lastFetchedAt.getTime() > 1000 * 60 * 60 * 24) {
+		// 繋がらないインスタンスに何回も試行するのを防ぐ, 後続の同様処理の連続試行を防ぐ ため 試行前にも更新する
+		await Users.update(user.id, {
+			lastFetchedAt: new Date(),
+		});
+
+		logger.info(`try resync: ${acctLower}`);
+		const self = await resolveSelf(acctLower);
+
+		if (user.uri !== self.href) {
+			// if uri mismatch, Fix (user@host <=> AP's Person id(IRemoteUser.uri)) mapping.
+			logger.info(`uri missmatch: ${acctLower}`);
+			logger.info(`recovery missmatch uri for (username=${username}, host=${host}) from ${user.uri} to ${self.href}`);
+
+			// validate uri
+			const uri = new URL(self.href);
+			if (uri.hostname !== host) {
+				throw new Error(`Invalid uri`);
+			}
+
+			await Users.update({
+				usernameLower,
+				host: host
+			}, {
+				uri: self.href
+			});
+		} else {
+			logger.info(`uri is fine: ${acctLower}`);
+		}
+
+		await updatePerson(self.href);
+
+		logger.info(`return resynced remote user: ${acctLower}`);
+		return await Users.findOne({ uri: self.href }).then(u => {
+			if (u == null) {
+				throw new Error('user not found');
+			} else {
+				return u;
+			}
+		});
+	}
+
+	logger.info(`return existing remote user: ${acctLower}`);
+	return user;
+}
+
+async function resolveSelf(acctLower: string) {
+	logger.info(`WebFinger for ${chalk.yellow(acctLower)}`);
+	const finger = await webFinger(acctLower).catch(e => {
+		logger.error(`Failed to WebFinger for ${chalk.yellow(acctLower)}: ${ e.statusCode || e.message }`);
+		throw new Error(`Failed to WebFinger for ${acctLower}: ${ e.statusCode || e.message }`);
+	});
+	const self = finger.links.find(link => link.rel != null && link.rel.toLowerCase() === 'self');
+	if (!self) {
+		logger.error(`Failed to WebFinger for ${chalk.yellow(acctLower)}: self link not found`);
+		throw new Error('self link not found');
+	}
+	return self;
+}
--- a/packages/backend/src/remote/webfinger.ts
+++ b/packages/backend/src/remote/webfinger.ts
@ -0,0 +1,34 @@
+import { URL } from 'url';
+import { getJson } from '@/misc/fetch';
+import { query as urlQuery } from '@/prelude/url';
+
+type ILink = {
+	href: string;
+	rel?: string;
+};
+
+type IWebFinger = {
+	links: ILink[];
+	subject: string;
+};
+
+export default async function(query: string): Promise<IWebFinger> {
+	const url = genUrl(query);
+
+	return await getJson(url, 'application/jrd+json, application/json');
+}
+
+function genUrl(query: string) {
+	if (query.match(/^https?:\/\//)) {
+		const u = new URL(query);
+		return `${u.protocol}//${u.hostname}/.well-known/webfinger?` + urlQuery({ resource: query });
+	}
+
+	const m = query.match(/^([^@]+)@(.*)/);
+	if (m) {
+		const hostname = m[2];
+		return `https://${hostname}/.well-known/webfinger?` + urlQuery({ resource: `acct:${query}` });
+	}
+
+	throw new Error(`Invalid query (${query})`);
+}