Follow actor on migration

Follow the "moving from" actor to force Mastodon to deliver the Move
activity.

backend/src/accounts/alias.ts

@@ -1,10 +1,13 @@
 import { setActorAlias } from 'wildebeest/backend/src/activitypub/actors'
+import { deliverToActor } from 'wildebeest/backend/src/activitypub/deliver'
+import { getSigningKey } from 'wildebeest/backend/src/mastodon/account'
+import * as follow from 'wildebeest/backend/src/activitypub/activities/follow'
 import type { Actor } from 'wildebeest/backend/src/activitypub/actors'
 import { parseHandle } from 'wildebeest/backend/src/utils/parse'
 import { queryAcct } from 'wildebeest/backend/src/webfinger'
 import { type Database } from 'wildebeest/backend/src/database'
 
-export async function addAlias(db: Database, alias: string, connectedActor: Actor) {
+export async function addAlias(db: Database, alias: string, connectedActor: Actor, userKEK: string, domain: string) {
 	const handle = parseHandle(alias)
 	const acct = `${handle.localPart}@${handle.domain}`
 	if (handle.domain === null) {
@@ -17,4 +20,12 @@ export async function addAlias(db: Database, alias: string, connectedActor: Acto
 	}
 
 	await setActorAlias(db, connectedActor.id, actor.id)
+
+	// For Mastodon to deliver the Move Activity we need to be following the
+	// "moving from" actor.
+	{
+		const activity = follow.create(connectedActor, actor)
+		const signingKey = await getSigningKey(userKEK, db, connectedActor)
+		await deliverToActor(signingKey, connectedActor, actor, activity, domain)
+	}
 }

backend/src/activitypub/activities/handle.ts

@@ -387,6 +387,8 @@ export async function handle(
 				break
 			}
 
+			// FIXME: Requires alsoKnownAs to be set in both directions
+
 			// move followers
 			{
 				const collection = await getMetadata(fromActor.followers)

backend/test/wildebeest/settings.spec.ts

@@ -12,6 +12,8 @@ describe('Wildebeest', () => {
 			const db = await makeDB()
 			const actor = await createPerson(domain, db, userKEK, 'sven@cloudflare.com')
 
+			let receivedActivity: any = null
+
 			globalThis.fetch = async (input: RequestInfo) => {
 				if (input.toString() === 'https://example.com/.well-known/webfinger?resource=acct%3Atest%40example.com') {
 					return new Response(
@@ -32,21 +34,33 @@ describe('Wildebeest', () => {
 						JSON.stringify({
 							id: 'https://social.com/someone',
 							type: 'Person',
+							inbox: 'https://social.com/someone/inbox',
 						})
 					)
 				}
 
+				const request = new Request(input)
+				if (request.url === 'https://social.com/someone/inbox') {
+					assert.equal(request.method, 'POST')
+					const data = await request.json()
+					receivedActivity = data
+					return new Response('')
+				}
+
 				throw new Error('unexpected request to ' + input)
 			}
 
-			await alias.addAlias(db, 'test@example.com', actor)
+			await alias.addAlias(db, 'test@example.com', actor, userKEK, domain)
 
 			// Ensure the actor has the alias set
 			const newActor = await getActorById(db, actor.id)
 			assert(newActor)
 			assert(newActor.alsoKnownAs)
 			assert.equal(newActor.alsoKnownAs.length, 1)
 			assert.equal(newActor.alsoKnownAs[0], 'https://social.com/someone')
+
+			assert(receivedActivity)
+			assert.equal(receivedActivity.type, 'Follow')
 		})
 	})
 })

frontend/src/routes/(admin)/settings/(auth)/aliases/index.tsx

@@ -8,15 +8,17 @@ const zodSchema = zod$({
 	alias: z.string().min(1),
 })
 
-export const action = action$(async (data, { platform, json }) => {
+export const action = action$(async (data, { platform, json, request }) => {
+	const url = new URL(request.url)
+	const domain = url.hostname
 	const db = await getDatabase(platform)
 	const connectedActor = platform.data.connectedActor
 	if (connectedActor === null) {
 		throw json(500, { error: 'user not present in context' })
 	}
 
 	try {
-		await addAlias(db, data.alias, connectedActor)
+		await addAlias(db, data.alias, connectedActor, platform.userKEK, domain)
 	} catch (e: unknown) {
 		const error = e as { stack: string; cause: string }
 		console.error(error.stack, error.cause)