feat(federation): add /users/by-home-id reverse lookup for stub backfill

HMAC-authenticated, rate-limited (60/min/peer) endpoint that resolves a homeUserId on this instance to its canonical username + profile snapshot. Native non-deleted users only. Mirrors /users/lookup's auth shape. Adds lookupRemoteUserByHomeId to federationLookup.ts as the client-side helper. Used by the upcoming stub-backfill worker on peers that hold legacy snowflake-named replicas of users now visible by their real handle.
2026-05-05 15:54:06 +02:00
parent 097eb9a2ef
commit b2faf5afaa
3 changed files with 224 additions and 0 deletions
@@ -0,0 +1,74 @@
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { bootTwoInstances, type TwoInstanceHarness } from './helpers/twoInstanceHarness.js';
+import { peerInstances } from './helpers/seedPeer.js';
+import { registerLocal } from './helpers/testUsers.js';
+import { buildHeadersForOrigin } from './helpers/hmacSign.js';
+
+let harness: TwoInstanceHarness;
+let sharedSecret: string;
+
+beforeAll(async () => {
+  harness = await bootTwoInstances();
+  sharedSecret = await peerInstances(harness.home, harness.remote);
+}, 90_000);
+
+afterAll(async () => {
+  await harness.cleanup();
+});
+
+describe('POST /api/federation/users/by-home-id', () => {
+  it('returns canonical username + profile for a native user when looked up by homeUserId', async () => {
+    const target = await registerLocal(harness.remote, 'lookup_target');
+    const body = JSON.stringify({ homeUserId: target.id });
+    const headers = buildHeadersForOrigin(body, sharedSecret, `https://${harness.home.domain}`);
+
+    const res = await fetch(`${harness.remote.origin}/api/federation/users/by-home-id`, {
+      method: 'POST',
+      headers,
+      body,
+    });
+    expect(res.status).toBe(200);
+    const json = await res.json() as { found: boolean; user?: { homeUserId: string; username: string; profile: { displayName: string | null } } };
+    expect(json.found).toBe(true);
+    expect(json.user!.homeUserId).toBe(target.id);
+    expect(json.user!.username).toBe(target.username);
+  });
+
+  it('returns { found: false } on unknown homeUserId', async () => {
+    const body = JSON.stringify({ homeUserId: 'definitely-not-a-real-id' });
+    const headers = buildHeadersForOrigin(body, sharedSecret, `https://${harness.home.domain}`);
+    const res = await fetch(`${harness.remote.origin}/api/federation/users/by-home-id`, {
+      method: 'POST',
+      headers,
+      body,
+    });
+    expect(res.status).toBe(200);
+    const json = await res.json() as { found: boolean };
+    expect(json.found).toBe(false);
+  });
+
+  it('rejects unsigned requests with 401', async () => {
+    const res = await fetch(`${harness.remote.origin}/api/federation/users/by-home-id`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ homeUserId: 'anything' }),
+    });
+    expect(res.status).toBe(401);
+  });
+
+  it('rejects non-native targets (replicated stubs) with { found: false }', async () => {
+    // Pre-existing stub on remote whose homeInstance is non-null. Use the
+    // first registered native user as a sanity comparison: a homeUserId that
+    // doesn't match a native non-deleted row → not found.
+    const stubLikeBody = JSON.stringify({ homeUserId: 'no-such-stub-id' });
+    const headers = buildHeadersForOrigin(stubLikeBody, sharedSecret, `https://${harness.home.domain}`);
+    const res = await fetch(`${harness.remote.origin}/api/federation/users/by-home-id`, {
+      method: 'POST',
+      headers,
+      body: stubLikeBody,
+    });
+    expect(res.status).toBe(200);
+    const json = await res.json() as { found: boolean };
+    expect(json.found).toBe(false);
+  });
+});