feat(federation): POST /api/federation/users/lookup endpoint

2026-04-25 21:32:49 +02:00
parent 069a1525ea
commit 03cef0e6b3
2 changed files with 343 additions and 0 deletions
@@ -1622,6 +1622,98 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
    },
  );

+  // ─── POST /api/federation/users/lookup ─────────────────────────────────────
+  // Server-to-server: resolve a username on this instance to its canonical
+  // (homeUserId, profile snapshot). Used by another instance to construct a
+  // friend_request_create event without requiring a federated user account.
+  //
+  // Returns 200 with profile snapshot for native users (regardless of the
+  // user's `discoverable` setting — exact-handle resolution).
+  // Returns 404 for tombstoned users, replicated stubs, or unknown usernames.
+  app.post<{ Body: { username?: unknown } }>(
+    '/api/federation/users/lookup',
+    { bodyLimit: 4 * 1024 },
+    async (request, reply) => {
+      const db = getDb();
+
+      // 1. Verify HMAC (mirror relay endpoint)
+      const fedHeaders = parseFederationHeaders(request.headers as Record<string, string | string[] | undefined>);
+      if (!fedHeaders) {
+        return reply.code(401).send({ error: 'Missing or malformed federation headers', statusCode: 401 });
+      }
+
+      const peer = db
+        .select()
+        .from(schema.federationPeers)
+        .where(eq(schema.federationPeers.origin, fedHeaders.origin))
+        .get();
+
+      if (!peer || peer.status !== 'active') {
+        return reply.code(403).send({ error: 'Unknown or inactive peer', statusCode: 403 });
+      }
+
+      if (isLookupRateLimited(peer.origin)) {
+        return reply.code(429).header('Retry-After', '60').send({ error: 'Rate limit exceeded', statusCode: 429 });
+      }
+
+      const bodyString = JSON.stringify(request.body);
+      if (!verifyPeerSignature(bodyString, fedHeaders.signature, fedHeaders.timestamp, fedHeaders.nonce, peer)) {
+        return reply.code(401).send({ error: 'Invalid signature', statusCode: 401 });
+      }
+
+      // 1b. Nonce-based replay protection
+      if (fedHeaders.nonce) {
+        if (isNonceDuplicate(peer.origin, fedHeaders.nonce)) {
+          return reply.code(409).send({ error: 'Duplicate nonce — possible replay', statusCode: 409 });
+        }
+      } else if (peer.nonceSupported) {
+        return reply.code(401).send({ error: 'Nonce required — peer previously supported nonces', statusCode: 401 });
+      }
+
+      // 2. Validate body
+      const rawUsername = (request.body as { username?: unknown } | null)?.username;
+      if (typeof rawUsername !== 'string') {
+        return reply.code(400).send({ error: 'username is required (string)', statusCode: 400 });
+      }
+      const username = rawUsername.trim().toLowerCase();
+      if (!username) {
+        return reply.code(400).send({ error: 'username is required', statusCode: 400 });
+      }
+
+      // 3. Native-only lookup with isDeleted filter; discoverable is NOT consulted.
+      const user = db
+        .select()
+        .from(schema.users)
+        .where(
+          and(
+            eq(schema.users.username, username),
+            eq(schema.users.isDeleted, 0),
+            isNull(schema.users.homeInstance),
+          ),
+        )
+        .get();
+
+      if (!user) {
+        return reply.code(404).send({ found: false, code: 'user_not_found' });
+      }
+
+      return reply.code(200).send({
+        found: true,
+        user: {
+          homeUserId: user.id,
+          username: user.username,
+          profile: {
+            displayName: user.displayName,
+            avatar: user.avatar,
+            avatarColor: user.avatarColor,
+            banner: user.banner,
+            bio: user.bio,
+          },
+        },
+      });
+    },
+  );
+
  // ─── POST /api/federation/sync ──────────────────────────────────────────────
  // Server-to-server: checkpoint catch-up sync. A peer calls this after downtime
  // to retrieve missed DM mutations from the mutation log.