feat(federation): lookupRemoteUser outbound HMAC helper

2026-04-25 21:37:41 +02:00
parent 03cef0e6b3
commit fbe2fb370b
2 changed files with 295 additions and 0 deletions
@@ -0,0 +1,77 @@
+import { eq } from 'drizzle-orm';
+import { getDb } from '../db/index.js';
+import * as schema from '../db/schema.js';
+import { buildFederationHeaders, getOurOrigin } from './federationAuth.js';
+import type { FederationUserLookupProfile, FederationUserLookupResponse } from '@backspace/shared';
+
+const LOOKUP_TIMEOUT_MS = 10_000;
+
+export type LookupResult =
+  | { ok: true; homeUserId: string; username: string; profile: FederationUserLookupProfile }
+  | { ok: false; reason: 'not_found' }
+  | { ok: false; reason: 'unreachable' }
+  | { ok: false; reason: 'rate_limited'; retryAfter?: number };
+
+/**
+ * Look up a username on a remote peer instance.
+ *
+ * - Looks up the peer's HMAC secret from the local federation_peers table.
+ * - Throws if the peer record is missing — caller must ensurePeered first.
+ * - Wraps fetch in a 10s timeout; network/timeout/AbortError → unreachable.
+ * - HTTP 404 → not_found; 429 → rate_limited (with retryAfter); 200 + valid body → ok;
+ *   anything else (5xx, unexpected 4xx, malformed body) → throws (logged at call site).
+ */
+export async function lookupRemoteUser(peerOrigin: string, username: string): Promise<LookupResult> {
+  const db = getDb();
+  const peer = db
+    .select()
+    .from(schema.federationPeers)
+    .where(eq(schema.federationPeers.origin, peerOrigin))
+    .get();
+
+  if (!peer) {
+    throw new Error(`lookupRemoteUser: no peer record for ${peerOrigin}`);
+  }
+
+  const body = JSON.stringify({ username });
+  const headers = buildFederationHeaders(body, peer.hmacSecret, getOurOrigin());
+
+  let response: Response;
+  try {
+    response = await fetch(`${peerOrigin}/api/federation/users/lookup`, {
+      method: 'POST',
+      headers,
+      body,
+      signal: AbortSignal.timeout(LOOKUP_TIMEOUT_MS),
+    });
+  } catch {
+    // Network error, timeout, AbortError — all unreachable.
+    return { ok: false, reason: 'unreachable' };
+  }
+
+  if (response.status === 404) {
+    return { ok: false, reason: 'not_found' };
+  }
+
+  if (response.status === 429) {
+    const raw = Number(response.headers.get('Retry-After') ?? '60');
+    const retryAfter = Number.isFinite(raw) ? raw : 60;
+    return { ok: false, reason: 'rate_limited', retryAfter };
+  }
+
+  if (!response.ok) {
+    throw new Error(`lookupRemoteUser: peer ${peerOrigin} returned HTTP ${response.status}`);
+  }
+
+  const json = (await response.json()) as FederationUserLookupResponse;
+  if (!json || json.found !== true || !json.user || typeof json.user.homeUserId !== 'string') {
+    throw new Error(`lookupRemoteUser: peer ${peerOrigin} returned malformed body`);
+  }
+
+  return {
+    ok: true,
+    homeUserId: json.user.homeUserId,
+    username: json.user.username,
+    profile: json.user.profile,
+  };
+}