feat(core-api): harden signed urls and llm rate limits

backend/core-api/src/routes/core.js

@@ -6,9 +6,11 @@ import { requireAuth, requirePolicy } from '../middleware/auth.js';
 import { createSignedUrlSchema } from '../contracts/core/create-signed-url.js';
 import { invokeLlmSchema } from '../contracts/core/invoke-llm.js';
 import { invokeVertexModel } from '../services/llm.js';
-import { generateReadSignedUrl, uploadToGcs } from '../services/storage.js';
+import { checkLlmRateLimit } from '../services/llm-rate-limit.js';
+import { generateReadSignedUrl, uploadToGcs, validateFileUriAccess } from '../services/storage.js';
 
 const DEFAULT_MAX_FILE_BYTES = 10 * 1024 * 1024;
+const DEFAULT_MAX_SIGNED_URL_SECONDS = 900;
 const ALLOWED_FILE_TYPES = new Set(['application/pdf', 'image/jpeg', 'image/jpg', 'image/png']);
 
 const upload = multer({
@@ -105,10 +107,25 @@ async function handleCreateSignedUrl(req, res, next) {
   try {
     const payload = parseBody(createSignedUrlSchema, req.body || {});
     const expiresInSeconds = payload.expiresInSeconds || 300;
+    const maxSignedUrlSeconds = Number.parseInt(
+      process.env.MAX_SIGNED_URL_SECONDS || `${DEFAULT_MAX_SIGNED_URL_SECONDS}`,
+      10
+    );
+    if (expiresInSeconds > maxSignedUrlSeconds) {
+      throw new AppError('VALIDATION_ERROR', `expiresInSeconds must be <= ${maxSignedUrlSeconds}`, 400);
+    }
+
     const signed = useMockSignedUrl()
-      ? mockSignedUrl(payload.fileUri, expiresInSeconds)
+      ? (() => {
+          validateFileUriAccess({
+            fileUri: payload.fileUri,
+            actorUid: req.actor.uid,
+          });
+          return mockSignedUrl(payload.fileUri, expiresInSeconds);
+        })()
       : await generateReadSignedUrl({
           fileUri: payload.fileUri,
+          actorUid: req.actor.uid,
           expiresInSeconds,
         });
 
@@ -124,6 +141,12 @@ async function handleCreateSignedUrl(req, res, next) {
 async function handleInvokeLlm(req, res, next) {
   try {
     const payload = parseBody(invokeLlmSchema, req.body || {});
+    const rateLimit = checkLlmRateLimit({ uid: req.actor.uid });
+    if (!rateLimit.allowed) {
+      throw new AppError('RATE_LIMITED', 'Too many model requests. Please retry shortly.', 429, {
+        retryAfterSeconds: rateLimit.retryAfterSeconds,
+      });
+    }
 
     const startedAt = Date.now();
     if (process.env.LLM_MOCK === 'false') {