feat(platform-service): restrict blob SAS/list/info to user scope

docs/workstreams/MOBILE_WORKSTREAM_REMAINING.md

@@ -89,6 +89,7 @@ Voice capture pipeline
 - [ ] **P0** — Integrate Azure Speech SDK for real-time STT on iOS (scaffolded) — https://github.com/saravanakumardb1/learning_multimodal_memory_agents/commit/8834322
 - [ ] **P0** — Integrate Azure Speech SDK for real-time STT on Android
 - [ ] **P1** — Upload raw audio to Azure Blob Storage after capture
+- [x] **P1** — Backend: user-scoped SAS URL generation for Blob uploads (`platform-service` `POST /api/blob/sas`)
 
 Text capture
 

services/platform-service/src/modules/blob/routes.ts

@@ -19,6 +19,13 @@ import {
 } from '../../lib/blob.js';
 import { GenerateSasSchema, ListBlobsSchema, DeleteBlobSchema, type BlobInfo } from './types.js';
 
+const USER_ALLOWED_CONTAINERS = new Set<string>([
+  BLOB_CONTAINERS.audio,
+  BLOB_CONTAINERS.transcripts,
+  BLOB_CONTAINERS.attachments,
+  BLOB_CONTAINERS.avatars,
+]);
+
 async function requireAuth(req: { headers: Record<string, string | string[] | undefined> }) {
   const authHeader = req.headers.authorization;
   if (!authHeader || typeof authHeader !== 'string') {
@@ -28,6 +35,27 @@ async function requireAuth(req: { headers: Record<string, string | string[] | un
   return verifyToken(token);
 }
 
+function isAdminRole(role: unknown): boolean {
+  return role === 'admin' || role === 'super_admin';
+}
+
+function userPrefix(auth: { productId?: string; sub: string }): string {
+  if (!auth.productId) return `${auth.sub}/`;
+  return `${auth.productId}/${auth.sub}/`;
+}
+
+function permissionsInclude(permissions: string, chars: string): boolean {
+  for (const ch of chars) {
+    if (permissions.includes(ch)) return true;
+  }
+  return false;
+}
+
+function normalizePrefix(input: string | undefined): string | undefined {
+  if (!input) return undefined;
+  return input.replace(/^\/+/, '');
+}
+
 export async function blobRoutes(app: FastifyInstance) {
   // Generate SAS URL for direct upload/download
   app.post('/blob/sas', async req => {
@@ -38,9 +66,21 @@ export async function blobRoutes(app: FastifyInstance) {
     }
     const { container, blobName, permissions, expiresInMinutes } = parsed.data;
 
-    // Only admins can generate write/delete SAS tokens
-    if (permissions !== 'r' && auth.role !== 'admin') {
-      throw new UnauthorizedError('Only admins can generate write SAS tokens');
+    const admin = isAdminRole(auth.role);
+    if (!admin) {
+      if (!USER_ALLOWED_CONTAINERS.has(container)) {
+        throw new UnauthorizedError(`Not allowed to access container: ${container}`);
+      }
+
+      const prefix = userPrefix({ productId: auth.productId, sub: auth.sub });
+      if (!blobName.startsWith(prefix)) {
+        throw new UnauthorizedError('Not allowed to access blobs outside your user scope');
+      }
+
+      // Never grant delete permissions to non-admins.
+      if (permissionsInclude(permissions, 'd')) {
+        throw new UnauthorizedError('Only admins can generate delete SAS tokens');
+      }
     }
 
     const sasUrl = generateSasUrl(container, blobName, permissions, expiresInMinutes);
@@ -56,17 +96,28 @@ export async function blobRoutes(app: FastifyInstance) {
 
   // List blobs in a container
   app.get('/blob/list', async req => {
-    await requireAuth(req);
+    const auth = await requireAuth(req);
     const parsed = ListBlobsSchema.safeParse(req.query);
     if (!parsed.success) {
       throw new BadRequestError(parsed.error.issues.map(i => i.message).join('; '));
     }
-    const { container, prefix, limit } = parsed.data;
+    const admin = isAdminRole(auth.role);
+    const { container, limit } = parsed.data;
+
+    if (!admin && !USER_ALLOWED_CONTAINERS.has(container)) {
+      throw new UnauthorizedError(`Not allowed to access container: ${container}`);
+    }
+
+    const requestedPrefix = normalizePrefix(parsed.data.prefix);
+    const effectivePrefix = admin
+      ? requestedPrefix
+      : `${userPrefix({ productId: auth.productId, sub: auth.sub })}${requestedPrefix ?? ''}`;
+
     const containerClient = await getContainerClient(container);
 
     const blobs: BlobInfo[] = [];
     let count = 0;
-    for await (const blob of containerClient.listBlobsFlat({ prefix: prefix || undefined })) {
+    for await (const blob of containerClient.listBlobsFlat({ prefix: effectivePrefix || undefined })) {
       if (count >= limit) break;
       blobs.push({
         name: blob.name,
@@ -80,7 +131,7 @@ export async function blobRoutes(app: FastifyInstance) {
       count++;
     }
 
-    return { blobs, count: blobs.length, container, prefix: prefix || null };
+    return { blobs, count: blobs.length, container, prefix: effectivePrefix || null };
   });
 
   // Delete a blob
@@ -109,13 +160,24 @@ export async function blobRoutes(app: FastifyInstance) {
 
   // Get blob metadata/info
   app.get('/blob/info/:container/:blobName', async req => {
-    await requireAuth(req);
+    const auth = await requireAuth(req);
     const { container, blobName } = req.params as { container: string; blobName: string };
 
     if (!Object.values(BLOB_CONTAINERS).includes(container as never)) {
       throw new BadRequestError(`Invalid container: ${container}`);
     }
 
+    const admin = isAdminRole(auth.role);
+    if (!admin) {
+      if (!USER_ALLOWED_CONTAINERS.has(container)) {
+        throw new UnauthorizedError(`Not allowed to access container: ${container}`);
+      }
+      const prefix = userPrefix({ productId: auth.productId, sub: auth.sub });
+      if (!blobName.startsWith(prefix)) {
+        throw new UnauthorizedError('Not allowed to access blobs outside your user scope');
+      }
+    }
+
     const containerClient = await getContainerClient(container);
     const blobClient = containerClient.getBlobClient(blobName);