security: brute-force protection on auth endpoints (v1.1.0)

- Nginx rate limit: 20 req/min per IP on /api/auth/login and /register
- slowapi rate limit: 10/min on login, 5/hour on register (Redis-backed)
- Real client IP extracted from X-Forwarded-For for accurate per-IP limiting

Authored by: Jack Levy

backend/app/api/auth.py

@@ -1,8 +1,9 @@
-from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi import APIRouter, Depends, HTTPException, Request, status
 from sqlalchemy import func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.dependencies import get_current_user
+from app.core.limiter import limiter
 from app.core.security import create_access_token, hash_password, verify_password
 from app.database import get_db
 from app.models.user import User
@@ -12,7 +13,8 @@ router = APIRouter()
 
 
 @router.post("/register", response_model=TokenResponse, status_code=201)
-async def register(body: UserCreate, db: AsyncSession = Depends(get_db)):
+@limiter.limit("5/hour")
+async def register(request: Request, body: UserCreate, db: AsyncSession = Depends(get_db)):
     if len(body.password) < 8:
         raise HTTPException(status_code=400, detail="Password must be at least 8 characters")
     if "@" not in body.email:
@@ -40,7 +42,8 @@ async def register(body: UserCreate, db: AsyncSession = Depends(get_db)):
 
 
 @router.post("/login", response_model=TokenResponse)
-async def login(body: UserCreate, db: AsyncSession = Depends(get_db)):
+@limiter.limit("10/minute")
+async def login(request: Request, body: UserCreate, db: AsyncSession = Depends(get_db)):
     result = await db.execute(select(User).where(User.email == body.email.lower()))
     user = result.scalar_one_or_none()
 

backend/app/core/limiter.py

@@ -0,0 +1,13 @@
+from slowapi import Limiter
+
+
+def _get_real_ip(request) -> str:
+    """Extract real client IP, respecting X-Forwarded-For from trusted proxies."""
+    forwarded = request.headers.get("X-Forwarded-For")
+    if forwarded:
+        return forwarded.split(",")[0].strip()
+    return request.client.host if request.client else "unknown"
+
+
+# Redis DB 1 keeps rate-limit counters separate from Celery (DB 0)
+limiter = Limiter(key_func=_get_real_ip, storage_uri="redis://redis:6379/1")

backend/app/main.py

@@ -1,8 +1,11 @@
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
+from slowapi import _rate_limit_exceeded_handler
+from slowapi.errors import RateLimitExceeded
 
 from app.api import bills, members, follows, dashboard, search, settings, admin, health, auth, notifications, notes, collections, share, alignment
 from app.config import settings as config
+from app.core.limiter import limiter
 
 app = FastAPI(
     title="PocketVeto",
@@ -10,6 +13,9 @@ app = FastAPI(
     version="1.0.0",
 )
 
+app.state.limiter = limiter
+app.add_exception_handler(RateLimitExceeded, _rate_limit_exceeded_handler)
+
 app.add_middleware(
     CORSMiddleware,
     allow_origins=[o for o in [config.LOCAL_URL, config.PUBLIC_URL] if o],

backend/requirements.txt

@@ -44,6 +44,10 @@ python-jose[cryptography]==3.3.0
 passlib[bcrypt]==1.7.4
 bcrypt==4.0.1
 
+# Rate limiting
+slowapi==0.1.9
+limits==3.13.0
+
 # Utilities
 python-dateutil==2.9.0
 tiktoken==0.8.0

nginx/nginx.conf

@@ -22,6 +22,10 @@ http {
                     '"$http_user_agent"';
     access_log /var/log/nginx/access.log main;
 
+    # Rate limiting — cap auth endpoints at 20 req/min per IP at the proxy layer
+    limit_req_zone $binary_remote_addr zone=auth:10m rate=20r/m;
+    limit_req_status 429;
+
     # Use Docker's internal DNS; valid=10s forces re-resolution after container restarts.
     # Variables in proxy_pass activate this resolver (upstream blocks do not).
     resolver 127.0.0.11 valid=10s ipv6=off;
@@ -32,6 +36,17 @@ http {
 
         client_max_body_size 10M;
 
+        # Auth endpoints — rate limited at proxy layer
+        location ~ ^/api/auth/(login|register)$ {
+            set $api http://api:8000;
+            limit_req zone=auth burst=5 nodelay;
+            proxy_pass $api;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+        }
+
         # API — variable forces re-resolution via resolver on each request cycle
         location /api/ {
             set $api http://api:8000;