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312"""API Key authentication middleware for FastAPI."""
import logging
import secrets
from collections.abc import Awaitable, Callable
from typing import Any
from fastapi import Request, Response, status
from fastapi.responses import JSONResponse
from starlette.middleware.base import BaseHTTPMiddleware
from ..auth.base import Identity
from ..config import settings
logger = logging.getLogger(__name__)
class APIKeyAuthMiddleware(BaseHTTPMiddleware):
"""
Middleware for API key authentication.
Validates API keys in the X-API-Key header (configurable).
Public endpoints (health, metrics, dev monitoring) bypass authentication.
"""
def __init__(self, app: Any) -> None:
"""
Initialize API key auth middleware.
Args:
app: FastAPI application instance
"""
super().__init__(app)
# Cache API keys at initialization to avoid reloading on every request
self._cached_keys: set[str] = self._load_api_keys()
def _load_api_keys(self) -> set[str]:
"""
Load valid API keys from settings.
Returns:
Set of valid API key strings
"""
if not settings.api_keys:
logger.warning("No API keys configured! All authenticated requests will be rejected.")
return set()
# Parse comma-separated keys from SecretStr
keys_str = settings.api_keys.get_secret_value()
keys = {key.strip() for key in keys_str.split(",") if key.strip()}
if not keys:
logger.warning("API keys configured but empty after parsing!")
return set()
logger.info(f"Loaded {len(keys)} API key(s) for authentication")
return keys
async def dispatch(self, request: Request, call_next: Callable[[Request], Awaitable[Response]]) -> Response:
"""
Validate API key before processing request.
Args:
request: Incoming request
call_next: Next middleware/handler
Returns:
Response object (401 if auth fails, otherwise normal response)
"""
# Skip authentication for public endpoints
if self._is_public_endpoint(request):
return await call_next(request)
# Extract API key from header
api_key = request.headers.get(settings.api_key_header_name)
# Check if API key is provided
if not api_key:
logger.warning(
f"Missing API key for {request.method} {request.url.path} from {self._get_client_ip(request)}"
)
return self._unauthorized_response(
detail=f"Missing API key. Provide a valid key in the '{settings.api_key_header_name}' header."
)
# Validate API key using constant-time comparison
if not self._is_valid_key(api_key):
logger.warning(
f"Invalid API key for {request.method} {request.url.path} from {self._get_client_ip(request)}"
)
return self._unauthorized_response(detail="Invalid API key")
# API key is valid, add to request state for potential use in handlers
request.state.api_key = api_key
# Process request
return await call_next(request)
def _is_public_endpoint(self, request: Request) -> bool:
"""
Check if endpoint is exempt from API key auth.
Only `/api/*` paths require an API key — everything else is served by
the (public) viewer, the LTI JWT flow, or is a public health check.
API routes themselves have three carve-outs:
- Development-only endpoints under /api/dev/monitoring, /api/dev/minimal,
/api/dev/pipeline-viewer are public when settings.environment == "dev"
- Same-origin requests from the viewer are exempt via
`_is_demo_ui_request` (checks Referer, Origin, and Sec-Fetch-Site)
so the viewer's JS can call the API without the browser having to
inject an X-API-Key header
- SSE stream endpoints with a `?token=` query parameter bypass API
key auth and validate the token in the endpoint handler instead
Args:
request: Incoming request
Returns:
True if the request is exempt from API key auth
"""
path = request.url.path
# API routes are the only ones gated by API key auth.
if path.startswith("/api/"):
# Session-authenticated requests (set by SessionAuthMiddleware
# when AUTH_MODE != 'none') short-circuit. Both auth paths
# coexist: an API key still works in parallel for programmatic
# clients regardless of AUTH_MODE.
#
# We isinstance-check rather than truthiness-check because mock
# tests upstream sometimes use MagicMock for request.state, and a
# MagicMock attribute is always truthy. Only a real Identity
# object should short-circuit.
if isinstance(getattr(request.state, "identity", None), Identity):
return True
# /api/v1/auth/* endpoints handle their own auth (config is
# always public; login/logout/me self-validate). Exempt the
# subtree here so an unauthenticated user can hit /auth/login.
if path.startswith("/api/v1/auth/"):
return True
# Dev-only endpoints are exempt when running in dev
if settings.environment == "dev" and (
path.startswith("/api/dev/monitoring")
or path.startswith("/api/dev/minimal")
or path.startswith("/api/dev/pipeline-viewer")
):
return True
# Same-origin requests from the viewer or demo UI.
# When AUTH_MODE != 'none', the SPA must establish a session
# before it can call the API — the same-origin shortcut is only
# safe in the open-default mode. Otherwise an unauthenticated
# browser session would defeat the new auth layer.
if settings.auth_mode == "none" and self._is_demo_ui_request(request):
return True
# SSE stream endpoints authenticate via ?token= query param
if self._is_stream_token_request(request):
return True
return False
# Everything outside /api/ is exempt from API key auth:
# - / and every SPA deep link → viewer HTML (public)
# - /viewer, /viewer/* → legacy 301 redirects to /
# - /health, /health/ready → public health checks
# - /docs, /openapi.json, /redoc → public API documentation
# - /lti/* → Canvas JWT auth
# - /static/canvas/* → dashboard assets
# - /metrics → Prometheus
# - /assets/*, favicons, fonts, etc. → public viewer static files
return True
def _is_demo_ui_request(self, request: Request) -> bool:
"""
Check if request is a same-origin browser fetch from the viewer SPA.
The viewer is served at `/` and is now publicly accessible. Its JS
calls /api/v1/* from the same origin without an X-API-Key header.
We identify these requests by the combination of:
- No X-API-Key header (external clients always send one)
- Sec-Fetch-Site: same-origin (set by the browser for genuinely
same-origin fetches, unforgeable by external callers)
This is safe because:
1. CORS prevents external sites from forging the Origin or reading
the response
2. External API clients must send X-API-Key, which takes the
normal-auth branch in dispatch() above before this code runs
3. Sec-Fetch-Site is a browser-controlled header — page scripts
cannot set or spoof it
Args:
request: Incoming request
Returns:
True if request appears to be a same-origin viewer fetch
"""
# If request has an API key, it's an external client - use normal auth
if request.headers.get(settings.api_key_header_name):
return False
# Same-origin fetch from the viewer SPA — trust the browser-set
# Sec-Fetch-Site header combined with absence of API key.
sec_fetch_site = request.headers.get("Sec-Fetch-Site", "")
if sec_fetch_site == "same-origin":
return True
return False
def _is_stream_token_request(self, request: Request) -> bool:
"""
Check if request has stream token for SSE endpoint.
Stream tokens allow bypassing API key auth for browser EventSource
connections which cannot send custom headers.
This only checks if the endpoint qualifies for token-based auth.
Actual token validation and consumption happens in the endpoint handler.
We mark it as "public" here to bypass API key check, then the
endpoint validates the token.
Args:
request: Incoming request
Returns:
True if this is a stream endpoint with a token parameter
"""
path = request.url.path
# Only applies to stream endpoints (not the token creation endpoint)
if not path.endswith("/stream"):
return False
# Must have token query parameter
token = request.query_params.get("token")
if not token:
return False
# Basic format validation (256-bit tokens are ~43 chars)
# Full validation happens in endpoint handler
if len(token) < 40:
return False
return True
def _is_valid_key(self, provided_key: str) -> bool:
"""
Validate API key using constant-time comparison.
Uses secrets.compare_digest() to prevent timing attacks.
Uses cached keys loaded at initialization for optimal performance.
Args:
provided_key: API key from request header
Returns:
True if key is valid
"""
if not self._cached_keys:
return False
# Use constant-time comparison to prevent timing attacks
for valid_key in self._cached_keys:
if secrets.compare_digest(provided_key, valid_key):
return True
return False
def _get_client_ip(self, request: Request) -> str:
"""
Extract client IP from request.
Handles X-Forwarded-For header for reverse proxy setups.
Args:
request: Incoming request
Returns:
Client IP address
"""
# Check X-Forwarded-For header (for reverse proxies)
forwarded = request.headers.get("X-Forwarded-For")
if forwarded:
return forwarded.split(",")[0].strip()
# Check X-Real-IP header (nginx)
real_ip = request.headers.get("X-Real-IP")
if real_ip:
return real_ip.strip()
# Fall back to direct connection IP
if request.client:
return request.client.host
return "unknown"
def _unauthorized_response(self, detail: str) -> JSONResponse:
"""
Create unauthorized error response.
Args:
detail: Error message
Returns:
401 Unauthorized response
"""
return JSONResponse(
status_code=status.HTTP_401_UNAUTHORIZED,
content={"detail": detail},
headers={"WWW-Authenticate": 'ApiKey realm="API", charset="UTF-8"'},
)