FastAPI-Login tries to provide similar functionality as Flask-Login does.
In-depth documentation can be found at fastapi-login.readthedocs.io.
Some examples can be found here.
pip install fastapi-loginTo begin we have to setup our FastAPI app:
from fastapi import FastAPI
SECRET = 'your-secret-key'
app = FastAPI()To obtain a suitable secret key you can run import os; print(os.urandom(24).hex()).
Now we can import and setup the LoginManager, which will handle the process of encoding and decoding our Json Web Tokens.
from fastapi_login import LoginManager
manager = LoginManager(SECRET, token_url='/auth/token')For the example we will use a dictionary to represent our user database. In your application this could also be a real database like sqlite or Postgres. It does not matter as you have to provide the function which retrieves the user.
fake_db = {'[email protected]': {'password': 'hunter2'}}Now we have to provide the LoginManager with a way to load our user. The
user_loader callback should either return your user object or None
@manager.user_loader()
def load_user(email: str): # could also be an asynchronous function
user = fake_db.get(email)
return userNow we have to define a way to let the user login in our app. Therefore we will create a new route:
from fastapi import Depends
from fastapi.security import OAuth2PasswordRequestForm
from fastapi_login.exceptions import InvalidCredentialsException
# the python-multipart package is required to use the OAuth2PasswordRequestForm
@app.post('/auth/token')
def login(data: OAuth2PasswordRequestForm = Depends()):
email = data.username
password = data.password
user = load_user(email) # we are using the same function to retrieve the user
if not user:
raise InvalidCredentialsException # you can also use your own HTTPException
elif password != user['password']:
raise InvalidCredentialsException
access_token = manager.create_access_token(
data=dict(sub=email)
)
return {'access_token': access_token, 'token_type': 'bearer'}Now whenever you want your user to be logged in to use a route, you can simply
use your LoginManager instance as a dependency.
@app.get('/protected')
def protected_route(user=Depends(manager)):
...If you also want to handle a not authenticated error, you can add your own subclass of Exception to the LoginManager.
from starlette.responses import RedirectResponse
class NotAuthenticatedException(Exception):
pass
# these two argument are mandatory
def exc_handler(request, exc):
return RedirectResponse(url='/login')
manager = LoginManager(..., not_authenticated_exception=NotAuthenticatedException)
# You also have to add an exception handler to your app instance
app.add_exception_handler(NotAuthenticatedException, exc_handler)To change the expiration date of the token use the expires_delta argument of the create_access_token method
with a timedelta. The default is set 15 min. Please be aware that setting a long expiry date is not considered a good practice
as it would allow an attacker with the token to use your application as long as he wants.
from datetime import timedelta
data = dict(sub=user.email)
# expires after 15 min
token = manager.create_access_token(
data=data
)
# expires after 12 hours
long_token = manager.create_access_token(
data=data, expires=timedelta(hours=12)
)Instead of checking the header for the token. fastapi-login also support access using cookies.
from fastapi_login import LoginManager
manager = LoginManager(SECRET, token_url='/auth/token', use_cookie=True)Now the manager will check the requests cookies the headers for the access token. The name of the cookie can be set using
manager.cookie_name.
If you only want to check the requests cookies you can turn the headers off using the use_header argument
For convenience the LoginManager also includes the set_cookie method which sets the cookie to your response,
with the recommended HTTPOnly flag and the manager.cookie_name as the key.
from fastapi import Depends
from starlette.responses import Response
@app.get('/auth')
def auth(response: Response, user=Depends(manager)):
token = manager.create_access_token(
data=dict(sub=user.email)
)
manager.set_cookie(response, token)
return response
