Implementing Secure JSON Web Token (JWT) Authentication in FastAPI
I'm getting frustrated with I've hit a wall trying to Currently developing an application using FastAPI that requires a secure authentication mechanism. I'm trying to implement JWT for user authentication, but I find myself confused about how to effectively encode and decode the tokens while ensuring security best practices. I've set up a basic login route that generates a token upon successful authentication. Here's a snippet of what I've tried so far: ```python from fastapi import FastAPI, Depends, HTTPException from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm from jose import JWTError, jwt from datetime import datetime, timedelta app = FastAPI() SECRET_KEY = "mysecret" ALGORITHM = "HS256" ACCESS_TOKEN_EXPIRE_MINUTES = 30 oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token") def create_access_token(data: dict, expires_delta: timedelta = None): to_encode = data.copy() if expires_delta: expire = datetime.utcnow() + expires_delta else: expire = datetime.utcnow() + timedelta(minutes=15) to_encode.update({"exp": expire}) encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM) return encoded_jwt ``` The token generation works, and I can successfully return it to the client. However, I need to ensure that the token validation is robust. When I attempt to decode the token in my protected routes, I sometimes receive a `JWTError` when the token is invalid, but I'm not sure how to handle this gracefully. Here’s a part of my decoding logic: ```python async def get_current_user(token: str = Depends(oauth2_scheme)): credentials_exception = HTTPException( status_code=HTTP_401_UNAUTHORIZED, detail="Could not validate credentials", headers={"WWW-Authenticate": "Bearer"}, ) try: payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM]) username: str = payload.get("sub") if username is None: raise credentials_exception except JWTError: raise credentials_exception ``` While this is functional, I suspect there might be better ways to encapsulate the error handling and token validation more securely. Also, how should I structure my token expiration checks to provide feedback to the client when they attempt to use an expired token? Any insights or resources that can help clarify the best practices for implementing JWT authentication in FastAPI would be greatly appreciated. I'm working with Python in a Docker container on Linux. For reference, this is a production desktop app. Any suggestions would be helpful.