FastAPI Authentication

Introduction

Implement JWT authentication in FastAPI applications.

JWT Setup

from datetime import datetime, timedelta
from jose import JWTError, jwt

SECRET_KEY = "secret_key_here"
ALGORITHM = "HS256"

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})
    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)

OAuth2 with Password

from fastapi.security import OAuth2PasswordBearer
from fastapi import Depends

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

async def get_current_user(token: str = Depends(oauth2_scheme)):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
    )
    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

Practice Problems

1. Implement JWT token creation
2. Create protected routes
3. Add login endpoint
4. Handle token refresh
5. Implement role-based access