Creating Token with OAuth2

We can follow the documentation here

• First we will have to install the python-jose library

pip install "python-jose[cryptography]"

• Next we will create a file called oauth2.py in the app folder

• In said file we will import the following:

from jose import JWTError, jwt

• We will need to provide 3 things

  • The Secret Key

  • The Algorithm that we want to use

  • The Expiration time of the token - if we do not provide this, the user is logged forever

from jose import JWTError, jwt

SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

• Creating the JWT function and returning the token

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

SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

def create_access_token(data: dict):

    # We do not want to modify the actual data, so we create a copy
    to_encode = data.copy()

    # We use the datetime.now() so we can update the time to expiry
    expire = datetime.now() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)

    # to_encode is a dirctionary so we are updating this with the expiration time
    to_encode.update({"exp": expire})

    # Now as we have the data, we can return the JWT by using the .encode method
    # and providing the data, the secret key, and the algorithm in the method
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)

    return encoded_jwt

• Now that we can create the token, we will update this in the auth.py file

from os import access
from fastapi import APIRouter, Depends, status, HTTPException, Response
from sqlalchemy.orm import Session

from .. import database, schemas, models, utils, oauth2

router = APIRouter(
    tags=['Authentification']
)

@router.post('/login')
def login(user_credentials: schemas.UserLogin, db: Session = Depends(database.get_db)):

    user = db.query(models.User).filter(models.User.email == user_credentials.email).first()

    if not user:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=f"Invalid Credentials")

    if not utils.verify(user_credentials.password, user.password):
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=f"Invalid Credentials")

    # REMEMBER: 
    # This is the data that we decide to put in the payload
    # In this case we only care about the user_id
    access_token = oauth2.create_access_token(data= {"user_id": user.id})

    return {"access_token" : access_token,
            "token_type": "bearer"
            }

• If we use postman to see how the login works we should get the following data back:

{
    "access_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjo4LCJleHAiOjE2NjE1MjM1NDV9.W6JBT_5xf-OQIYBiXiH4ZXp2jpVLxl4AgPccChVx2Ic",
    "token_type": "bearer"
}

Now go to jwt.io and paste the token in there.

• This will automatically decode our JWT Token