Invalid format string at _generate_jwt_token

Question

this is the tutorial I'm following, the link

https://thinkster.io/tutorials/django-json-api/authentication

As the title says, I'm getting this error "Invalid format string" at this line:

'exp': int(dt.strftime('%s'))

of _generate_jwt_token.

I looked at the documentation of strftime and there is no such format '%s' there is a uppercase S ('%S'), I changed the format to the uppercase S, but I'm getting an error down the road at trying to decode the Authorization Token where i get the following error

{"user": {"detail": "Invalid authentication. Could not decode token."}}

If I leave the lowercase s I get the "Invalid format string" error.

(authentication/backends.py)
def _authenticate_credentials(self, request, token):
    """
    Try to authenticate the given credentials. If authentication is
    successful, return the user and token. If not, throw an error.
    """
    try:
        payload = jwt.decode(token, settings.SECRET_KEY)
    except:
        msg = 'Invalid authentication. Could not decode token.'
        raise exceptions.AuthenticationFailed(msg)


(authentication/models.py)
def _generate_jwt_token(self):
        """
        Generates a JSON Web Token that stores this user's ID and has an expiry
        date set to 60 days into the future.
        """
        dt = datetime.now() + timedelta(days=60)

        token = jwt.encode({
            'id': self.pk,
            'exp': int(dt.strftime('%s'))
        }, settings.SECRET_KEY, algorithm='HS256')

        return token.decode('utf-8') 

I expect the following token "Token eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6MiwiZXhwIjo0fQ.TWICRQ6BgjWMXFMizjNAXgZ9T2xFnpGiQQuhRKtjckw" to return a user.

Answer 1

It should be:

token = jwt.encode({
             'id': self.pk,
             'exp': dt.utcfromtimestamp(dt.timestamp())    #CHANGE HERE
    }, settings.SECRET_KEY, algorithm='HS256')

This is because jwt compares the expiration times to the utc time. You can double check your secret key is correct by using the jwt debug tool here: https://jwt.io/

More reading here: https://pyjwt.readthedocs.io/en/latest/usage.html#encoding-decoding-tokens-with-hs256

Answer 2

I also got stuck here and it was the %s that is platform specific that caused the bug. I changed is to %S (note capital)