Authentication & Authorization

This section covers how the ZipRight back-end application authenticates and authorizes itself to interact with the EPC platforms Partner facing API.


Authentication/Authorization Implementation in ZipRight

ZipRight has a utility class in its back-end that handles maintaining a valid EPC oAuth token at the application level - caching the token for a little under 7200 seconds (as a buffer).

Whenever the cached token is needed for an API request to the EPC platform, it is accessed from the single instance of the token_manager object shared across the back-end:

...

""" Token Manager module for oAuth token re-use """

class token_manager:
    def __init__(self, grant_type, scope):
        self.url = EPC_BASE_URL + EPC_OAUTH_URL
        self.client_id = EPC_CLIENT_ID
        self.client_secret = EPC_CLIENT_SECRET
        self.grant_type = grant_type
        self.scope = scope

        self.access_token = ""
        self.expiry = None

        self.create_token()

        
    """ Internal function for creating EPC oAuth token """
    
    def _create_token(self):
        if self.client_secret is not None and self.client_id is not None:
            body = {
                'grant_type': self.grant_type,
                'client_id': self.client_id,
                'client_secret': self.client_secret,
                'scope': self.scope
            }

            content_type = MIMETYPES.get('FORM')
            response = post(url=self.url, content_type=content_type, body=body)

            if response is not None:
                response_obj = response.json()
                self.access_token = response_obj.get('access_token')
                
                # Set expiry to a little under 2 hrs - 7200 seconds
                self.expiry = time.time() + 7190
                return True

        return False
      

    """ Public function for retrieving cached EPC oAuth token """
    
    def get_token(self) -> str:
        current_time = time.time()

        if current_time >= self.expiry:
            self._create_token()

        return self.access_token

📘

oAuth Access Token Life-time

As mentioned in Getting Authorized, EPC oAuth tokens expire in two hours - or 7200 seconds - which is why the token cache expiry time in the snippet above is set to slightly under that time.


A single instance of the token_manager is initialized within the root level back-end application instance:

...

""" Initializing the back-end application """

def create_app():
    # Application Factory
    app = connexion.FlaskApp(
        __name__,
        specification_dir="specifications/"
    )

    setup_token_manager(app)
    setup_routes(app)
    setup_request_tracker(app)
    add_cors_support(app)

    return app


""" Initializing the token manager"""

def setup_token_manager(app):
    # Flask App context is encapsulated with Connexion app object
    app.app.token_manager = token_manager(
        grant_type='client_credentials',
        scope='pc pcapi'
    )
    
...

The token_manager is then utilized whenever the cached oAuth token is needed for an API call to the EPC platform. For example - when retrieving origin information from EPC:

...

"""" Internal function to pull down Origin information """

def _get_origin(origin_id, partner_access_token) -> dict:
    # Ask token_manager for current oAuth token
    access_token = app.token_manager.get_token()

    url = EPC_BASE_URL + EPC_ORIGINS_URL + origin_id
    headers = {
        'Authorization': 'Bearer' + ' ' + access_token,
        'X-Elli-PAT': partner_access_token
    }
    response = get(url=url, headers=headers)

    return response

...

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