Simple SSO for Django
Project description
Terminology
Server
The server is a Django website that holds all the user information and authenticates users.
Client
The client is a Django website that provides login via SSO using the Server. It does not hold any user information.
Key
A unique key identifying a Client. This key can be made public.
Secret
A secret key shared between the Server and a single Client. This secret should never be shared with anyone other than the Server and Client and must not be transferred unencrypted.
Workflow
User wants to log into a Client by clicking a “Login” button. The initially requested URL can be passed using the next GET parameter.
The Client’s Python code does a HTTP request to the Server to request a authentication token, this is called the Request Token Request.
The Server returns a Request Token.
The Client redirects the User to a view on the Server using the Request Token, this is the Authorization Request.
If the user is not logged in the the Server, they are prompted to log in.
The user is redirected to the Client including the Request Token and a Auth Token, this is the Authentication Request.
The Client’s Python code does a HTTP request to the Server to verify the Auth Token, this is called the Auth Token Verification Request.
If the Auth Token is valid, the Server returns a serialized Django User object.
The Client logs the user in using the Django User recieved from the Server.
Requests
General
All requests have a signature and key parameter, see Security.
Request Token Request
Client: Python
Target: Server
Method: GET
Extra Parameters: None
Responses:
200: Everything went fine, the body of the response is a url encoded query string containing with the request_token key holding the Request Token as well as the signature.
400: Bad request (missing GET parameters)
403: Forbidden (invalid signature)
Authentication Request
Client: Browser (User)
Target: Client
Method: GET
Extra Parameters:
request_token: The Request Token returned by the Request Token Request.
auth_token: The Auth Token generated by the Authorization Request.
Responses:
200: Everything went fine, the user is now logged in.
400: Bad request (missing GET parameters).
403: Forbidden (invalid Request Token).
Auth Token Verification Request
Client: Python
Target: Server
Method: GET
Extra Parameters:
auth_token: The Auth Token obtained by the Authentication Request.
Responses:
200: Everything went fine, the body of the response is a url encoded query string containing the user key which is the JSON serialized representation of the Django user to create as well as the signature.
Security
Ever request is signed using HMAC-SHA256. The signature is in the signature parameter. The signature message is the urlencoded, alphabetically ordered query string. The signature key is the Secret of the Client. To verify the signature the key paramater holding the key of the Client is also sent with every request from the Client to the Server.
Example
GET Request with the GET parameters key=bundle123 and the private key secret key: fbf6396d0fc40d563e2be3c861f7eb5a1b821b76c2ac943d40a7a63b288619a9
The User object
The User object returned by a successful Auth Token Verification Request does not contain all the information about the Django User, in particular, it does not contain the password.
The user object contains must contain at least the following data:
username: The unique username of this user.
email: The email of this user.
first_name: The first name of this user, this field is required, but may be empty.
last_name: The last name of this user, this field is required, but may be empty.
is_staff: Can this user access the Django admin on the Client?
is_superuser: Does this user have superuser access to the Client?
is_active: Is the user active?
Implementation
On the server
Add simple_sso.sso_server to INSTALLED_APPS.
Create an instance (potentially of a subclass) of simple_sso.server.SimpleSSOServer and include the return value of the get_urls method on that instance into your url patterns.
On the client
Create a new instance of simple_sso.sso_server.models.Client on the Server.
Add the SIMPLE_SSO_SECRET and SIMPLE_SSO_KEY settings as provided by the Server’s simple_sso.sso_server.models.Client model.
Add the SIMPLE_SSO_SERVER setting which is the absolute URL pointing to the root where the simple_sso.sso_server.urls where include on the Server.
Add the simple_sso.sso_client.urls patterns somewhere on the client.
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