Handeling Discourse SSO using Python 3

discourse_sso.py

# Sources:
# 1. https://meta.discourse.org/t/using-discourse-as-a-sso-provider/32974
# 2. https://meta.discourse.org/t/official-single-sign-on-for-discourse-sso/13045

import hmac
import hashlib
import random
import base64
from urllib import parse


# credits to: https://stackoverflow.com/a/28186447/1573477
def generate_nonce(length=8):
    """Generate pseudorandom number."""
    return ''.join([str(random.randint(0, 9)) for i in range(length)])


class Discourse:
    def __init__(self, base_url, sso_secret, return_url):
        self.encoding = 'utf-8'
        self.base_url = base_url
        self.sso_secret = bytes(sso_secret, encoding=self.encoding)
        self.return_url = return_url

        self.__nonce = None
        self.__payload = None

    @property
    def nonce(self):
        if not self.__nonce:
            self.__nonce = generate_nonce(20)

        return self.__nonce

    @property
    def payload(self):
        if not self.__payload:
            payload = parse.urlencode({
                'nonce': self.nonce,
                'return_sso_url': self.return_url
            })
            self.__payload = bytes(payload, encoding=self.encoding)

        return self.__payload

    @property
    def base64_payload(self):
        return base64.encodestring(self.payload)

    @property
    def hmac(self):
        h = hmac.new(
            self.sso_secret, self.base64_payload, digestmod=hashlib.sha256)
        return h.hexdigest()

    @property
    def auth_request(self):
        params = parse.urlencode({
            'sso': self.base64_payload,
            'sig': self.hmac
        })
        return f'{self.base_url}/session/sso_provider?{params}'