Google OAuth Python

gistfile1.py

# Google OAuth 3.0 auth provider
from flask import request, redirect, session, url_for, current_app
from urllib import quote_plus
import requests
from util.common import make_url, url_for_view


client_id = "***"
client_secret = "***"


def _redir_host():
    return "http://" + current_app.config["BASE_DOMAIN"]


class GoogleAuthProvider():

    def __init__(self, blueprint):
        blueprint.add_url_rule("/google/cb", view_func=self.ga_callback)

    def first_step_url(self, return_url):
        return make_url("https://accounts.google.com/o/oauth2/auth", {
            "response_type": "code",
            "client_id": client_id,
            "redirect_uri": _redir_host() + url_for("auth.ga_callback"),
            "scope": "email profile",
            "state": return_url})

    def ga_callback(self):
        try:
            # 0. handle possible error
            error = request.args.get("error", "")
            if error:
                raise Exception("Google auth failed, says: " + error)
            # 1. get "code" from GA
            return_url = request.args.get("state", "/")
            code = request.args.get("code", "")
            if not code:
                raise Exception("Absent or empty <code> param")
            # 2. get "in_token", identifying current user
            in_token = session.get("in_token", "")
            if not in_token:
                raise Exception("Absent or empty <in_token> param")
            # 3. exchange GA code to api access token
            access_token = self._get_access_token(code)
            # 4. with access token - get user info
            email, fullname = self._get_user_info(access_token)
            # 5. send to login.py
            import auth
            auth.do_authenticate_user(in_token, "ga", email, fullname)
            # 6. redirect to return_url
            return redirect(return_url)
        except Exception as e:
            # TODO: log exception
            return redirect(url_for("auth.login", return_url=return_url, error=e.message))

    def _get_access_token(self, code):

        r = requests.post("https://accounts.google.com/o/oauth2/token", data={
                            "code": code,
                            "client_id": client_id,
                            "client_secret": client_secret,
                            "redirect_uri": _redir_host() + url_for("auth.ga_callback"),
                            "grant_type": "authorization_code"
        })

        try:
            data = r.json()
            return data["access_token"]
        except Exception as e:
            raise Exception("Failed to exchange google code to api access token, (" + e.message + ")")

    def _get_user_info(self, access_token):

        r = requests.get("https://www.googleapis.com/oauth2/v1/userinfo?alt=json&access_token=" + access_token)

        try:
            data = r.json()
            return data["email"], data["name"]
        except Exception as e:
            raise Exception("Failed to get email and full name from google API: (" + e.message + ")")