Web App Example of OAuth 2 web application flow

OAuth is commonly used by web applications. The example below shows what such a web application might look like using the Flask web framework and GitHub as a provider. It should be easily transferrable to any web framework.

Note

While the flow remains the same across most providers, Github is special in that the redirect_uri parameter is optional. This means that it may be necessary to explicitly pass a redirect_uri to the OAuth2Session object (e.g. when creating a custom OAuthProvider with flask-oauthlib).

from requests_oauthlib import OAuth2Session
from flask import Flask, request, redirect, session, url_for
from flask.json import jsonify
import os

app = Flask(__name__)


# This information is obtained upon registration of a new GitHub OAuth
# application here: https://github.com/settings/applications/new
client_id = "<your client key>"
client_secret = "<your client secret>"
authorization_base_url = 'https://github.com/login/oauth/authorize'
token_url = 'https://github.com/login/oauth/access_token'


@app.route("/")
def demo():
    """Step 1: User Authorization.

    Redirect the user/resource owner to the OAuth provider (i.e. Github)
    using an URL with a few key OAuth parameters.
    """
    github = OAuth2Session(client_id)
    authorization_url, state = github.authorization_url(authorization_base_url)

    # State is used to prevent CSRF, keep this for later.
    session['oauth_state'] = state
    return redirect(authorization_url)


# Step 2: User authorization, this happens on the provider.

@app.route("/callback", methods=["GET"])
def callback():
    """ Step 3: Retrieving an access token.

    The user has been redirected back from the provider to your registered
    callback URL. With this redirection comes an authorization code included
    in the redirect URL. We will use that to obtain an access token.
    """

    github = OAuth2Session(client_id, state=session['oauth_state'])
    token = github.fetch_token(token_url, client_secret=client_secret,
                               authorization_response=request.url)

    # At this point you can fetch protected resources but lets save
    # the token and show how this is done from a persisted token
    # in /profile.
    session['oauth_token'] = token

    return redirect(url_for('.profile'))


@app.route("/profile", methods=["GET"])
def profile():
    """Fetching a protected resource using an OAuth 2 token.
    """
    github = OAuth2Session(client_id, token=session['oauth_token'])
    return jsonify(github.get('https://api.github.com/user').json())


if __name__ == "__main__":
    # This allows us to use a plain HTTP callback
    os.environ['OAUTHLIB_INSECURE_TRANSPORT'] = "1"

    app.secret_key = os.urandom(24)
    app.run(debug=True)

This example is lovingly borrowed from this gist.

N.B: You should note that Oauth2 works through SSL layer. If your server is not parametrized to allow HTTPS, the fetch_token method will raise an oauthlib.oauth2.rfc6749.errors.InsecureTransportError. Most people don’t set SSL on their server while testing and that is fine. You can disable this check in two ways:

1. By setting an environment variable.

export OAUTHLIB_INSECURE_TRANSPORT=1

2. Equivalent to above you can set this in Python (if you have problems setting environment variables)

# Somewhere in webapp_example.py, before the app.run for example
import os
os.environ['OAUTHLIB_INSECURE_TRANSPORT'] = '1'