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Flask-OAuth

Flask-OAuth is an extension to Flask that allows you to interact with remote OAuth enabled applications. Currently it only implements the consumer interface so you cannot expose your own API with OAuth.

Flak-OAuth depends on the python-oauth2 module.

Features

  • Support for OAuth 1.0a
  • Friendly API
  • Direct integration with Flask
  • Basic support for remote method invocation of RESTful APIs

Installation

Install the extension with one of the following commands:

$ pip install Flask-OAuth

Alternatively, use easy_install:

$ easy_install Flask-OAuth

Defining Remote Applications

To connect to a remote application create a :class:`OAuth` object and register a remote application on it using the :meth:`~OAuth.remote_app` method:

from flask_oauth import OAuth

oauth = OAuth()
the_remote_app = oauth.remote_app('the remote app',
    ...
)

A remote application must define several URLs required by the OAuth machinery:

  • request_token_url
  • access_token_url
  • authorize_url

Additionally the application should define an issued consumer_key and consumer_secret.

You can find these values by registering your application with the remote application you want to connect with.

Additionally you can provide a base_url that is prefixed to all relative URLs used in the remote app.

For Twitter the setup would look like this:

twitter = oauth.remote_app('twitter',
    base_url='https://api.twitter.com/1/',
    request_token_url='https://api.twitter.com/oauth/request_token',
    access_token_url='https://api.twitter.com/oauth/access_token',
    authorize_url='https://api.twitter.com/oauth/authenticate',
    consumer_key='<your key here>',
    consumer_secret='<your secret here>'
)

Now that the application is created one can start using the OAuth system. One thing is missing: the tokengetter. OAuth uses a token and a secret to figure out who is connecting to the remote application. After authentication/authorization this information is passed to a function on your side and it is your responsibility to remember it.

The following rules apply:

  • It's your responsibility to store that information somewhere
  • That information lives for as long as the user did not revoke the access for your application on the remote application. If it was revoked and the user re-enabled the application you will get different keys, so if you store them in the database don't forget to check if they changed in the authorization callback.
  • During the authorization handshake a temporary token and secret are issued. Your tokengetter is not used during that period.

For a simple test application, storing that information in the session is probably sufficient:

from flask import session

@twitter.tokengetter
def get_twitter_token(token=None):
    return session.get('twitter_token')

If the token does not exist, the function must return None, and otherwise return a tuple in the form (token, secret). The function might also be passed a token parameter. This is user defined and can be used to indicate another token. Imagine for instance you want to support user and application tokens or different tokens for the same user.

The name of the token can be passed to to the :meth:`~OAuthRemoteApp.request` function.

Signing in / Authorizing

To sign in with Twitter or link a user account with a remote Twitter user, simply call into :meth:`~OAuthRemoteApp.authorize` and pass it the URL that the user should be redirected back to. For example:

@app.route('/login')
def login():
    return twitter.authorize(callback=url_for('oauth_authorized',
        next=request.args.get('next') or request.referrer or None))

If the application redirects back, the remote application will have passed all relevant information to the oauth_authorized function: a special response object with all the data, or None if the user denied the request. This function must be decorated as :meth:`~OAuthRemoteApp.authorized_handler`:

from flask import redirect

@app.route('/oauth-authorized')
@twitter.authorized_handler
def oauth_authorized(resp):
    next_url = request.args.get('next') or url_for('index')
    if resp is None:
        flash(u'You denied the request to sign in.')
        return redirect(next_url)

    session['twitter_token'] = (
        resp['oauth_token'],
        resp['oauth_token_secret']
    )
    session['twitter_user'] = resp['screen_name']

    flash('You were signed in as %s' % resp['screen_name'])
    return redirect(next_url)

We store the token and the associated secret in the session so that the tokengetter can return it. Additionally we also store the Twitter username that was sent back to us so that we can later display it to the user. In larger applications it is recommended to store satellite information in a database instead to ease debugging and more easily handle additional information associated with the user.

Facebook OAuth

For Facebook the flow is very similar to Twitter or other OAuth systems but there is a small difference. You're not using the request_token_url at all and you need to provide a scope in the request_token_params:

facebook = oauth.remote_app('facebook',
    base_url='https://graph.facebook.com/',
    request_token_url=None,
    access_token_url='/oauth/access_token',
    authorize_url='https://www.facebook.com/dialog/oauth',
    consumer_key=FACEBOOK_APP_ID,
    consumer_secret=FACEBOOK_APP_SECRET,
    request_token_params={'scope': 'email'}
)

Furthermore the callback is mandatory for the call to :meth:`~OAuthRemoteApp.authorize` and has to match the base URL that was specified in the Facebook application control panel. For development you can set it to localhost:5000.

The APP_ID and APP_SECRET can be retrieved from the Facebook app control panel. If you don't have an application registered yet you can do this at facebook.com/developers.

Invoking Remote Methods

Now the user is signed in, but you probably want to use OAuth to call protected remote API methods and not just sign in. For that, the remote application object provides a :meth:`~OAuthRemoteApp.request` method that can request information from an OAuth protected resource. Additionally there are shortcuts like :meth:`~OAuthRemoteApp.get` or :meth:`~OAuthRemoteApp.post` to request data with a certain HTTP method.

For example to create a new tweet you would call into the Twitter application as follows:

resp = twitter.post('statuses/update.json', data={
    'status':   'The text we want to tweet'
})
if resp.status == 403:
    flash('Your tweet was too long.')
else:
    flash('Successfully tweeted your tweet (ID: #%s)' % resp.data['id'])

Or to display the users' feed we can do something like this:

resp = twitter.get('statuses/home_timeline.json')
if resp.status == 200:
    tweets = resp.data
else:
    tweets = None
    flash('Unable to load tweets from Twitter. Maybe out of '
          'API calls or Twitter is overloaded.')

Flask-OAuth will do its best to send data encoded in the right format to the server and to decode it when it comes back. Incoming data is encoded based on the mimetype the server sent and is stored in the :attr:`~OAuthResponse.data` attribute. For outgoing data a default of 'urlencode' is assumed. When a different format is needed, one can specify it with the format parameter. The following formats are supported:

Outgoing:
  • 'urlencode' - form encoded data (GET as URL and POST/PUT as request body)
  • 'json' - JSON encoded data (POST/PUT as request body)
Incoming
  • 'urlencode' - stored as flat unicode dictionary
  • 'json' - decoded with JSON rules, most likely a dictionary
  • 'xml' - stored as elementtree element

Unknown incoming data is stored as a string. If outgoing data of a different format is needed, content_type should be specified instead and the data provided should be an encoded string.

API Reference

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