Client

The client part keeps the same API as Flask-OAuth. The only changes are the imports:

from flask_oauthlib.client import OAuth

Attention

If you are testing the provider and the client locally, do not make them start listening on the same address because they will override the session of each other leading to strange bugs. eg: start the provider listening on 127.0.0.1:4000 and client listening on localhost:4000 to avoid this problem.

OAuth1 Client

The difference between OAuth1 and OAuth2 in the configuation is request_token_url. In OAuth1 it is required, in OAuth2 it should be None.

To connect to a remote application create a OAuth object and register a remote application on it using the remote_app() method:

from flask_oauthlib.client 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 If it was revoked and the user re-enabled the application you will get different keys, so if you store them in the database don’t forget to check if they changed in the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 request() function.

Signing in / Authorizing

To sign in with Twitter or link a user account with a remote Twitter user, simply call into 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 can fetch all relevant information in the oauth_authorized function with authorized_response():

from flask import redirect

@app.route('/oauth-authorized')
def oauth_authorized():
    next_url = request.args.get('next') or url_for('index')
    resp = twitter.authorized_response()
    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 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 request() method that can request information from an OAuth protected resource. Additionally there are shortcuts like get() or 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-OAuthlib 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 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.

Find the OAuth1 client example at twitter.py.

OAuth2 Client

Find the OAuth2 client example at github.py.

New in version 0.4.2.

Request state parameters in authorization can be a function:

from werkzeug import security

remote = oauth.remote_app(
    request_token_params={
        'state': lambda: security.gen_salt(10)
    }
)

Lazy Configuration

New in version 0.3.0.

When creating an open source project, we need to keep our consumer key and consumer secret secret. We usually keep them in a config file, and don’t keep track of the config in the version control.

Client of Flask-OAuthlib has a mechanism for you to lazy load your configuration from your Flask config object:

from flask_oauthlib.client import OAuth

oauth = OAuth()
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',
    app_key='TWITTER'
)

At this moment, we didn’t put the consumer_key and consumer_secret in the remote_app, instead, we set a app_key. It will load from Flask config by the key TWITTER, the configuration looks like:

app.config['TWITTER'] = {
    'consumer_key': 'a random string key',
    'consumer_secret': 'a random string secret',
}

oauth.init_app(app)

New in version 0.4.0.

Or looks like that:

app.config['TWITTER_CONSUMER_KEY'] = 'a random string key'
app.config['TWITTER_CONSUMER_SECRET'] = 'a random string secret'

Twitter can get consumer key and secret from the Flask instance now.

You can put all the configuration in app.config if you like, which means you can do it this way:

from flask_oauthlib.client import OAuth

oauth = OAuth()
twitter = oauth.remote_app(
    'twitter',
    app_key='TWITTER'
)

app.config['TWITTER'] = dict(
    consumer_key='a random key',
    consumer_secret='a random secret',
    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',
)
oauth.init_app(app)

Fix non-standard OAuth

There are services that claimed they are providing OAuth API, but with a little differences. Some services even return with the wrong Content Type.

This library takes all theses into consideration. Take an Chinese clone of twitter which is called weibo as the example. When you implement the authorization flow, the content type changes in the progress. Sometime it is application/json which is right. Sometime it is text/plain, which is wrong. And sometime, it didn’t return anything.

We can force to parse the returned response in a specified content type:

from flask_oauthlib.client import OAuth

oauth = OAuth()

weibo = oauth.remote_app(
    'weibo',
    consumer_key='909122383',
    consumer_secret='2cdc60e5e9e14398c1cbdf309f2ebd3a',
    request_token_params={'scope': 'email,statuses_to_me_read'},
    base_url='https://api.weibo.com/2/',
    authorize_url='https://api.weibo.com/oauth2/authorize',
    request_token_url=None,
    access_token_method='POST',
    access_token_url='https://api.weibo.com/oauth2/access_token',

    # force to parse the response in applcation/json
    content_type='application/json',
)

The weibo site didn’t follow the Bearer token, the acceptable header is:

'OAuth2 a-token-string'

The original behavior of Flask OAuthlib client is:

'Bearer a-token-string'

We can configure with a pre_request method to change the headers:

def change_weibo_header(uri, headers, body):
    auth = headers.get('Authorization')
    if auth:
        auth = auth.replace('Bearer', 'OAuth2')
        headers['Authorization'] = auth
    return uri, headers, body

weibo.pre_request = change_weibo_header

You can change uri, headers and body in the pre request.