# `tornado.auth` — Third-party login with OpenID and OAuth

This module contains implementations of various third-party authentication schemes.

All the classes in this file are class mixins designed to be used with the `tornado4.web.RequestHandler` class. They are used in two ways:

- On a login handler, use methods such as `authenticate_redirect()`, `authorize_redirect()`, and `get_authenticated_user()` to establish the user’s identity and store authentication tokens to your database and/or cookies.
- In non-login handlers, use methods such as `facebook_request()` or `twitter_request()` to use the authentication tokens to make requests to the respective services.

They all take slightly different arguments due to the fact all these services implement authentication and authorization slightly differently. See the individual service classes below for complete documentation.

Example usage for Google OAuth:

    class GoogleOAuth2LoginHandler(tornado4.web.RequestHandler,
                                   tornado4.auth.GoogleOAuth2Mixin):
        @tornado4.gen.coroutine
        def get(self):
            if self.get_argument('code', False):
                user = yield self.get_authenticated_user(
                    redirect_uri='http://your.site.com/auth/google',
                    code=self.get_argument('code'))
                # Save the user with e.g. set_secure_cookie
            else:
                yield self.authorize_redirect(
                    redirect_uri='http://your.site.com/auth/google',
                    client_id=self.settings['google_oauth']['key'],
                    scope=['profile', 'email'],
                    response_type='code',
                    extra_params={'approval_prompt': 'auto'})

Changed in version 4.0: All of the callback interfaces in this module are now guaranteed to run their callback with an argument of `None` on error. Previously some functions would do this while others would simply terminate the request on their own. This change also ensures that errors are more consistently reported through the `Future` interfaces.

## Common protocols

These classes implement the OpenID and OAuth standards. They will generally need to be subclassed to use them with any particular site. The degree of customization required will vary, but in most cases overridding the class attributes (which are named beginning with underscores for historical reasons) should be sufficient.

class `tornado.auth.``OpenIdMixin`

  Abstract implementation of OpenID and Attribute Exchange.

  Class attributes:

  - `_OPENID_ENDPOINT`: the identity provider’s URI.
  `authenticate_redirect`(callback_uri=None, ax_attrs=['name', 'email', 'language', 'username'], callback=None)

    Redirects to the authentication URL for this service.

    After authentication, the service will redirect back to the given callback URI with additional parameters including `openid.mode`.

    We request the given attributes for the authenticated user by default (name, email, language, and username). If you don’t need all those attributes for your app, you can request fewer with the ax_attrs keyword argument.

    Changed in version 3.1: Returns a `Future` and takes an optional callback. These are not strictly necessary as this method is synchronous, but they are supplied for consistency with `OAuthMixin.authorize_redirect`.

  `get_authenticated_user`(callback, http_client=None)

    Fetches the authenticated user data upon redirect.

    This method should be called by the handler that receives the redirect from the `authenticate_redirect()` method (which is often the same as the one that calls it; in that case you would call `get_authenticated_user` if the `openid.mode` parameter is present and `authenticate_redirect` if it is not).

    The result of this method will generally be used to set a cookie.

  `get_auth_http_client`()

    Returns the `AsyncHTTPClient` instance to be used for auth requests.

    May be overridden by subclasses to use an HTTP client other than the default.

class `tornado.auth.``OAuthMixin`

  Abstract implementation of OAuth 1.0 and 1.0a.

  See `TwitterMixin` below for an example implementation.

  Class attributes:

  - `_OAUTH_AUTHORIZE_URL`: The service’s OAuth authorization url.
  - `_OAUTH_ACCESS_TOKEN_URL`: The service’s OAuth access token url.
  - `_OAUTH_VERSION`: May be either “1.0” or “1.0a”.
  - `_OAUTH_NO_CALLBACKS`: Set this to True if the service requires advance registration of callbacks.

  Subclasses must also override the `_oauth_get_user_future` and `_oauth_consumer_token` methods.

  `authorize_redirect`(callback_uri=None, extra_params=None, http_client=None, callback=None)

    Redirects the user to obtain OAuth authorization for this service.

    The `callback_uri` may be omitted if you have previously registered a callback URI with the third-party service. For some services (including Friendfeed), you must use a previously-registered callback URI and cannot specify a callback via this method.

    This method sets a cookie called `_oauth_request_token` which is subsequently used (and cleared) in `get_authenticated_user` for security purposes.

    Note that this method is asynchronous, although it calls `RequestHandler.finish` for you so it may not be necessary to pass a callback or use the `Future` it returns. However, if this method is called from a function decorated with `gen.coroutine`, you must call it with `yield` to keep the response from being closed prematurely.

    Changed in version 3.1: Now returns a `Future` and takes an optional callback, for compatibility with `gen.coroutine`.

  `get_authenticated_user`(callback, http_client=None)

    Gets the OAuth authorized user and access token.

    This method should be called from the handler for your OAuth callback URL to complete the registration process. We run the callback with the authenticated user dictionary. This dictionary will contain an `access_key` which can be used to make authorized requests to this service on behalf of the user. The dictionary will also contain other fields such as `name`, depending on the service used.

  `_oauth_consumer_token`()

    Subclasses must override this to return their OAuth consumer keys.

    The return value should be a `dict` with keys `key` and `secret`.

  `_oauth_get_user_future`(access_token, callback)

    Subclasses must override this to get basic information about the user.

    Should return a `Future` whose result is a dictionary containing information about the user, which may have been retrieved by using `access_token` to make a request to the service.

    The access token will be added to the returned dictionary to make the result of `get_authenticated_user`.

    For backwards compatibility, the callback-based `_oauth_get_user` method is also supported.

  `get_auth_http_client`()

    Returns the `AsyncHTTPClient` instance to be used for auth requests.

    May be overridden by subclasses to use an HTTP client other than the default.

class `tornado.auth.``OAuth2Mixin`

  Abstract implementation of OAuth 2.0.

  See `FacebookGraphMixin` or `GoogleOAuth2Mixin` below for example implementations.

  Class attributes:

  - `_OAUTH_AUTHORIZE_URL`: The service’s authorization url.
  - `_OAUTH_ACCESS_TOKEN_URL`: The service’s access token url.
  `authorize_redirect`(redirect_uri=None, client_id=None, client_secret=None, extra_params=None, callback=None, scope=None, response_type='code')

    Redirects the user to obtain OAuth authorization for this service.

    Some providers require that you register a redirect URL with your application instead of passing one via this method. You should call this method to log the user in, and then call `get_authenticated_user` in the handler for your redirect URL to complete the authorization process.

    Changed in version 3.1: Returns a `Future` and takes an optional callback. These are not strictly necessary as this method is synchronous, but they are supplied for consistency with `OAuthMixin.authorize_redirect`.

  `oauth2_request`(url, callback, access_token=None, post_args=None, **args)

    Fetches the given URL auth an OAuth2 access token.

    If the request is a POST, `post_args` should be provided. Query string arguments should be given as keyword arguments.

    Example usage:

    ..testcode:

        class MainHandler(tornado4.web.RequestHandler,
                          tornado4.auth.FacebookGraphMixin):
            @tornado4.web.authenticated
            @tornado4.gen.coroutine
            def get(self):
                new_entry = yield self.oauth2_request(
                    "https://graph.facebook.com/me/feed",
                    post_args={"message": "I am posting from my Tornado application!"},
                    access_token=self.current_user["access_token"])

                if not new_entry:
                    # Call failed; perhaps missing permission?
                    yield self.authorize_redirect()
                    return
                self.finish("Posted a message!")

    New in version 4.3.

  `get_auth_http_client`()

    Returns the `AsyncHTTPClient` instance to be used for auth requests.

    May be overridden by subclasses to use an HTTP client other than the default.

    New in version 4.3.

## Google

class `tornado.auth.``GoogleOAuth2Mixin`

  Google authentication using OAuth2.

  In order to use, register your application with Google and copy the relevant parameters to your application settings.

  - Go to the Google Dev Console at http://console.developers.google.com
  - Select a project, or create a new one.
  - In the sidebar on the left, select APIs & Auth.
  - In the list of APIs, find the Google+ API service and set it to ON.
  - In the sidebar on the left, select Credentials.
  - In the OAuth section of the page, select Create New Client ID.
  - Set the Redirect URI to point to your auth handler
  - Copy the “Client secret” and “Client ID” to the application settings as {“google_oauth”: {“key”: CLIENT_ID, “secret”: CLIENT_SECRET}}

  New in version 3.2.

  `get_authenticated_user`(redirect_uri, code, callback)

    Handles the login for the Google user, returning an access token.

    The result is a dictionary containing an `access_token` field ([among others](https://developers.google.com/identity/protocols/OAuth2WebServer#handlingtheresponse)). Unlike other `get_authenticated_user` methods in this package, this method does not return any additional information about the user. The returned access token can be used with `OAuth2Mixin.oauth2_request` to request additional information (perhaps from `https://www.googleapis.com/oauth2/v2/userinfo`)

    Example usage:

        class GoogleOAuth2LoginHandler(tornado4.web.RequestHandler,
                                       tornado4.auth.GoogleOAuth2Mixin):
            @tornado4.gen.coroutine
            def get(self):
                if self.get_argument('code', False):
                    access = yield self.get_authenticated_user(
                        redirect_uri='http://your.site.com/auth/google',
                        code=self.get_argument('code'))
                    user = yield self.oauth2_request(
                        "https://www.googleapis.com/oauth2/v1/userinfo",
                        access_token=access["access_token"])
                    # Save the user and access token with
                    # e.g. set_secure_cookie.
                else:
                    yield self.authorize_redirect(
                        redirect_uri='http://your.site.com/auth/google',
                        client_id=self.settings['google_oauth']['key'],
                        scope=['profile', 'email'],
                        response_type='code',
                        extra_params={'approval_prompt': 'auto'})

## Facebook

class `tornado.auth.``FacebookGraphMixin`

  Facebook authentication using the new Graph API and OAuth2.

  `get_authenticated_user`(redirect_uri, client_id, client_secret, code, callback, extra_fields=None)

    Handles the login for the Facebook user, returning a user object.

    Example usage:

        class FacebookGraphLoginHandler(tornado4.web.RequestHandler,
                                        tornado4.auth.FacebookGraphMixin):
          @tornado4.gen.coroutine
          def get(self):
              if self.get_argument("code", False):
                  user = yield self.get_authenticated_user(
                      redirect_uri='/auth/facebookgraph/',
                      client_id=self.settings["facebook_api_key"],
                      client_secret=self.settings["facebook_secret"],
                      code=self.get_argument("code"))
                  # Save the user with e.g. set_secure_cookie
              else:
                  yield self.authorize_redirect(
                      redirect_uri='/auth/facebookgraph/',
                      client_id=self.settings["facebook_api_key"],
                      extra_params={"scope": "read_stream,offline_access"})

    This method returns a dictionary which may contain the following fields:

    - `access_token`, a string which may be passed to `facebook_request`
    - `session_expires`, an integer encoded as a string representing the time until the access token expires in seconds. This field should be used like `int(user['session_expires'])`; in a future version of Tornado it will change from a string to an integer.
    - `id`, `name`, `first_name`, `last_name`, `locale`, `picture`, `link`, plus any fields named in the `extra_fields` argument. These fields are copied from the Facebook graph API user object

    Changed in version 4.5: The `session_expires` field was updated to support changes made to the Facebook API in March 2017.

  `facebook_request`(path, callback, access_token=None, post_args=None, **args)

    Fetches the given relative API path, e.g., “/btaylor/picture”

    If the request is a POST, `post_args` should be provided. Query string arguments should be given as keyword arguments.

    An introduction to the Facebook Graph API can be found at http://developers.facebook.com/docs/api

    Many methods require an OAuth access token which you can obtain through `authorize_redirect` and `get_authenticated_user`. The user returned through that process includes an `access_token` attribute that can be used to make authenticated requests via this method.

    Example usage:

    ..testcode:

        class MainHandler(tornado4.web.RequestHandler,
                          tornado4.auth.FacebookGraphMixin):
            @tornado4.web.authenticated
            @tornado4.gen.coroutine
            def get(self):
                new_entry = yield self.facebook_request(
                    "/me/feed",
                    post_args={"message": "I am posting from my Tornado application!"},
                    access_token=self.current_user["access_token"])

                if not new_entry:
                    # Call failed; perhaps missing permission?
                    yield self.authorize_redirect()
                    return
                self.finish("Posted a message!")

    The given path is relative to `self._FACEBOOK_BASE_URL`, by default “https://graph.facebook.com”.

    This method is a wrapper around `OAuth2Mixin.oauth2_request`; the only difference is that this method takes a relative path, while `oauth2_request` takes a complete url.

    Changed in version 3.1: Added the ability to override `self._FACEBOOK_BASE_URL`.

## Twitter

class `tornado.auth.``TwitterMixin`

  Twitter OAuth authentication.

  To authenticate with Twitter, register your application with Twitter at http://twitter.com/apps. Then copy your Consumer Key and Consumer Secret to the application `settings` `twitter_consumer_key` and `twitter_consumer_secret`. Use this mixin on the handler for the URL you registered as your application’s callback URL.

  When your application is set up, you can use this mixin like this to authenticate the user with Twitter and get access to their stream:

      class TwitterLoginHandler(tornado4.web.RequestHandler,
                                tornado4.auth.TwitterMixin):
          @tornado4.gen.coroutine
          def get(self):
              if self.get_argument("oauth_token", None):
                  user = yield self.get_authenticated_user()
                  # Save the user using e.g. set_secure_cookie()
              else:
                  yield self.authorize_redirect()

  The user object returned by `get_authenticated_user` includes the attributes `username`, `name`, `access_token`, and all of the custom Twitter user attributes described at https://dev.twitter.com/docs/api/1.1/get/users/show

  `authenticate_redirect`(callback_uri=None, callback=None)

    Just like `authorize_redirect`, but auto-redirects if authorized.

    This is generally the right interface to use if you are using Twitter for single-sign on.

    Changed in version 3.1: Now returns a `Future` and takes an optional callback, for compatibility with `gen.coroutine`.

  `twitter_request`(path, callback=None, access_token=None, post_args=None, **args)

    Fetches the given API path, e.g., `statuses/user_timeline/btaylor`

    The path should not include the format or API version number. (we automatically use JSON format and API version 1).

    If the request is a POST, `post_args` should be provided. Query string arguments should be given as keyword arguments.

    All the Twitter methods are documented at http://dev.twitter.com/

    Many methods require an OAuth access token which you can obtain through `authorize_redirect` and `get_authenticated_user`. The user returned through that process includes an ‘access_token’ attribute that can be used to make authenticated requests via this method. Example usage:

        class MainHandler(tornado4.web.RequestHandler,
                          tornado4.auth.TwitterMixin):
            @tornado4.web.authenticated
            @tornado4.gen.coroutine
            def get(self):
                new_entry = yield self.twitter_request(
                    "/statuses/update",
                    post_args={"status": "Testing Tornado Web Server"},
                    access_token=self.current_user["access_token"])
                if not new_entry:
                    # Call failed; perhaps missing permission?
                    yield self.authorize_redirect()
                    return
                self.finish("Posted a message!")