Add support for device authorization flow (RFC8628) (#795)

* rfc8628: Add client implementation for token retrieval

This change adds an implementation of the Device Authorization flow
client from RFC8628.  The initial structure is derived from the
existing BackendApplicationClient with the addition of the device_code
in the client.

This change does not provide the support necessary for querying the
device code endpoint in order to generate the initial device_code and
URL that is required for completing the full end to end device
authorization process.

* Add device token fetch URI generator

In order to perform the full device authorization flow it's necessary
to first generate the device code and get the authorization flow URL.

prepare_request_uri() allows us to do this while providing scopes and
additional parameters.

* Remove encoding lines

These lines are not required for python3

1 files changed, 94 insertions, 0 deletions

diff --git a/oauthlib/oauth2/rfc8628/clients/device.py b/oauthlib/oauth2/rfc8628/clients/device.py
new file mode 100644
index 0000000..df7ff68
--- /dev/null
+++ b/oauthlib/oauth2/rfc8628/clients/device.py
@@ -0,0 +1,94 @@
+"""
+oauthlib.oauth2.rfc8628
+~~~~~~~~~~~~~~~~~~~~~~~
+
+This module is an implementation of various logic needed
+for consuming and providing OAuth 2.0 Device Authorization RFC8628.
+"""
+
+from oauthlib.oauth2 import BackendApplicationClient, Client
+from oauthlib.oauth2.rfc6749.errors import InsecureTransportError
+from oauthlib.oauth2.rfc6749.parameters import prepare_token_request
+from oauthlib.oauth2.rfc6749.utils import is_secure_transport, list_to_scope
+from oauthlib.common import add_params_to_uri
+
+
+class DeviceClient(Client):
+
+    """A public client utilizing the device authorization workflow.
+
+    The client can request an access token using a device code and
+    a public client id associated with the device code as defined
+    in RFC8628.
+
+    The device authorization grant type can be used to obtain both
+    access tokens and refresh tokens and is intended to be used in
+    a scenario where the device being authorized does not have a
+    user interface that is suitable for performing authentication.
+    """
+
+    grant_type = 'urn:ietf:params:oauth:grant-type:device_code'
+
+    def __init__(self, client_id, **kwargs):
+        super().__init__(client_id, **kwargs)
+        self.client_secret = kwargs.get('client_secret')
+
+    def prepare_request_uri(self, uri, scope=None, **kwargs):
+        if not is_secure_transport(uri):
+            raise InsecureTransportError()
+
+        scope = self.scope if scope is None else scope
+        params = [(('client_id', self.client_id)), (('grant_type', self.grant_type))]
+
+        if self.client_secret is not None:
+            params.append(('client_secret', self.client_secret))
+
+        if scope:
+            params.append(('scope', list_to_scope(scope)))
+
+        for k in kwargs:
+            if kwargs[k]:
+                params.append((str(k), kwargs[k]))
+
+        return add_params_to_uri(uri, params)
+
+    def prepare_request_body(self, device_code, body='', scope=None,
+                             include_client_id=False, **kwargs):
+        """Add device_code to request body
+
+        The client makes a request to the token endpoint by adding the
+        device_code as a parameter using the
+        "application/x-www-form-urlencoded" format to the HTTP request
+        body.
+
+        :param body: Existing request body (URL encoded string) to embed parameters
+                     into. This may contain extra paramters. Default ''.
+        :param scope:   The scope of the access request as described by
+                        `Section 3.3`_.
+
+        :param include_client_id: `True` to send the `client_id` in the
+                                  body of the upstream request. This is required
+                                  if the client is not authenticating with the
+                                  authorization server as described in
+                                  `Section 3.2.1`_. False otherwise (default).
+        :type include_client_id: Boolean
+
+        :param kwargs:  Extra credentials to include in the token request.
+
+        The prepared body will include all provided device_code as well as
+        the ``grant_type`` parameter set to
+        ``urn:ietf:params:oauth:grant-type:device_code``::
+
+            >>> from oauthlib.oauth2 import BackendApplicationClient
+            >>> client = DeviceClient('your_id', 'your_code')
+            >>> client.prepare_request_body(scope=['hello', 'world'])
+            'grant_type=urn:ietf:params:oauth:grant-type:device_code&scope=hello+world'
+
+        .. _`Section 3.4`: https://datatracker.ietf.org/doc/html/rfc8628#section-3.4
+        """
+
+        kwargs['client_id'] = self.client_id
+        kwargs['include_client_id'] = include_client_id
+        scope = self.scope if scope is None else scope
+        return prepare_token_request(self.grant_type, body=body, device_code=device_code,
+                                     scope=scope, **kwargs)