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.

docs/oauth2/clients/deviceclient.rst

@@ -0,0 +1,5 @@
+DeviceClient
+------------------------
+
+.. autoclass:: oauthlib.oauth2.DeviceClient
+    :members:

oauthlib/oauth2/__init__.py

@@ -33,3 +33,4 @@
 from .rfc6749.request_validator import RequestValidator
 from .rfc6749.tokens import BearerToken, OAuth2Token
 from .rfc6749.utils import is_secure_transport
+from .rfc8628.clients import DeviceClient

oauthlib/oauth2/rfc8628/__init__.py

@@ -0,0 +1,10 @@
+"""
+oauthlib.oauth2.rfc8628
+~~~~~~~~~~~~~~~~~~~~~~~
+
+This module is an implementation of various logic needed
+for consuming and providing OAuth 2.0 Device Authorization RFC8628.
+"""
+import logging
+
+log = logging.getLogger(__name__)

oauthlib/oauth2/rfc8628/clients/__init__.py

@@ -0,0 +1,9 @@
+# -*- coding: utf-8 -*-
+"""
+oauthlib.oauth2.rfc8628
+~~~~~~~~~~~~~~~~~~~~~~~
+
+This module is an implementation of various logic needed
+for consuming OAuth 2.0 Device Authorization RFC8628.
+"""
+from .device import DeviceClient

oauthlib/oauth2/rfc8628/clients/device.py

@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+"""
+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.parameters import prepare_token_request
+
+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 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)

tests/oauth2/rfc8628/clients/test_device.py

@@ -0,0 +1,42 @@
+# -*- coding: utf-8 -*-
+import os
+from unittest.mock import patch
+
+from oauthlib import signals
+from oauthlib.oauth2 import DeviceClient
+
+from tests.unittest import TestCase
+
+
+@patch('time.time', new=lambda: 1000)
+class DeviceClientTest(TestCase):
+
+    client_id = "someclientid"
+    kwargs = {
+        "some": "providers",
+        "require": "extra arguments"
+    }
+
+    body = "not=empty"
+
+    body_up = "not=empty&grant_type=urn:ietf:params:oauth:grant-type:device_code"
+    body_code = body_up + "&device_code=somedevicecode"
+    body_kwargs = body_code + "&some=providers&require=extra+arguments"
+
+    device_code = 'somedevicecode'
+
+    def test_request_body(self):
+        client = DeviceClient(self.client_id)
+
+        # Basic, no extra arguments
+        body = client.prepare_request_body(self.device_code, body=self.body)
+        self.assertFormBodyEqual(body, self.body_code)
+
+        rclient = DeviceClient(self.client_id)
+        body = rclient.prepare_request_body(self.device_code, body=self.body)
+        self.assertFormBodyEqual(body, self.body_code)
+
+        # With extra parameters
+        body = client.prepare_request_body(
+            self.device_code, body=self.body, **self.kwargs)
+        self.assertFormBodyEqual(body, self.body_kwargs)