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Add device authorization grant (device code flow - rfc 8628) #1539

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@duzumaki duzumaki commented Jan 7, 2025

Note to reviewers: I've made this a "commit by commit" pr which means it's easier to review the pr if you go commit by commit rather than look at all files changed at once

Fixes #962

Description of the Change

Checklist

  • PR only contains one change (considered splitting up PR)
  • unit-test added
  • documentation updated
  • CHANGELOG.md updated (only for user relevant changes)
  • author name in AUTHORS

@duzumaki duzumaki force-pushed the add-device-flow branch 2 times, most recently from 85991ac to 87bbf79 Compare January 7, 2025 16:04
This model represents the device session for the request and response stage
See section 3.1(https://datatracker.ietf.org/doc/html/rfc8628#section-3.1)
and 3.2(https://datatracker.ietf.org/doc/html/rfc8628#section-3.2)
Django represents headers according to the common gateway interface(CGI)
standard. This means it's in all caps with words divided with a hyphen

However a lot of libraries follow the pattern of Something-Something
so this ensures the header is set correctly so libraries like oauthlib
can read it
This method calls the server's create_device_authorization_response method
(https://datatracker.ietf.org/doc/html/rfc8628#section-3.2)

and is returns to the caller the information adhering to the rfc
The device flow is initiated by sending the client_id and and a scope.
This check should not fail if the client is public
OAUTH_DEVICE_VERIFICATION_URI = the uri that comes back from the response
so the user knows where to go to. e.g example.com/device

OAUTH_DEVICE_USER_CODE_GENERATOR = Allows a custom callable to be passed in to control
how the user code is generated, stored in the db and returned back to the caller
DEVICE_MODEL = the device model

DEVICE_FLOW_INTERVAL = The time in seconds to wait before the device should poll again
This view is to be used in an authorization server in order to provide
a /device endpoint
The grant type for device code is 44 characters
This commit will not be merged(I think).
Currently oauthlib is due a release so I'm pointing this
to master
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This looks excellent, Only one thing grabbed my attention in my cursory code review, the type of the request parameter. Take a moment to double check that type. I've been bitten by OAuthLib's recasting of Request on a number of occasions. I hope to get time to more thoroughly review this by the end of the week

@@ -148,6 +151,16 @@ def create_authorization_response(self, request, scopes, credentials, allow):
except oauth2.OAuth2Error as error:
raise OAuthToolkitError(error=error, redirect_uri=credentials["redirect_uri"])

def create_device_authorization_response(self, request: HttpRequest):
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Are you sure this is a django.http.HttpRequest and not an oauthlib.common.Request?

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This looks awesome! I left some comments even though I'm not a maintainer, I'm just an excited downstream user :). If you're too busy to address any of my feedback let me know, I'd be happy to spend some time on it.

I got this up and running locally and was able to complete the authorization flow. Other than the comments I left inline, I have a few thoughts.

  1. Were you planning on adding a default view and template to complete the flow, similar to the way other grant types operate? Obviously the device flow user interaction can be highly customized, but I think a simple view could provide a decent out of the box experience. This was the code I wrote on my application to test this end-to-end:
from oauthlib.oauth2.rfc8628.errors import (
    AccessDenied,
    ExpiredTokenError,
)
from oauth2_provider.models import get_device_model
from django import forms


class DeviceForm(forms.Form):
    user_code = forms.CharField(required=True)


@login_required
def oauth_device_authenticate(request):
    form = DeviceForm(request.POST or None)

    if request.method == "POST" and form.is_valid():
        user_code = form.cleaned_data["user_code"]
        device = get_device_model().objects.filter(user_code=user_code).first()

        if device is None:
            form.add_error("user_code", "Incorrect user code")
        else:
            if timezone.now() > device.expires:
                device.status = device.EXPIRED
                device.save(update_fields=["status"])
                raise ExpiredTokenError

            if device.status in (device.DENIED, device.AUTHORIZED):
                raise AccessDenied

            if device.user_code == user_code:
                device.status = device.AUTHORIZED
                device.save(update_fields=["status"])
                return HttpResponseRedirect(reverse("oauth-device-authenticate-success"))

    return render(request, "device_authenticate.html", {"form": form})


@login_required
def oauth_device_authenticate_success(request):
    return render(request, "device_authenticate_success.html")
  1. Likewise, are downstreams expected to implement their own /token endpoint?

  2. Should DOT be a little bit more opinionated about how to generate things like user_code? There seems to be a good bit in the RFC (6.1) about best practices that we could encode for downstreams: e.g. using a shorter code with enough entropy that has readable characters and is compared case-insensitively.

Thanks again for all this work :)

id = models.BigAutoField(primary_key=True)
device_code = models.CharField(max_length=100, unique=True)
user_code = models.CharField(max_length=100)
scope = models.CharField(max_length=64, default="openid")

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Why is scope mandatory and defaults to openid? Is there a reason it should deviate from what AbstractGrant does?

constraints = [
models.UniqueConstraint(
fields=["device_code"],
name="unique_device_code",

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Suggested change
name="unique_device_code",
name="%(app_label)s_%(class)s_unique_device_code",


@dataclass
class DeviceCodeResponse:
verification_uri: str

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Should there perhaps be some way of configuring verification_uri_complete similar to verification_uri? That way clients wanting to use a QR code won't have to do their own URI assembly.

instance.
:param request: The current django.http.HttpRequest object
"""
oauth2_settings.EXTRA_SERVER_KWARGS = {

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Should this be moved into OAuth2ProviderSettings.server_kwargs where the rest of these are set? It seems like this might cause issues depending on the order of requests when the OAuthlibCore instance is cached.

headers, response, status = self.create_device_authorization_response(request)

device_request = DeviceRequest(
client_id=request.POST["client_id"], scope=request.POST.get("scope", oauth2_settings.READ_SCOPE)

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Should this default to leaving the scope empty?

@@ -650,11 +654,93 @@ class Meta(AbstractIDToken.Meta):
swappable = "OAUTH2_PROVIDER_ID_TOKEN_MODEL"


class AbstractDevice(models.Model):

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Maybe this should be named AbstractDeviceGrant?

# there should only be one
device: Device = get_device_model().objects.get(user_code=user_code)

if datetime.now(tz=UTC) > device.expires:

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Should the Device/DeviceGrant have an is_expired method similar to Grant so downstreams don't have to reimplement?

return http.HttpResponseRedirect(...)

# user is logged in and typed the user code in correctly. redirect to the the approve deny endpoint now
return http.HttpResponseRedirect(reverse("device-confirm", kwargs={"device_code": device.device_code}))

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This issues a redirect but the example endpoint expects POST data.

return self.get(client_id=client_id, device_code=device_code, user_code=user_code)


class Device(AbstractDevice):

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Likewise maybe DeviceGrant?

status = models.CharField(
max_length=64, blank=True, choices=DEVICE_FLOW_STATUS, default=AUTHORIZATION_PENDING
)
client_id = models.CharField(max_length=100, default=generate_client_id, db_index=True)

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Is there a reason this generates its own client_id instead of pointing to an Application that has one? I'm not too familiar with this part of the codebase so feel free to ignore.

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Device Authorization Grant
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