feat: Allow trusted apps to perform cookie login.

[xitij2000]

Description

This pull request allows Oauth applications with the 'skip_authorization' flag to use the cookie login view. This view is used to grant a session cookie as though the user had logged in directly with their username and password. This functionality already works with 'Resource Owner Password Based' grants.

Previous discussion as to why this view was only permitted for Resource Owner Password Based grants pointed toward the need to support third party applications but not allow them to leapfrog privileges.

However, for applications which have the 'skip authorization' flag set, no restrictions on scope are enforced, as the application is permitted to grant itself all scopes without requiring the user's explicit authorization. This kind of power already nearly mirrors cookie login, however some endpoints on the platform are unable to support non-cookie functionality, such as the loading of units and XBlocks.

Supporting information

Rebase of yameducation#1

Testing instructions

The easiest way to test is to run the software tests via the devstack using:

pytest openedx/core/djangoapps/auth_exchange

But to test it more practically, you would need to:

Create an Oauth Application in the Django admin that uses a grant type of Authorization
Use a client OAuth app with the new application credentials to log in
Have the authenticated client post to /oauth2/login/ on the LMS
Verify that the cookie was set and a successful status code (204) was returned.

Deadline

"None" if there's no rush, or provide a specific date or event (and reason) if there is one.

Other information

This change has some implication for security. While it is of the author's opinion that any application which has the 'skip_authorization' flag set should be considered a trusted application anyway, since it can grant all scopes (and thus has the full power of the API available to the user) any application with this flag may as well be able to log in via cookie.

However that does not necessarily mean that deployments are set up with this assumption. It is conceivable that there could be misconfigured applications that would have the ability to login that otherwise wouldn't, and which would have additional powers unexpected. It seems unlikely that these powers would be especially material, since full privileged API access is already so vast.

private-ref: BB-8998,

[openedx-webhooks]

Thanks for the pull request, @xitij2000!

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[navinkarkera]

@xitij2000 👍

• I tested this: (Tested this as part of feat: Support for login and registration via a browser custom tab openedx-app-android#371)
• I read through the code
• I checked for accessibility issues
• Includes documentation

[xitij2000]

@openedx/wg-maintenance-edx-platform Just checking in about this.

CC: @itsjeyd

[feanil]

@xitij2000 this makes sense to me but I'm also curious about the endpoints you mentioned, do you mean the html rendering endpoints for blocks or do you mean some RESTful API endpoints that only support cookie based access?

[xitij2000]

@xitij2000 this makes sense to me but I'm also curious about the endpoints you mentioned, do you mean the html rendering endpoints for blocks or do you mean some RESTful API endpoints that only support cookie based access?

The primary use-case we had is for enabling logging in the mobile app using a third-party auth provider. To enable that, the app will initiate the SSO-based auth process in the mobile browser and be set up to redirect back to the app. This doesn't use password-based credentials, but still needs full login privileges for the user.

So in this case it will involve the XBlock HTML view, however, more generally we'd want the user to have the same level of access as a user who used password-based login. It seemed like an overkill to add another field to designate whether that auth client should support Cookie-based logins, so we felt that skip authorization is a good proxy for that.

[feanil]

Makes sense to me, I've also tagged a couple of Auth oriented folks at 2U for review but if I don't hear anything back before tomorrow I'll merge this.

[timmc-edx]

Sounds reasonable. Robert is out until Wednesday, though, if you wanted his take on it.

[robrap]

@xitij2000:

• [question] In the legacy mobile app login, I believe the mobile app uses username/password to retrieve a token that can be used in auth_exchange. Can you help me understand your proposed flow? How is the token created that is used in the auth_exchange?
• [inform] Separately, there is a draft DEPR that might interest you: [DEPR]: BearerAuthentication edx-drf-extensions#284. The legacy (edx/2U) mobile apps switched to JWT tokens, but I think that happened just around or after code may have been taken for the newer mobile apps. This is something to consider as you invest in authentication.

[xitij2000]

@xitij2000:

* [question] In the legacy mobile app login, I believe the mobile app uses username/password to retrieve a token that can be used in `auth_exchange`. Can you help me understand your proposed flow? How is the token created that is used in the `auth_exchange`?

Some of our clients exclusively use their own SSO solution and don't have user login via the LMS at all. So for them, username/password authentication is not an option at all. So we've created an alternative login flow for the mobile app that initiates an OAuth2 flow from the app to use the LMS to log in. This is an authorization-code-based flow, so what the app gets in this case is a token that linked to an application is code-based, not password-based, however we want the user to be able to still access the platform the same way a user would that used a regular username and password.

* [inform] Separately, there is a draft DEPR that might interest you: [[DEPR]: BearerAuthentication edx-drf-extensions#284](https://github.com/openedx/edx-drf-extensions/issues/284). The legacy (edx/2U) mobile apps switched to JWT tokens, but I think that happened just around or after code may have been taken for the newer mobile apps. This is something to consider as you invest in authentication.

Noted! Thanks.

[robrap]

Thanks @xitij2000. I understood username/password was not an option, but I wasn't quite getting how it worked. I know you are just saying the same thing with different words, but I think it clicked. Thank you. I also don't see any issue with the approach.

[feanil]

@xitij2000 can you rebase this, I think it's good to merge once that's done.

[xitij2000]

@xitij2000 can you rebase this, I think it's good to merge once that's done.

Sure, I've rebased it, will check and update if there are any test failures.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.