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.

[openedx-webhooks]

Thanks for the pull request, @xitij2000!

What's next?

Please work through the following steps to get your changes ready for engineering review:

🔘 Get product approval

If you haven't already, check this list to see if your contribution needs to go through the product review process.

• If it does, you'll need to submit a product proposal for your contribution, and have it reviewed by the Product Working Group.
  • This process (including the steps you'll need to take) is documented here.
• If it doesn't, simply proceed with the next step.

🔘 Provide context

To help your reviewers and other members of the community understand the purpose and larger context of your changes, feel free to add as much of the following information to the PR description as you can:

• Dependencies

  This PR must be merged before / after / at the same time as ...

• Blockers

  This PR is waiting for OEP-1234 to be accepted.

• Timeline information

  This PR must be merged by XX date because ...

• Partner information

  This is for a course on edx.org.

• Supporting documentation
• Relevant Open edX discussion forum threads

🔘 Get a green build

If one or more checks are failing, continue working on your changes until this is no longer the case and your build turns green.

🔘 Let us know that your PR is ready for review:

Who will review my changes?

This repository is currently maintained by @openedx/wg-maintenance-edx-platform. Tag them in a comment and let them know that your changes are ready for review.

Where can I find more information?

If you'd like to get more details on all aspects of the review process for open source pull requests (OSPRs), check out the following resources:

• Overview of Review Process for Community Contributions
• Pull Request Status Guide
• Making changes to your pull request

When can I expect my changes to be merged?

Our goal is to get community contributions seen and reviewed as efficiently as possible.

However, the amount of time that it takes to review and merge a PR can vary significantly based on factors such as:

• The size and impact of the changes that it introduces
• The need for product review
• Maintenance status of the parent repository

💡 As a result it may take up to several weeks or months to complete a review and merge your PR.

[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