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gitea/services/auth
Marcell Mars a3881ffa3d
Enhancing Gitea OAuth2 Provider with Granular Scopes for Resource Access (#32573)
Resolve #31609

This PR was initiated following my personal research to find the
lightest possible Single Sign-On solution for self-hosted setups. The
existing solutions often seemed too enterprise-oriented, involving many
moving parts and services, demanding significant resources while
promising planetary-scale capabilities. Others were adequate in
supporting basic OAuth2 flows but lacked proper user management
features, such as a change password UI.

Gitea hits the sweet spot for me, provided it supports more granular
access permissions for resources under users who accept the OAuth2
application.

This PR aims to introduce granularity in handling user resources as
nonintrusively and simply as possible. It allows third parties to inform
users about their intent to not ask for the full access and instead
request a specific, reduced scope. If the provided scopes are **only**
the typical ones for OIDC/OAuth2—`openid`, `profile`, `email`, and
`groups`—everything remains unchanged (currently full access to user's
resources). Additionally, this PR supports processing scopes already
introduced with [personal
tokens](https://docs.gitea.com/development/oauth2-provider#scopes) (e.g.
`read:user`, `write:issue`, `read:group`, `write:repository`...)

Personal tokens define scopes around specific resources: user info,
repositories, issues, packages, organizations, notifications,
miscellaneous, admin, and activitypub, with access delineated by read
and/or write permissions.

The initial case I wanted to address was to have Gitea act as an OAuth2
Identity Provider. To achieve that, with this PR, I would only add
`openid public-only` to provide access token to the third party to
authenticate the Gitea's user but no further access to the API and users
resources.

Another example: if a third party wanted to interact solely with Issues,
it would need to add `read:user` (for authorization) and
`read:issue`/`write:issue` to manage Issues.

My approach is based on my understanding of how scopes can be utilized,
supported by examples like [Sample Use Cases: Scopes and
Claims](https://auth0.com/docs/get-started/apis/scopes/sample-use-cases-scopes-and-claims)
on auth0.com.

I renamed `CheckOAuthAccessToken` to `GetOAuthAccessTokenScopeAndUserID`
so now it returns AccessTokenScope and user's ID. In the case of
additional scopes in `userIDFromToken` the default `all` would be
reduced to whatever was asked via those scopes. The main difference is
the opportunity to reduce the permissions from `all`, as is currently
the case, to what is provided by the additional scopes described above.

Screenshots:

![Screenshot_20241121_121405](https://github.com/user-attachments/assets/29deaed7-4333-4b02-8898-b822e6f2463e)

![Screenshot_20241121_120211](https://github.com/user-attachments/assets/7a4a4ef7-409c-4116-9d5f-2fe00eb37167)

![Screenshot_20241121_120119](https://github.com/user-attachments/assets/aa52c1a2-212d-4e64-bcdf-7122cee49eb6)

![Screenshot_20241121_120018](https://github.com/user-attachments/assets/9eac318c-e381-4ea9-9e2c-3a3f60319e47)
---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
3 months ago
..
source Update go dependencies (#32389) 4 months ago
auth.go Refactor CSRF token (#32216) 5 months ago
auth_test.go Fix attachment download bug (#27486) 1 year ago
auth_token.go Enhanced auth token / remember me (#27606) 1 year ago
auth_token_test.go Refactor timeutil package (#28623) 1 year ago
basic.go Enhancing Gitea OAuth2 Provider with Granular Scopes for Resource Access (#32573) 3 months ago
group.go Remove `Named` interface (#26913) 1 year ago
httpsign.go Remove SHA1 for support for ssh rsa signing (#31857) 6 months ago
interface.go Reduce usage of `db.DefaultContext` (#27073) 1 year ago
main_test.go Enhanced auth token / remember me (#27606) 1 year ago
oauth2.go Enhancing Gitea OAuth2 Provider with Granular Scopes for Resource Access (#32573) 3 months ago
oauth2_test.go allow the actions user to login via the jwt token (#32527) 3 months ago
reverseproxy.go Save initial signup information for users to aid in spam prevention (#31852) 6 months ago
session.go Fix the bug that user may logout if he switch pages too fast (#29962) 11 months ago
signin.go remove util.OptionalBool and related functions (#29513) 12 months ago
source.go Final round of `db.DefaultContext` refactor (#27587) 1 year ago
sspi.go Save initial signup information for users to aid in spam prevention (#31852) 6 months ago
sspiauth_posix.go Make SSPI auth mockable (#27036) 1 year ago
sspiauth_windows.go Make SSPI auth mockable (#27036) 1 year ago
sync.go Use db.Find instead of writing methods for every object (#28084) 1 year ago