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gitea/routers/web
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
..
admin Move admin routers from /admin to /-/admin (#32189) 5 months ago
auth Enhancing Gitea OAuth2 Provider with Granular Scopes for Resource Access (#32573) 3 months ago
devtest Refactor names (#31405) 8 months ago
events Move context from modules to services (#29440) 1 year ago
explore Respect UI.ExploreDefaultSort setting again (#32357) 4 months ago
feed Fix and refactor markdown rendering (#32522) 3 months ago
healthcheck Always enable caches (#28527) 1 year ago
misc Refactor render system (#32492) 3 months ago
org Fix and refactor markdown rendering (#32522) 3 months ago
repo Add line-through for deleted branch on pull request view page (#32500) 3 months ago
shared Fix and refactor markdown rendering (#32522) 3 months ago
user Refactor render system (#32492) 3 months ago
base.go Fix `missing signature key` error when pulling Docker images with `SERVE_DIRECT` enabled (#32365) 4 months ago
githttp.go Fix LFS route mock, realm, middleware names (#32488) 3 months ago
goget.go Refactor RepoRefByType (#32413) 4 months ago
home.go migrate some more "OptionalBool" to "Option[bool]" (#29479) 12 months ago
metrics.go Implement FSFE REUSE for golang files (#21840) 2 years ago
nodeinfo.go Move context from modules to services (#29440) 1 year ago
passkey.go Move context from modules to services (#29440) 1 year ago
swagger_json.go Move context from modules to services (#29440) 1 year ago
web.go Support HTTP POST requests to `/userinfo`, aligning to OpenID Core specification (#32578) 3 months ago
webfinger.go Move context from modules to services (#29440) 1 year ago