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forgejo/docs/content/doc/developers/oauth2-provider.md
Johnny Oskarsson a07e67d9cc
Minimal OpenID Connect implementation (#14139)
This is "minimal" in the sense that only the Authorization Code Flow
from OpenID Connect Core is implemented.  No discovery, no configuration
endpoint, and no user scope management.

OpenID Connect is an extension to the (already implemented) OAuth 2.0
protocol, and essentially an `id_token` JWT is added to the access token
endpoint response when using the Authorization Code Flow.  I also added
support for the "nonce" field since it is required to be used in the
id_token if the client decides to include it in its initial request.

In order to enable this extension an OAuth 2.0 scope containing
"openid" is needed. Other OAuth 2.0 requests should not be impacted by
this change.

This minimal implementation is enough to enable single sign-on (SSO)
for other sites, e.g. by using something like `mod_auth_openidc` to
only allow access to a CI server if a user has logged into Gitea.

Fixes: #1310

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>
2021-01-02 00:33:27 +08:00

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3.9 KiB
Markdown

---
date: "2019-04-19:44:00+01:00"
title: "OAuth2 provider"
slug: "oauth2-provider"
weight: 41
toc: false
draft: false
menu:
sidebar:
parent: "developers"
name: "OAuth2 Provider"
weight: 41
identifier: "oauth2-provider"
---
# OAuth2 provider
**Table of Contents**
{{< toc >}}
Gitea supports acting as an OAuth2 provider to allow third party applications to access its resources with the user's consent. This feature is available since release 1.8.0.
## Endpoints
| Endpoint | URL |
| ---------------------- | --------------------------- |
| Authorization Endpoint | `/login/oauth/authorize` |
| Access Token Endpoint | `/login/oauth/access_token` |
## Supported OAuth2 Grants
At the moment Gitea only supports the [**Authorization Code Grant**](https://tools.ietf.org/html/rfc6749#section-1.3.1) standard with additional support of the following extensions:
- [Proof Key for Code Exchange (PKCE)](https://tools.ietf.org/html/rfc7636)
- [OpenID Connect (OIDC)](https://openid.net/specs/openid-connect-core-1_0.html#CodeFlowAuth)
To use the Authorization Code Grant as a third party application it is required to register a new application via the "Settings" (`/user/settings/applications`) section of the settings.
## Scopes
Currently Gitea does not support scopes (see [#4300](https://github.com/go-gitea/gitea/issues/4300)) and all third party applications will be granted access to all resources of the user and his/her organizations.
## Example
**Note:** This example does not use PKCE.
1. Redirect to user to the authorization endpoint in order to get his/her consent for accessing the resources:
```curl
https://[YOUR-GITEA-URL]/login/oauth/authorize?client_id=CLIENT_ID&redirect_uri=REDIRECT_URI& response_type=code&state=STATE
```
The `CLIENT_ID` can be obtained by registering an application in the settings. The `STATE` is a random string that will be send back to your application after the user authorizes. The `state` parameter is optional but should be used to prevent CSRF attacks.
![Authorization Page](/authorize.png)
The user will now be asked to authorize your application. If they authorize it, the user will be redirected to the `REDIRECT_URL`, for example:
```curl
https://[REDIRECT_URI]?code=RETURNED_CODE&state=STATE
```
2. Using the provided `code` from the redirect, you can request a new application and refresh token. The access token endpoints accepts POST requests with `application/json` and `application/x-www-form-urlencoded` body, for example:
```curl
POST https://[YOUR-GITEA-URL]/login/oauth/access_token
```
```json
{
"client_id": "YOUR_CLIENT_ID",
"client_secret": "YOUR_CLIENT_SECRET",
"code": "RETURNED_CODE",
"grant_type": "authorization_code",
"redirect_uri": "REDIRECT_URI"
}
```
Response:
```json
{
"access_token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJnbnQiOjIsInR0IjowLCJleHAiOjE1NTUxNzk5MTIsImlhdCI6MTU1NTE3NjMxMn0.0-iFsAwBtxuckA0sNZ6QpBQmywVPz129u75vOM7wPJecw5wqGyBkmstfJHAjEOqrAf_V5Z-1QYeCh_Cz4RiKug",
"token_type": "bearer",
"expires_in": 3600,
"refresh_token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJnbnQiOjIsInR0IjoxLCJjbnQiOjEsImV4cCI6MTU1NzgwNDMxMiwiaWF0IjoxNTU1MTc2MzEyfQ.S_HZQBy4q9r5SEzNGNIoFClT43HPNDbUdHH-GYNYYdkRfft6XptJBkUQscZsGxOW975Yk6RbgtGvq1nkEcklOw"
}
```
The `CLIENT_SECRET` is the unique secret code generated for this application. Please note that the secret will only be visible after you created/registered the application with Gitea and cannot be recovered. If you lose the secret you must regenerate the secret via the application's settings.
The `REDIRECT_URI` in the `access_token` request must match the `REDIRECT_URI` in the `authorize` request.
3. Use the `access_token` to make [API requests](https://docs.gitea.io/en-us/api-usage#oauth2) to access the user's resources.