forked from NYANDEV/forgejo
7d855efb1f
The PKCE flow according to [RFC 7636](https://datatracker.ietf.org/doc/html/rfc7636) allows for secure authorization without the requirement to provide a client secret for the OAuth app. It is implemented in Gitea since #5378 (v1.8.0), however without being able to omit client secret. Since #21316 Gitea supports setting client type at OAuth app registration. As public clients are already forced to use PKCE since #21316, in this PR the client secret check is being skipped if a public client is detected. As Gitea seems to implement PKCE authorization correctly according to the spec, this would allow for PKCE flow without providing a client secret. Also add some docs for it, please check language as I'm not a native English speaker. Closes #17107 Closes #25047
205 lines
10 KiB
Markdown
205 lines
10 KiB
Markdown
---
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date: "2023-06-01T08:40:00+08:00"
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title: "OAuth2 provider"
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slug: "oauth2-provider"
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weight: 41
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toc: false
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draft: false
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aliases:
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- /en-us/oauth2-provider
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menu:
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sidebar:
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parent: "development"
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name: "OAuth2 Provider"
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weight: 41
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identifier: "oauth2-provider"
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---
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# OAuth2 provider
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**Table of Contents**
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{{< toc >}}
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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.
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## Endpoints
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| Endpoint | URL |
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| ------------------------ | ----------------------------------- |
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| OpenID Connect Discovery | `/.well-known/openid-configuration` |
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| Authorization Endpoint | `/login/oauth/authorize` |
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| Access Token Endpoint | `/login/oauth/access_token` |
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| OpenID Connect UserInfo | `/login/oauth/userinfo` |
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| JSON Web Key Set | `/login/oauth/keys` |
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## Supported OAuth2 Grants
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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:
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- [Proof Key for Code Exchange (PKCE)](https://tools.ietf.org/html/rfc7636)
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- [OpenID Connect (OIDC)](https://openid.net/specs/openid-connect-core-1_0.html#CodeFlowAuth)
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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. To test or debug you can use the web-tool https://oauthdebugger.com/.
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## Scopes
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Gitea supports the following scopes for tokens:
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| Name | Description |
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| ---- | ----------- |
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| **(no scope)** | Grants read-only access to public user profile and public repositories. |
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| **repo** | Full control over all repositories. |
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| **repo:status** | Grants read/write access to commit status in all repositories. |
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| **public_repo** | Grants read/write access to public repositories only. |
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| **admin:repo_hook** | Grants access to repository hooks of all repositories. This is included in the `repo` scope. |
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| **write:repo_hook** | Grants read/write access to repository hooks |
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| **read:repo_hook** | Grants read-only access to repository hooks |
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| **admin:org** | Grants full access to organization settings |
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| **write:org** | Grants read/write access to organization settings |
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| **read:org** | Grants read-only access to organization settings |
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| **admin:public_key** | Grants full access for managing public keys |
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| **write:public_key** | Grant read/write access to public keys |
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| **read:public_key** | Grant read-only access to public keys |
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| **admin:org_hook** | Grants full access to organizational-level hooks |
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| **admin:user_hook** | Grants full access to user-level hooks |
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| **notification** | Grants full access to notifications |
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| **user** | Grants full access to user profile info |
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| **read:user** | Grants read access to user's profile |
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| **user:email** | Grants read access to user's email addresses |
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| **user:follow** | Grants access to follow/un-follow a user |
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| **delete_repo** | Grants access to delete repositories as an admin |
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| **package** | Grants full access to hosted packages |
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| **write:package** | Grants read/write access to packages |
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| **read:package** | Grants read access to packages |
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| **delete:package** | Grants delete access to packages |
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| **admin:gpg_key** | Grants full access for managing GPG keys |
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| **write:gpg_key** | Grants read/write access to GPG keys |
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| **read:gpg_key** | Grants read-only access to GPG keys |
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| **admin:application** | Grants full access to manage applications |
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| **write:application** | Grants read/write access for managing applications |
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| **read:application** | Grants read access for managing applications |
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| **sudo** | Allows to perform actions as the site admin. |
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## Client types
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Gitea supports both confidential and public client types, [as defined by RFC 6749](https://datatracker.ietf.org/doc/html/rfc6749#section-2.1).
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For public clients, a redirect URI of a loopback IP address such as `http://127.0.0.1/` allows any port. Avoid using `localhost`, [as recommended by RFC 8252](https://datatracker.ietf.org/doc/html/rfc8252#section-8.3).
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## Examples
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### Confidential client
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**Note:** This example does not use PKCE.
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1. Redirect the user to the authorization endpoint in order to get their consent for accessing the resources:
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```curl
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https://[YOUR-GITEA-URL]/login/oauth/authorize?client_id=CLIENT_ID&redirect_uri=REDIRECT_URI&response_type=code&state=STATE
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```
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The `CLIENT_ID` can be obtained by registering an application in the settings. The `STATE` is a random string that will be sent back to your application after the user authorizes. The `state` parameter is optional, but should be used to prevent CSRF attacks.
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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:
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```curl
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https://[REDIRECT_URI]?code=RETURNED_CODE&state=STATE
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```
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2. Using the provided `code` from the redirect, you can request a new application and refresh token. The access token endpoint accepts POST requests with `application/json` and `application/x-www-form-urlencoded` body, for example:
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```curl
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POST https://[YOUR-GITEA-URL]/login/oauth/access_token
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```
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```json
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{
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"client_id": "YOUR_CLIENT_ID",
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"client_secret": "YOUR_CLIENT_SECRET",
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"code": "RETURNED_CODE",
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"grant_type": "authorization_code",
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"redirect_uri": "REDIRECT_URI"
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}
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```
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Response:
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```json
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{
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"access_token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJnbnQiOjIsInR0IjowLCJleHAiOjE1NTUxNzk5MTIsImlhdCI6MTU1NTE3NjMxMn0.0-iFsAwBtxuckA0sNZ6QpBQmywVPz129u75vOM7wPJecw5wqGyBkmstfJHAjEOqrAf_V5Z-1QYeCh_Cz4RiKug",
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"token_type": "bearer",
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"expires_in": 3600,
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"refresh_token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJnbnQiOjIsInR0IjoxLCJjbnQiOjEsImV4cCI6MTU1NzgwNDMxMiwiaWF0IjoxNTU1MTc2MzEyfQ.S_HZQBy4q9r5SEzNGNIoFClT43HPNDbUdHH-GYNYYdkRfft6XptJBkUQscZsGxOW975Yk6RbgtGvq1nkEcklOw"
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}
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```
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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.
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The `REDIRECT_URI` in the `access_token` request must match the `REDIRECT_URI` in the `authorize` request.
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3. Use the `access_token` to make [API requests](https://docs.gitea.io/en-us/api-usage#oauth2) to access the user's resources.
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### Public client (PKCE)
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PKCE (Proof Key for Code Exchange) is an extension to the OAuth flow which allows for a secure credential exchange without the requirement to provide a client secret.
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**Note**: Please ensure you have registered your OAuth application as a public client.
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To achieve this, you have to provide a `code_verifier` for every authorization request. A `code_verifier` has to be a random string with a minimum length of 43 characters and a maximum length of 128 characters. It can contain alphanumeric characters as well as the characters `-`, `.`, `_` and `~`.
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Using this `code_verifier` string, a new one called `code_challenge` is created by using one of two methods:
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- If you have the required functionality on your client, set `code_challenge` to be a URL-safe base64-encoded string of the SHA256 hash of `code_verifier`. In that case, your `code_challenge_method` becomes `S256`.
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- If you are unable to do so, you can provide your `code_verifier` as a plain string to `code_challenge`. Then you have to set your `code_challenge_method` as `plain`.
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After you have generated this values, you can continue with your request.
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1. Redirect the user to the authorization endpoint in order to get their consent for accessing the resources:
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```curl
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https://[YOUR-GITEA-URL]/login/oauth/authorize?client_id=CLIENT_ID&redirect_uri=REDIRECT_URI&response_type=code&code_challenge_method=CODE_CHALLENGE_METHOD&code_challenge=CODE_CHALLENGE&state=STATE
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```
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The `CLIENT_ID` can be obtained by registering an application in the settings. The `STATE` is a random string that will be sent back to your application after the user authorizes. The `state` parameter is optional, but should be used to prevent CSRF attacks.
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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:
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```curl
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https://[REDIRECT_URI]?code=RETURNED_CODE&state=STATE
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```
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2. Using the provided `code` from the redirect, you can request a new application and refresh token. The access token endpoint accepts POST requests with `application/json` and `application/x-www-form-urlencoded` body, for example:
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```curl
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POST https://[YOUR-GITEA-URL]/login/oauth/access_token
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```
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```json
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{
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"client_id": "YOUR_CLIENT_ID",
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"code": "RETURNED_CODE",
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"grant_type": "authorization_code",
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"redirect_uri": "REDIRECT_URI",
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"code_verifier": "CODE_VERIFIER",
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}
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```
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Response:
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```json
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{
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"access_token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJnbnQiOjIsInR0IjowLCJleHAiOjE1NTUxNzk5MTIsImlhdCI6MTU1NTE3NjMxMn0.0-iFsAwBtxuckA0sNZ6QpBQmywVPz129u75vOM7wPJecw5wqGyBkmstfJHAjEOqrAf_V5Z-1QYeCh_Cz4RiKug",
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"token_type": "bearer",
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"expires_in": 3600,
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"refresh_token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJnbnQiOjIsInR0IjoxLCJjbnQiOjEsImV4cCI6MTU1NzgwNDMxMiwiaWF0IjoxNTU1MTc2MzEyfQ.S_HZQBy4q9r5SEzNGNIoFClT43HPNDbUdHH-GYNYYdkRfft6XptJBkUQscZsGxOW975Yk6RbgtGvq1nkEcklOw"
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}
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```
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The `REDIRECT_URI` in the `access_token` request must match the `REDIRECT_URI` in the `authorize` request.
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3. Use the `access_token` to make [API requests](https://docs.gitea.io/en-us/api-usage#oauth2) to access the user's resources.
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