From 7d855efb1fe6b97c5d87492f67ed6aefd31b2474 Mon Sep 17 00:00:00 2001 From: Denys Konovalov Date: Sat, 3 Jun 2023 05:59:28 +0200 Subject: [PATCH] Allow for PKCE flow without client secret + add docs (#25033) 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 --- .../doc/development/oauth2-provider.en-us.md | 78 +++++++++++++++++-- routers/web/auth/oauth.go | 4 +- tests/integration/oauth_test.go | 23 ++++++ 3 files changed, 96 insertions(+), 9 deletions(-) diff --git a/docs/content/doc/development/oauth2-provider.en-us.md b/docs/content/doc/development/oauth2-provider.en-us.md index cf045ac2f..5f9960a47 100644 --- a/docs/content/doc/development/oauth2-provider.en-us.md +++ b/docs/content/doc/development/oauth2-provider.en-us.md @@ -1,5 +1,5 @@ --- -date: "2019-04-19:44:00+01:00" +date: "2023-06-01T08:40:00+08:00" title: "OAuth2 provider" slug: "oauth2-provider" weight: 41 @@ -40,7 +40,7 @@ At the moment Gitea only supports the [**Authorization Code Grant**](https://too - [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. +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/. ## Scopes @@ -87,17 +87,19 @@ Gitea supports both confidential and public client types, [as defined by RFC 674 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). -## Example +## Examples + +### Confidential client **Note:** This example does not use PKCE. -1. Redirect to user to the authorization endpoint in order to get their consent for accessing the resources: +1. Redirect the user to the authorization endpoint in order to get their 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. + 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. ![Authorization Page](/authorize.png) @@ -107,7 +109,7 @@ For public clients, a redirect URI of a loopback IP address such as `http://127. 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: +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: ```curl POST https://[YOUR-GITEA-URL]/login/oauth/access_token @@ -134,7 +136,69 @@ For public clients, a redirect URI of a loopback IP address such as `http://127. } ``` - 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 `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. + +### Public client (PKCE) + +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. + +**Note**: Please ensure you have registered your OAuth application as a public client. + +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 `~`. + +Using this `code_verifier` string, a new one called `code_challenge` is created by using one of two methods: + +- 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`. +- 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`. + +After you have generated this values, you can continue with your request. + +1. Redirect the user to the authorization endpoint in order to get their consent for accessing the resources: + + ```curl + 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 + ``` + + 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. + + ![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 endpoint 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", + "code": "RETURNED_CODE", + "grant_type": "authorization_code", + "redirect_uri": "REDIRECT_URI", + "code_verifier": "CODE_VERIFIER", + } + ``` + + 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 `REDIRECT_URI` in the `access_token` request must match the `REDIRECT_URI` in the `authorize` request. diff --git a/routers/web/auth/oauth.go b/routers/web/auth/oauth.go index 92a06e7c1..80f149d80 100644 --- a/routers/web/auth/oauth.go +++ b/routers/web/auth/oauth.go @@ -695,7 +695,7 @@ func handleRefreshToken(ctx *context.Context, form forms.AccessTokenForm, server } // "The authorization server MUST ... require client authentication for confidential clients" // https://datatracker.ietf.org/doc/html/rfc6749#section-6 - if !app.ValidateClientSecret([]byte(form.ClientSecret)) { + if app.ConfidentialClient && !app.ValidateClientSecret([]byte(form.ClientSecret)) { errorDescription := "invalid client secret" if form.ClientSecret == "" { errorDescription = "invalid empty client secret" @@ -753,7 +753,7 @@ func handleAuthorizationCode(ctx *context.Context, form forms.AccessTokenForm, s }) return } - if !app.ValidateClientSecret([]byte(form.ClientSecret)) { + if app.ConfidentialClient && !app.ValidateClientSecret([]byte(form.ClientSecret)) { errorDescription := "invalid client secret" if form.ClientSecret == "" { errorDescription = "invalid empty client secret" diff --git a/tests/integration/oauth_test.go b/tests/integration/oauth_test.go index 9649b256a..e9b69f5f1 100644 --- a/tests/integration/oauth_test.go +++ b/tests/integration/oauth_test.go @@ -120,6 +120,29 @@ func TestAccessTokenExchange(t *testing.T) { assert.True(t, len(parsed.RefreshToken) > 10) } +func TestAccessTokenExchangeWithPublicClient(t *testing.T) { + defer tests.PrepareTestEnv(t)() + req := NewRequestWithValues(t, "POST", "/login/oauth/access_token", map[string]string{ + "grant_type": "authorization_code", + "client_id": "ce5a1322-42a7-11ed-b878-0242ac120002", + "redirect_uri": "http://127.0.0.1", + "code": "authcodepublic", + "code_verifier": "N1Zo9-8Rfwhkt68r1r29ty8YwIraXR8eh_1Qwxg7yQXsonBt", + }) + resp := MakeRequest(t, req, http.StatusOK) + type response struct { + AccessToken string `json:"access_token"` + TokenType string `json:"token_type"` + ExpiresIn int64 `json:"expires_in"` + RefreshToken string `json:"refresh_token"` + } + parsed := new(response) + + assert.NoError(t, json.Unmarshal(resp.Body.Bytes(), parsed)) + assert.True(t, len(parsed.AccessToken) > 10) + assert.True(t, len(parsed.RefreshToken) > 10) +} + func TestAccessTokenExchangeJSON(t *testing.T) { defer tests.PrepareTestEnv(t)() req := NewRequestWithJSON(t, "POST", "/login/oauth/access_token", map[string]string{