Implement authorization by grant type

This guide explains how to implement an OAuth 2.0 Implicit flow for your app with Okta.

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Learning outcomes

• Understand the OAuth 2.0 Implicit flow.
• Set up your app with the Implicit grant type.
• Implement the Implicit flow in Okta.

What you need

• Okta Integrator Free Plan org (opens new window)
• An app that you want to implement OAuth 2.0 authorization with Okta

Note: The Okta Integrator Free Plan org makes most key developer features available by default for testing purposes. Okta's API Access Management product — a requirement to use Custom Authorization Servers — is an optional add-on in production environments.

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About the Implicit grant

The Implicit flow is extremely challenging to implement securely. As a result, Okta recommends that you use the Authorization Code flow with PKCE instead. Use the Implicit flow only for SPAs that can't support PKCE.

To select the appropriate flow to use for your application, see OAuth 2.0 and OpenID Connect overview's decision flowchart.

The Implicit flow is intended for applications where the confidentiality of the client secret can't be guaranteed. In this flow, the client doesn't make a request to the /token endpoint. Instead, it receives the access token directly from the /authorize endpoint. The client must be able to interact with the resource owner's user agent and to receive incoming requests (through redirection) from the authorization server.

Grant-type flow

Implicit flow

At a high level, this flow has the following steps:

1. Your application sends a request to the authorization server (Okta) for an access token.

   Before implementing this redirect request to the authorization server, you need to set up your app in Okta. See Request for tokens.

2. The authorization server presents an authentication prompt (the Okta sign-in page) to the user's browser.

3. The user authenticates with the authorization server and provides consent.

   For Okta to authenticate the user credentials, Okta needs user profile data. See Add a user using the Admin Console (opens new window), Import Users, and the Users API (opens new window). Alternatively, you can set up self-service registration to allow users to register their membership with the app.

4. Okta redirects the browser back to the specified redirect URI. Access and ID tokens are included as a hash fragment in the URI. Your app extracts the tokens from the URI. See Extract tokens from redirect URI.

5. Your app can now use these tokens to call the resource server (for example an API) on behalf of the user.

6. The resource server validates the token before responding to the request. See Validate access token.

Set up your app

Before you can implement authorization, you need to register your app in Okta by creating an app integration from the Admin Console.

1. Open the Admin Console for your org.
2. Choose Applications > Applications to view the current app integrations.
3. Click Create App Integration.
4. Select

   OIDC - OpenID Connect

   as the Sign-in method.

5. Select Single-Page Application as the Application type, then click Next.

   Note: It's important to choose the appropriate application type for apps that are public clients. Not doing so may result in an Okta API attempting to verify an app's client secret, which public clients aren't designed to have. This would break the app's sign-in and sign-out flows.

6. Enter the App integration name.

7. Click Advanced in the Grant type section, and then select Implicit (hybrid).

   Note: If you're using Classic Engine, select Implicit (hybrid) in the Grant type section.

8. In the Sign-in redirect URIs box, enter the callback location where Okta returns the browser (along with the access token).

9. Complete the remaining details for your app integration, then click Save.

On the General tab, the Client Credentials section contains the Client ID for your app integration. Save the Client ID to implement your authorization flow.

Use an SDK

Okta recommends using existing libraries and OAuth 2.0 helper methods to implement your authentication flow. You can use one of Okta's SDKs or an open-source library if an appropriate Okta SDK isn't available. See Recommended Okta SDKs for a list of Okta SDKs that you can download to start using with your app.

Flow specifics

The following sections outline the main requests required to implement the Implicit flow using direct requests to the OIDC & OAuth 2.0 API (opens new window) /authorize endpoint.

Request for tokens

This flow is similar to the Authorization Code flow, except that the response_type is token and/or id_token instead of code.

Your application redirects the user's browser to your authorization server's /authorize endpoint. If you are using the org authorization server, then your request URL would look something like this:

https://{yourOktaDomain}/oauth2/v1/authorize?
   client_id=0oabv6kx4qq6h1U5l0h7&
   response_type=token&scope=openid&
   redirect_uri=https%3A%2F%2Fexample.com&
   state=state-296bc9a0-a2a2-4a57-be1a-d0e2fd9bb601&
   nonce=foo'

Note the parameters that are being passed:

• client_id is the client ID of the app integration that you created earlier. Find it in the Admin Console on your app integration's General tab.
• response_type is token. It could also be id_token or both.
• scope is openid, which is required, but you can request other scopes. See the Create Scopes section of the Create an authorization server guide.
• redirect_uri is the callback location where the user agent is directed to along with the access_token. This must match one of the Sign-in redirect URIs that you specified when you created your app integration earlier.
• state is an arbitrary alphanumeric string that the authorization server reproduces when redirecting the user agent back to the client. This is used to help prevent cross-site request forgery.

See the OAuth 2.0 API reference (opens new window) for more information on these parameters.

Extract tokens from redirect URI

If the user doesn't have an existing session, the request opens the Okta sign-in page. If they have an existing session, or after they authenticate, the user is redirected back to the specified redirect_uri along with a token as a hash fragment:

https://{yourOktaDomain}/#access_token=eyJhb[...]erw&
   token_type=Bearer&
   expires_in=3600&
   scope=openid&
   state=state-296bc9a0-a2a2-4a57-be1a-d0e2fd9bb601

Your application must now extract the tokens from the URI and store them.

Validate access token

When your application passes a request with an access token, the resource server needs to validate it. See Validate access tokens.

Next steps

Now that you have implemented authorization in your app, you can add features such as:

• Brand customization (custom domain, custom SMS messages, custom emails, and custom error pages).
• Self-service enrollment.