If you are building a modern app or API, you likely want to know if your end-user is authenticated. This is important to give context or to protect APIs from unauthenticated users. You can use Okta to authenticate your end-users and issue them signed access and ID tokens, which your application can then use. It is important that your application only uses the access token to grant access, and not the ID token. For more information about this, see the Access Tokens VS ID Tokens section below.
Once the signed tokens are issued to the end-users they can be passed to your application, which must validate them. There are two ways to verify a token: locally, or remotely with Okta. The token has been signed with a JSON Web Key (JWK) using the RS256 algorithm. To validate the signature, Okta provides your application with a public key that can be used.
We will now cover the terms used in this document, and an explanation of why you should use access tokens instead of ID tokens for this use case.
A high-level overview of OAuth 2.0 can be found here.
More information about Okta's access tokens can be found in the OIDC & OAuth 2.0 Reference.
As mentioned above, it is important that the resource server (your server-side application) accept only the access token from a client. This is because access tokens are intended for authorizing access to a resource.
ID Tokens, on the other hand, are intended for authentication. They provide information about the resource owner, to allow you verify that they are who they say they are. Authentication is the concern of the clients. Because of this, when a client makes an authentication request, the ID Token that is returned contains the
client_id in the ID Token's
The high-level overview of validating an access token looks like this:
The JSON Web Keys (JWK) need to be retrieved from your Okta Authorization Server, though your application should have them cached. Specifically, your Authorization Server's Metadata endpoint contains the
jwks_uri, which you can use to get the JWK.
For more information about retrieving this metadata, see Retrieve Authorization Server Metadata.
You will have to decode the access token, which is in JWT format. A list of libraries to help you do this can be found below.
You verify the Access or ID token's signature by matching the key that was used to sign in with one of the keys that you retrieved from your Okta Authorization Server's JWK endpoint. Specifically, each public key is identified by a
kid attribute, which corresponds with the
kid claim in the Access or ID token header.
kid claim doesn't match, it's possible that the signing keys have changed. Check the
jwks_uri value in the Authorization Server metadata and try retrieving the keys again from Okta.
You should verify the following:
iss(issuer) claim matches the identifier of your Okta Authorization Server.
aud(audience) claim is the value configured in the Authorization Server.
cidclaim is your Okta application's Client ID.
exp(expiry time) claim is the time at which this token will expire, expressed in Unix time. You should make sure that this has not already passed.
Alternatively, you can also validate an access or refresh Token using the Token Introspection endpoint: Introspection Request. This endpoint takes your token as a URL query parameter and returns back a simple JSON response with a boolean
This incurs a network request which is slower to do verification, but can be used when you want to guarantee that the access token hasn't been revoked.
The Okta JWT Verifier is available for the following languages:
Don't see the language you're working in? Get in touch: firstname.lastname@example.org