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Validate ID Tokens
This guide explains how to validate ID tokens with Okta.
- Retrieve and parse your Okta JSON Web Keys (JWK).
- Decode the ID token.
- Verify the signature that was used to sign the ID token.
- Verify the claims in the ID token.
About ID token validation
If your client application requires authentication and would like to obtain information about the authenticated person, then it should use the OpenID Connect protocol to get an ID token.
OpenID Connect (OIDC) is an authentication protocol built on top of OAuth 2.0. With OAuth 2.0, a user can authenticate with an authorization server and get you an access token that authorizes access to some server resources. With OIDC, they can also give you a token called an ID token. The ID token contains information about a user and their authentication status. It can be used by your client both for authentication and as a store of information about that user. One OIDC flow can return both access and ID tokens.
ID Tokens vs Access Tokens
The ID Token is a security token granted by the OpenID Provider that contains information about an End-User. This information tells your client application that the user is authenticated, and can also give you information like their username or locale.
You can pass an ID Token around different components of your client, and these components can use the ID Token to confirm that the user is authenticated and also to retrieve information about them.
Access tokens, on the other hand, are not intended to carry information about the user. They simply allow access to certain defined server resources. More discussion about when to use access tokens can be found in Validate Access Tokens.
What to Check When Validating an ID Token
The high-level overview of validating an ID token looks like this:
- Retrieve and parse your Okta JSON Web Keys (JWK), which should be checked periodically and cached by your application.
- Decode the ID token, which is in JWK format.
- Verify the signature used to sign the ID token.
- Verify the claims found inside the ID token.
Retrieve The JSON Web Key Set
The JSON Web Key Set (JWKS) needs to be retrieved from your Okta authorization server, though your application should have it cached. Specifically, your authorization server's Metadata endpoint contains the
jwks_uri, which you can use to get the JWKS.
Note: For more information about retrieving this metadata, see Retrieve Authorization Server Metadata.
Decode the ID Token
You will have to decode the ID token, which is in JWT format. A list of libraries to help you do this can be found below.
Verify the Token Signature
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.
Verify the Claims
You should verify the following:
iss(issuer) claim matches the identifier of your Okta authorization server.
aud(audience) claim should match the Client ID that you used to request the ID Token. This will be the Client ID for the Application you created in Okta.
iat(issued at time) claim indicates when this ID token was issued, expressed in Unix time.
exp(expiry time) claim is the time at which this token will expire., expressed in Unix time. You should make sure that this time has not already passed.
nonceclaim value should match whatever was passed when you requested the ID token.
Validating A Token Remotely With Okta
Alternatively, you can also validate an ID Token using the Token Introspection endpoint: Introspection Request. This endpoint takes your token as a URL query and returns back a JSON response with a boolean
active property. If
true then further information about the token is returned as well.
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.
Okta Libraries to Help You Verify ID Tokens
The Okta JWT Verifier is available for the following languages:
- A high-level overview of OpenID Connect can be found here.
- The ID tokens are in JSON Web Token (JWT) format, the specification for which can be found here: https://tools.ietf.org/html/rfc7519 (opens new window). They are signed using private JSON Web Keys (JWK), the specification for which you can find here: https://tools.ietf.org/html/rfc7517 (opens new window).
- More information about Okta's ID tokens can be found in the OIDC & OAuth 2.0 API Reference.