# Client and audience validation for OIDC providers
<a name="oidc-validation"></a>

When you add an identity source to a policy store, Verified Permissions has configuration options that verify that ID and access tokens are being used as intended. This validation happens in the processing of `IsAuthorizedWithToken` and `BatchIsAuthorizedWithToken` API requests. The behavior differs between ID and access tokens, and between Amazon Cognito and OIDC identity sources. With Amazon Cognito user pools providers, Verified Permissions can validate the client ID in both ID and access tokens. With OIDC providers, Verified Permissions can validate the client ID in ID tokens, and the audience in access tokens.

A *client ID* is an identifier associated with the identity provider instance that your application uses, for example `1example23456789`. An *audience* is a URL path associated with the intended *relying party*, or destination, of the access token, for example `https://mytoken.example.com`. When using access tokens, the `aud` claim is always associated with the audience.

OIDC ID tokens have an `aud` claim that contains client IDs, such as `1example23456789`.

OIDC Access tokens have an `aud` claim that contains the audience URL for the token, such as `https://myapplication.example.com`, and a `client_id` claim that contains client IDs, such as `1example23456789`.

When setting up your policy store, enter one or more values for **Audience validation** that your policy store with use to validate the audience of a token.
+ **ID tokens** – Verified Permissions validates the client ID by checking that at least one member of the client IDs in the `aud` claim matches an audience validation value.
+ **Access tokens** – Verified Permissions validates the audience by checking that the URL in the `aud` claim matches an audience validation value. If no `aud` claim exists, the audience can be validated using the `cid` or `client_id` claims. Check with your identity provider for the correct audience claim and format.

## Client-side authorization for JWTs
<a name="oidc-validation-other-idp"></a>

You might want to process JSON web tokens in your application and pass their claims to Verified Permissions without using a policy store identity source. You can extract your entity attributes from a JSON Web Token (JWT) and parse it into Verified Permissions.

This example shows how you might call Verified Permissions from an application using a JWT.¹

```
async function authorizeUsingJwtToken(jwtToken) {
  
    const payload = await verifier.verify(jwtToken);
   
    let principalEntity = {
        entityType: "PhotoFlash::User", // the application needs to fill in the relevant user type
        entityId: payload["sub"], // the application need to use the claim that represents the user-id
    };
    let resourceEntity = {
        entityType: "PhotoFlash::Photo", //the application needs to fill in the relevant resource type
        entityId: "jane_photo_123.jpg", // the application needs to fill in the relevant resource id
    };
    let action = {
        actionType: "PhotoFlash::Action", //the application needs to fill in the relevant action id
        actionId: "GetPhoto", //the application needs to fill in the relevant action type
    };
    let entities = {
        entityList: [],
    };
    entities.entityList.push(...getUserEntitiesFromToken(payload));
    let policyStoreId = "PSEXAMPLEabcdefg111111"; // set your own policy store id
    
    const authResult = await client
        .isAuthorized({
        policyStoreId: policyStoreId,
        principal: principalEntity,
        resource: resourceEntity,
        action: action,
        entities,
        })
        .promise();
        
    return authResult; 
  
}

function getUserEntitiesFromToken(payload) {
  let attributes = {};
  let claimsNotPassedInEntities = ['aud', 'sub', 'exp', 'jti', 'iss'];
  Object.entries(payload).forEach(([key, value]) => {
    if (claimsNotPassedInEntities.includes(key)) {
        return;
    }
    if (Array.isArray(value)) {
      var attibuteItem = [];
      value.forEach((item) => {
        attibuteItem.push({
          string: item,
        });
      });
      attributes[key] = {
        set: attibuteItem,
      };
    } else if (typeof value === 'string') {
      attributes[key] = {
        string: value,
      } 
    } else if (typeof value === 'bigint' || typeof value ==='number') {
        attributes[key] = {
            long: value,
          } 
    } else if (typeof value === 'boolean') {
        attributes[key] = {
            boolean: value,
       } 
    }

  });

  let entityItem = {
    attributes: attributes,
    identifier: {
      entityType: "PhotoFlash::User",
      entityId: payload["sub"], // the application needs to use the claim that represents the user-id
    }
  };
  return [entityItem];
}
```

¹ This code example uses the [aws-jwt-verify](https://github.com/awslabs/aws-jwt-verify) library for verifying JWTs signed by OIDC-compatible IdPs.