Handling Custom Claims with the JWT Bearer Grant Type

WSO2 Identity Server (WSO2 IS) allows you to handle custom claims in a self contained access token with the JWT bearer grant type.

Let's take a look at how you can use WSO2 Identity Server to handle custom claims in a self contained access token with the JWT bearer grant type depending on the server level configurations at the time of calling the token endpoint with the JWT bearer grant type. For this, let's use two instances of WSO2 Identity Server, where one instance acts as a federated identity provider, and the other acts as the service provider. Let’s call the WSO2 Identity Server instance that acts as the identity provider as IS-IP, and the other instance as IS-SP.

The following topics walk you through the steps you need to follow: 

Now that you have set up the Identity Server instances, you can proceed with the configuration steps.

Configuring IS-IP and IS-SP

• Follow the steps below to configure IS-IP to generate a JWT token by using the password grant type and passing the scope as openid.

  1. Open the <IS-IP_HOME>/repository/conf/identity/identity.xml file and uncomment the following entry under the <OAuth> element.

     <IdentityOAuthTokenGenerator>org.wso2.carbon.identity.oauth2.token.JWTTokenIssuer</IdentityOAuthTokenGenerator>

  2. Restart IS-IP.
  3. Configure an OAuth service provider.

  4. Initiate an access token request to IS-IP over a known grant type. The following curl command illustrates the syntax of an access token request that can be initiated using the Resource Owner Password Credential grant type, and specifying the scope as openid. For more information, see Configuring WSO2 Identity Server to issue self-contained access tokens.

     Request curl -u <CLIENT_ID>:<CLIENT_SECRET> -k -d "grant_type=password&username=<USERNAME>&password=<PASSWORD>&scope=openid" -H "Content-Type:application/x-www-form-urlencoded" https://<IS_HOST>:<IS_HTTPS_PORT>/oauth2/token Navigate to your service provider, expand Inbound Authentication Configurations, and then expand OAuth/OpenID Connect Configuration. Copy the OAuth Client Key as the value for <CLIENT_ID>. Copy the OAuth Client Secret as the value for <CLIENT_SECRET>. Enter the user name and password of the user you want to get the token as the value for <USERNAME> and <PASSWORD> respectively. By default, <IS_HOST> is localhost. However, if you are using a public IP, the respective IP address or domain needs to be specified. By default, <IS_HTTPS_PORT> has been set to 9443. However, in this scenario since the port offset for IS-IP is incremented by 1, the default port value needs to be incremented by 1.

     
     Let's assume that the request sent is as follows:

     curl -u q4h7UhUyt0wC8A2Awu_kfmxEpr0a:vlTwUeCAyYPRzkeayJpmdW0xfxAa -k -d "grant_type=password&username=megala&password=megala" -H "Content-Type:application/x-www-form-urlencoded" https://localhost:9444/oauth2/token?scope=openid

     Then the self contained JWT access token that returns in response to the request would be as follows:

     eyJ4NXQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJraWQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJhbGciOiJSUzI1NiJ9.eyJjb3VudHJ5IjoiU3JpIExhbmthIiwic3ViIjoibWVnYWxhQGNhcmJvbi5zdXBlciIsImF1ZCI6WyJxNGg3VWhVeXQwd0M4QTJBd3Vfa2ZteEVwcjBhIl0sImF6cCI6InE0aDdVaFV5dDB3QzhBMkF3dV9rZm14RXByMGEiLCJzY29wZSI6Im9wZW5pZCIsImlzcyI6Imh0dHBzOlwvXC9sb2NhbGhvc3Q6OTQ0NFwvb2F1dGgyXC90b2tlbiIsImV4cCI6MTUyODA5ODE1OCwiaWF0IjoxNTI4MDk0NTU4LCJlbWFpbCI6Im1lZ2FsYUB3c28yLmNvbSIsImp0aSI6IjIyMjMyNDZhLWI5MmUtNDMwNC1iYmY1LTE3MzExNTU3Y2FmNSJ9.c-WKt87FL24WAy24E2mp2uusPJAR2aDZDujqKkVlM5yDjUQ9hYvDX96KTo4ew1j9LGIb8cN9npX5NK-DtLeNHNuR1ypKhcyQ9Gwsqp42wEswH_IMHVRxERv5X0giz8rH-z7LGo2IGmGjLjhfGXP9C-_1r00krtkCTZpWPmUTW1BneFEEVF-WLaNmjC28CUdTcVealZOD9ByA44WTiA-nUmAp2j1zWb7K-rDm0cMaJ_ucYsnObmDovKyT-7y02zutBNm5plfn2cQbsLo0cAzWmTtdpX5gXmqtJHANRXwM8LriVJMTG7nDU5zDcU4GRYz5aWPQn3RgTA4donzpPvPYQw

     When you use a JWT decoder to decode the access token, you can see the following payload:

     {
       "country": "Sri Lanka",
       "sub": "megala@carbon.super",
       "aud": [
         "q4h7UhUyt0wC8A2Awu_kfmxEpr0a"
       ],
       "azp": "q4h7UhUyt0wC8A2Awu_kfmxEpr0a",
       "scope": "openid",
       "iss": "https://localhost:9444/oauth2/token",
       "exp": 1528098158,
       "iat": 1528094558,
       "email": "megala@wso2.com",
       "jti": "2223246a-b92e-4304-bbf5-17311557caf5"
     }

     Here, the country and email are custom claims related to the user.

• Follow the steps below to configure IS-IP as the identity provider in IS-SP.
  1. Sign in to the management console of IS-SP. For detailed instructions on starting the management console, see Getting Started with the Management Console.
  2. On the Main tab, go to Identity -> Identity Providers, and click Add.
  3. Provide appropriate values to configure IS-IP as the identity provider. For detailed instructions on how to add a new identity provider, see Adding and Configuring an Identity Provider.
  4. Click  Register.

Now that you have configured IS-IP and IS-SP, let's take a look at how WSO2 Identity Server handles custom claims with the JWT bearer grant type depending on the server level configurations at the time of calling the token endpoint with the JWT bearer grant type.

Calling the token endpoint with JWT bearer grant type

Scenario 1

First, let's take a look at how WSO2 Identity Server handles custom claims with the JWT bearer grant type when the ConvertToOIDCDialect element is set to false in the identity.xml file.

• Send the following sample request to call the token endpoint:

  curl -i -X POST -u EcvBCz8CDWFdALzavlakTTKkSPUa:LpElcqthcTOqilN1K_zAHf48fL4a -k -d 'grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer&assertion=<jwt_assertion>' -H 'Content-Type: application/x-www-form-urlencoded' https://localhost:9443/oauth2/token?scope=openid

  You will see the following payload when you use a JWT decoder and decode the JWT token:

  {
    "country": "Sri Lanka",
    "sub": "megala@carbon.super",
    "aud": [
      "EcvBCz8CDWFdALzavlakTTKkSPUa"
    ],
    "azp": "EcvBCz8CDWFdALzavlakTTKkSPUa",
    "scope": "openid",
    "iss": "https://localhost:9443/oauth2/token",
    "exp": 1528098158,
    "iat": 1528096102,
    "email": "megala@wso2.com",
    "jti": "243702fe-8087-49c2-a439-f6dc7258021a"
  }

  You will see that the country and email are directly copied to the generated JWT token.

Here, the country and email are directly copied to the generated JWT token because the ConverToOIDCDialect element is set to false, which results in all custom claims coming from incoming JWT assertions  being directly copied to the generated JWT token.

Scenario 2

Now, let's take a look at how WSO2 Identity Server handles custom claims with the JWT bearer grant type when the ConvertToOIDCDialect element is set to true and the AddUnmappedUserAttributes element is set to false in the identity.xml file.

• Sub-scenario 1: In this scenario, if we consider a sub-scenario assuming that identity provider claim mappings and service provider requested claims are empty. You will see the following payload when you use a JWT decoder and decode the JWT token:

  {
    "country": "Sri Lanka",
    "sub": "megala@carbon.super",
    "aud": [
      "q4h7UhUyt0wC8A2Awu_kfmxEpr0a"
    ],
    "azp": "q4h7UhUyt0wC8A2Awu_kfmxEpr0a",
    "scope": "openid",
    "iss": "https://localhost:9444/oauth2/token",
    "exp": 1528100688,
    "iat": 1528097088,
    "email": "megala@wso2.com",
    "jti": "d90bb7f4-25ce-466c-8ea8-8eb6f6624992"
  }

  You will see that this is similar to scenario 1. This means that when there are missing claim mappings in the identity provider level and service provider level, all custom claims are directly copied to the generated JWT token.

  
  

  
  

• Sub-scenario 2: If we consider a sub-scenario assuming that an identity provider claim mapping exists, whereas a service provider requested claim mapping does not exist. Then you will see the following payload when you use a JWT decoder and decode the JWT token:

  {
    "sub": "megala@carbon.super",
    "aud": [
      "EcvBCz8CDWFdALzavlakTTKkSPUa"
    ],
    "azp": "EcvBCz8CDWFdALzavlakTTKkSPUa",
    "scope": "openid",
    "iss": "https://localhost:9443/oauth2/token",
    "exp": 1528100688,
    "iat": 1528097449,
    "jti": "528dd371-df53-46a5-8276-62271eae53d4"
  }

  
  This scenario is considered as a user configuration error from WSO2 Identity Server point of view. In such a scenario, none of the custom claims are passed with the self contained access token.

• Sub-scenario 3: If we consider a sub-scenario assuming that identity provider claim mappings and service provider requested claim mappings exist. For example, assume you do the following in your local set up:

• 1. Map the  http://wso2.org/claims/country local claim to customclaim in the OIDC dialect.
  2. Add the customclaim to the openid scope.
     
  3. Add the following identity provider mapping.
     
  4. Add following service provider requested claim.
     

Then you will see the following payload when you use a JWT decoder and decode the JWT token:

{
  "sub": "megala@carbon.super",
  "aud": [
    "EcvBCz8CDWFdALzavlakTTKkSPUa"
  ],
  "azp": "EcvBCz8CDWFdALzavlakTTKkSPUa",
  "scope": "openid",
  "iss": "https://localhost:9443/oauth2/token",
  "customclaim": "Sri Lanka",
  "exp": 1528100688,
  "iat": 1528098298,
  "jti": "2e355311-f96d-4028-ae8a-edec5bfdf7a8"
}

Here, you can see that customclaim is added to the generated token. This is added based on the claim mapping in the identity provider and service provider level, and the OIDC claim mapping configuration. Since the email does not have any claim mapping in the identity provider level, it is not added to the generated token. 

In this scenario, all incoming claims go through the mapping process and are filtered according to the scope.Then the relevant claims are sent back with the self contained token.

Scenario 3

Let's take a look at how WSO2 Identity Server handles custom claims with the JWT bearer grant type when both ConvertToOIDCDialect and AddUnmappedUserAttributes elements are set to true in the identity.xml file.

You will see the following payload when you use a JWT decoder and decode the JWT token:

{
  "sub": "megala@carbon.super",
  "aud": [
    "EcvBCz8CDWFdALzavlakTTKkSPUa"
  ],
  "azp": "EcvBCz8CDWFdALzavlakTTKkSPUa",
  "scope": "openid",
  "iss": "https://localhost:9443/oauth2/token",
  "customclaim": "Sri Lanka",
  "exp": 1528102874,
  "iat": 1528099309,
  "email": "megala@wso2.com",
  "jti": "031902cd-a624-4d11-ba70-335bc9edbcb2"
}

You will see that the incoming JWT contains the country as a customclaim and that email is directly copied.

Here, country is converted to customclaim because it has claim mappings. email does not have any claim mapping, hence it is directly copied to the generated token .