How to create a Script Mapper in Keycloak?

Question

I need to create a Protocol Mapper of type Script Mapper in Keycloak. The script should get a user attribute, check its size, and put it on the token. I found no documentation or examples of how a script should be created. From the bits and pieces I could gather, I guess I the script would need to look something like:

var value = user.getAttribute("myAttribute");
if (value.length > LIMIT) {
    value = value.substring(0,LIMIT);
}
token.setOtherClaims("myAttribute",value);

• Is this right? I made up user.getAttribute("myAttribute"). Is there a source of documentation where I can find how to get a Keycloak user attribute?
• does the script need to return anything? Any help would be mostly welcome.

Answer 1

The magic of Script Mappers can be understood by looking at the keycloak sources here: Source

The script can return something by using the exports variable like this

exports = "Claim Value"

The different types:

• user: Source JavaDoc
• realm: Source JavaDoc
• token: Source JavaDoc
• userSession: Source JavaDoc
• keycloakSession: Source JavaDoc

Here is an example script:

// you can set standard fields in token
token.setAcr("test value");

// you can set claims in the token
token.getOtherClaims().put("claimName", "claim value");

// multi-valued claim (thanks to @ErwinRooijakkers)
token.getOtherClaims().put('foo', Java.to(['bars'], "java.lang.String[]"))

// work with variables and return multivalued token value
var ArrayList = Java.type("java.util.ArrayList");
var roles = new ArrayList();
var client = keycloakSession.getContext().getClient();
var forEach = Array.prototype.forEach;
forEach.call(user.getClientRoleMappings(client).toArray(), function(roleModel) {
  roles.add(roleModel.getName());
});

exports = roles;

Hope it helps!