Custom "statusMsg" not working as expected

After adding the following adaptive authentication script, if the username is not according to the format I should be getting the custom status message saying, Access Denied, invalid username format. But instead I get the default status message, Something went wrong during the authentication process. Please try signing in again.

function onLoginRequest(context) {
    executeStep(1, {
        onSuccess: function(context) {
            var user = context.currentKnownSubject;
            if(user!= null && user.username != null && !user.username.equals('')) {
                Log.info("username: " + user.username);
            } else {
                sendError('',{'status':'AUTHENTICATION USERNAME ERROR', 'statusMsg': 'Access denied, invalid username format.'});
            }
        }
    });
}

In addition, I get the following error in the wso2carbon.log file as well.

TID: [-1234] [authenticationendpoint] [2022-10-05 15:44:12,715] [37951f7d-8240-48d4-ad4f-1d4c8a6a3ec4] ERROR {org.wso2.carbon.identity.application.authentication.endpoint.util.AuthContextAPIClient} - Sending GET request to URL : https://dev.wso2istemp.com/api/identity/auth/v1.1/data/AuthenticationError/0b0efc37-819d-4b39-85b2-517126c3c9cb, failed. java.io.IOException: Server returned HTTP response code: 401 for URL: https://dev.wso2istemp.com/api/identity/auth/v1.1/data/AuthenticationError/0b0efc37-819d-4b39-85b2-517126c3c9cb
...
org.wso2.carbon.identity.application.authentication.endpoint.util.AuthContextAPIClient.getContextProperties(AuthContextAPIClient.java:70)
        at org.apache.jsp.retry_jsp._jspService(retry_jsp.java:194)
...
org.wso2.carbon.ui.filters.cache.ContentTypeBasedCachePreventionFilter.doFilter(ContentTypeBasedCachePreventionFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
...
org.wso2.carbon.identity.application.authentication.endpoint.util.filter.AuthenticationEndpointFilter.doFilter(AuthenticationEndpointFilter.java:190)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
...

The <IS_HOME>/repository/conf/deployment.toml configurations for [server] are as follows.

[server]
hostname = "dev.wso2istemp.com"
node_ip = "127.0.0.1"
base_path = "https://$ref{server.hostname}:${carbon.management.port}"

What is the reason for the following issue in the wso2carbon.log and why the custom status message is not shown properly?

Solution

When the adaptive authentication script is running, the values are passed to the Identity Server(IS) encrypted. In above case, the encrypted data chunk is passed to the IS,

https://dev.wso2istemp.com/api/identity/auth/v1.1/data/AuthenticationError/24e56d99-9494-4989-a3e2-4008b73ebd9b

with the last segment of the URL is being the data chunk. When the server tries to get that data chunk with a GET request, java.io.IOException: Server returned HTTP response code: 401 for URL which is the code for unauthorized is thrown. Since that data chunk is not properly received, the default status message is shown instead of the custom status message. The steps to resolve this are given below.

First clarify whether the dev.wso2istemp.com which you were using is not mapped with the localhost in /etc/hosts file.
Go to <IS_HOME>/repository/conf/deployment.toml file and check for the following configuration [identity.auth_framework.endpoint] and check whether the mutual SSL is set to false via mutual_ssl_manager_enabled=false
If so, enable that by commenting the mutual_ssl_manager_enabled=false, since using mutual SSL is recommended for IS. If you go to the <IS_HOME>/repository/resources/conf/default.json file, you can notice that the default value for mutual_ssl_manager_enabled is true
In a multi-node situation, the above error can occur if the mutual SSL is not enabled, If that does not resolves the issue, then you have to check whether the internal_hostname has been set properly so that the internal API calls are being sent properly.
To do that, if you have not added the following configuration to <IS_HOME>/repository/conf/deployment.toml file, you can check whether it has been properly applied to the <IS_HOME>/repository/conf/identity/identity.xml by checking for <ServerHostName>localhost</ServerHostName>

[server]
internal_hostname="localhost"

If you are using a multi-node deployment, this localhost value should be added to the SAN for the certificate when the certificate is generated (-ext SAN=dns:localhost)

keytool -genkey -alias newcert -keyalg RSA -keysize 2048 -keystore newkeystore.jks -dname "CN=dev.wso2istemp.com, OU=Is,O=Wso2,L=SL,S=WS,C=LK" -storepass mypassword -keypass mypassword -ext SAN=dns:localhost

But if you are using a single node you can add the following configuration to the deployment.toml and check whether it resolves things. (In single node case the internal_hostname should be similar to hostname)

[server]
hostname = "dev.wso2istemp.com"
internal_hostname = "dev.wso2istemp.com"

If that is not working[https://github.com/wso2/product-is/issues/11878] then go to <IS_HOME>/repository/deployment/server/webapps/authenticationendpoint/WEB-INF/web.xml and uncomment the following commented snippet.

<!--context-param>
    <param-name>AuthenticationRESTEndpointURL</param-name>
    <param-value>https://localhost:9443/api/identity/auth/v1.1/</param-value>
</context-param-->

This might route the internal_hostname being reflected on the request since the internal API calls are blocked when hostname of the server being replaced instead of the internal_hostname for the internal API calls(https://dev.wso2istemp.com/api/identity/auth/v1.1/data/AuthenticationError/24e56d99-9494-4989-a3e2-4008b73ebd9b).