Validate system authenticators names at registering.

components/authentication-framework/org.wso2.carbon.identity.application.authentication.framework/src/main/java/org/wso2/carbon/identity/application/authentication/framework/internal/FrameworkServiceComponent.java

@@ -115,6 +115,7 @@
 import org.wso2.carbon.identity.role.v2.mgt.core.RoleManagementService;
 import org.wso2.carbon.identity.secret.mgt.core.SecretResolveManager;
 import org.wso2.carbon.identity.user.profile.mgt.association.federation.FederatedAssociationManager;
+import org.wso2.carbon.idp.mgt.IdentityProviderManagementServerException;
 import org.wso2.carbon.idp.mgt.IdpManager;
 import org.wso2.carbon.idp.mgt.listener.IdentityProviderMgtListener;
 import org.wso2.carbon.stratos.common.listeners.TenantMgtListener;
@@ -477,8 +478,16 @@ protected void unsetRealmService(RealmService realmService) {
             policy = ReferencePolicy.DYNAMIC,
             unbind = "unsetAuthenticator"
     )
-    protected void setAuthenticator(ApplicationAuthenticator authenticator) {
-
+    protected void setAuthenticator(ApplicationAuthenticator authenticator)
+            throws IdentityProviderManagementServerException {
+
+        /* All custom authenticator names must start with the `custom_` prefix. If a system-defined authenticator is
+         attempted to be registered at server startup with a name starting with this prefix, an error will be thrown.*/
+        if (authenticator.getName().startsWith("custom_")) {
+            throw new IdentityProviderManagementServerException(String.format("System-defined authenticator names " +
+                    "are not allowed to have the custom_ prefix. Therefore, %s cannot be registered.",
+                    authenticator.getName()));
+        }
         ApplicationAuthenticatorManager.getInstance().addSystemDefinedAuthenticator(authenticator);
 
         Property[] configProperties = null;