@Override
    public UserContext getUserContext(AuthenticatedUser authenticatedUser)
            throws GuacamoleException {

        // Verify user against Duo service
        verificationService.verifyAuthenticatedUser(authenticatedUser);

        // User has been verified, and authentication should be allowed to
        // continue
        return null;

    }
Creates a new DuoAuthenticationProvider that verifies users
using the Duo authentication service

@throws GuacamoleException
    If a required property is missing, or an error occurs while parsing
    a property.
extensions/guacamole-auth-duo/src/main/java/org/apache/guacamole/auth/duo/DuoAuthenticationProvider.java