If your authorization is based on simple username/password, then it's really easy to write your own "LdapLoginModule" (or whatever). All you need to do is subclass org.jboss.security.auth.spi.UsernamePasswordLoginModule
and provide an implementation for
protected String getUsersPassword() throws LoginException
protected Group getRoleSets() throws LoginException
You will find examples of this in the JBoss source code or in the JBossSX documentation.
The only tricky thing (in my opinion) is that you need to define your login module in your auth.conf as follows: