Refer to the documentation that comes with the StreamNameAlias package.
Edit your Application.xml and add the following as the last module in the Modules section.
Then add the following to the properties section at the end of Application.xml
The aliases work very simply. each line in the alias file which starts wth # is a comment and then each alias is defined [pattern]=[alias] where pattern is what the player requests and [alias] is the real stream name. When a stream is requested, it will go through the list until it finds a pattern match and then play the stream with the alias name. Wildcards and and special variables can also be used but are probably not needed in your case.
You will want to create a file called aliasmap.stream.txt in the conf folder and have the following in it
# Expands stream names to SHOUTcast urls
# Omit default rule to block users from entering any url
The player would now have to request station1 to play the stream.
This will tell the system that when station1 is requested, start restreaming http://authorized_ip:8000
If someone trys to play http://authorized_ip:8000 directly or http://not-authorized_ip:8000 it will fail.
Depending on your setup, you may also need a aliasmap.play.txt file as well. This will allow or disallow other file types from being played.