You may inspect the file: <install_dir>/domains/<domain-name>/config/keyfile
But it will be encrypted and so unreadable.
You can create a new username/password and remove the current one.
To remove the username, stop the server, comment the <security-constraint> in the web.xml file. Now, start the server and execute the following:
asadmin create-file-user --user <dummy> --password <dummy>
--userpassword <new_secret> --groups asadmin <new_user_id>
Now, uncomment the line you had commented.
Restart the server for changes to take effect.
I sincerely hope that this is useful.
keyfile passwords have no relationship to the trust database password. asadmin create-file-user will not reset the trust database password.
There is no way to recover the trust database password; if there was, it wouldn't be an effective way to protect your private keys. The only way to "reset" the trust database password is to remove the trust database. To do this, rename the server instance's cert7.db and key3.db files.