I've forgotten my password but am logged in--what tools can I use to assist in recovery and limit damages?

I have an encrypted hard drive. The hard drive, root user, and primary user all share the same password. I have successfully logged in but seem to have forgotten the password. I'm looking to limit the damage of this forgotten password and attempt to recover it. The steps I am taking so far are the following: * Write down the password as best I can remember it. * Email a copy of /etc/passwd to myself so I can attempt to run a brute force attack on it with the characters from the prior step. * Backup unsaved data and files as best I can. Does anyone have any suggestions on a tool to use to brute force /etc/passwd? Update: It looks like the hashed passwords are now in /etc/shadow so if I want to run this brute force I need to do it now while I have a login prompt... I have no root shell and cannot sudo since it's the same password.