I have noticed brake fluid leaking from the point where the brake pedal is going into the firewall. There is a rubber tube that the end has broken off of. Can someone tell me what this is called and how I can go about fixing it?

I'm not certain of the official name for the rubber boot that fits around the pedal push rod. But, this is not the seal for the master cylinder piston. It is not designed to hold pressure, just to keep dirt and moisture out.

Just forward of the firewall is the brake master cylinder (MC) and if you have power brakes it would be the vacuum assist booster with the master cylinder mounted in front of it. If you see brake fluid you likely have a leaking master cylinder and you don't have power brakes. The rubber tube you mention is probably a rubber boot that covers the rear of the MC. If you replace the MC you will need to bleed the brakes.

If you have manual drum brakes I have a manual drum brake master cylinder I just took out of my car last week because I swapped to power disk brakes. You can have it if you want if you are on a tight budget. Just pay for shipping. It does not leak but I don't know how long it's been in the car. I would replace it with a new one though.