Chapter 14. Secure Connectivity

Difficult-o-Meter: 2 (light Linux skill required)

Covers:

OpenSSH 2.1.1

http://www.openssh.com

This chapter is in two major sections. The first covers secure login and file transfer. The second covers getting through a firewall (breaking security) and then applying tools to make secure firewall penetration possible.

Question: I've been logging in to various machines using Telnet for several years now. Apparently people can see everything you type when you use Telnet. I found this out when the bank called asking when they could expect my next payment on the QE-2 and when the very polite Secret Service man asked me to explain my e-mail to the First Lady. Now that I've cleared up these little misunderstandings, how can I avoid these problems in the future? Also, my boss is mad at me because I sent a certain patient's medical records by FTP to his new doctor and shortly thereafter he got a phone call from Tom Brokaw asking just exactly how the senator got syphilis. How can I avoid that little problem in the future?

Answer: You've learned yet another lesson. It isn't just e-mail and Web activity that needs protection from prying eyes. You should secure everything you use. There is a wonderful tool called secure shell, or SSH, that can secure your logins and your file transfers (and ”as you will see if your read the next section as well ”so much more). We'll here introduce you to a completely free implementation of SSH called OpenSSH. Let's be careful out there.

We've all used Telnet to log in to another machine. We've all used FTP to transfer files to and from our accounts on Linux boxes. We've all been running around a global network, offering everyone out there the keys to our computers. "What's that?" you say. "I've done no such thing! I have strong passwords and I change them every month. No one can get into my system." Sure. And I've got a bridge to sell you.

If you use Telnet and FTP, you have been broadcasting your user names and passwords all over the Internet. Don't believe me? See Chapter 11 , and then come back here with a renewed sense of fear and dread. This chapter will take away that fear and dread . I'm going to show you both how to log in to remote machines and how to transfer files between machines in such a way that not only will it be impossible to see your passwords, but it will also be impossible to see what you are typing or what you are transferring.