Saturday, June 1, 2002

Gain secure remote login with SSH

PALM NETWORKING

By Stephen Vance

"Tools for Palm networking" seems to be the theme of this and my last couple of PalmPower Magazine Enterprise Edition articles. Maybe it's the geek in me, but there's something cool about having a complete remote access toolbox in your shirt pocket. When the alternative is multiple pieces of equipment weighing in excess of ten pounds, it's even better.

This month I'll write about SSH for the Palm OS. SSH stands for Secure SHell. It's essentially a securely encrypted variation on the traditional telnet program, which allows remote access to a command prompt on a server. Generally, a program called sshd (for SSH Daemon) runs on the UNIX machine. People who need secure command line access to the UNIX machine use an SSH client to talk to the server.

Unlike telnet, SSH securely encrypts the user name, the password, and the content of the login session to keep them hidden from network snoopers. Many network administrators require some form of secure access when logging in from public or untrusted networks like the Internet. Another common use is to ensure security when monitoring and controlling network hardware such as routers, caching servers, application servers, or Web servers installed in hosting centers.

Getting started

Several implementations of SSH exist, and there are other programs and protocols that serve similar functions. The main open source SSH implementation (OpenSSH) was developed for FreeBSD and is available for a wide variety of UNIX and other platforms including Windows, Macintosh, Palm OS and Java.

I recommend you have an SSH client available to test your SSH access before trying it from your PDA. Personally, I use TeraTermSSH (at http://www.zip.com.au/~roca/ttssh.html) for Windows, an extension to the TeraTerm Pro terminal emulation software (at http://hp.vector.co.jp/authors/VA002416/teraterm.html). I find it to be a good terminal emulation package, but it only supports SSH1. This is sufficient and actually beneficial for our purposes, as the Palm OS client we'll use also only supports SSH1. Other clients are available.

I have found three Palm OS SSH clients. Two of these are commercial products or part of commercial suites, MochaSoft's Mocha Pocket Telnet (at http://www.mochasoft.dk/palm.html#palmtelnet) and Expand Beyond's PocketAdmin (at http://www.xb.com/products.html). The other one, Top Gun SSH (at http://www.offshore.com.ai/~iang/TGssh/), is freeware with requested donations to the Party Fund if you like it. Instructions for donation can be found at the Top Gun SSH home page. I'll use Top Gun SSH in this article.