Linux Tech Tips

• A basic ipchains firewall you can put into your startup routine.
• A perl script that monitors logs and alerts you to anything matching, or not matching, a particular pattern
• Does your Slackware installation identd you as '1000'? It's showing the UID rather than your username; fix supplied by aero_ (marc@c-xx-xxx-x-xxx.mn.client2.attbi.com) just before 2 AM EDT on 2002-08-02: comment out or remove the line "uid-only=yes" in /etc/identd.conf. Setting it to 'no' does not fix it, for some reason.
• Ever tried using a CGI to show manpages? I'd been trying for years, off and on, in my "spare time"; one night I stayed up all night on it, finally realizing that 'less' uses isatty(3) to determine if it is outputting to a terminal, and if not, dumps the raw data, which shows up as M M A A N N on the screen, since backspaces are rendered in html like any other spaces. So, the time I spent starting a termcap/terminfo description for an 'html' terminal was probably wasted. But anyway, once I had that established, it wasn't hard coming up with a quick bash CGI script to do what I wanted, man man for example.
• After attempting to install LIRC, having already downloaded almost 100MB of files and had problems compiling it, I gave up and decided to implement an extremely simple instant messaging protocol using perl. The first test programs for it are jcimsend and jcimrecv. I didn't have to modify my firewall because I was already allowing UDP on high-numbered ports for DNS and traceroute.
• I've been concerned about the lack of security in identd for a while, as there have been some exploits in various daemons and, while I couldn't get one of the exploits on the net to give me a rootshell, I still don't trust any code I didn't write myself (not that I can trust that, either, but at least I can hopefully fix it easier if I find it's broken). Anyway, I finally accomplished two things: (1) learned the basics of the auth protocol from rfc1413, and (2) cobbled together enough python for a working "fake" identd that runs from inet. This and identcheck (I know, I could have just telneted to the port) are my first two working python scripts, klunky as they are, so to me it was worth the effort.

John Comeau
P. O. Box 100632
Ft. Lauderdale, FL 33310-0632