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                        MSN nearly killed my Linux box

And not because I tried dialing up to MSN (Microsoft Network) either. It was
a referer string, from their search engine, that nearly killed my Linux box.

Seriously.

A while ago I wrote a program to go through the web log files, pulling out
referers from search engines (more or less). It wouldn't quite run through an
entire log file before quitting on some input it apparently didn't like. It
hasn't bothered me that much until today. So I figured I would run it under
the debugger, see what it doesn't like and fix the program.

It's amazing what garbage you get from search engines.

The spec for query strings is pretty straight forward—a series of name/value
pairs separated by ampersands—“&” (except perhaps for the last pair) and each
name/value pair is in the form of name “=” value. Pretty easy, right?

AOL/UK (America Online in the United Kingdom. Um ... yea ... does anyone else
see anything odd about that?) [1]'s search engine was sending a query string
with two consecutive ampersands. Fixed that, go on to the next problem.

The dreaded referer string from MSN.

Usually when a variable that has no value is sent, what you get is:

foobar=&

Basically, the name, then the equal sign, and either the end of the query
string, or the start (signified by the ampersand) of the next name/value
pair. But not MSN.

Nope. You get:

foobar&

And it was in the process of testing my work around that my Linux box
seriously went dead.

Okay, so technically MSN didn't nearly killed my Linux system, my program
did.

But still … it's an accessory to attempted murder!

Ahem.

Back to the drawing board.

[1] http://aol.co.uk/

Email author at [email protected]

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