Obfuscated Ruby

Originally published on: Wed, 05 May 2010 00:42:28 +0000

In March of 2005, I spotted a blurb somewhere on the vastness of the Internet stating that a new obfuscated code contest was being held. This contest called for entries in the Ruby programming language. I had already taken second place in a category for one of The Perl Journal's obfuscated Perl coding contests. I thought that this might be a good way to introduce me to the Ruby programming language.

I downloaded a version of Ruby and played with it for a short while. I decided to write a short program that would generate prime numbers and then I'd attempt to obfuscate it.

primes.rb ( Click here to see the MIT / X11 license for this program )

Note that I had removed the indentation already. Also note that the example is broken as it misses 2 and 3 as primes. This was pointed out by someone else on the 'net who later dissected my entry. He also cited the availability of better algorithms for producing primes.

I decided to use Ruby's eval() function to ultimately evaluate the above program as a string. As I recall, the contest rules specified that the obfuscated source could be no more than 4K in size.

I built three Ruby methods. One that would simply set an accumulator to zero, one that would increment the accumulator, and one that would append the character represented by the accumulator to a string. I wrote a short C program to encode the program this way.

Here is the generated code: obf.rb( Click here to see the MIT / X11 license for this program )

Unfortunatley, this code was around 20 times the maximum size allowed by the contest. So, I had to take a slightly different approach. I changed the approach so that I now would have five methods.

1. a() - Increment the accumulator ($a)
2. b() - Increment the accumulator by 5
3. c() - Append the character represented by the accumulator to initially empty string variable $e
4. d() - Increment the accumulator by 10
5. e() - Increment the accumulator by 16

The encoder program is as follows: enc.c( Click here to see the MIT / X11 license for this program )

The final output of the code ( with the addition of requisite comments at the top ) looked like this:

obfprime.rb

I didn't win.

There were some very creative entries. Most of them were all much more creative than my simple encoder / eval schtick. The contest seemed to start and end very quickly without a whole lot of press. I enjoyed the process.

Unless otherwise noted, all code and text entries are Copyright ©1999, 2010 by James K. Lawless

Save to StumbleUpon
Digg it
Save to Reddit
Share on Facebook
Share on Twitter
More bookmarks