25/05/2010

scanning for base64_decode references

A friend’s site was recently hit by the massive infections/hacks on Dreamhost‘s servers, so I decided to do some scanning on some servers that I administrate for base64_decode references.

The simple command I used to find suspect files was:
# find . -name \*.php -exec grep -l "eval(base64_decode" {} \;

The results could be sorted in just 2 categories. Malware and stupidity. There was no base64_decode reference that did something useful in any possible way.

The best malware I found was a slightly modified version of the c99 php shell on a hacked joomla installation (the site has been hacked multiple times but the client insists on just re-installing the same joomla installation over and over and always wonders how the hell do they find him and hack him…oh well). c99 is impressive though…excellent work. I won’t post the c99 shell here…google it, you can even find infected sites running it and you can “play” with them if you like…

And now comes the good part, stupidity.
My favorite php code containing a base64_decode reference that I found:

$hash  = 'aW5jbHVkZSgnLi4vLi';
$hash .= '4vaW5jX2NvbmYvY29u';
$hash .= 'Zi5pbmMucGhwJyk7aW';
$hash .= '5jbHVkZSgnLi4vLi4v';
$hash .= 'aW5jX2xpYi9kZWZhdW';
$hash .= 'x0LmluYy5waHAnKTtl';
$hash .= 'Y2hvICRwaHB3Y21zWy';
$hash .= 'd2ZXJzaW9uJ107';
eval(base64_decode($hash));

Let’s see what this little diamond does:


% base64 -d 
aW5jbHVkZSgnLi4vLi4vaW5jX2NvbmYvY29uZi5pbmMucGhwJyk7aW5jbHVkZSgnLi4vLi4vaW5jX2xpYi9kZWZhdWx0LmluYy5waHAnKTtlY2hvICRwaHB3Y21zWyd2ZXJzaW9uJ107
include('../../inc_conf/conf.inc.php');include('../../inc_lib/default.inc.php');echo $phpwcms['version'];

So this guy used a series of strings which all of them together create a base64 encoded string in order to prevent someone from changing the version tag of his software. That’s not software, that’s crapware. Hiding the code where the version string appears ? That’s how you protect your software ? COME OOOOON….

* Filed by kargig at 01:36 under Internet,Linux,Privacy
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