用PHP写的简单AJAX跨域代理

proxy.php

<?php

define('REFERER', 'joyqi.github.io');
define('REDIS_CACHE', '127.0.0.1:6379');
define('TIMEOUT', 5);

function check_host($host) {
    if ('localhost' == $host) {
        return false;
    }

    $address = gethostbyname($host);
    $inet = inet_pton($address);

    if (false === $inet) {
        // 有可能是ipv6的地址
        $records = dns_get_record($host, DNS_AAAA);

        if (empty($records)) {
            $status = 200;
            return false;
        }

        $address = $records[0]['ipv6'];
        $inet = inet_pton($address);
    }

    if (strpos($address, '.')) {
        // ipv4
        // 非公网地址
        $privateNetworks = array(
                '10.0.0.0|10.255.255.255',
                '172.16.0.0|172.31.255.255',
                '192.168.0.0|192.168.255.255',
                '169.254.0.0|169.254.255.255',
                '127.0.0.0|127.255.255.255'
                );

        $long = ip2long($address);

        foreach ($privateNetworks as $network) {
            list ($from, $to) = explode('|', $network);

            if ($long >= ip2long($from) && $long <= ip2long($to)) {
                return false;
            }
        }
    } else {
        // ipv6
        // https://en.wikipedia.org/wiki/Private_network
        $from = inet_pton('fd00::');
        $to = inet_pton('fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff');

        if ($inet >= $from && $inet <= $to) {
            return false;
        }
    }

    return true;
}

function request($url, &$status = 500) {
    if (defined('REDIS_CACHE') && REDIS_CACHE) {
        $redis = new Redis();
        list ($host, $port) = explode(':', REDIS_CACHE);
        $redis->connect($host, $port);
        $key = 'proxy:' . md5($url);

        $content = $redis->get($key);
        if (false !== $content) {
            return $content;
        }
    }

    $ch = curl_init();

    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_TIMEOUT, TIMEOUT);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($ch, CURLOPT_MAXREDIRS, 2);
    curl_setopt($ch, CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT']);

    $encoding = 'UTF-8';
    curl_setopt($ch, CURLOPT_HEADERFUNCTION, function ($ch, $line) use (&$encoding) {
        list($key, $value) = explode(':', $line, 2);
        $key = strtolower(trim($key));

        if ($key == 'content-type' && preg_match("/charset=([_a-z0-9-]+)/i", $value, $matches)) {
            $encoding = strtoupper($matches[1]);
        }

        return strlen($line);
    });

    $result = curl_exec($ch);

    if (false === $result) {
        curl_close($ch);
        return false;
    }

    if ('UTF-8' !== $encoding) {
        $result = mb_convert_encoding($result, 'UTF-8', $encoding);
    }

    if (isset($redis)) {
        $redis->set($key, $result, 300);
    }

    $status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);
    return $result;
}

if (defined('REFERER') && REFERER) {
    $referer = $_SERVER['HTTP_REFERER'];

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

    $refHost = parse_url($referer, PHP_URL_HOST);
    if (empty($refHost) || $refHost != REFERER) {
        exit;
    }
}

$url = $_GET['url'] ?: NULL;
$callback = $_GET['callback'] ?: 'callback';

if (!preg_match("/^[_a-z0-9]+$/i", $callback)) {
    $callback = 'callback';
}

header('Content-Type: application/x-javascript');
if (empty($url)) {
    exit;
}

$parts = parse_url($url);
if (false === $parts) {
    exit;
}

$host = strtolower($parts['host']);
if ($host == $_SERVER['HTTP_HOST'] || !check_host($host) 
    || empty($parts['scheme']) || !preg_match("/^https?$/i", $parts['scheme'])) {
    exit;
}

$result = request($url, $status);
if (false === $request) {
    exit;
}

$json = json_encode(['contents' => $result, 'status' => $status]);
echo "{$callback}({$json});";