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Fix for simple-proxy.php WordPress plugin to get it working with Varnish (addresses a gzip headers error)
<?php
/*
Plugin Name: Simple Proxy
Description: A very simple proxy. Useful when you're moving from one server to another.
Author: Greg Priday
Author URI: http://siteorigin.com/
Version: 1.0
*/
function simple_proxy_admin_menu(){
add_submenu_page('options-general.php', __('Simple Proxy Settings', 'simple-proxy'), __('Simple Proxy', 'simple-proxy'), 'manage_options', 'so-simple-proxy', 'simple_proxy_admin_page');
if(!empty($_POST['simple_proxy']) && !empty($_POST['_spnonce']) && wp_verify_nonce($_POST['_spnonce'], 'simple-proxy-save')) {
$settings = $_POST['simple_proxy'];
$settings['enabled'] = !empty($settings['enabled']);
$settings['url'] = rtrim($settings['url'], '/');
update_option('simple_proxy_settings', $settings);
if( !empty( $_POST['simple_proxy_clear'] ) && WP_Filesystem() ) {
// Clear the proxy cache
global $wp_filesystem;
$cache_folder = $wp_filesystem->wp_content_dir().'proxy_cache/';
$wp_filesystem->rmdir($cache_folder, true);
}
}
}
add_action('admin_menu', 'simple_proxy_admin_menu');
function simple_proxy_admin_page(){
$settings = get_option( 'simple_proxy_settings', array() );
?>
<div class="wrap">
<h2><?php _e('Simple Proxy Settings', 'simple-proxy') ?></h2>
<form action="<?php echo add_query_arg(false, false) ?>" method="post">
<table class="form-table">
<tbody>
<tr valign="top">
<th scope="row"><?php _e('Proxy URL', 'simple-proxy') ?></th>
<td>
<input type="text" class="widefat" name="simple_proxy[url]" value="<?php echo (!empty($settings['url'])) ? esc_attr($settings['url']) : '' ?>" placeholder="http://">
</td>
</tr>
<tr valign="top">
<th scope="row"><?php _e('Proxy Enabled', 'simple-proxy') ?></th>
<td>
<label>
<input type="checkbox" name="simple_proxy[enabled]" <?php checked(!empty($settings['enabled'])) ?>>
<?php _e('enabled', 'simple-proxy') ?>
</label>
</td>
</tr>
<tr valign="top">
<th scope="row"><?php _e('Clear Cache', 'simple-proxy') ?></th>
<td>
<label>
<input type="checkbox" name="simple_proxy_clear">
<?php _e('check to clear the cache (once off)', 'simple-proxy') ?>
</label>
</td>
</tr>
</tbody>
</table>
<p class="submit"><input type="submit" name="submit" id="submit" class="button button-primary" value="<?php esc_attr_e('Save Changes', 'simple-proxy') ?>"></p>
<?php wp_nonce_field('simple-proxy-save', '_spnonce') ?>
</form>
</div>
<?php
}
function simple_proxy_init() {
// Don't process this if we're in the admin or login/register pages
if( is_admin() || in_array( $GLOBALS['pagenow'], array( 'wp-login.php', 'wp-register.php', 'wp-cron.php' ) ) ) return;
$settings = get_option( 'simple_proxy_settings', array() );
if(empty($settings['enabled']) || empty($settings['url'])) return;
require_once(ABSPATH . 'wp-admin/includes/file.php');
if(!WP_Filesystem()) return;
global $wp_filesystem;
$cache_folder = $wp_filesystem->wp_content_dir().'proxy_cache/';
if(!$wp_filesystem->is_dir( $cache_folder )) {
$wp_filesystem->mkdir($cache_folder);
}
$url = esc_url( $settings['url'] ) . $_SERVER['REQUEST_URI'];
// Check if we have this in cache
$cache_file = $cache_folder.md5($url).'.dat';
if( $wp_filesystem->is_file($cache_file) && ( time() - $wp_filesystem->mtime($cache_file) < 86400 ) ) {
$response = unserialize($wp_filesystem->get_contents($cache_file));
}
else {
$response = wp_remote_get(
add_query_arg('no_cache', rand(0, 65536), $url),
array(
'timeout' => 120,
'decompress' => false,
)
);
if(!is_wp_error($response) && isset($response['response']['code']) && $response['response']['code'] == 200) {
$wp_filesystem->put_contents($cache_file, serialize($response));
}
elseif($wp_filesystem->is_file($cache_file)) {
// The cache file still exists, use it so long
$response = unserialize($wp_filesystem->get_contents($cache_file));
}
}
foreach($response['headers'] as $name => $value) {
if (strtolower($name) != 'content-encoding') {
header($name.': '.$value, true);
}
}
$body = str_replace($settings['url'], site_url(), $response['body']);
if(empty($body)) return;
echo $body;
exit();
}
add_action('init', 'simple_proxy_init');
@simonw

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@simonw simonw commented Dec 11, 2016

I was trying to use this plugin on a WordPress install hosted on DreamPress. DreamPress comes with a pre-configured Varnish, and I was getting 503 errors from Varnish when it attempted to delivered proxied pages.

I ran varnishlog from an SSH session and saw the following:

10 FetchError   c Invalid Gzip data: incorrect header check

To fix this, I changed a couple of things. Firstly, I modified the call to the wp_remote_get() function to turn off gzip compression in that HTTP call, which should have prevented my proxied-to backend from serving gzipped content. Upon further inspection the backend still appeared to be returning a 'content-encoding: gzip' header for some reason even though the body wasn't gzipped, so I exclude that header from the headers that are copied across into the final response from the proxy plugin.

This seems to work now.

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@simonw simonw commented Dec 11, 2016

The original plugin can be found here: https://wordpress.org/plugins/simple-proxy/

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