From c3e42709fbf3a84f8aa56bb381119ab28a588400 Mon Sep 17 00:00:00 2001
From: Alexander Ebert <ebert@woltlab.com>
Date: Wed, 28 Sep 2016 12:04:20 +0200
Subject: [PATCH] Always disable browser caching of pages

This affects the HTML send to the browser only and has no influence of
any other assets, such as JavaScript or images.
---
 com.woltlab.wcf/option.xml                           | 6 +-----
 constants.php                                        | 1 -
 wcfsetup/install/files/lib/system/WCFSetup.class.php | 1 -
 wcfsetup/install/files/lib/util/HeaderUtil.class.php | 8 ++------
 wcfsetup/install/files/options.inc.php               | 1 -
 wcfsetup/install/lang/de.xml                         | 2 --
 wcfsetup/install/lang/en.xml                         | 2 --
 7 files changed, 3 insertions(+), 18 deletions(-)

diff --git a/com.woltlab.wcf/option.xml b/com.woltlab.wcf/option.xml
index 86d9637b36..034d3d2384 100644
--- a/com.woltlab.wcf/option.xml
+++ b/com.woltlab.wcf/option.xml
@@ -534,11 +534,6 @@ private:wcf.acp.option.exception_privacy.private</selectoptions>
 			<!-- /general.system.cookie-->
 			
 			<!-- general.system.http -->
-			<option name="http_enable_no_cache_headers">
-				<categoryname>general.system.http</categoryname>
-				<optiontype>boolean</optiontype>
-				<defaultvalue>1</defaultvalue>
-			</option>
 			<option name="http_send_x_frame_options">
 				<categoryname>general.system.http</categoryname>
 				<optiontype>boolean</optiontype>
@@ -1550,6 +1545,7 @@ DESC:wcf.global.sortOrder.descending</selectoptions>
 	
 	<delete>
 		<option name="cache_source_memcached_use_pconnect" />
+		<option name="http_enable_no_cache_headers" />
 		<option name="http_gzip_level" />
 		<option name="enable_pluginstore_widget" />
 		<option name="mail_use_formatted_address" />
diff --git a/constants.php b/constants.php
index 1d34370db8..2482b5e06a 100644
--- a/constants.php
+++ b/constants.php
@@ -66,7 +66,6 @@ define('IMAGE_ADAPTER_TYPE', 'gd');
 define('SEARCH_ENGINE', 'mysql');
 define('EXCEPTION_PRIVACY', 'public');
 define('COOKIE_PREFIX', 'wcf21_');
-define('HTTP_ENABLE_NO_CACHE_HEADERS', 0);
 define('HTTP_SEND_X_FRAME_OPTIONS', 1);
 define('HTTP_ENABLE_GZIP', 1);
 define('PACKAGE_SERVER_AUTH_CODE', '');
diff --git a/wcfsetup/install/files/lib/system/WCFSetup.class.php b/wcfsetup/install/files/lib/system/WCFSetup.class.php
index a11dd8a64d..bc4c666ddd 100644
--- a/wcfsetup/install/files/lib/system/WCFSetup.class.php
+++ b/wcfsetup/install/files/lib/system/WCFSetup.class.php
@@ -28,7 +28,6 @@ use wcf\util\XML;
 
 // define
 define('PACKAGE_ID', 0);
-define('HTTP_ENABLE_NO_CACHE_HEADERS', 0);
 define('HTTP_ENABLE_GZIP', 0);
 define('HTTP_GZIP_LEVEL', 0);
 define('HTTP_SEND_X_FRAME_OPTIONS', 0);
diff --git a/wcfsetup/install/files/lib/util/HeaderUtil.class.php b/wcfsetup/install/files/lib/util/HeaderUtil.class.php
index 347332a420..e7671f0d23 100644
--- a/wcfsetup/install/files/lib/util/HeaderUtil.class.php
+++ b/wcfsetup/install/files/lib/util/HeaderUtil.class.php
@@ -55,13 +55,9 @@ final class HeaderUtil {
 		@header('Content-Type: text/html; charset=UTF-8');
 		
 		// send no cache headers
-		if (HTTP_ENABLE_NO_CACHE_HEADERS && !WCF::getSession()->spiderID) {
+		if (!WCF::getSession()->spiderID) {
 			self::sendNoCacheHeaders();
 		}
-		else if (!empty($_SERVER['HTTP_USER_AGENT']) && strpos($_SERVER['HTTP_USER_AGENT'], 'Firefox') !== false) {
-			// Firefox serves pages from cache, causing certain HTML elements to stay in an outdated state
-			@header('Cache-Control: no-store');
-		}
 		
 		if (HTTP_ENABLE_GZIP && !defined('HTTP_DISABLE_GZIP')) {
 			if (function_exists('gzcompress') && !@ini_get('zlib.output_compression') && !@ini_get('output_handler') && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strstr($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip')) {
@@ -93,7 +89,7 @@ final class HeaderUtil {
 	public static function sendNoCacheHeaders() {
 		@header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');
 		@header('Last-Modified: '.gmdate('D, d M Y H:i:s').' GMT');
-		@header('Cache-Control: no-cache, must-revalidate');
+		@header('Cache-Control: max-age=0, no-cache, no-store, must-revalidate');
 		@header('Pragma: no-cache');
 	}
 	
diff --git a/wcfsetup/install/files/options.inc.php b/wcfsetup/install/files/options.inc.php
index 019c6713b0..3e2c577eab 100644
--- a/wcfsetup/install/files/options.inc.php
+++ b/wcfsetup/install/files/options.inc.php
@@ -12,7 +12,6 @@ define('COOKIE_PREFIX', 'wsc30_');
 define('COOKIE_PATH', '');
 define('COOKIE_DOMAIN', '');
 
-define('HTTP_ENABLE_NO_CACHE_HEADERS', 0);
 define('HTTP_ENABLE_GZIP', 0);
 define('HTTP_GZIP_LEVEL', 1);
 define('HTTP_SEND_X_FRAME_OPTIONS', 0);
diff --git a/wcfsetup/install/lang/de.xml b/wcfsetup/install/lang/de.xml
index 8418ed0c72..b6e7ce1093 100644
--- a/wcfsetup/install/lang/de.xml
+++ b/wcfsetup/install/lang/de.xml
@@ -897,8 +897,6 @@
 		<item name="wcf.acp.option.error.tooLow"><![CDATA[Der angegebene Wert ist zu gering.{if $option->minvalue !== null} Der minimale Wert ist {#$option->minvalue}.{/if}]]></item>
 		<item name="wcf.acp.option.http_enable_gzip"><![CDATA[Gzip-Komprimierung aktivieren]]></item>
 		<item name="wcf.acp.option.http_enable_gzip.description"><![CDATA[Aktiviert die Komprimierung der Inhalte bei der Übertragung vom Server an den Client. Dies reduziert den Traffic und kann den Ladevorgang erheblich beschleunigen.]]></item>
-		<item name="wcf.acp.option.http_enable_no_cache_headers"><![CDATA[Seitencaching im Client-Browser verhindern]]></item>
-		<item name="wcf.acp.option.http_enable_no_cache_headers.description"><![CDATA[Verhindert zuverlässig das Cachen von einzelnen Seiten und sorgt somit dafür, dass beim Seitenaufruf immer die neueste Version der Seite geladen wird. Führt umgekehrt aber zu höherem Traffic und mehr Serverlast.]]></item>
 		<item name="wcf.acp.option.http_send_x_frame_options"><![CDATA[Einbindung in einem Frame verhindern]]></item>
 		<item name="wcf.acp.option.http_send_x_frame_options.description"><![CDATA[Sendet den <a href="{@$__wcf->getPath()}acp/dereferrer.php?url={'http://de.wikipedia.org/wiki/Clickjacking'|rawurlencode}" class="externalURL">„X-Frame-Options“</a> Header um die Einbettung dieser Seite in einem Frame zu verhindern (sendet „SAMEORIGIN“).]]></item>
 		<item name="wcf.acp.option.image_adapter_type"><![CDATA[Grafik-Bibliothek]]></item>
diff --git a/wcfsetup/install/lang/en.xml b/wcfsetup/install/lang/en.xml
index cf7291e7df..0d0e4ebbb3 100644
--- a/wcfsetup/install/lang/en.xml
+++ b/wcfsetup/install/lang/en.xml
@@ -896,8 +896,6 @@ Examples for medium ID detection:
 		<item name="wcf.acp.option.error.tooLow"><![CDATA[Under the minimum value{if $option->minvalue !== null} of {#$option->minvalue}{/if}.]]></item>
 		<item name="wcf.acp.option.http_enable_gzip"><![CDATA[Enable gzip-compression]]></item>
 		<item name="wcf.acp.option.http_enable_gzip.description"><![CDATA[Compresses content transferred to users, reduces traffic and page load time. Does not affect files, e.g. images.]]></item>
-		<item name="wcf.acp.option.http_enable_no_cache_headers"><![CDATA[Prevent browser-caching]]></item>
-		<item name="wcf.acp.option.http_enable_no_cache_headers.description"><![CDATA[Prevents browser’s caching ensuring your users are always viewing the latest content. Increases both traffic and server load.]]></item>
 		<item name="wcf.acp.option.http_send_x_frame_options"><![CDATA[Disallow embedding in a frame]]></item>
 		<item name="wcf.acp.option.http_send_x_frame_options.description"><![CDATA[Sends the <a href="{@$__wcf->getPath()}acp/dereferrer.php?url={'http://en.wikipedia.org/wiki/Clickjacking'|rawurlencode}" class="externalURL">“X-Frame-Options”</a> header to prevent 3rd party sites from embedding this site in a frame (sends “SAMEORIGIN”).]]></item>
 		<item name="wcf.acp.option.image_adapter_type"><![CDATA[Graphics Library]]></item>
-- 
2.20.1