From ff74627e62e6d1749bb36ec4b096137e3262f3dc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20S=CC=8Ckoda?= <commits@skodak.org>
Date: Fri, 12 Jul 2013 21:48:21 +0200
Subject: [PATCH] MDL-40546 send proper caching headers when $CFG->cachejs = 0

This should help developers writing old style JS that is served via lib/javascript.php.
---
 lib/javascript.php            |  8 +++++---
 lib/outputrequirementslib.php | 11 ++++++++---
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/lib/javascript.php b/lib/javascript.php
index 380334f52ad..7a97dfc7ea8 100644
--- a/lib/javascript.php
+++ b/lib/javascript.php
@@ -42,7 +42,7 @@ if ($slashargument = min_get_slash_argument()) {
     $file = '/'.min_clean_param($file, 'SAFEPATH');
 
 } else {
-    $rev  = min_optional_param('rev', 0, 'INT');
+    $rev  = min_optional_param('rev', -1, 'INT');
     $file = min_optional_param('jsfile', '', 'RAW'); // 'file' would collide with URL rewriting!
 }
 
@@ -76,9 +76,11 @@ if (!$jsfiles) {
 }
 
 $etag = sha1($rev.implode(',', $jsfiles));
-$candidate = $CFG->cachedir.'/js/'.$etag;
 
-if ($rev > -1) {
+// Use the caching only for meaningful revision numbers which prevents future cache poisoning.
+if ($rev > 0 and $rev < (time() + 60*60)) {
+    $candidate = $CFG->cachedir.'/js/'.$etag;
+
     if (file_exists($candidate)) {
         if (!empty($_SERVER['HTTP_IF_NONE_MATCH']) || !empty($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
             // we do not actually need to verify the etag value because our files
diff --git a/lib/outputrequirementslib.php b/lib/outputrequirementslib.php
index 76310d94a2f..abbc903c47b 100644
--- a/lib/outputrequirementslib.php
+++ b/lib/outputrequirementslib.php
@@ -613,12 +613,17 @@ class page_requirements_manager {
                     throw new coding_exception('Attempt to require a JavaScript file that does not exist.', $url);
                 }
             }
-            if (!empty($CFG->cachejs) and !empty($CFG->jsrev) and $CFG->jsrev > 0 and substr($url, -3) === '.js') {
+            if (substr($url, -3) === '.js') {
+                if (empty($CFG->cachejs) or !isset($CFG->jsrev)) {
+                    $jsrev = -1;
+                } else {
+                    $jsrev = (int)$CFG->jsrev;
+                }
                 if (empty($CFG->slasharguments)) {
-                    return new moodle_url($CFG->httpswwwroot.'/lib/javascript.php', array('rev'=>$CFG->jsrev, 'jsfile'=>$url));
+                    return new moodle_url($CFG->httpswwwroot.'/lib/javascript.php', array('rev'=>$jsrev, 'jsfile'=>$url));
                 } else {
                     $returnurl = new moodle_url($CFG->httpswwwroot.'/lib/javascript.php');
-                    $returnurl->set_slashargument('/'.$CFG->jsrev.$url);
+                    $returnurl->set_slashargument('/'.$jsrev.$url);
                     return $returnurl;
                 }
             } else {