MDL-26028 implement Nginx X-Sendfile directory aliases setting

config-dist.php

@@ -225,6 +225,16 @@ $CFG->admin = 'admin';
 //     $CFG->xsendfile = 'X-Sendfile';           // Apache {@see https://tn123.org/mod_xsendfile/}
 //     $CFG->xsendfile = 'X-LIGHTTPD-send-file'; // Lighttpd {@see http://redmine.lighttpd.net/projects/lighttpd/wiki/X-LIGHTTPD-send-file}
 //     $CFG->xsendfile = 'X-Accel-Redirect';     // Nginx {@see http://wiki.nginx.org/XSendfile}
+// If your X-Sendfile implementation (usually Nginx) uses directory aliases specify them
+// in the following array setting:
+//     $CFG->xsendfilealiases = array(
+//         '/dataroot/' => $CFG->dataroot,
+//         '/cachedir/' => '/var/www/moodle/cache',    // for custom $CFG->cachedir locations
+//         '/tempdir/'  => '/var/www/moodle/temp',     // for custom $CFG->tempdir locations
+//         '/filedir'   => '/var/www/moodle/filedir',  // for custom $CFG->filedir locations
+//     );
+//
+//
 //
 // This setting will prevent the 'My Courses' page being displayed when a student
 // logs in. The site front page will always show the same (logged-out) view.

lib/xsendfilelib.php

@@ -47,19 +47,30 @@ function xsendfile($filepath) {
         return false;
     }
 
+    $filepath = realpath($filepath);
+
+    $aliased = false;
+    if (!empty($CFG->xsendfilealiases) and is_array($CFG->xsendfilealiases)) {
+        foreach ($CFG->xsendfilealiases as $alias=>$dir) {
+            $dir = realpath($dir).PATH_SEPARATOR;
+            if (strpos($filepath, $dir) === 0) {
+                $filepath = $alias.substr($filepath, strlen($dir));
+                $aliased = true;
+                break;
+            }
+        }
+    }
+
     if ($CFG->xsendfile === 'X-LIGHTTPD-send-file') {
         // http://redmine.lighttpd.net/projects/lighttpd/wiki/X-LIGHTTPD-send-file says 1.4 it does not support byteserving
         header('Accept-Ranges: none');
 
     } else if ($CFG->xsendfile === 'X-Accel-Redirect') {
         // http://wiki.nginx.org/XSendfile
-        // Nginx is using relative path to protected folder, please note you can not use cache dir, tempdir and file pool outside of dataroot!
-        $filepath = realpath($filepath);
-        $dataroot = realpath($CFG->dataroot);
-        if (strpos($filepath, $dataroot) !== 0) {
+        // Nginx requires paths relative to aliases, you need to specify them in config.php
+        if (!$aliased) {
             return false;
         }
-        $filepath = substr($filepath, strlen($dataroot));
     }
 
     header("$CFG->xsendfile: $filepath");