From 6c159262f016b74a474d31c613387b00f03ad589 Mon Sep 17 00:00:00 2001
From: Paul Holden <paulh@moodle.com>
Date: Tue, 20 Apr 2021 12:06:03 +0100
Subject: [PATCH] MDL-70970 quizaccess_seb: consistent property array sorting
 by key.

In PHP8.0 using `ksort` was producing incorrect results by sorting
keys differing only in case in the wrong order. This change makes
sorting consistent between PHP versions.

Co-Authored-By: Tim Hunt <T.J.Hunt@open.ac.uk>
---
 .../accessrule/seb/classes/property_list.php  | 23 +++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/mod/quiz/accessrule/seb/classes/property_list.php b/mod/quiz/accessrule/seb/classes/property_list.php
index 57525e6573d..d6f47c88b81 100644
--- a/mod/quiz/accessrule/seb/classes/property_list.php
+++ b/mod/quiz/accessrule/seb/classes/property_list.php
@@ -34,9 +34,9 @@ use CFPropertyList\CFNumber;
 use CFPropertyList\CFPropertyList;
 use CFPropertyList\CFString;
 use CFPropertyList\CFType;
+use \Collator;
 use \DateTime;
 
-defined('MOODLE_INTERNAL') || die();
 
 /**
  * Wrapper for CFPropertyList to handle low level iteration.
@@ -322,6 +322,8 @@ class property_list {
     /**
      * Recursively sort array alphabetically by key.
      *
+     * @link https://safeexambrowser.org/developer/seb-config-key.html
+     *
      * @param array $array Top level array to process.
      * @return array Processed array.
      */
@@ -331,10 +333,23 @@ class property_list {
                 $array[$key] = $this->array_sort($array[$key]);
             }
         }
-        // Sort assoc array. From SEB docs - "Use non-localized (culture invariant), non-ASCII value based case
-        // insensitive ordering."
+        // Sort assoc array. From SEB docs:
+        //
+        // All <dict> elements from the plist XML must be ordered (alphabetically sorted) by their key names. Use
+        // a recursive method to apply ordering also to nested dictionaries contained in the root-level dictionary
+        // and in arrays. Use non-localized (culture invariant), non-ASCII value based case insensitive ordering.
+        // For example the key <key>allowWlan</key> comes before <key>allowWLAN</key>. Cocoa/Obj-C and .NET/C#
+        // usually use this case insensitive ordering as default, but PHP for example doesn't.
         if ($this->is_associative_array($array)) {
-            ksort($array, SORT_STRING | SORT_FLAG_CASE);
+            // Note this is a pragmatic solution as none of the native PHP *sort method appear to sort strings that
+            // differ only in case (e.g. ["allowWLAN", "allowWlan"] is expected to have the lower version first).
+            $keys = array_keys($array);
+            (new Collator('root'))->asort($keys); // Use Unicode Collation Algorithm (UCA).
+            $original = $array;
+            $array = [];
+            foreach ($keys as $key) {
+                $array[$key] = $original[$key];
+            }
         }
 
         return $array;