From b1b9141dcc2a595bbd79997ee0428ea34195ac0b Mon Sep 17 00:00:00 2001
From: fansaien <ericy@captive.ca>
Date: Fri, 21 Jun 2019 00:24:08 -0600
Subject: [PATCH] Improve support for protected files on S3 (#4390)

Credit to @fansaien. S3 supports generating temporaryUrls to files that don't exist yet so this adds a check to make sure temp URLs are only generated for valid files.
---
 modules/backend/controllers/Files.php | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/modules/backend/controllers/Files.php b/modules/backend/controllers/Files.php
index 2ac62a722..51fcded78 100644
--- a/modules/backend/controllers/Files.php
+++ b/modules/backend/controllers/Files.php
@@ -77,11 +77,18 @@ class Files extends Controller
             if (empty($path)) {
                 $path = $file->getDiskPath();
             }
-            $expires = now()->addSeconds(Config::get('cms.storage.uploads.temporaryUrlTTL', 3600));
 
-            $url = Cache::remember('backend.file:' . $path, $expires, function () use ($disk, $path, $expires) {
-                return $disk->temporaryUrl($path, $expires);
-            });
+            // Check to see if the URL has already been generated
+            $pathKey = 'backend.file:' . $path;
+            $url = Cache::get($pathKey);
+
+            // The AWS S3 storage drivers will return a valid temporary URL even if the file does not exist
+            if (is_null($url) && $disk->exists($path)) {
+                $expires = now()->addSeconds(Config::get('cms.storage.uploads.temporaryUrlTTL', 3600));
+                $url = Cache::remember($pathKey, $expires, function () use ($disk, $path, $expires) {
+                    return $disk->temporaryUrl($path, $expires);
+                });
+            }
         }
 
         return $url;