From b91c564b91f7a190e6cdf89592d38682eee08e7e Mon Sep 17 00:00:00 2001
From: Alexander Ebert <ebert@woltlab.com>
Date: Thu, 25 Apr 2024 16:28:27 +0200
Subject: [PATCH] Prevent the generation of thumbnails for small images

---
 .../lib/system/file/processor/FileProcessor.class.php  |  6 ++++++
 .../lib/system/image/adapter/ImageAdapter.class.php    | 10 +++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/wcfsetup/install/files/lib/system/file/processor/FileProcessor.class.php b/wcfsetup/install/files/lib/system/file/processor/FileProcessor.class.php
index fe6639b445..2ffb4e40cf 100644
--- a/wcfsetup/install/files/lib/system/file/processor/FileProcessor.class.php
+++ b/wcfsetup/install/files/lib/system/file/processor/FileProcessor.class.php
@@ -102,6 +102,12 @@ final class FileProcessor extends SingletonFactory
                 continue;
             }
 
+            // Check if we the source image is larger than the dimensions of the
+            // requested thumbnails.
+            if ($format->width > $file->width && $format->height > $file->height) {
+                continue;
+            }
+
             if ($imageAdapter === null) {
                 $imageAdapter = ImageHandler::getInstance()->getAdapter();
                 $imageAdapter->loadFile($file->getPathname());
diff --git a/wcfsetup/install/files/lib/system/image/adapter/ImageAdapter.class.php b/wcfsetup/install/files/lib/system/image/adapter/ImageAdapter.class.php
index 2f59a1c949..9420f2d51a 100644
--- a/wcfsetup/install/files/lib/system/image/adapter/ImageAdapter.class.php
+++ b/wcfsetup/install/files/lib/system/image/adapter/ImageAdapter.class.php
@@ -80,7 +80,15 @@ class ImageAdapter implements IImageAdapter, IMemoryAwareImageAdapter
     public function createThumbnail($maxWidth, $maxHeight, $preserveAspectRatio = true)
     {
         if ($maxWidth > $this->getWidth() && $maxHeight > $this->getHeight()) {
-            throw new SystemException("Dimensions for thumbnail can not exceed image dimensions.");
+            throw new SystemException(
+                \sprintf(
+                    "Dimensions for thumbnail can not exceed image dimensions (requested: %d × %d, actual: %d × %d).",
+                    $maxWidth,
+                    $maxHeight,
+                    $this->getWidth(),
+                    $this->getHeight(),
+                )
+            );
         }
 
         $maxHeight = \min($maxHeight, $this->getHeight());
-- 
2.20.1