Add an option to strip EXIF data from files

Author: dtdesign

com.woltlab.wcf/option.xml

@@ -539,6 +539,11 @@ imagick:wcf.acp.option.image_adapter_type.imagick</selectoptions>
 				<selectoptions>keep:wcf.acp.option.image_convert_format.keep
 webp:wcf.acp.option.image_convert_format.webp</selectoptions>
 			</option>
+			<option name="image_strip_exif">
+				<categoryname>general.system.image</categoryname>
+				<optiontype>boolean</optiontype>
+				<defaultvalue>1</defaultvalue>
+			</option>
 			<!-- /general.system.image -->
 			<!-- general.system.search -->
 			<option name="search_engine">

constants.php

@@ -228,3 +228,4 @@
 \define('SERVICE_WORKER_PUBLIC_KEY', '');
 \define('RECAPTCHA_PRIVATEKEY_V3', '');
 \define('IMAGE_CONVERT_FORMAT', 'webp');
+\define('IMAGE_STRIP_EXIF', 1);

wcfsetup/install/files/lib/system/endpoint/controller/core/files/GenerateThumbnails.class.php

@@ -30,6 +30,7 @@ public function __invoke(ServerRequestInterface $request, array $variables): Res
 
         FileProcessor::getInstance()->generateWebpVariant($file);
         $file = FileProcessor::getInstance()->convertImageFormat($file);
+        $file = FileProcessor::getInstance()->stripExif($file);
         FileProcessor::getInstance()->generateThumbnails($file);
 
         $thumbnails = [];

wcfsetup/install/files/lib/system/file/processor/FileProcessor.class.php

@@ -13,13 +13,15 @@
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\event\EventHandler;
 use wcf\system\exception\SystemException;
+use wcf\system\file\command\ReplaceFileSource;
 use wcf\system\file\command\ReplaceWithWebpVariant;
 use wcf\system\file\processor\exception\DamagedImage;
 use wcf\system\image\adapter\exception\ImageNotProcessable;
 use wcf\system\image\adapter\exception\ImageNotReadable;
 use wcf\system\image\ImageHandler;
 use wcf\system\SingletonFactory;
 use wcf\system\WCF;
+use wcf\util\ExifUtil;
 use wcf\util\FileUtil;
 use wcf\util\JSON;
 use wcf\util\StringUtil;
@@ -441,6 +443,24 @@ public function convertImageFormat(File $file): File
         }
     }
 
+    #[\NoDiscard("as the file itself could change")]
+    public function stripExif(File $file): File
+    {
+        if (!\IMAGE_STRIP_EXIF) {
+            return $file;
+        }
+
+        $fileWithoutExif = ExifUtil::getFileWithoutExifData($file->getPathname());
+        if ($fileWithoutExif === null) {
+            return $file;
+        }
+
+        $command = new ReplaceFileSource($file, $fileWithoutExif);
+        $newFile = $command();
+
+        return $newFile;
+    }
+
     private function copyThumbnails(int $oldFileID, int $newFileID): void
     {
         $thumbnailList = new FileThumbnailList();

wcfsetup/install/files/lib/system/worker/FileRebuildDataWorker.class.php

@@ -54,6 +54,7 @@ public function execute()
             try {
                 FileProcessor::getInstance()->generateWebpVariant($file);
                 $file = FileProcessor::getInstance()->convertImageFormat($file);
+                $file = FileProcessor::getInstance()->stripExif($file);
                 FileProcessor::getInstance()->generateThumbnails($file);
             } catch (DamagedImage $e) {
                 logThrowable($e);

wcfsetup/install/files/lib/util/ExifUtil.class.php

@@ -3,6 +3,7 @@
 namespace wcf\util;
 
 use WoltLab\WebpExif\Decoder;
+use WoltLab\WebpExif\Encoder;
 use WoltLab\WebpExif\Exception\WebpExifException;
 
 /**
@@ -265,6 +266,72 @@ public static function getOrientation(array $exifData): int
         return $orientation;
     }
 
+    #[\NoDiscard("as the sanitized version is written to a temporary file")]
+    public static function getFileWithoutExifData(string $pathname): ?string
+    {
+        $fileExtension = match (FileUtil::getMimeType($pathname)) {
+            'image/jpeg' => 'jpg',
+            'image/gif' => 'gif',
+            'image/png' => 'png',
+            'image/webp' => 'webp',
+            default => 'bin',
+        };
+
+        if ($fileExtension === 'webp') {
+            return self::getWebpWithoutExif($pathname);
+        }
+
+        if (!\class_exists(\Imagick::class)) {
+            return null;
+        }
+
+        $exifData = self::getExifData($pathname);
+        $hasIdf0 = ($exifData['IFD0'] ?? []) !== [];
+        $hasGPS = ($exifData['GPS'] ?? []) !== [];
+        $hasEXIF = ($exifData['EXIF'] ?? []) !== [];
+        if (!$hasIdf0 && !$hasGPS && !$hasEXIF) {
+            return null;
+        }
+
+        $img = new \Imagick($pathname);
+        $profiles = $img->getImageProfiles('icc', true);
+        $img->stripImage();
+        if ($profiles !== []) {
+            $img->profileImage('icc', $profiles['icc']);
+        }
+
+        $tmpFile = FileUtil::getTemporaryFilename('fileWithoutExif_', ".{$fileExtension}");
+        $img->writeImage($tmpFile);
+
+        return $tmpFile;
+    }
+
+    private static function getWebpWithoutExif(string $pathname): ?string
+    {
+        $decoder = new Decoder();
+
+        try {
+            $webp = $decoder->fromBinary(\file_get_contents($pathname));
+        } catch (WebpExifException) {
+            return null;
+        }
+
+        if ($webp->getExif() !== null) {
+            $webp = $webp->withExif(null);
+        }
+        if ($webp->getXmp() !== null) {
+            $webp = $webp->withXmp(null);
+        }
+
+        $encoder = new Encoder();
+        $bytes = $encoder->fromWebP($webp);
+
+        $tmpFile = FileUtil::getTemporaryFilename('fileWithoutExif_', '.webp');
+        \file_put_contents($tmpFile, $bytes);
+
+        return $tmpFile;
+    }
+
     /**
      * Converts the format of exif geo tagging coordinates.
      */