From 3756441a8aa5af8b05e5acc6c0a3b01cfdcf5244 Mon Sep 17 00:00:00 2001
From: glubsy <glubsy@users.noreply.github.com>
Date: Sat, 23 Jan 2021 18:30:19 +0000
Subject: [PATCH] Limit thumbnail generation

* This fixes a denial-of-service exploit that would allow the client to
generate an infinite number of thumbnails and fill up the storage completely.
Since the client had control over the requested thumbnail sizes, it could make arbitrary requests for thumbnails, and every time the backend did not find an already generated thumbnail with the specified sizes, it would happily generate a new one.
* Remove the ability of the client to decide thumbnail dimensions and
only let the back-end do this by reading the configuration.
* Limit the number of generated thumbnails per file to only one, with
"landscape" dimensions (4/3).
* Use CSS "object-fit" property to adjust displaying of landscape thumbnails into squares. Ref: https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit
---
 src/_h5ai/private/conf/options.json          | 2 +-
 src/_h5ai/private/php/core/class-context.php | 5 ++++-
 src/_h5ai/private/php/ext/class-thumb.php    | 4 ++--
 src/_h5ai/public/css/lib/view/view.less      | 2 ++
 src/_h5ai/public/js/lib/ext/thumbnails.js    | 5 -----
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/_h5ai/private/conf/options.json b/src/_h5ai/private/conf/options.json
index a570da26f..2e9e83d14 100644
--- a/src/_h5ai/private/conf/options.json
+++ b/src/_h5ai/private/conf/options.json
@@ -355,7 +355,7 @@
     - mov: array of strings
     - doc: array of strings
     - delay: number, delay in milliseconds after "dom-ready" before thumb-requesting starts
-    - size: number, size in pixel of the generated thumbnails
+    - size: number, height in pixel of the generated thumbnails
     - exif: boolean, use included EXIF thumbs if possible
     - chunksize: int, number of thumbs per request
     */
diff --git a/src/_h5ai/private/php/core/class-context.php b/src/_h5ai/private/php/core/class-context.php
index 5484f8f9c..ae50f10fc 100644
--- a/src/_h5ai/private/php/core/class-context.php
+++ b/src/_h5ai/private/php/core/class-context.php
@@ -17,6 +17,9 @@ public function __construct($session, $request, $setup) {
 
         $this->options = Json::load($this->setup->get('CONF_PATH') . '/options.json');
 
+        $this->thumbnail_height = $this->options['thumbnails']['size'] ?? 240;
+        $this->thumbnail_width = floor($this->thumbnail_height * (4 / 3));
+
         $this->passhash = $this->query_option('passhash', '');
         $this->options['hasCustomPasshash'] = strcasecmp($this->passhash, Context::$DEFAULT_PASSHASH) !== 0;
         unset($this->options['passhash']);
@@ -240,7 +243,7 @@ public function get_thumbs($requests) {
 
         foreach ($requests as $req) {
             $thumb = new Thumb($this);
-            $hrefs[] = $thumb->thumb($req['type'], $req['href'], $req['width'], $req['height']);
+            $hrefs[] = $thumb->thumb($req['type'], $req['href']);
         }
 
         return $hrefs;
diff --git a/src/_h5ai/private/php/ext/class-thumb.php b/src/_h5ai/private/php/ext/class-thumb.php
index d52d3e85e..0f9823fb4 100644
--- a/src/_h5ai/private/php/ext/class-thumb.php
+++ b/src/_h5ai/private/php/ext/class-thumb.php
@@ -23,7 +23,7 @@ public function __construct($context) {
         }
     }
 
-    public function thumb($type, $source_href, $width, $height) {
+    public function thumb($type, $source_href) {
         $source_path = $this->context->to_path($source_href);
         if (!file_exists($source_path) || Util::starts_with($source_path, $this->setup->get('CACHE_PUB_PATH'))) {
             return null;
@@ -46,7 +46,7 @@ public function thumb($type, $source_href, $width, $height) {
             }
         }
 
-        return $this->thumb_href($capture_path, $width, $height);
+        return $this->thumb_href($capture_path, $this->context->thumbnail_width, $this->context->thumbnail_height);
     }
 
     private function thumb_href($source_path, $width, $height) {
diff --git a/src/_h5ai/public/css/lib/view/view.less b/src/_h5ai/public/css/lib/view/view.less
index aef93ecbb..1be5170dc 100644
--- a/src/_h5ai/public/css/lib/view/view.less
+++ b/src/_h5ai/public/css/lib/view/view.less
@@ -48,6 +48,8 @@
         .thumb {
             max-width: none;
             max-height: none;
+            object-fit: cover;
+            object-position: 50% 50%;
         }
     }
 
diff --git a/src/_h5ai/public/js/lib/ext/thumbnails.js b/src/_h5ai/public/js/lib/ext/thumbnails.js
index d71898cc2..d92c14554 100644
--- a/src/_h5ai/public/js/lib/ext/thumbnails.js
+++ b/src/_h5ai/public/js/lib/ext/thumbnails.js
@@ -13,7 +13,6 @@ const settings = Object.assign({
     exif: false,
     chunksize: 20
 }, allsettings.thumbnails);
-const landscapeRatio = 4 / 3;
 
 
 const queueItem = (queue, item) => {
@@ -35,7 +34,6 @@ const queueItem = (queue, item) => {
         queue.push({
             type,
             href: item.absHref,
-            ratio: 1,
             callback: src => {
                 if (src && item.$view) {
                     item.thumbSquare = src;
@@ -51,7 +49,6 @@ const queueItem = (queue, item) => {
         queue.push({
             type,
             href: item.absHref,
-            ratio: landscapeRatio,
             callback: src => {
                 if (src && item.$view) {
                     item.thumbRational = src;
@@ -67,8 +64,6 @@ const requestQueue = queue => {
         return {
             type: req.type,
             href: req.href,
-            width: Math.round(settings.size * req.ratio),
-            height: settings.size
         };
     });