Comments: Added HTML filter on load, tinymce elem filtering

- Added filter on load to help prevent potentially dangerous comment
  HTML in DB at load time (if it gets passed input filtering, or is
  existing).
- Added TinyMCE valid_elements for input wysiwygs, to gracefully degrade
  content at point of user-view, rather than surprising the user by
  stripping content, which TinyMCE would show, post-save.

app/Activity/Models/Comment.php

@@ -4,6 +4,7 @@ namespace BookStack\Activity\Models;
 
 use BookStack\App\Model;
 use BookStack\Users\Models\HasCreatorAndUpdater;
+use BookStack\Util\HtmlContentFilter;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\MorphTo;
@@ -73,4 +74,9 @@ class Comment extends Model implements Loggable
     {
         return "Comment #{$this->local_id} (ID: {$this->id}) for {$this->entity_type} (ID: {$this->entity_id})";
     }
+
+    public function safeHtml(): string
+    {
+        return HtmlContentFilter::removeScriptsFromHtmlString($this->html ?? '');
+    }
 }

resources/js/wysiwyg/config.js

@@ -339,6 +339,7 @@ export function buildForInput(options) {
         toolbar: 'bold italic link bullist numlist',
         content_style: getContentStyle(options),
         file_picker_types: 'file',
+        valid_elements: 'p,a[href|title],ol,ul,li,strong,em,br',
         file_picker_callback: filePickerCallback,
         init_instance_callback(editor) {
             addCustomHeadContent(editor.getDoc());

resources/views/comments/comment.blade.php

@@ -1,3 +1,6 @@
+@php
+    $commentHtml = $comment->safeHtml();
+@endphp
 <div component="{{ $readOnly ? '' : 'page-comment' }}"
      option:page-comment:comment-id="{{ $comment->id }}"
      option:page-comment:comment-local-id="{{ $comment->local_id }}"
@@ -71,13 +74,13 @@
                 <a class="text-muted text-small" href="#comment{{ $comment->parent_id }}">@icon('reply'){{ trans('entities.comment_in_reply_to', ['commentId' => '#' . $comment->parent_id]) }}</a>
             </p>
         @endif
-        {!! $comment->html  !!}
+        {!! $commentHtml  !!}
     </div>
 
     @if(!$readOnly && userCan('comment-update', $comment))
         <form novalidate refs="page-comment@form" hidden class="content pt-s px-s block">
             <div class="form-group description-input">
-                <textarea refs="page-comment@input" name="html" rows="3" placeholder="{{ trans('entities.comment_placeholder') }}">{{ $comment->html }}</textarea>
+                <textarea refs="page-comment@input" name="html" rows="3" placeholder="{{ trans('entities.comment_placeholder') }}">{{ $commentHtml }}</textarea>
             </div>
             <div class="form-group text-right">
                 <button type="button" class="button outline" refs="page-comment@form-cancel">{{ trans('common.cancel') }}</button>

tests/Entity/CommentTest.php

@@ -82,11 +82,10 @@ class CommentTest extends TestCase
 
     public function test_scripts_cannot_be_injected_via_comment_html()
     {
-        $this->asAdmin();
         $page = $this->entities->page();
 
         $script = '<script>const a = "script";</script><p onclick="1">My lovely comment</p>';
-        $this->postJson("/comment/$page->id", [
+        $this->asAdmin()->postJson("/comment/$page->id", [
             'html' => $script,
         ]);
 
@@ -104,6 +103,20 @@ class CommentTest extends TestCase
         $pageView->assertSee('<p>My lovely comment</p><p>updated</p>');
     }
 
+    public function test_scripts_are_removed_even_if_already_in_db()
+    {
+        $page = $this->entities->page();
+        Comment::factory()->create([
+            'html' => '<script>superbadscript</script><p onclick="superbadonclick">scriptincommentest</p>',
+            'entity_type' => 'page', 'entity_id' => $page
+        ]);
+
+        $resp = $this->asAdmin()->get($page->getUrl());
+        $resp->assertSee('scriptincommentest', false);
+        $resp->assertDontSee('superbadscript', false);
+        $resp->assertDontSee('superbadonclick', false);
+    }
+
     public function test_reply_comments_are_nested()
     {
         $this->asAdmin();