From a64973aecff0595bd34a6e70393d471b8dbf1841 Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Fri, 7 Feb 2020 15:24:22 +0100
Subject: [PATCH] Fix malformed HTML causing uncaught error (#13042)

Fix OEmbed preview API leaking existence of private statuses (see #12930)
---
 app/controllers/api/web/embeds_controller.rb | 16 +++++++++++-----
 app/lib/formatter.rb                         |  2 ++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/app/controllers/api/web/embeds_controller.rb b/app/controllers/api/web/embeds_controller.rb
index 6231733b7..4aa31695c 100644
--- a/app/controllers/api/web/embeds_controller.rb
+++ b/app/controllers/api/web/embeds_controller.rb
@@ -7,15 +7,21 @@ class Api::Web::EmbedsController < Api::Web::BaseController
 
   def create
     status = StatusFinder.new(params[:url]).status
+
+    return not_found if status.hidden?
+
     render json: status, serializer: OEmbedSerializer, width: 400
   rescue ActiveRecord::RecordNotFound
     oembed = FetchOEmbedService.new.call(params[:url])
-    oembed[:html] = Formatter.instance.sanitize(oembed[:html], Sanitize::Config::MASTODON_OEMBED) if oembed[:html].present?
 
-    if oembed
-      render json: oembed
-    else
-      render json: {}, status: :not_found
+    return not_found if oembed.nil?
+
+    begin
+      oembed[:html] = Formatter.instance.sanitize(oembed[:html], Sanitize::Config::MASTODON_OEMBED)
+    rescue ArgumentError
+      return not_found
     end
+
+    render json: oembed
   end
 end
diff --git a/app/lib/formatter.rb b/app/lib/formatter.rb
index 2c5674869..e6f5d7a63 100644
--- a/app/lib/formatter.rb
+++ b/app/lib/formatter.rb
@@ -46,6 +46,8 @@ class Formatter
 
   def reformat(html)
     sanitize(html, Sanitize::Config::MASTODON_STRICT)
+  rescue ArgumentError
+    ''
   end
 
   def plaintext(status)