From 17df0f88489be6cd1ed65dfd9bbed3e9ece3fea4 Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <takowl@gmail.com>
Date: Sun, 18 Mar 2018 08:00:12 +0000
Subject: [PATCH] Disable jQuery prefilter specifically to parse sanitized HTML
 (#29)

* Add and use sanitize_html_and_parse() function

* Describe return type in doc comment

* Reset htmlPrefilter even if parsing HTML fails

* Return directly from try block

* Move toinsert to inner scope
---
 notebook/static/base/js/security.js       | 20 ++++++++++++++++++++
 notebook/static/notebook/js/outputarea.js | 10 +++++++---
 notebook/static/notebook/js/textcell.js   |  6 ++----
 3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/notebook/static/base/js/security.js b/notebook/static/base/js/security.js
index 696361beb..195c0a5cb 100644
--- a/notebook/static/base/js/security.js
+++ b/notebook/static/base/js/security.js
@@ -122,9 +122,29 @@ define([
         
         return sanitized;
     };
+
+    var sanitize_html_and_parse = function (html, allow_css) {
+        /**
+         * Sanitize HTML and parse it safely using jQuery.
+         *
+         * This disable's jQuery's html 'prefilter', which can make invalid
+         * HTML valid after the sanitizer has checked it.
+         *
+         * Returns an array of DOM nodes.
+         */
+        var sanitized_html = sanitize_html(html, allow_css);
+        var prev_htmlPrefilter = $.htmlPrefilter;
+        $.htmlPrefilter = function(html) {return html;};  // Don't modify HTML
+        try {
+            return $.parseHTML(sanitized_html);
+        } finally {
+            $.htmlPrefilter = prev_htmlPrefilter;  // Set it back again
+        }
+    };
     
     var security = {
         caja: caja,
+        sanitize_html_and_parse: sanitize_html_and_parse,
         sanitize_html: sanitize_html
     };
 
diff --git a/notebook/static/notebook/js/outputarea.js b/notebook/static/notebook/js/outputarea.js
index 219cee29f..8cffa32ba 100644
--- a/notebook/static/notebook/js/outputarea.js
+++ b/notebook/static/notebook/js/outputarea.js
@@ -674,19 +674,23 @@ define([
             var type = OutputArea.display_order[i];
             var append = OutputArea.append_map[type];
             if ((json.data[type] !== undefined) && append) {
+                var md = json.metadata || {};
                 var value = json.data[type];
+                var toinsert;
                 if (!this.trusted && !OutputArea.safe_outputs[type]) {
                     // not trusted, sanitize HTML
                     if (type===MIME_HTML || type==='text/svg') {
-                        value = security.sanitize_html(value);
+                        var parsed = $(security.sanitize_html_and_parse(value));
+                        toinsert = append.apply(this, [parsed, md, element, handle_inserted]);
                     } else {
                         // don't display if we don't know how to sanitize it
                         console.log("Ignoring untrusted " + type + " output.");
                         continue;
                     }
+                } else {
+                    toinsert = append.apply(this, [value, md, element, handle_inserted]);
                 }
-                var md = json.metadata || {};
-                var toinsert = append.apply(this, [value, md, element, handle_inserted]);
+
                 // Since only the png and jpeg mime types call the inserted
                 // callback, if the mime type is something other we must call the 
                 // inserted callback only when the element is actually inserted
diff --git a/notebook/static/notebook/js/textcell.js b/notebook/static/notebook/js/textcell.js
index 58ca9ca78..68124403c 100644
--- a/notebook/static/notebook/js/textcell.js
+++ b/notebook/static/notebook/js/textcell.js
@@ -248,8 +248,7 @@ define([
                 // HTML <img>)
                 var text = this.get_text();
                 marked(text, function (err, html) {
-                    html = security.sanitize_html(html);
-                    html = $($.parseHTML(html));
+                    html = $(security.sanitize_html_and_parse(html));
                     html.find('img[src^="attachment:"]').each(function (i, h) {
                         h = $(h);
                         var key = h.attr('src').replace(/^attachment:/, '');
@@ -402,8 +401,7 @@ define([
             };
             marked(text, { renderer: renderer }, function (err, html) {
                 html = mathjaxutils.replace_math(html, math);
-                html = security.sanitize_html(html);
-                html = $($.parseHTML(html));
+                html = $(security.sanitize_html_and_parse(html));
                 // add anchors to headings
                 html.find(":header").addBack(":header").each(function (i, h) {
                     h = $(h);