From 77ec41bb6f542077503106cacc1dbd28118c50b4 Mon Sep 17 00:00:00 2001
From: Felix Hammerl <fhammerl@thoughtworks.com>
Date: Wed, 24 Feb 2016 10:13:25 +0100
Subject: Issue #617: Sanitize received content

Sanitizes received HTML content with DOMPurify, making it safe
for displaying and templating. Sanitizes received plain text content
by encoding every single character as HTML entity.
---
 web-ui/app/js/helpers/sanitizer.js | 108 +++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 web-ui/app/js/helpers/sanitizer.js

(limited to 'web-ui/app/js/helpers/sanitizer.js')

diff --git a/web-ui/app/js/helpers/sanitizer.js b/web-ui/app/js/helpers/sanitizer.js
new file mode 100644
index 00000000..eea1f0f7
--- /dev/null
+++ b/web-ui/app/js/helpers/sanitizer.js
@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2016 ThoughtWorks, Inc.
+ *
+ * Pixelated is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Pixelated is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Pixelated. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+define(['DOMPurify', 'he'], function (DOMPurify, he) {
+  'use strict';
+
+  /**
+   * Sanitizes a mail body to safe-to-display HTML
+   */
+  var sanitizer = {};
+
+  /**
+   * Adds html line breaks to a plaintext with line breaks (incl carriage return)
+   *
+   * @param {string} textPlainBody Plaintext input
+   * @returns {string} Plaintext with HTML line breals (<br/>)
+   */
+  sanitizer.addLineBreaks = function (textPlainBody) {
+    return textPlainBody.replace(/(\r)?\n/g, '<br/>').replace(/(&#xD;)?&#xA;/g, '<br/>');
+  };
+
+  /**
+   * Runs a given dirty body through DOMPurify, thereby removing
+   * potentially hazardous XSS attacks. Please be advised that this
+   * will not act as a privacy leak prevention. Contained contents
+   * will still point to remote sources.
+   *
+   * For future reference: Running DOMPurify with these parameters
+   * can help mitigate some of the most widely used privacy leaks.
+   * FORBID_TAGS: ['style', 'svg', 'audio', 'video', 'math'],
+   * FORBID_ATTR: ['src']
+   *
+   * @param  {string} dirtyBody The unsanitized string
+   * @return {string} Safe-to-display HTML string
+   */
+  sanitizer.purifyHtml = function (dirtyBody) {
+    return DOMPurify.sanitize(dirtyBody, {
+      SAFE_FOR_JQUERY: true,
+      SAFE_FOR_TEMPLATES: true
+    });
+  };
+
+  /**
+  * Runs a given dirty body through he, thereby encoding everything
+  * as HTML entities.
+  *
+  * @param  {string} dirtyBody The unsanitized string
+  * @return {string} Safe-to-display HTML string
+  */
+  sanitizer.purifyText = function (dirtyBody) {
+    return he.encode(dirtyBody, {
+      encodeEverything: true
+    });
+  };
+
+  /**
+   * Calls #purify and #addLineBreaks to turn untrusted mail body content
+   * into safe-to-display HTML.
+   *
+   * NB: HTML content is preferred to plaintext content.
+   *
+   * @param  {object} mail Pixelated Mail Object
+   * @return {string} Safe-to-display HTML string
+   */
+  sanitizer.sanitize = function (mail) {
+    var body;
+
+    if (mail.htmlBody) {
+      body = this.purifyHtml(mail.htmlBody);
+    } else {
+      body = this.purifyText(mail.textPlainBody);
+      body = this.addLineBreaks(body);
+    }
+
+    return body;
+  };
+
+  /**
+   * Add hooks to DOMPurify for opening links in new windows
+   */
+  DOMPurify.addHook('afterSanitizeAttributes', function (node) {
+    // set all elements owning target to target=_blank
+    if ('target' in node) {
+      node.setAttribute('target', '_blank');
+    }
+
+    // set non-HTML/MathML links to xlink:show=new
+    if (!node.hasAttribute('target') && (node.hasAttribute('xlink:href') || node.hasAttribute('href'))) {
+      node.setAttribute('xlink:show', 'new');
+    }
+  });
+
+  return sanitizer;
+});
-- 
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