Sanitize SVG preview, preventing script execution in instance context, while dropping support for attachment download in IE

CHANGELOG.md

@@ -10,11 +10,13 @@
     * ADDED: Oracle database support (#868)
     * ADDED: Configuration option to limit paste creation and commenting to certain IPs (#883)
     * ADDED: Set CSP also as meta tag, to deal with misconfigured webservers mangling the HTTP header
+    * ADDED: Sanitize SVG preview, preventing script execution in instance context
     * CHANGED: Language selection cookie only transmitted over HTTPS (#472)
     * CHANGED: Upgrading libraries to: base-x 4.0.0, bootstrap 3.4.1 (JS), DOMpurify 2.3.6, ip-lib 1.18.0, jQuery 3.6.0, random_compat 2.0.21 & Showdown 2.0.0
     * CHANGED: Removed automatic `.ini` configuration file migration (#808)
     * CHANGED: Removed configurable `dir` for `traffic` & `purge` limiters (#419)
     * CHANGED: Server salt, traffic and purge limiter now stored in the storage backend (#419)
+    * CHANGED: Drop support for attachment download in IE
   * **1.3.5 (2021-04-05)**
     * ADDED: Translations for Hebrew, Lithuanian, Indonesian and Catalan
     * ADDED: Make the project info configurable (#681)

js/privatebin.js

@@ -52,6 +52,31 @@ jQuery.PrivateBin = (function($, RawDeflate) {
      */
     let z;
 
+    /**
+     * DOMpurify settings for HTML content
+     *
+     * @private
+     */
+     const purifyHtmlConfig = {
+        ALLOWED_URI_REGEXP: /^(?:(?:(?:f|ht)tps?|mailto|magnet):)/i,
+        SAFE_FOR_JQUERY: true,
+        USE_PROFILES: {
+            html: true
+        }
+    };
+
+    /**
+     * DOMpurify settings for SVG content
+     *
+     * @private
+     */
+     const purifySvgConfig = {
+        USE_PROFILES: {
+            svg: true,
+            svgFilters: true
+        }
+    };
+
     /**
      * CryptoData class
      *
@@ -409,7 +434,8 @@ jQuery.PrivateBin = (function($, RawDeflate) {
                     element.html().replace(
                         /(((https?|ftp):\/\/[\w?!=&.\/-;#@~%+*-]+(?![\w\s?!&.\/;#~%"=-]>))|((magnet):[\w?=&.\/-;#@~%+*-]+))/ig,
                         '<a href="$1" rel="nofollow noopener noreferrer">$1</a>'
-                    )
+                    ),
+                    purifyHtmlConfig
                 )
             );
         };
@@ -2536,7 +2562,8 @@ jQuery.PrivateBin = (function($, RawDeflate) {
                 // let showdown convert the HTML and sanitize HTML *afterwards*!
                 $plainText.html(
                     DOMPurify.sanitize(
-                        converter.makeHtml(text)
+                        converter.makeHtml(text),
+                        purifyHtmlConfig
                     )
                 );
                 // add table classes from bootstrap css
@@ -2751,6 +2778,34 @@ jQuery.PrivateBin = (function($, RawDeflate) {
             attachmentHasPreview = false,
             $dropzone;
 
+        /**
+         * get blob URL from string data and mime type
+         *
+         * @name   AttachmentViewer.getBlobUrl
+         * @private
+         * @function
+         * @param {string} data - raw data of attachment
+         * @param {string} data - mime type of attachment
+         * @return {string} objectURL
+         */
+         function getBlobUrl(data, mimeType)
+         {
+            // Transform into a Blob
+            const buf = new Uint8Array(data.length);
+            for (let i = 0; i < data.length; ++i) {
+                buf[i] = data.charCodeAt(i);
+            }
+            const blob = new window.Blob(
+                [buf],
+                {
+                    type: mimeType
+                }
+            );
+
+            // Get Blob URL
+            return window.URL.createObjectURL(blob);
+         }
+
          /**
          * sets the attachment but does not yet show it
          *
@@ -2761,44 +2816,39 @@ jQuery.PrivateBin = (function($, RawDeflate) {
          */
         me.setAttachment = function(attachmentData, fileName)
         {
-            // data URI format: data:[<mediaType>][;base64],<data>
+            // data URI format: data:[<mimeType>][;base64],<data>
 
             // position in data URI string of where data begins
             const base64Start = attachmentData.indexOf(',') + 1;
-            // position in data URI string of where mediaType ends
+            // position in data URI string of where mimeType ends
-            const mediaTypeEnd = attachmentData.indexOf(';');
+            const mimeTypeEnd = attachmentData.indexOf(';');
 
-            // extract mediaType
+            // extract mimeType
-            const mediaType = attachmentData.substring(5, mediaTypeEnd);
+            const mimeType = attachmentData.substring(5, mimeTypeEnd);
             // extract data and convert to binary
             const rawData = attachmentData.substring(base64Start);
             const decodedData = rawData.length > 0 ? atob(rawData) : '';
 
-            // Transform into a Blob
+            let blobUrl = getBlobUrl(decodedData, mimeType);
-            const buf = new Uint8Array(decodedData.length);
-            for (let i = 0; i < decodedData.length; ++i) {
-                buf[i] = decodedData.charCodeAt(i);
-            }
-            const blob = new window.Blob([ buf ], { type: mediaType });
-
-            // Get Blob URL
-            const blobUrl = window.URL.createObjectURL(blob);
-
-            // IE does not support setting a data URI on an a element
-            // Using msSaveBlob to download
-            if (window.Blob && navigator.msSaveBlob) {
-                $attachmentLink.off('click').on('click', function () {
-                    navigator.msSaveBlob(blob, fileName);
-                });
-            } else {
             $attachmentLink.attr('href', blobUrl);
-            }
 
             if (typeof fileName !== 'undefined') {
                 $attachmentLink.attr('download', fileName);
             }
 
-            me.handleBlobAttachmentPreview($attachmentPreview, blobUrl, mediaType);
+            // sanitize SVG preview
+            // prevents executing embedded scripts when CSP is not set and user
+            // right-clicks/long-taps and opens the SVG in a new tab - prevented
+            // in the preview by use of an img tag, which disables scripts, too
+            if (mimeType.match(/image\/svg/i)) {
+                const sanitizedData = DOMPurify.sanitize(
+                    decodedData,
+                    purifySvgConfig
+                );
+                blobUrl = getBlobUrl(sanitizedData, mimeType);
+            }
+
+            me.handleBlobAttachmentPreview($attachmentPreview, blobUrl, mimeType);
         };
 
         /**
@@ -3665,7 +3715,14 @@ jQuery.PrivateBin = (function($, RawDeflate) {
             for (let i = 0; i < $head.length; ++i) {
                 newDoc.write($head[i].outerHTML);
             }
-            newDoc.write('</head><body><pre>' + DOMPurify.sanitize(Helper.htmlEntities(paste)) + '</pre></body></html>');
+            newDoc.write(
+                '</head><body><pre>' +
+                DOMPurify.sanitize(
+                    Helper.htmlEntities(paste),
+                    purifyHtmlConfig
+                ) +
+                '</pre></body></html>'
+            );
             newDoc.close();
         }
 
@@ -5394,11 +5451,6 @@ jQuery.PrivateBin = (function($, RawDeflate) {
             // first load translations
             I18n.loadTranslations();
 
-            DOMPurify.setConfig({
-                ALLOWED_URI_REGEXP: /^(?:(?:(?:f|ht)tps?|mailto|magnet):)/i,
-                SAFE_FOR_JQUERY: true
-            });
-
             // Add a hook to make all links open a new window
             DOMPurify.addHook('afterSanitizeAttributes', function(node) {
                 // set all elements owning target to target=_blank

tpl/bootstrap.php

@@ -73,7 +73,7 @@ endif;
 ?>
 		<script type="text/javascript" data-cfasync="false" src="js/purify-2.3.6.js" integrity="sha512-N1GGPjbqLbwK821ZN7C925WuTwU4aDxz2CEEOXQ6/s6m6MBwVj8fh5fugiE2hzsm0xud3q7jpjZQ4ILnpMREYQ==" crossorigin="anonymous"></script>
 		<script type="text/javascript" data-cfasync="false" src="js/legacy.js?<?php echo rawurlencode($VERSION); ?>" integrity="sha512-LYos+qXHIRqFf5ZPNphvtTB0cgzHUizu2wwcOwcwz/VIpRv9lpcBgPYz4uq6jx0INwCAj6Fbnl5HoKiLufS2jg==" crossorigin="anonymous"></script>
-		<script type="text/javascript" data-cfasync="false" src="js/privatebin.js?<?php echo rawurlencode($VERSION); ?>" integrity="sha512-EdUms2nI12Cmtv014stIEBlyPjeKMHlkg7NiBJup1b7jJF5amKhev2RwTaldINXK4UaWbZtQ6hGuMPNvvNQZFA==" crossorigin="anonymous"></script>
+		<script type="text/javascript" data-cfasync="false" src="js/privatebin.js?<?php echo rawurlencode($VERSION); ?>" integrity="sha512-5fNML95dptjIMzFG4KAGE2nNbORbyrCWq4ql9tkvoUF2HSnemlxzngQ5PlWhpi0J2ttKIEqfGMBjU5MywzzdWQ==" crossorigin="anonymous"></script>
 		<!-- icon -->
 		<link rel="apple-touch-icon" href="<?php echo I18n::encode($BASEPATH); ?>img/apple-touch-icon.png" sizes="180x180" />
 		<link rel="icon" type="image/png" href="img/favicon-32x32.png" sizes="32x32" />

tpl/page.php

@@ -51,7 +51,7 @@ endif;
 ?>
 		<script type="text/javascript" data-cfasync="false" src="js/purify-2.3.6.js" integrity="sha512-N1GGPjbqLbwK821ZN7C925WuTwU4aDxz2CEEOXQ6/s6m6MBwVj8fh5fugiE2hzsm0xud3q7jpjZQ4ILnpMREYQ==" crossorigin="anonymous"></script>
 		<script type="text/javascript" data-cfasync="false" src="js/legacy.js?<?php echo rawurlencode($VERSION); ?>" integrity="sha512-LYos+qXHIRqFf5ZPNphvtTB0cgzHUizu2wwcOwcwz/VIpRv9lpcBgPYz4uq6jx0INwCAj6Fbnl5HoKiLufS2jg==" crossorigin="anonymous"></script>
-		<script type="text/javascript" data-cfasync="false" src="js/privatebin.js?<?php echo rawurlencode($VERSION); ?>" integrity="sha512-EdUms2nI12Cmtv014stIEBlyPjeKMHlkg7NiBJup1b7jJF5amKhev2RwTaldINXK4UaWbZtQ6hGuMPNvvNQZFA==" crossorigin="anonymous"></script>
+		<script type="text/javascript" data-cfasync="false" src="js/privatebin.js?<?php echo rawurlencode($VERSION); ?>" integrity="sha512-5fNML95dptjIMzFG4KAGE2nNbORbyrCWq4ql9tkvoUF2HSnemlxzngQ5PlWhpi0J2ttKIEqfGMBjU5MywzzdWQ==" crossorigin="anonymous"></script>
 		<!-- icon -->
 		<link rel="apple-touch-icon" href="img/apple-touch-icon.png?<?php echo rawurlencode($VERSION); ?>" sizes="180x180" />
 		<link rel="icon" type="image/png" href="img/favicon-32x32.png?<?php echo rawurlencode($VERSION); ?>" sizes="32x32" />