fix for possible xss exploits

src/lib/utils.js

@@ -66,7 +66,7 @@ export function arrayEqual(a, b) {
 // as close to E.164 as possible.
 export function asPhone(val) {
   val = val.trim();
-  if (/^\s*(?:\+?(\d{1,3}))?[- (.]*(\d{3})[- ).]*(\d{3})[- .]*(\d{2})[- .]*(\d{2})?\s*$/.test(val)) {
+  if (/^(?:\+?(\d{1,3}))?[- (.]*(\d{3})[- ).]*(\d{3})[- .]*(\d{2})[- .]*(\d{2})?$/.test(val)) {
     return val.replace(/[- ().]*/, '');
   }
   return null;
@@ -80,3 +80,38 @@ export function asEmail(val) {
   }
   return null;
 }
+
+// Checks if URL is a relative url, i.e. has no 'scheme://', including the case of missing scheme '//'.
+// The scheme is expected to be RFC-compliant, e.g. [a-z][a-z0-9+.-]*
+// example.html - ok
+// https:example.com - not ok.
+// http:/example.com - not ok.
+// ' ↲ https://example.com' - not ok. (↲ means carriage return)
+export function isUrlRelative(url) {
+  return !/^\s*([a-z][a-z0-9+.-]*:|\/\/)/im.test(url);
+}
+
+// Ensure URL is valid and does not present an XSS risk. Optional allowedSchemes may contain an array of
+// strings with permitted URL schemes, such as ['ftp', 'ftps']; otherwise accept http and https only.
+export function sanitizeUrl(url, allowedSchemes) {
+  if (!url) {
+    return null;
+  }
+
+  // Strip control characters and whitespace. They are not valid URL characters anyway.
+  url = url.replace(/[^\x20-\x7E]/gmi, '').trim();
+
+  // Relative URLs are safe.
+  if (!/^([a-z][a-z0-9+.-]*:|\/\/)/i.test(url)) {
+    return url;
+  }
+
+  // Absolute URL. Accept only safe schemes, or no scheme.
+  const schemes = Array.isArray(allowedSchemes) ? allowedSchemes.join('|') : 'http|https';
+  const re = new RegExp('^((' + schemes + '):|//)', 'i');
+  if (!re.test(url)) {
+    return null;
+  }
+
+  return url;
+}

src/widgets/attachment.jsx

@@ -3,6 +3,7 @@ import { FormattedMessage } from 'react-intl';
 
 import FileProgress from './file-progress.jsx';
 import { bytesToHumanSize } from '../lib/strformat.js';
+import { isUrlRelative, sanitizeUrl } from '../lib/utils.js';
 
 export default class Attachment extends React.Component {
   constructor(props) {
@@ -53,8 +54,7 @@ export default class Attachment extends React.Component {
     // If the URL is relative use LargeFileHelper to attach authentication
     // credentials to the request.
     let url, helperFunc;
-    if (!this.props.uploader && !this.state.downloader &&
-        !(/^(?:(?:[a-z]+:)?\/\/)/i.test(this.props.downloadUrl))) {
+    if (!this.props.uploader && !this.state.downloader && isUrlRelative(this.props.downloadUrl)) {
       // Relative URL. Use download helper.
       url = '#';
       helperFunc = (e) => {
@@ -62,7 +62,7 @@ export default class Attachment extends React.Component {
         this.downloadFile(this.props.downloadUrl, this.props.filename, this.props.mimetype);
       };
     } else {
-      url = this.props.downloadUrl;
+      url = sanitizeUrl(this.props.downloadUrl) || 'about:blank';
       helperFunc = null;
     }
     return (

src/widgets/chat-message.jsx

@@ -6,6 +6,7 @@ import { Drafty } from 'tinode-sdk'
 import Attachment from './attachment.jsx';
 import LetterTile from './letter-tile.jsx';
 import ReceivedMarker from './received-marker.jsx'
+import { sanitizeUrl } from '../lib/utils.js';
 
 export default class ChatMessage extends React.Component {
   constructor(props) {
@@ -48,7 +49,7 @@ export default class ChatMessage extends React.Component {
         e.target.dataset.val === undefined ? 1 : '' + e.target.dataset.val;
     }
     if (e.target.dataset.act == 'url') {
-      data.ref = '' + e.target.dataset.ref;
+      data.ref = sanitizeUrl(e.target.dataset.ref) || 'about:blank';
     }
     const text = e.target.dataset.title || 'unknown';
     this.props.onFormResponse(e.target.dataset.act, text, data);
@@ -163,6 +164,7 @@ function draftyFormatter(style, data, values, key) {
             Math.min(this.props.viewportWidth - REM_SIZE * 4, REM_SIZE * 36), REM_SIZE * 24, false);
           dim = dim || {dstWidth: BROKEN_IMAGE_SIZE, dstHeight: BROKEN_IMAGE_SIZE};
           attr.style = { width: dim.dstWidth + 'px', height: dim.dstHeight + 'px' };
+          attr.src = sanitizeUrl(attr.src);
           if (attr.src) {
             attr.onClick = this.handlePreviewImage;
             attr.className += ' image-clickable';