Use data:// URI rather than blob: URI to avoid XSS

src/components/views/messages/MAudioBody.js

@@ -49,12 +49,10 @@ export default class MAudioBody extends React.Component {
     componentDidMount() {
         var content = this.props.mxEvent.getContent();
         if (content.file !== undefined && this.state.decryptedUrl === null) {
-            decryptFile(content.file).then((blob) => {
+            decryptFile(content.file).then((url) => {
-                if (!this._unmounted) {
                 this.setState({
-                        decryptedUrl: window.URL.createObjectURL(blob),
+                    decryptedUrl: url
                 });
-                }
             }).catch((err) => {
                 console.warn("Unable to decrypt attachment: ", err)
                 // Set a placeholder image when we can't decrypt the image.
@@ -63,13 +61,6 @@ export default class MAudioBody extends React.Component {
         }
     }
 
-    componentWillUnmount() {
-        this._unmounted = true;
-        if (this.state.decryptedUrl) {
-            window.URL.revokeObjectURL(this.state.decryptedUrl);
-        }
-    }
-
     render() {
         var content = this.props.mxEvent.getContent();
 

src/components/views/messages/MFileBody.js

@@ -22,6 +22,7 @@ var MatrixClientPeg = require('../../../MatrixClientPeg');
 var sdk = require('../../../index');
 var DecryptFile = require('../../../utils/DecryptFile');
 
+
 module.exports = React.createClass({
     displayName: 'MFileBody',
 
@@ -66,12 +67,10 @@ module.exports = React.createClass({
         var content = this.props.mxEvent.getContent();
         var self = this;
         if (content.file !== undefined && this.state.decryptedUrl === null) {
-            DecryptFile.decryptFile(content.file).then(function(blob) {
+            DecryptFile.decryptFile(content.file).then(function(url) {
-                if (!self._unmounted) {
                 self.setState({
-                        decryptedUrl: window.URL.createObjectURL(blob),
+                    decryptedUrl: url,
                 });
-                }
             }).catch(function (err) {
                 console.warn("Unable to decrypt attachment: ", err)
                 // Set a placeholder image when we can't decrypt the image.
@@ -80,13 +79,6 @@ module.exports = React.createClass({
         }
     },
 
-    componentWillUnmount: function() {
-        this._unmounted = true;
-        if (this.state.decryptedUrl) {
-            window.URL.revokeObjectURL(this.state.decryptedUrl);
-        }
-    },
-
     render: function() {
         var content = this.props.mxEvent.getContent();
 

src/components/views/messages/MImageBody.js

@@ -109,12 +109,10 @@ module.exports = React.createClass({
         var content = this.props.mxEvent.getContent();
         var self = this;
         if (content.file !== undefined && this.state.decryptedUrl === null) {
-            DecryptFile.decryptFile(content.file).then(function(blob) {
+            DecryptFile.decryptFile(content.file).then(function(url) {
-                if (!self._unmounted) {
                 self.setState({
-                        decryptedUrl: window.URL.createObjectURL(blob),
+                    decryptedUrl: url,
                 });
-                }
             }).catch(function (err) {
                 console.warn("Unable to decrypt attachment: ", err)
                 // Set a placeholder image when we can't decrypt the image.
@@ -125,10 +123,6 @@ module.exports = React.createClass({
 
     componentWillUnmount: function() {
         dis.unregister(this.dispatcherRef);
-        this._unmounted = true;
-        if (this.state.decryptedUrl) {
-            window.URL.revokeObjectURL(this.state.decryptedUrl);
-        }
     },
 
     onAction: function(payload) {

src/components/views/messages/MVideoBody.js

@@ -88,21 +88,13 @@ module.exports = React.createClass({
                     content.info.thumbnail_file
                 );
             }
-            thumbnailPromise.then(function(thumbnailBlob) {
+            thumbnailPromise.then(function(thumbnailUrl) {
                 DecryptFile.decryptFile(
                     content.file
-                ).then(function(contentBlob) {
+                ).then(function(contentUrl) {
-                    if (self._unmounted) {
-                        return;
-                    }
-                    var contentUrl = window.URL.createObjectURL(contentBlob);
-                    var thumbUrl = null;
-                    if (thumbnailBlob) {
-                        thumbUrl = window.URL.createObjectURL(thumbnailBlob);
-                    }
                     self.setState({
                         decryptedUrl: contentUrl,
-                        decryptedThumbnailUrl: thumbUrl,
+                        decryptedThumbnailUrl: thumbnailUrl,
                     });
                 });
             }).catch(function (err) {
@@ -113,17 +105,6 @@ module.exports = React.createClass({
         }
     },
 
-    componentWillUnmount: function() {
-        this._unmounted = true;
-        if (this.state.decryptedUrl) {
-            window.URL.revokeObjectURL(this.state.decryptedUrl);
-        }
-        if (this.state.decryptedThumbnailUrl) {
-            window.URL.revokeObjectURL(this.state.decryptedThumbnailUrl);
-        }
-    },
-
-
     render: function() {
         var content = this.props.mxEvent.getContent();
 

src/utils/DecryptFile.js

@@ -22,6 +22,26 @@ var encrypt = require("browser-encrypt-attachment");
 require("isomorphic-fetch");
 // Grab the client so that we can turn mxc:// URLs into https:// URLS.
 var MatrixClientPeg = require('../MatrixClientPeg');
+var q = require('q');
+
+
+/**
+ * Read blob as a data:// URI.
+ * @return {Promise} A promise that resolves with the data:// URI.
+ */
+
+function readBlobAsDataUri(file) {
+    var deferred = q.defer();
+    var reader = new FileReader();
+    reader.onload = function(e) {
+        deferred.resolve(e.target.result);
+    };
+    reader.onerror = function(e) {
+        deferred.reject(e);
+    };
+    reader.readAsDataURL(file);
+    return deferred.promise;
+}
 
 
 export function decryptFile(file) {
@@ -37,6 +57,6 @@ export function decryptFile(file) {
     }).then(function(dataArray) {
         // Turn the array into a Blob and give it the correct MIME-type.
         var blob = new Blob([dataArray], {type: file.mimetype});
-        return blob;
+        return readBlobAsDataUri(blob);
     });
 }