MM-14446: consider subpath when evaluating if url is internal (#946)

* MM-14446: consider subpath when evaluating if url is internal

When clicking on an URL with `target=_blank`, the webview decides if it should launch an external browser or a new window within the Electron application. Update this logic to consider the application's configured subpath so as to treat links outside the subpath but on the same domain as external.

* fix licensing on new file

* fix .eslintrc.json indentation

* tweak header eslint rules for specific files

src/browser/components/MattermostView.jsx

@@ -12,6 +12,7 @@ import PropTypes from 'prop-types';
 import {ipcRenderer, remote, shell} from 'electron';
 
 import contextMenu from '../js/contextMenu';
+import Utils from '../../utils/util';
 import {protocols} from '../../../electron-builder.json';
 const scheme = protocols[0].schemes[0];
 
@@ -31,6 +32,7 @@ export default class MattermostView extends React.Component {
       isContextMenuAdded: false,
       reloadTimeoutID: null,
       isLoaded: false,
+      basename: '/',
     };
 
     this.handleUnreadCountChange = this.handleUnreadCountChange.bind(this);
@@ -94,7 +96,7 @@ export default class MattermostView extends React.Component {
         return;
       }
 
-      if (currentURL.host === destURL.host) {
+      if (Utils.isInternalURL(destURL, currentURL, this.state.basename)) {
         if (destURL.path.match(/^\/api\/v[3-4]\/public\/files\//)) {
           ipcRenderer.send('download-url', e.url);
         } else {
@@ -137,6 +139,7 @@ export default class MattermostView extends React.Component {
       case 'onGuestInitialized':
         self.setState({
           isLoaded: true,
+          basename: event.args[0] || '/',
         });
         break;
       case 'onBadgeChange': {

src/browser/webview/mattermost.js

@@ -46,7 +46,7 @@ window.addEventListener('load', () => {
     return;
   }
   watchReactAppUntilInitialized(() => {
-    ipcRenderer.sendToHost('onGuestInitialized');
+    ipcRenderer.sendToHost('onGuestInitialized', window.basename);
   });
 });
 

src/utils/util.js

@@ -8,4 +8,22 @@ function getDomain(inputURL) {
   return `${parsedURL.protocol}//${parsedURL.host}`;
 }
 
-export default {getDomain};
+// isInternalURL determines if the target url is internal to the application.
+// - currentURL is the current url inside the webview
+// - basename is the global export from the Mattermost application defining the subpath, if any
+function isInternalURL(targetURL, currentURL, basename = '/') {
+  if (targetURL.host !== currentURL.host) {
+    return false;
+  }
+
+  if (!(targetURL.pathname || '/').startsWith(basename)) {
+    return false;
+  }
+
+  return true;
+}
+
+export default {
+  getDomain,
+  isInternalURL,
+};