block drag and drop data from Brave inside webviews

app/extensions/brave/content/scripts/inputHandler.js

@@ -151,3 +151,34 @@ document.addEventListener('keydown', (e /*: Event*/) => {
       break
   }
 })
+
+function hasBraveDragData (dataTransfer) {
+  if (!dataTransfer || !dataTransfer.types) {
+    return false
+  }
+  for (let i = 0; i < dataTransfer.types.length; i++) {
+    let type = dataTransfer.types[i]
+    if (type && type.startsWith('application/x-brave-')) {
+      return true
+    }
+  }
+  return false
+}
+
+function blockDndData (e) {
+  if (hasBraveDragData(e.dataTransfer)) {
+    // Block drag data from the Brave UI
+    try {
+      e.dataTransfer.dropEffect = 'none'
+    } catch (e) {}
+    e.preventDefault()
+    e.stopPropagation()
+    return false
+  }
+  return true
+}
+
+window.addEventListener('dragover', blockDndData, true)
+window.addEventListener('dragenter', blockDndData, true)
+window.addEventListener('dragleave', blockDndData, true)
+window.addEventListener('drop', blockDndData, true)

app/renderer/components/main/main.js

@@ -68,6 +68,7 @@ const {isSourceAboutUrl} = require('../../../../js/lib/appUrlUtil')
 const {getCurrentWindowId, isMaximized, isFocused, isFullScreen} = require('../../currentWindow')
 const platformUtil = require('../../../common/lib/platformUtil')
 const urlUtil = require('../../../../js/lib/urlutil')
+const {hasBraveDragData} = require('../../../../js/dndData')
 const isDarwin = platformUtil.isDarwin()
 const isWindows = platformUtil.isWindows()
 const isLinux = platformUtil.isLinux()
@@ -445,8 +446,10 @@ class Main extends React.Component {
 
     // disable dnd by default
     window.addEventListener('dragover', function (event) {
-      // allow webviews to handle dnd
-      if (event.target.tagName === 'WEBVIEW') {
+      // allow webviews to handle dnd as long as the dragged object isn't from
+      // Brave itself
+      if (event.target.tagName === 'WEBVIEW' &&
+        !hasBraveDragData(event.dataTransfer)) {
         return true
       }
       event.dataTransfer.dropEffect = 'none'
@@ -455,8 +458,10 @@ class Main extends React.Component {
     }, true)
 
     window.addEventListener('drop', function (event) {
-      // allow webviews to handle dnd
-      if (event.target.tagName === 'WEBVIEW') {
+      // allow webviews to handle dnd as long as the dragged object isn't from
+      // Brave itself
+      if (event.target.tagName === 'WEBVIEW' &&
+        !hasBraveDragData(event.dataTransfer)) {
         return true
       }
       event.preventDefault()

js/dndData.js

@@ -4,18 +4,33 @@
 
 const Immutable = require('immutable')
 
+const braveDragTypePrefix = 'application/x-brave-'
+
 module.exports.hasDragData = (dataTransfer, dragType) => {
-  return dataTransfer.types.includes(`application/x-brave-${dragType}`)
+  return dataTransfer.types.includes(`${braveDragTypePrefix}${dragType}`)
 }
 
 module.exports.getDragData = (dataTransfer, dragType) => {
-  const data = dataTransfer.getData(`application/x-brave-${dragType}`)
+  const data = dataTransfer.getData(`${braveDragTypePrefix}${dragType}`)
   if (!data) {
     return undefined
   }
   return Immutable.fromJS(JSON.parse(data))
 }
 
+module.exports.hasBraveDragData = (dataTransfer) => {
+  if (!dataTransfer || !dataTransfer.types) {
+    return false
+  }
+  for (let i = 0; i < dataTransfer.types.length; i++) {
+    let type = dataTransfer.types[i]
+    if (type && type.startsWith(braveDragTypePrefix)) {
+      return true
+    }
+  }
+  return false
+}
+
 module.exports.setupDataTransferURL = (dataTransfer, location, title) => {
   dataTransfer.setData('text/plain', location)
   dataTransfer.setData('text/uri-list', location)

test/unit/dndDataTest.js

@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* global describe, it */
+
+const dndData = require('../../js/dndData')
+const assert = require('assert')
+
+describe('dndData', function () {
+  describe('hasBraveDragData', function () {
+    it('returns false for empty transfer', () => {
+      assert.equal(dndData.hasBraveDragData(), false)
+      assert.equal(dndData.hasBraveDragData({types: []}), false)
+      assert.equal(dndData.hasBraveDragData({}), false)
+    })
+    it('returns false for regular transfer', () => {
+      assert.equal(dndData.hasBraveDragData({types: ['text/plain']}), false)
+      assert.equal(dndData.hasBraveDragData({types: ['text/plain', 'text/html']}), false)
+    })
+    it('returns true for brave transfer', () => {
+      assert.equal(dndData.hasBraveDragData({types: ['application/x-brave-tab']}), true)
+      assert.equal(dndData.hasBraveDragData({types: ['text/plain', 'text/uri-list', 'application/x-brave-bookmark']}), true)
+    })
+  })
+})