lib,build: use Web Crypto API in browser

PR-URL: #360
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>

lib/common-crypto-fallback.js

@@ -0,0 +1,30 @@
+'use strict';
+
+/* eslint-env browser */
+
+// Browser adapter for required functions from Node.js crypto module.
+const crypto = {};
+
+crypto.randomBytes = (count) => {
+  const buf = Buffer.alloc(count);
+  crypto.randomFillSync(buf);
+  return buf;
+};
+
+if (window.crypto && window.crypto.getRandomValues) {
+  crypto.randomFillSync = (buf) => {
+    window.crypto.getRandomValues(buf);
+  };
+} else {
+  console.warn(
+    'Web Crypto API is not supported in your browser!',
+    'Using Math.random() instead.'
+  );
+  crypto.randomFillSync = (buf) => {
+    for (let i = 0; i < buf.length; i++) {
+      buf[i] = Math.floor(0x100 * Math.random());
+    }
+  };
+}
+
+module.exports = crypto;

lib/common.js

@@ -1,6 +1,12 @@
 'use strict';
 
-const crypto = require('crypto');
+let crypto;
+
+if (typeof window !== 'undefined') {
+  crypto = require('./common-crypto-fallback');
+} else {
+  crypto = require('crypto');
+}
 
 // Forward an event from one EventEmitter to another.
 //   from - EventEmitter to listen for event

webpack.config.js

@@ -34,7 +34,6 @@ module.exports = {
   node: {
     net: false,
     tls: false,
-    // TODO: support WebCrypto API in lib/common.js and uncomment this
-    // crypto: 'empty',
+    crypto: 'empty',
   },
 };