net: add symbol to normalized connect() args

This commit attaches a Symbol to the result of
net._normalizeArgs(). This prevents normal arrays from being
passed to the internal Socket.prototype.connect() bypass logic.

PR-URL: nodejs#13069
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

lib/internal/net.js

@@ -10,5 +10,6 @@ function isLegalPort(port) {
 }
 
 module.exports = {
-  isLegalPort
+  isLegalPort,
+  normalizedArgsSymbol: Symbol('normalizedArgs')
 };

lib/net.js

@@ -49,6 +49,7 @@ var dns;
 const errnoException = util._errnoException;
 const exceptionWithHostPort = util._exceptionWithHostPort;
 const isLegalPort = internalNet.isLegalPort;
+const normalizedArgsSymbol = internalNet.normalizedArgsSymbol;
 
 function noop() {}
 
@@ -118,8 +119,12 @@ function connect() {
 // For Server.prototype.listen(), the [...] part is [, backlog]
 // but will not be handled here (handled in listen())
 function normalizeArgs(args) {
+  var arr;
+
   if (args.length === 0) {
-    return [{}, null];
+    arr = [{}, null];
+    arr[normalizedArgsSymbol] = true;
+    return arr;
   }
 
   const arg0 = args[0];
@@ -140,9 +145,12 @@ function normalizeArgs(args) {
 
   var cb = args[args.length - 1];
   if (typeof cb !== 'function')
-    return [options, null];
+    arr = [options, null];
   else
-    return [options, cb];
+    arr = [options, cb];
+
+  arr[normalizedArgsSymbol] = true;
+  return arr;
 }
 
 
@@ -947,7 +955,7 @@ Socket.prototype.connect = function() {
   // already been normalized (so we don't normalize more than once). This has
   // been solved before in https://github.com/nodejs/node/pull/12342, but was
   // reverted as it had unintended side effects.
-  if (arguments.length === 1 && Array.isArray(arguments[0])) {
+  if (Array.isArray(arguments[0]) && arguments[0][normalizedArgsSymbol]) {
     normalized = arguments[0];
   } else {
     var args = new Array(arguments.length);

test/parallel/test-net-normalize-args.js

@@ -0,0 +1,55 @@
+'use strict';
+// Flags: --expose-internals
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+const { normalizedArgsSymbol } = require('internal/net');
+
+function validateNormalizedArgs(input, output) {
+  const args = net._normalizeArgs(input);
+
+  assert.deepStrictEqual(args, output);
+  assert.strictEqual(args[normalizedArgsSymbol], true);
+}
+
+// Test creation of normalized arguments.
+validateNormalizedArgs([], [{}, null]);
+validateNormalizedArgs([{ port: 1234 }], [{ port: 1234 }, null]);
+validateNormalizedArgs([{ port: 1234 }, assert.fail],
+                       [{ port: 1234 }, assert.fail]);
+
+// Connecting to the server should fail with a standard array.
+{
+  const server = net.createServer(common.mustNotCall('should not connect'));
+
+  server.listen(common.mustCall(() => {
+    const possibleErrors = ['ECONNREFUSED', 'EADDRNOTAVAIL'];
+    const port = server.address().port;
+    const socket = new net.Socket();
+
+    socket.on('error', common.mustCall((err) => {
+      assert(possibleErrors.includes(err.code));
+      assert(possibleErrors.includes(err.errno));
+      assert.strictEqual(err.syscall, 'connect');
+      server.close();
+    }));
+
+    socket.connect([{ port }, assert.fail]);
+  }));
+}
+
+// Connecting to the server should succeed with a normalized array.
+{
+  const server = net.createServer(common.mustCall((connection) => {
+    connection.end();
+    server.close();
+  }));
+
+  server.listen(common.mustCall(() => {
+    const port = server.address().port;
+    const socket = new net.Socket();
+    const args = net._normalizeArgs([{ port }, common.mustCall()]);
+
+    socket.connect(args);
+  }));
+}