From 2484c5b158aa03eb5d7a106126f74146697f57bd Mon Sep 17 00:00:00 2001
From: cjihrig <cjihrig@gmail.com>
Date: Mon, 28 May 2018 17:03:12 -0400
Subject: [PATCH] events: prevent undefined as an event name

This commit prevents undefined as an event name in
addListener(), removeListener(), and emit().
---
 lib/events.js                                      | 14 ++++++++++++++
 test/parallel/test-event-emitter-add-listeners.js  | 11 +++++++++++
 test/parallel/test-event-emitter-errors.js         | 10 ++++++++++
 .../test-event-emitter-remove-listeners.js         | 11 +++++++++++
 4 files changed, 46 insertions(+)

diff --git a/lib/events.js b/lib/events.js
index ff1648d6aa13e7..1a0f7f078992cc 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -138,6 +138,8 @@ function enhanceStackTrace(err, own) {
 }
 
 EventEmitter.prototype.emit = function emit(type, ...args) {
+  validateEventName(type, 'eventName');
+
   let doError = (type === 'error');
 
   const events = this._events;
@@ -200,6 +202,7 @@ function _addListener(target, type, listener, prepend) {
     throw new errors.ERR_INVALID_ARG_TYPE('listener', 'Function', listener);
   }
 
+  validateEventName(type, 'eventName');
   events = target._events;
   if (events === undefined) {
     events = target._events = Object.create(null);
@@ -311,6 +314,7 @@ EventEmitter.prototype.removeListener =
         throw new errors.ERR_INVALID_ARG_TYPE('listener', 'Function', listener);
       }
 
+      validateEventName(type, 'eventName');
       events = this._events;
       if (events === undefined)
         return this;
@@ -480,3 +484,13 @@ function unwrapListeners(arr) {
   }
   return ret;
 }
+
+function validateEventName(name, paramName) {
+  if (name === undefined) {
+    const { ERR_INVALID_ARG_TYPE } = lazyErrors();
+    const err = new ERR_INVALID_ARG_TYPE(paramName, ['string', 'symbol'], name);
+
+    Error.captureStackTrace(err, validateEventName);
+    throw err;
+  }
+}
diff --git a/test/parallel/test-event-emitter-add-listeners.js b/test/parallel/test-event-emitter-add-listeners.js
index 45bfd3832caaaf..0c7740b358f48d 100644
--- a/test/parallel/test-event-emitter-add-listeners.js
+++ b/test/parallel/test-event-emitter-add-listeners.js
@@ -95,3 +95,14 @@ common.expectsError(() => {
   message: 'The "listener" argument must be of type Function. ' +
            'Received type object'
 });
+
+// Verify that the event type cannot be undefined.
+common.expectsError(() => {
+  const ee = new EventEmitter();
+  ee.on(undefined, () => {});
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "eventName" argument must be one of type string or symbol. ' +
+           'Received type undefined'
+});
diff --git a/test/parallel/test-event-emitter-errors.js b/test/parallel/test-event-emitter-errors.js
index ef2bbee93f8bfd..cd6e3dc3e30ba3 100644
--- a/test/parallel/test-event-emitter-errors.js
+++ b/test/parallel/test-event-emitter-errors.js
@@ -21,3 +21,13 @@ common.expectsError(
     message: 'Unhandled error. ([object Object])'
   }
 );
+
+// Verify that the event type cannot be undefined.
+common.expectsError(() => {
+  EE.emit(undefined, new Error());
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "eventName" argument must be one of type string or symbol. ' +
+           'Received type undefined'
+});
diff --git a/test/parallel/test-event-emitter-remove-listeners.js b/test/parallel/test-event-emitter-remove-listeners.js
index 925f828f93da36..4af966f35ebf12 100644
--- a/test/parallel/test-event-emitter-remove-listeners.js
+++ b/test/parallel/test-event-emitter-remove-listeners.js
@@ -154,6 +154,17 @@ common.expectsError(() => {
            'Received type object'
 });
 
+// Verify that the event type cannot be undefined.
+common.expectsError(() => {
+  const ee = new EventEmitter();
+  ee.removeListener(undefined, () => {});
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "eventName" argument must be one of type string or symbol. ' +
+           'Received type undefined'
+});
+
 {
   const ee = new EventEmitter();
   const listener = () => {};