Tag: javascript

RetireJS javascript libary vulnerability scanning with Maven

It’s important to note that even though your site is using a vulnerable library, that does not necessarily mean your site is vulnerable. It depends on whether and how your site exercises
the vulnerable code. That said, it’s better to be safe than sorry.

I identified this method of using the asset after reading the instructions for the Burp/Gulp scanner from h3xstream after the following section caught my eye:
https://github.com/h3xstream/burp-retire-js#maven-plugin-, it contained a small reference to Maven and even showed output but no configuration for use. A couple of attempts later I came up with the following:

Add to pom.xml:

<build>
<plugins>
<plugin>
<groupId>com.h3xstream.retirejs</groupId>
<artifactId>retirejs-maven-plugin</artifactId>
<version>2.1.0</version>
<executions>
<execution>
<id>scanProjectJavascript</id>
<phase>install</phase>
<goals>
<goal>scan</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

After adding this to your pom.xml, the console output for each build will contain information regarding each vulnerable JavaScript library.

One small problem exists in the current version, use behind corporate firewalls can often be blocked, resulting in an error in the console and use of an older version of the vulnerability library to be used in scans.

Error example:

[ERROR] Exception while loading the repository (Most likely unable to access the internet) java.net.UnknownHostException: raw.githubusercontent.com

See the following for updates:
https://github.com/h3xstream/burp-retire-js/issues/8

See https://www.owasp.org/index.php/Top_10_2013-A9-Using_Components_with_Known_Vulnerabilities.

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HTML4 script defer

This HTML4 attribute was intended to defer/delay execution of specific javascript code until after the page is rendered. In theory, this makes the website “appear” faster as the functions relevant to the User-Interface can be executed before other “background” processes that would otherwise block the screen from displaying.


<script defer="defer" src="example.js"></script>

NOTE: Do not use defer for external scripts that might depend on each other if you need to support MSIE9 and earlier.

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HTML5 script async

The HTML5 “async” attribute simplifies page-load performance improvements and dynamic script loading, it can be useful in modern web browsers.

Simply put, this tag allows for the browser to asynchronously load and execute external javascript files in a parallel vs. serial manner. Unfortunately while most modern browser support it, MSIE versions prior to MSIE10+ are problematic.


<script src="example.js" async="async"></script>

This is particularly useful when using third-party javascript libraries and utilities that have no dependeny relationships with your existing website javascript.

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Javascript “this” keyword

The “this” keyword is an indispensable, yet often mis-understood, concept in JavaScript object-oriented programming. When used in a JavaScript constructor function, “this” refers to the specific instance of the Object. Through the “this” keyword, properties and methods can be assigned object, also known as a class.

For example:

function Square(intSideLength)
{
this.sideLength = intSideLength;
}

In the preceding example the “this” keyword is used to assign the variable “sideLength” as a property of the Square class.
The “this” keyword is also frequently passed as a parameter on JavaScript events, such as when a checkbox is clicked. In such an instance, “this” refers to the current object, the checkbox.

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Eclipse FileSync plugin

I’ve done a lot of front-end java coding over my career,  one particularly annoying aspect is the wait for a build (compile-deploy) cycle in my local developement servers to view or test a small change.  One particularly useful tool that I’ve been using for some time is a FileSync plugin for Eclipse.  It is useful as you can “map” folders from your Eclipse project to a path on your local filesystem, as such the individual files are automatically copied to your server installation.  I’ve personally used this approache with JBoss, Tomcat and WebSphere, but there is no reason that it should not work for other servers.

Comcast Business Class gateway forwarding port 22 for SSH

For as long as I’ve had Comcast, and other providers for that matter, I’ve been able to configure my internet gateway/router to allow port 22 (SSH) access to an internal machine. It came as a surprise to me earlier this week that I was blocked when I tried to use their web admin console to change the internal forwarding to a newer machine. As usual, Technical Support was less that helpful and said that it was not possible to do so, and never should have been as Comcast uses that port to administer the gateway. To make matters more disturbing, I was told that I could not have similar SSH access to the gateway, and that replacing their hardware, while permitted, would prevent my use of a static IP.

Back to the solution, as I know that I had only setup this forwarding about a year ago, and it was working only minutes before I tried to change it, I knew that the configuration was possible if I could figure out how it was being blocked. The message in the web console was a javascript alert(); and gave me a starting point. I opened up Firefox and used Firebug to look for the message. Here are a few interesting findings from:

http://HOSTNAME/user/feat-firewall-port-forward-edit.asp

var RemoteManagementPortsCgiBase = “8080,8080,1\|8181,8181,1\|2323,2323,1\|22,22,1\|”;
…
msg += “Public Port Range conflict with Remote Management Ports.\n”;
…
if (msg.length > 1)
{
alert(msg);
return false;
}
return true;
}

If you even a little bit of javascript (or simple computer programming for that matter), the solution is clear…. if the ‘msg’ value is empty you will not see the alert or be prevented from making the change you desire.

Lesson to be learned by the Comcast developers (or most likely = subcontractors), always validate submitted form data in your application code, NEVER rely upon javascript alone to verify user entered data!

I also find it interesting that they are also preventing 8080, 8081 and 2323… perhaps that’s their other back doors in these gateways for their access. The same approach should work for those ports if you need it!

Device Fingerprinting

Often it can be beneficial to ‘more’ uniquely identify your users. For applications this is trivial, but in a web browser this can be accomplished via only a few attributes.

  • HTTP – User-Agent, IP Address, Content types and languages accepted.
  • HTTPS/SSL – the keys and encryption methods available to a specific user may vary for each client configuration.
  • HTML5 – local storage and capabilities supported.
  • Geolocation – this is included in HTML5, but also supported in many clients without full HTML5 support, or via browser extensions.
  • JavaScript – Installed version – and many DOM attributes/capabilities such as timezone, installed plugins, screen sizes and fonts from the browser can be detected.
  • Java (Applet) – Installed version – this can often be used to get additional information regarding the client system directly from the VM or Operating System itself. (* Persistent Cookies possible)
  • Flash – Installed version – this can often be used to get additional information regarding the client system directly from the Operating System itself. (* Persistent Cookies possible)
  • Silverlight (for Microsoft Windows) – – Installed version and additional information from Operating System?
  • GoogleGEARS (deprecated) – Installed version and additional information from Operating System such as Geolocation

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JQuery equivalent to Element.identify(el)

Migrating between various javascript frameworks can often prove difficult, especially when developers become comfortable with the specific features of one library. Here is a feature that I’ve seen used in PrototypeJS that does not exist in jQuery, but can easily be added with a new function.

PrototypeJS provides an identify(el);function … Element.identify(el);. This is powerful in the sense that it returns the ‘id’ of an element, or automatically generates and assigns one when it is empty.

For jQuery the following can be added to emulate the functionality.

jQuery.fn.identify = function(prefix) {
var i = 0;
return this.each(function() {
if($(this).attr('id')) return;
do {
i++;
var id = prefix + '_' + i;
} while(document.getElementById(id) != null);
$(this).attr('id', id);
});
};

(function($) {// Compliant with jquery.noConflict()
$('span').identify('test');
})(jQuery);

Google Web Fonts

The use of non-traditional web fonts was once a very challenging task due to various browser specific implementations. Thankfully Google WebFonts have made this easy enough for most developers to add in a cross-browser manner in a matter of minutes.

WARNING, there are a few considerations to make here…

  1. Some browsers displays a blank space in place of the text that uses the font.
  2. … and then re-render text in the web font once it has loaded

Method 1: (most compatible, but cross-browser loading behavior varies)

<link href='http://fonts.googleapis.com/css?family=Ubuntu:400,700' rel='stylesheet' type='text/css' />
<style type="text/css">
h1,p { font-family: 'Ubuntu', sans-serif; }
</style>

Method 2: (requires javascript, but is consistent cross-browser)

<script type="text/javascript">
WebFontConfig = {
google: { families: [ 'Ubuntu Mono','Ubuntu' ] }
};
(function() {
var wf = document.createElement('script');
wf.src = ('https:' == document.location.protocol ? 'https' : 'http') + '://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js';
wf.type = 'text/javascript';
wf.async = 'true';
var s = document.getElementsByTagName('script')[0];
s.parentNode.insertBefore(wf, s);
})();
</script>
<style type="text/css">
h1 { font-family: 'Ubuntu Mono','Courier New',monospace; }
p { font-family: 'Ubuntu','sans-serif'; }
</style>

JavaScript “use strict”

ECMAScript 5 added Strict Mode to JavaScript. Many of you may have first seen mention of this if you’ve used JSLint. It helps to remember that JavaScript still behaves much like an interpreted vs. compiled language as each browser/parser makes assumptions to execute code faster in different manners.

There are four primary features/goals of strict mode:

  • Throws errors for some common coding issues, that are sometimes obscure but previously didn’t throw an error.
  • Prevents or throws errors for potentially “unsafe” actions (such as gaining access to the global object).
  • Disables functions that are confusing or poorly thought out
  • Potentially code in strict mode could run faster by eliminating mistakes that would make it difficult for JavaScript engines to perform optimizations

Initial support added in FireFox 4 and MSIE10:

WARNING: if you chose to do this at a ‘file’ level, be sure to never concatenate several files together that are not ALL strict.

JS File Example:
"use strict";
function testFunction(){
var testvar = 1;
return testvar;
}

// This causes a syntax error.
testvar = 2;

JS Function Example:
function testFunction(){
"use strict";
// This causes a syntax error.
testvar = 1;
return testvar;
}
testvar = 2;

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