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Interesting Browser Difference

Update 8/16/19 – It appears that not long after I published this, Chrome sent an update that now mimics FireFox. In Chrome you now get a new tab that has a URL of “about:blank#blocked”.

When working on a recent test I noticed something pretty interesting when I had found what I thought was a Cross-Site Scripting vulnerability. I have posted previously on the ability to execute XSS when you control the HREF attribute of a link tag. This is done by setting a url to javascript:alert(9);. This might look like:

<a href=”javascript:alert(9);”>Click Me</a>

This is similar to the situation I had. However, when I was testing with FireFox, I found that the alert box was not appearing. Instead, when I clicked the link, it would open a new tab and the URL would be javascript:alert(9);. No Alert box. What gives??

So I could see the payload there, but it wouldn’t execute. I was confused. I decided to load up Chrome and see what happens there. To my surprise, although it is what I originally expected, the alert box was displayed.

It turns out, the link tag wasn’t as simple as the above example. Instead it looked more like this:

<a href=”javascript:alert(9);” target=”_blank” rel=”noopener no referrer”>Click Me</a>

After performing a little more testing, it appears that when the target and red attributes exist, Firefox opens a new tab instead of executing the specified JavaScript. I m not sure if this is a bug in how FireFox handles this scenario or not, but it does highlight an interesting point about differences with browsers.

In the event your testing runs across this same type of scenario, take the time to try different browsers to see if the results change.

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Apple Mail: Highlighting External Email Addresses

A simple error to make when sending an email with sensitive data is to send it to the wrong email address. Imagine you are sending some information to Dave down in accounting. When you fill out the email you start typing Dave and the auto-complete pops up and you select the first one (out of habit). You think you have selected the right Dave, but what if you didn’t? How would you know that you were about to send potentially sensitive information outside of the organization?

Apple Mail and iOS mail has a built in feature to highlight any email address outside of a specified domain. The steps to enable this are a little different based on the desktop vs. an iPad/iPhone. Let’s look at each one.

Desktop

By default, email addresses all appear the same when composing a new message. The image below shows me composing an email with two addresses:

  • To: james@jardinesoftware.com
  • CC: james@developsec.com

Mail 1

To change this, in the Mail program, go to Preferences…Composing. Under the Addressing: section there is a checkbox for “Mark addresses not ending with“. Check the box and enter your organization’s domain name in the text box. In the image below, I have entered my domain of @jardinesoftware.com.

Mail 2

Now, go back and compose a new message entering in an email address that is in the org and one that is out of it. The email address that is outside of your domain should be highlighted in red. The below image shows my configuration with the same 2 email addresses. Notice that the james@developsec.com address is now listed in red indicating it is external to my organization.

Mail 3

iPhone/iPad

The mail application with the iPhone/iPad also has this capability. To enable this, go into Settings->Mail. Scroll down to the Composing section and click the “Mark Addresses” button (shown below).

Mail 4

On the next screen, enter the email address you don’t want to highlight. In my case, I entered my domain of @jardinesoftware.com. (shown below)

Mail 5

Once the change is stored, go to mail and compose a new message. In my example, I used the same emails as above. Notice that the james@developsec.com email address is now highlighted in red:

Mail 6

Although this is not a fool proof way to stop this type of mistake, it does add in a visual clue that just might catch your attention. Simple changes like this can help reduce your risk of accidentally leaking sensitive information out of your organization.

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Installing OWASP JuiceShop with Heroku

I am often asked the question by clients and students where people can go to learn hacking techniques for application security. For years, we have had many purposely vulnerable applications available to us. These applications provide a safe environment for us to learn more about hacking applications and the vulnerabilities that are exposed without the legal ramifications.

In this post I want to show you how simple it is to install the OWASP Juice Shop application using Heroku. Juice Shop is a purposely vulnerable application written using NodeJS and Angular. It goes beyond just being an application with some vulnerabilities. It is set up to be a capture the flag (CTF) style application with its own scoreboard.

To learn more about the Juice Shop project, head over to https://www.owasp.org/index.php/OWASP_Juice_Shop_Project. This is the main landing page and looks like the following:

Juice Shop

The first step in installing on Heroku is to make sure you are logged into your Heroku account. If you haven’t created one, do that first. Once you are logged in you should be in your dashboard that looks something like this:

HerokuInstall 1

Now that we are logged into Heroku, let’s head over to the Juice-shop GitHub page at https://github.com/bkimminich/juice-shop.

HerokuInstall 2

As you can see there is a button to “Deploy to Heroku”. Clicking this button will take you back to Heroku and ask for the app name as shown below:

HerokuInstall 3

Once you select a unique app name and the region clicking deploy starts the process. It doesn’t take very long (maybe 3-4 minutes) for the deploy to complete. While it is deploying you will see the build output as shown below:

HerokuInstall 4

Once the deployment is complete, you can click the button to View your new app. This will basically open a new tab at the location of your named instance which is the [name you picked].herokuapp.com as shown below:

HerokuInstall 5

The Juice Shop has a lot of vulnerabilities in it. It is a great way to learn more about how to exploit some of these vulnerabilities and test your skills. If you have little knowledge of application security vulnerabilities or the OWASP Top 10 check out our training courses we have available:

Please remember that hacking is illegal. If you want to learn more about application security and test your skills, do it responsibly and use great applications like the Juice Shop as your targets.

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Installing OWASP JuiceShop with Docker

I am often asked the question by clients and students where people can go to learn hacking techniques for application security. For years, we have had many purposely vulnerable applications available to us. These applications provide a safe environment for us to learn more about hacking applications and the vulnerabilities that are exposed without the legal ramifications.

In this post I want to show you how simple it is to install the OWASP Juice Shop application using a Docker container. Juice Shop is a purposely vulnerable application written using NodeJS and Angular. It goes beyond just being an application with some vulnerabilities. It is set up to be a capture the flag (CTF) style application with its own scoreboard.

To learn more about the Juice Shop project, head over to https://www.owasp.org/index.php/OWASP_Juice_Shop_Project. This is the main landing page and looks like the following:

Juice Shop

On the right hadn’t side there are links to Installation instructions. Clicking on the Docker Link takes us to the following page (https://hub.docker.com/r/bkimminich/juice-shop/) (Scroll down to the section on docker):

Juice Shop Docker

As you can see, there are only 4 steps to getting up and running with Docker. The first step is to install Docker. I won’t cover that here, but make sure you do have it installed before continuing on.

The next step is to pull the Juice-Shop docker container. This container is all set up and configured to run the Juice-Shop. No configurations necessary. To do this enter the command: docker pull bkimminich/juice-shop

Docker Install Step 2

The next step is to run the container. It is performed by simply running the following command: docker run –rm -p 3000:3000 bkimminich/juice-shop

Docker Install Step 3

As you can see, the juice shop is up and running, listening on port 3000. Port 3000 was specified when we called run passing in the -p option. ** If you get an error about the container not being able to start up, try restarting docker. I ran into this a few different times and a docker restart resolved the issue.

If everything is running as expected, we should be able to browse to http://localhost:3000 and access the Juice Shop as shown below:

JuiceShop Running

The Juice Shop has a lot of vulnerabilities in it. It is a great way to learn more about how to exploit some of these vulnerabilities and test your skills. If you have little knowledge of application security vulnerabilities or the OWASP Top 10 check out our training courses we have available:

Please remember that hacking is illegal. If you want to learn more about application security and test your skills, do it responsibly and use great applications like the Juice Shop as your targets.

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XSS in a Script Tag

Cross-site scripting is a pretty common vulnerability, even with many of the new advances in UI frameworks. One of the first things we mention when discussing the vulnerability is to understand the context. Is it HTML, Attribute, JavaScript, etc.? This understanding helps us better understand the types of characters that can be used to expose the vulnerability.

In this post, I want to take a quick look at placing data within a <script> tag. In particular, I want to look at how embedded <script> tags are processed. Let’s use a simple web page as our example.

<html>
	<head>
	</head>
	<body>
	<script>
		var x = "<a href=test.html>test</a>";
	</script>
	</body>
</html>

The above example works as we expect. When you load the page, nothing is displayed. The link tag embedded in the variable is rated as a string, not parsed as a link tag. What happens, though, when we embed a <script> tag? 

<html>
	<head>
	</head>
	<body>
	<script>
		var x = "<script>alert(9)</script>";
	</script>
	</body>
</html>

In the above snippet, actually nothing happens on the screen. Meaning that the alert box does not actually trigger. This often misleads people into thinking the code is not vulnerable to cross-site scripting. if the link tag is not processes, why would the script tag be. In many situations, the understanding is that we need to break out of the (“) delimiter to start writing our own JavaScript commands. For example, if I submitted a payload of (test”;alert(9);t = “). This type of payload would break out of the x variable and add new JavaScript commands. Of course, this doesn’t work if the (“) character is properly encoded to not allow breaking out.

Going back to our previous example, we may have overlooked something very simple. It wasn’t that the script wasn’t executing because it wasn’t being parsed. Instead, it wasn’t executing because our JavaScript was bad. Our issue was that we were attempting to open a <script> within a <script>. What if we modify our value to the following:

<html>
	<head>
	</head>
	<body>
	<script>
		var x = "</script><script>alert(9)</script>";
	</script>
	</body>
</html>

In the above code, we are first closing out the original <script> tag and then we are starting a new one. This removes the embedded nuance and when the page is loaded, the alert box will appear.

This technique works in many places where a user can control the text returned within the <script> element. Of course, the important remediation step is to make sure that data is properly encoded when returned to the browser. By default, Content Security Policy may not be an immediate solution since this situation would indicate that inline scripts are allowed. However, if you are limiting the use of inline scripts to ones with a registered nonce would help prevent this technique. This reference shows setting the nonce (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src).

When testing our applications, it is important to focus on the lack of output encoding and less on the ability to fully exploit a situation. Our secure coding standards should identify the types of encoding that should be applied to outputs. If the encodings are not properly implemented then we are citing a violation of our standards.

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Equifax Take-aways

By now, you must have heard about the Equifax breach that may have affected up to 143 million records of user people’s information. At this point, I don’t think they can confirm exactly how many records were actually compromised, leading to going with the larger of the numbers just to be safe. While many are quick to jump to conclusions and attempt to Monday morning quarterback what they did or didn’t do to get breached, I like to focus on what we can learn for our own organizations. There are a few topics I want to discuss that hopefully will be useful within your organization.

Patching

Well, it appears to be pretty clear that the avenue of attack was a Struts patch that was missing on the server. The patch was apparently released a few months prior to the attack, or at least acknowledgement of the attack. On the surface, patching appears to be a pretty easy task. A patch is released, you apply it.

Simple, right?

Patching is actually much more complex than that. It may be that simple when you have a single system to work with and maintain with very few software packages. Unfortunately, that is not the reality for so many places. Many organizations are dealing with hundreds or even thousands of systems to attempt to keep fully patched. This is a pretty big task, even if there were no other variables. Automate it they say. Sure, automation can be done, and needs to be done. How can anyone patch that many systems in a reasonable time frame manually?

There are other factors to consider. First, lets consider that there are many different types of patches. You have patches for the operating system, patches for applications, patches for frameworks, even patches for client-side libraries. Does your automation cover all of these sources? Some software has automatic update capabilities and will update on their own. Others require that you explicitly go out and download the patch and apply it.

Second, you have custom written applications with millions of lines of code pulling in multiple frameworks and packages to make development easier. It would be foolish to apply the patch without testing it first. This becomes more of a challenge with application patches because the entire application needs to be retested. This is more than a test to make sure the computer still boots. This needs to make sure that all the functionality, especially that functionality around the component is still properly functioning. The testing alone can be a time consuming piece. Add on to that if the patch makes any other changes within the code that breaks something. How bad does it break it. How much code needs to be rewritten for your custom code to work correctly again? Does that component have other components that are dependent on that version? Does this end up affecting other components?

Finally, who is tasked with patching the systems? Is this defined within the business? Are the same people that apply OS patches to the server the ones responsible for the application component patches? How do they track those type of patches? Do they need to get the go ahead from the application team that the patch is OK to implement?

As you can see, there are a lot of factors that go into apply what may appear to be a simple patch. What it highlights to me is the importance of understanding what components our application uses, how they interact with each other, and understanding how patches are applied when made available. Worst case scenario, we didn’t even know a patch was released.

Patching, however, is just one control for helping protect our systems. Similar to how input validation is a control to help with injection attacks. We shouldn’t be relying on it alone. The Equifax breach shows this well, that we must consider other controls in place in the event another control breaks down.

Encryption

I hear a lot of people talk about the data should have been encrypted. I believe that to be an easy statement to make, but without more details on how the data was actually accessed, it is not very helpful. Hopefully, your organization has a data classification policy. Hopefully, that data classification policy describes how data should be protected. This is the policy that determines how data should be protected and it should exist. If you have not seen this policy, ask for it.

Now that we know some data needs to be encrypted, what is the right method to use? Should we use disk encryption or column level encryption? Should we use Tokenization? The each have their pros and cons. Maybe the answer is you have to implement all of them, just to be safe, but how might that affect your ability to have a high performing functioning application?

You may decide to implement disk encryption for your database. That is a good step, in the event that someone is able to steal the actual files of the database. That doesn’t help much if the application has a vulnerability that allows access to the data that the attacker can just enumerate through. This can be similar to column level encryption as well. Often times application flaws may be able to bypass the encryption if incorrectly implemented. I guess at the very least, you get to say the data was encrypted.

The point with encryption is to make sure you know what you are doing and how you are implementing it. What attack vectors will it protect against and which ones may still be vulnerable. If you are going to take the time to implement it, it is important to make the best use of it.

Auditing and Logging

Auditing and Logging are important parts of the security of an application. They help us see and act upon events that may be malicious. How do you get vision into 3rd party components, like Struts, to see what they are doing? Are you relying on system event logs if the component throws an exception? Within our own applications we can use the logging to identify queries run, data accessed, and authorization failures, etc. When a system gets compromised, that logging may not be useful. It may be a combination of system and application events that help identify an attack as it is happening or after the fact. This is a great reminder that logging mechanisms can cross boundaries and this needs to be reviewed. Take a moment to look at how your applications and your web server are configured to identify potential malicious attacks. Consider different attack scenarios and see how those may get logged and if/when someone might see them.

Risk Management

Business run on the concept of taking risks. Sometimes this works in favor of the organization, sometimes not. In order to make better decisions, they must understand the risks they face. In a situation like this, we know there may be a patch available for a platform. The patch is critical since it allows for remote code execution. But what was known about the risk? What applications were effected on that server? What type of data did those applications maintain? Where does that application fit into our business model? Often times, we don’t look at the real details of a vulnerability or risk, rather we focus on the numbers. A patch that may compromise a system with no records and access is very different than one that relates to all your customer data that may be sensitive.

Don’t mistake this as an alternative to patch management. It is, however, a reality that in the midst of doing business, decisions will be made and not all of them will be popular. When working in your organization, think about the information you may be providing in regards to the decision making process. Is it sufficient? Does it tell the whole story?

Wrap Up

Companies are always at risk of being breached. As we see new breaches appear in the news we need to take a little time to skip the hype and personal opinions, and take a look at what it means to our programs. Look for the facts of what happened, how decisions may have been made, and the effect those had on the organization. Then apply that to your organization. Maybe you learn a new perspective on how a vulnerability can be used. Maybe you see a control that was bypassed that you also use and you want to review how your processes work. In any case, there are lessons we can learn from any situation. Take those and see how they can be used to help your processes and procedures to provide security in your organization.