Some security tips for ruby hackers: prelude

Next Friday I’ll give a talk about using ruby and gems to quick test a webapp for security issues.

It won’t be a “Evil attacker for dummies” training nor a “Appsec Certification” talk.

I will simply show some basic security checks to make before deploying an app and how to use some opensource ruby gem to help you.

This week I’ll blog about the roadmap in building my talk


Why Ruby?

The specific programming language you choose to make some security checks it’s not important. You can make the all the tests either in Java, C, C#, Bash scripting or with a Turing machine.

I choose ruby mainly because:

  • it’s sexy to be used in writing web apps with great frameworks like rails or sinatra;
  • it has a well documented api and developers are trained to write documentation;
  • Net::HTTP and mechanize are amazing pieces of code

Why testing?

If you just forgot linkedin password leakage I can recall you that there are a lot of criminal crews out there attacking websites to steal accounts, infecting people with malware and taking servers control.

Testing for security issues is important but today I don’t want to bother you with recommendations about being aware of the problem.

What to test?

The Owasp testing guide will be the framework I’ll use underneath my talk.

The Testing Guide by owasp is one of the greatest piece of documentation Owasp community has ever wrote. It’s a 300-or-something pages volume describing the most important checks a secure web application must pass.

Here there is a list of security areas we will cover and we will find a ruby piece of code to manage:

  1. Information Gathering
  2. Configuration Management Testing
  3. Authentication Testing
  4. Session Management
  5. Authorization Testing
  6. Business logic testing
  7. Data Validation Testing
  8. Denial of Service Testing
  9. Web Services Testing
  10. AJAX Testing

Owasp testing guide driven assessments are a walk-through between those top 10 topics that they can recall the Owasp Top 10 security risks

Covering all of those points it will take more than days in a serious in deep talk. I’ll just give an overview on Friday but I’ll go in deep here in my blog.

Information gathering

I guess what are you thinking: “it’s my web application. It’s not even published on the Net. I have all the information about it, what re you talking about?

You must start thinking as one of your evil users. When you put online something, you almost lose control over it. Your users become the real protagonists, they registers to the site and they take the stage asking for services and obtaining results. But we are not in an ideal world and users can be either lawful people asking for services or unlawful people who wants to crack the site.

And the first step the latters have to solve is to gather more information they can to make targeted attacks.

That’s why it is truly important you start thinking about how much information you will disclose for free to a potential attacker, just deploying your code.

Configuration management

It’s all about configuration. A well written web application can be compromised if the administration backend is not password protected or there is no control over API calls so a non authenticated user can delete items in the database.

What if a user can find a backup file containing passwords? What if source code can be disclosed under some circumstances?

What if the password for admin user is either password or admin?

Authentication, sessions and authorization

Writing an ad-hoc authentication, authorization and session management framework can be risky if your application is designed to hit the market and become a profitable startup.

Something an attacker will try is to SQL injecting something into your login form to bypass the authentication query. It’s the classic ‘ OR ‘1’=’1 lame attempt. But most of times it works and you’re logged as admin without bruteforcing passwords.

Make sure your legitimate users can’t call APIs or URLs they are not supposed to even know because, in example, they don’t pay for that service.

Consider this scenario, you’re allowing photo resizing API only to premium service subscribed users. However you build the API link for photo resizing in a nice to see web-2.0-javascript. Users can try to call that URL asking for photo resizing and it will be up to the authorization schema to deny the request.

In the Owasp Top 10 slang, this is called failure to restrict url access, but in terms of your startup it’s called people that ask for a service without paying for it… or better, without paying you for it.

Telling stories about anonymous or other crews attacking systems for activism can make your blog to have tons of readers.

Telling stories about a normal person can leverage your application weakness to use your paid service free as in beer it’s more efficient to make you understand application security do is a concern.

Business logic

Testing for business logic is the trickiest part of all the game. This is about testing the logical flow you imagine when you wrote the code can’t be subverted.

Consider an online shop checkout system. What if we can checkout the goods without passing to the credit cards details? What if we can inject an arbitrary number as checkout result?

Yes, it’s all about money and please believe me… ordinary people will exploit a checkout weakness to purchase a mobile phone or an ebook for free if they can.

You write the rules so make sure to write a strong business logic.

This is an important check in a real world penetration test but it can’t be fully automated. The attacker must study and understand the logic behind the application and then exploit it. A tool most of times can’t do it very well

Data Validation

Do you remember Cross site scripting and SQL injection attacks? Ok, it’s time to check them.

As you may wonder, making a full penetration test involved much more work that just checking for a XSS or a SQL injection.

The good news is that submitting attack patterns and see how the code reacts can be full automated here.

Something not covered in this talk

If I’m lucky enough, I would spent all of my talk timeslot just to explain people all the stuff they have to check with some example. For such a reason I won’t cover denial of service, web service or ajax testing.

Wrap up

This is my talk backend. I would then try to give some ruby code (most of them written by myself) to automated some tests.

The idea behind my talk is not to make my audience experienced in web application penetration tests. I just want to make them aware that they can introduce some tests in their daily programming workout.

And writing this post can help me in preparing the talk as well :-)

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