jtimberman's Code Blog

Chef, Ops, Ruby, Linux/Unix. Opinions are mine, not my employer's (CHEF).

Github Is Classy

Fact: GitHub is classy. This isn’t just because Scott Chacon works there, either. Their handling of a security issue today was very professional. That said, I have some words to say about the issue itself and the aftermath, and things you as an application developer can do to help, and to avoid this kind of problem.

Disclaimer: I’m not an application developer. I am a sysadmin with a diverse background in operating system security, including previously held GSEC and GCUX certifications from the SANS Institute/GIAC.

Second disclaimer: This is not an anti-Rails post. All web frameworks need to be conscious of security, and take bug reports for security issues seriously.


Update – Preface: I am not talking about a security vulnerability (a la an exploit) in Rails. I am talking about a feature that allows automatically generated code to do things that are not secure and it is apparently on purpose and by design. This is the wrong thing to do. Deny by default with whitelisting is the right thing to do.

There is a security issue in Ruby on Rails. The bug is closed, but I haven’t dug into find out if the actual problem is fixed.

The bug itself is very serious. It allows a malicious user to send arbitrary parameters to a Rails application without requiring whitelisting up front. In fact, three months ago an issue was opened in the Rails project to force new applications to enforce whitelist mode by default. That bug was subsequently closed just a few days ago. I’m not going to do an analysis of the issue itself, you can go read the linked tickets and do further research on the issue.

Update I missed clarifying this. There is a second issue at hand. GitHub resolved the mass assignment bug by fixing their application. The second issue is that they had a vulnerability in their public key form update.

Resolution and Aftermath

You can read all about the initial resolution and retrospective on the GitHub blog. You can also read their follow-up post on responsible disclosure.

The manner in which they handled the situation is a class act: they behaved like professionals. Here’s why:

  • A user reported a problem with their app.
  • They worked with the user to resolve the problem.
  • The same user exploited another vulnerability to prove a point to the Rails project, which is against the GitHub terms of service.
  • GitHub suspended the user’s account in accordance with their terms of service.

As an unauthorized breach of a computer system, what Egor Homakov did is illegal in the United States. It was also irresponsible and unprofessional. However, his intent was not malicious. I think GitHub did the right thing by giving him another chance in reinstating Mr. Homakov’s account several hours after the incident.

GitHub has issued two apologies about this incident. First for the vulnerability existing in the first place, and second for not being clear how customers and users can responsibly disclose security vulnerabilities. They also committed to doing a security audit of their code base.

GitHub is classy.


After the above, I feel compelled to say some more things about security in general. You are responsible for a lot of things regarding the web applications in your infrastructure. One of those is security, and you should do everything you can to write stable, secure code.

In a hackernews thread about this incident, Yehuda Katz said, “Not all security vulnerabilities can be protected automatically by a web framework.”

That is a fact. However, web frameworks should provide sane, secure settings by default. Those settings should be modifiable by the end-user, the developer. If a developer wishes to disable those controls, they totally have that right. I think that they need to understand the potential risk that they are accepting, and what impact that might have on the business/organization implementing the application.

This is exactly like the default setting of Red Hat Enterprise Linux to enable SELinux by default on new installations. Whether you love or hate this default, it is sane and secure. System administrators can then use the system as is, or disable SELinux if that is an acceptable level of risk.

Clearly in this incident, it is not an acceptable level of risk for GitHub, as they have repaired their application. It would have better to do that long ago, but at least it’s fixed now.

Security and convenience are quite often polar opposites and mutually exclusive. This is not always the case, but it is true much of the time, if not most of the time. The choice for Rails to not have whitelisting by default is in favor of developer convenience. Yes, it is up to the developer to make their application secure, but that was already the case. This simply creates extra work for them to do so.

Deny-all by default is the sane, correct and secure posture to take when building systems. This is the practice of many tools and operating system defaults – SELinux as mentioned, or “no open ports” per Ubuntu’s practice. You don’t have to agree with it, and you certainly can change it, but that doesn’t change the fact that it is correct and sane.

Vulnerability Disclosure

There is an entire field in information technology devoted to vulnerability disclosure. This is typically done by people performing “ethical hacking” and is one thing done when a code base goes through a security audit. This is a field that has responsible professionals participating in a variety of companies, and if it sounds interesting to you, I recommend the variety of courses offered by the SANS Institute:

What You Can Do

First of all, understand the security guidelines and best practices for the programming language you’re using. Doing things that are typesafe, or avoid buffer overflows, that kind of thing. Also understand and follow the security guideslines and best practices for the web framework you’re using. The Ruby on Rails project has a fairly detailed security guide. If you’re taking shortcuts, understand the possible risks with that. If you don’t know the risks, or understand the guidelines, please ask someone in the community for help.

I strongly recommend you also learn the security guidelines and associated best practices for the operating system or distribution that your application will run on in production. If your organization has operations staff, I’m sure they can help you learn and understand. If they don’t, they’re not doing their job :).

Every organization and every application is different. The security implications are going to vary by industry. Talk to the business owners and find out what the level of security risk they are comfortable accepting.

Above all, be a professional. Don’t flippantly close security bugs. Don’t be a dick on discussions about security topics.

In other words, be classy. Like GitHub.

Thank you.