alex gaynor's blago-blog

Security process for Open Source Projects

Posted October 19th, 2013.

This post is intended to describe how open source projects should handle security vulnerabilities. This process is largely inspired by my involvement in the Django project, whose process is in turn largely drawn from the PostgreSQL project's process. For every recommendation I make I'll try to explain why I've made it, and how it serves to protect you and your users. This is largely tailored at large, high impact, projects, but you should able to apply it to any of your projects.

Why do you care?

Security vulnerabilities put your users, and often, in turn, their users at risk. As an author and distributor of software, you have a responsibility to your users to handle security releases in a way most likely to help them avoid being exploited.

Finding out you have a vulnerability

The first thing you need to do is make sure people can report security issues to you in a responsible way. This starts with having a page in your documentation (or on your website) which clearly describes an email address people can report security issues to. It should also include a PGP key fingerprint which reporters can use to encrypt their reports (this ensures that if the email goes to the wrong recipient, that they will be unable to read it).

You also need to describe what happens when someone emails that address. It should look something like this:

  1. You will respond promptly to any reports to that address, this means within 48 hours. This response should confirm that you received the issue, and ideally whether you've been able to verify the issue or more information is needed.
  2. Assuming you're able to reproduce the issue, now you need to figure out the fix. This is the part with a computer and programming.
  3. You should keep in regular contact with the reporter to update them on the status of the issue if it's taking time to resolve for any reason.
  4. Now you need to inform the reporter of your fix and the timeline (more on this later).

Timeline of events

From the moment you get the initial report, you're on the clock. Your goal is to have a new release issued within 2-weeks of getting the report email. Absolutely nothing that occurs until the final step is public. Here are the things that need to happen:

  1. Develop the fix and let the reporter know.
  2. You need to obtain a CVE (Common Vulnerabilities and Exposures) number. This is a standardized number which identifies vulnerabilities in packages. There's a section below on how this works.
  3. If you have downstream packagers (such as Linux distributions) you need to reach out to their security contact and let them know about the issue, all the major distros have contact processes for this. (Usually you want to give them a week of lead time).
  4. If you have large, high visibility, users you probably want a process for pre-notifying them. I'm not going to go into this, but you can read about how Django handles this in our documentation.
  5. You issue a release, and publicize the heck out of it.

Obtaining a CVE

In short, follow these instructions from Red Hat.

What goes in the release announcement

Your release announcement needs to have several things:

  1. A precise and complete description of the issue.
  2. The CVE number
  3. Actual releases using whatever channel is appropriate for your project (e.g. PyPI, RubyGems, CPAN, etc.)
  4. Raw patches against all support releases (these are in addition to the release, some of your users will have modified the software, and they need to be able to apply the patches easily too).
  5. Credit to the reporter who discovered the issue.

Why complete disclosure?

I've recommended that you completely disclose what the issue was. Why is that? A lot of people's first instinct is to want to keep that information secret, to give your users time to upgrade before the bad guys figure it out and start exploiting it.

Unfortunately it doesn't work like that in the real world. In practice, not disclosing gives more power to attackers and hurts your users. Dedicated attackers will look at your release and the diff and figure out what the exploit is, but your average users won't be able to. Even embedding the fix into a larger release with many other things doesn't mask this information.

In the case of yesterday's Node.JS release, which did not practice complete disclosure, and did put the fix in a larger patch, this did not prevent interested individuals from finding out the attack, it took me about five minutes to do so, and any serious individual could have done it much faster.

The first step for users in responding to a security release in something they use is to assess exposure and impact. Exposure means "Am I affected and how?", impact means "What is the result of being affected?". Denying users a complete description of the issue strips them of the ability to answer these questions.

What happens if there's a zero-day?

A zero-day is when an exploit is publicly available before a project has any chance to reply to it. Sometimes this happens maliciously (e.g. a black-hat starts using the exploit against your users) and sometimes it is accidentally (e.g. a user reports a security issue to your mailing list, instead of the security contact). Either way, when this happens, everything goes to hell in a handbasket.

When a zero-day happens basically everything happens in 16x fast-forward. You need to immediately begin preparing a patch and issuing a release. You should be aiming to issue a release on the same day as the issue is made public.

Unfortunately there's no secret to managing zero-days. They're quite simply a race between people who might exploit the issue, and you to issue a release and inform your users.

Conclusion

Your responsibility as a package author or maintainer is to protect your users. The name of the game is keeping your users informed and able to judge their own security, and making sure they have that information before the bad guys do.

This entry was tagged with django, python, open-source, community.
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