Code signatures help prevent unauthorized code execution. They bridge trust between build and execution environments. This post shows you how to sign AWS Lambda function code built with GitHub Actions. Background In November 2020 AWS released support for signing AWS Lambda code. Lambda function owners can specify signing verification requirements using…

Security invariants are a pattern for solving problems. We know what we want to be true, with minimal subjectivity. We know how to verify its truth, with minimal interpretation. It may not be true everywhere, but we know everywhere where it isn’t true. An example of an invariant is: All…

If your security team is concerned about supply chain risk, it’s a good idea to look at your GitHub settings. GitHub describes several security features and best practices in their documentation for account security and organization security, but this post goes beyond the documentation. …

Service accounts for Software-as-a-Service (SaaS) applications have high levels of access and are shared between multiple people — a tempting target for attackers. But service accounts aren’t just a source of security risk. They can also slow down engineering teams. Laggy approvals for access, flaky integrations, and risky manual changes…

Security vulnerabilities result from interactions between thousands of well-intentioned decisions. What systems or libraries do we use? Should I click yes or no on this authorization prompt? Should we make this system more simple or more safe? Only in the aftermath of security incidents do the regrettable decisions become clear. …

Login CSRF allows an attacker to force a victim to log in to an attacker-controlled account. It often shows up in vulnerability scans and bug bounties. If you see a Login CSRF vulnerability, should you fix it? As defenders, we should only spend time fixing Login CSRF if attackers can…

It was a running joke at Twitter for new hires to post to the company-wide list asking why we couldn’t change the “dogs in the office” policy. At Clever we developed a theory that someone on the executive team had an allergy given the continued resistance to bringing dogs to…

This is an abridged version of my LocoMocoSec 2020 conference talk How do you set the strategy for a security team? If your goals are vague, people on your team will work on whatever they’re interested in because there’s no clear mission. …

We use HTTPS to verify web server identities with X.509 certificates, but TLS also supports mutual authentication, where the server uses certs to verify the client’s identity. …