March 9, 2021

Introducing sigstore: Easy Code Signing & Verification for Supply Chain Integrity

One of the fundamental security issues with open source is that it’s difficult to know where the software comes from or how it was built, making it susceptible to supply chain attacks. A few recent examples of this include dependency confusion attack and malicious RubyGems package to steal cryptocurrency.

Today we welcome the announcement of sigstore, a new project in the Linux Foundation that aims to solve this issue by improving software supply chain integrity and verification.

Installing most open source software today is equivalent to picking up a random thumb-drive off the sidewalk and plugging it into your machine. To address this we need to make it possible to verify the provenance of all software - including open source packages. We talked about the importance of this in our recent Know, Prevent, Fix post.

The mission of sigstore is to make it easy for developers to sign releases and for users to verify them. You can think of it like Let’s Encrypt for Code Signing. Just like how Let’s Encrypt provides free certificates and automation tooling for HTTPS, sigstore provides free certificates and tooling to automate and verify signatures of source code. Sigstore also has the added benefit of being backed by transparency logs, which means that all the certificates and attestations are globally visible, discoverable and auditable.

Sigstore is designed with open source maintainers, for open source maintainers. We understand long-term key management is hard, so we've taken a unique approach of issuing short-lived certificates based on OpenID Connect grants. Sigstore also stores all activity in Transparency Logs, backed by Trillian so that we can more easily detect compromises and recover from them when they do occur. Key distribution is notoriously difficult, so we've designed away the need for them by building a special Root CA just for code signing, which will be made available for free.

We have a working prototype and proof of concepts that we're excited to share for feedback. Our goal is to make it seamless and easy to sign and verify code:

It has been fun collaborating with the folks from Red Hat and the open source community on this project. Luke Hinds, one of the lead developers on sigstore and Security Engineering Lead at Red Hat says, "I am very excited about sigstore and what this means for improving the security of software supply chains. sigstore is an excellent example of an open source community coming together to collaborate and develop a solution to ease the adoption of software signing in a transparent manner." We couldn’t agree more.

Mike Malone, the CEO of Smallstep, helped with the overall design of sigstore. He adds, “In less than a generation, open source has grown from a niche community to a critical ecosystem that powers our global economy and institutions of society and culture. We must ensure the security of this ecosystem without undermining the open, decentralized collaboration that makes it work. By building on a clever composition of existing technologies that respect privacy and work at scale, sigstore is the core infrastructure we need to solve this fundamental problem. It’s an ambitious project with potential for global impact. I’m impressed by the rapid progress that’s been made by Google, Red Hat, and Linux Foundation over the past few months, and I’m excited to hear feedback from the broader community.”

While we are happy with the progress that has been made, we know there is still work to be done before this can be widely relied upon. Upcoming plans for sigstore include: hardening the system, adding support for other OpenID Connect providers, updating documentation and responding to community feedback.

Sigstore is in its early days, but we're really excited about its future. Now is a great time to provide feedback, try out the tooling and get involved with the project as design details are still being refined.

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