This critical role would not be possible without funding from the Alpha-Omega project. Massive thank-you to Alpha-Omega for investing in the security of the Python ecosystem!

The first stage of the CPython release process produces source and docs artifacts. In terms of "supply chain integrity", the source artifacts are the most important artifact produced by this process. These tarballs are what propagates down into containers, pyenv, and operating system distributions, so reducing the risk that these artifacts are modified in-flight is critical.

A few weeks ago I published that CPythons' release process for source and docs artifacts was moved from developers machines onto GitHub Actions, which provides an isolated build environment.

This already reduces risk of artifacts being accidentally or maliciously modified during the release process. The layout of the build and release process before used a build script which built the software from source, built the docs, and then ran tests all in the same isolated job. This was totally fine on a developers' machine where there isn't any isolation possible between different stages.

With GitHub Actions we can isolate each stage from the others and remove the need to install all dependencies for all jobs into the same stage. This drastically reduces the number of dependencies, each representing a small amount of risk, for the stages that are critical for supply chain security of CPython (specifically the building of source artifacts).

Above you can see on the left the previous process which pulls all dependencies into the same job (represented as a gray box) and the right being the new process having split up the builds and testing and the source and docs builds.

After doing this split the "Build Source" task only needs ~170 dependencies instead of over 800 dependencies (mostly for documentation LaTeX and PDFs) and all of those dependencies either come with the operating system and thus can't be reduced further or are pinned in a lock file.

The testing stage still has access to the source artifacts, but only after they've been uploaded to GitHub Action Artifacts and aren't able to modify them.

I plan to write a separate in-depth article about dependencies, pinning, and related topics, stay tuned for that.

SOSS Community Day 2024 recordings

The recordings for my talk and the OpenSSF tabletop session have been published to YouTube:

In the talk I discuss the technical and also social aspects of why it's sometimes difficult to adopt security changes into an open source ecosystem. Ecosystem-agnostic work (think memory safety, provenance, reproducible builds, vulnerabilities) tends to operate at a much higher level than the individual ecosystems where the work ends up being applied.

OpenSSF Tabletop Session

The tabletop session had many contributors representing all the different aspects of discovering, debugging, disclosing, fixing, and patching a zero-day vulnerability in an open source component that's affecting production systems.

Mentoring for Google Summer of Code

Google Summer of Code 2024 recently published its program and among the projects and contributors accepted was CPython's project for adopting the Hardened Compiler Options Guide for C/C++. I'm mentoring the contributor through the process of contributing to CPython and hopefully being successful in adopting hardened compiler options.

Other items

• Windows artifacts on python.org will have Software Bill-of-Materials documents after the next CPython release. Final step of uploading the documents to python.org has been merged.
• SBOM generation has been added to the Windows build scripts for core developers using Windows.
• Working on PyCon US 2024 talk slides with Michael Winser.
• Co-authoring the "Trusted Publishing for All Package Repositories" guide for the OpenSSF Securing Software Repos WG.
• Submitted a few bugfixes and released Truststore v0.9.0, upgraded pip's vendored copy.
• Created the April report for Alpha-Omega

That's all for this week! 👋 If you're interested in more you can read last week's report.

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