SLSA GitHub Generator
Overview
What is SLSA?
Supply chain Levels for Software Artifacts, or SLSA (salsa), is a security framework, a check-list of standards and controls to prevent tampering, improve integrity, and secure packages and infrastructure in your projects, businesses or enterprises.
SLSA defines an incrementally adoptable set of levels which are defined in terms of increasing compliance and assurance. SLSA levels are like a common language to talk about how secure software, supply chains and their component parts really are.
What is provenance?
Provenance is information, or metadata, about how a software artifact was created. This could include information about what source code, build system, and build steps were used, as well as who and why the build was initiated. Provenance can be used to determine the authenticity and trustworthiness of software artifacts that you use.
As part of the framework, SLSA defines a provenance format which can be used to hold this metadata.
What is slsa-github-generator?
slsa-github-generator is a set of tools for generation of SLSA3+ provenance for native GitHub projects. It allows projects to generate SLSA provenance safely and accurately using GitHub Actions.
Specifically, this repository contains tools for generating non-forgeable SLSA provenance on GitHub that meets the provenance generation and isolation requirements for SLSA Build level 3 and above.
While slsa-github-generator can help you achieve SLSA Build level 3, use of the provided GitHub Actions reusable workflows only is not sufficient to meet all of the requirements at SLSA Build level 3. Specifically, these workflows do not address provenance distribution or verification. Those requirements must be handled separately to meet SLSA Build level 3+.
Roadmap
The project roadmap is tracked via milestones. You can track progress and open issues via the milestones page. Each milestone includes a description of what is being worked on and a rough timeline for completion.
Generation of provenance
Below we describe the various builders and generators in this repository. They let you build and / or generate non-forgeable provenance using a trusted / isolated re-usable workflow. You can read up on the design in our technical design document.
Referencing SLSA builders and generators
At present, the GitHub Actions provided in this repository as builders and generators MUST be referenced
by tag in order for the slsa-verifier to be able to verify the ref of the trusted builder/generator's
reusable workflow. It also needs to be referred as @vX.Y.Z, because the build will fail if you reference it via a shorter tag like @vX.Y or @vX.
This is contrary to the GitHub best practice for third-party actions which recommends referencing by digest, but intentional due to limits in GitHub Actions. The desire to be able to verify reusable workflows pinned by hash, and the reasons for the current status, are tracked as Issue #12 in the slsa-verifier project.
For guidance on how to configure renovate see RENOVATE.md.
Builders
Build platforms build and generate provenance. They let you meet the provenance generation and isolation strength requirements for SLSA Build level 3 and above.
Builder platforms are able to report the commands used to generate your artifact in the provenance.
This repository hosts the following builders:
- Go Builder SLSA Level 3. Status: available since v1.0.0. This builder builds and generates provenance for your Go projects. To use it, follow the Go builder's README.md.
- Node.js Builder SLSA Level 3. Status: Beta since v1.6.0. Expected GA release Jun 2023.
- Container-based Builder SLSA Level 3. Status: Beta release since v1.7.0. This builder will build arbitrary artifacts by executing a user-supplied container image.
- Container Builder SLSA Level 3. Status: WIP. This builder will build your container image and generate provenance. The generated provenance will be compatible with cosign's attestation format.
If you would rather build your project yourself, use the generators instead as explained in the next section.
Provenance-only generators
Provenance-only generators let you build your artifact, and only generate provenance for you. They let you meet the provenance generation requirements for SLSA Build level 3.
Generators create an attestation to a software artifact coming from your repository.
Generators are not able to report the commands used to generate your artifact in the provenance.
This repository hosts the following generators:
- Generic generator SLSA Level 3. Status: available since v1.2.0. This generator generates provenance for arbitrary artifacts of your choice. To use it, follow the Generic generator's README.md.
- Container generator SLSA Level 3. Status: available since v1.4.0. This generator will generate provenance for container images. The generated provenance will be compatible with cosign's attestation format.
Verification of provenance
To verify the provenance, use the github.com/slsa-framework/slsa-verifier project.
Installation
To install the verifier, see slsa-framework/slsa-verifier#installation.
Inputs
The inputs of the verifier are described in slsa-framework/slsa-verifier#available-options.
Command line examples
A command line example is provided in slsa-framework/slsa-verifier#example.
Technical design
The initial technical design was described in the blog post "Improving software supply chain security with tamper-proof builds".
Specifications
For a more in-depth technical dive, read the SPECIFICATIONS.md.
Provenance format
The format of the provenance is available in PROVENANCE_FORMAT.md.
Contributing
Please see the Contributor Guide for more info.