Ratchet

Ratchet is a tool for improving the security of CI/CD workflows by automating the process of pinning and unpinning upstream versions. It's like Bundler, Cargo, Go modules, NPM, Pip, or Yarn, but for CI/CD workflows. Ratchet supports:

• Circle CI
• GitHub Actions
• GitLab CI
• Google Cloud Build
• Harness Drone
• Tekton

⚠️ Warning! The README corresponds to the main branch of ratchet's development, and it may contain unreleased features.

Problem statement

Most CI/CD systems are one layer of indirection away from curl | sudo bash. Unless you are specifically pinning CI workflows, containers, and base images to checksummed versions, everything is mutable: GitHub labels are mutable and Docker tags are mutable. This poses a substantial security and reliability risk.

What you're probably doing:

uses: 'actions/checkout@v3'
# or
image: 'ubuntu:20.04'

What you should really be doing:

uses: 'actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b'
# or
image: 'ubuntu@sha256:47f14534bda344d9fe6ffd6effb95eefe579f4be0d508b7445cf77f61a0e5724'

But resolving those checksums and managing the update lifecycle is extremely toilsome. That's what ratchet aims to solve! Ratchet resolves and updates unpinned references to the latest version that matches their constraint, and then keeps a record of the original constraint.

uses: 'actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b' # ratchet:actions/checkout@v3
# or
image: 'ubuntu@sha256:47f14534bda344d9fe6ffd6effb95eefe579f4be0d508b7445cf77f61a0e5724' # ratchet:ubuntu:20.04

Installation

There are a few options for installing ratchet:

• Via homebrew:

  brew install ratchet

  Note this option is community supported and may not be the latest available verson.

• As a single-static binary from the releases page.

• As a container image from the container registry.

• Via nix:

  nix run 'github:NixOS/nixpkgs/nixpkgs-unstable#ratchet' -- --help

  Note this option is community supported and may not be the latest available version.

• Compiled from source yourself. Note this option is not supported.

Usage

For more information about available commands and options, run a command with -help to use detailed usage instructions. Also see CLI Options.

Pin

The pin command pins to specific versions:

# pin the input file
ratchet pin workflow.yml

# pin a circleci file
ratchet pin -parser circleci circleci.yml

# pin a cloudbuild file
ratchet pin -parser cloudbuild cloudbuild.yml

# pin a drone file
ratchet pin -parser drone drone.yml

# pin a gitlab file
ratchet pin -parser gitlabci gitlabci.yml

# output to a tekton file
ratchet pin -out -parser tekton tekton.yml

# output to a different path
ratchet pin -out workflow-compiled.yml workflow.yml

Unpin

The unpin command unpins any pinned versions:

# unpin the input file
ratchet unpin workflow.yml

# output to a different path
ratchet unpin -out workflow.yml workflow-compiled.yml

Update

The update command updates all versions to the latest matching constraint:

# update the input file
ratchet update workflow.yml

# update a circleci file
ratchet update -parser circleci circleci.yml

# update a cloudbuild file
ratchet update -parser cloudbuild cloudbuild.yml

# output to a different path
ratchet update -out workflow-compiled.yml workflow.yml

Upgrade

Note

This command only works with GitHub Actions references. It does not support container or Docker-based references.

The upgrade command upgrades all versions to the latest version, changing the ratchet comment and also updating the ref.

# upgrade the input file
ratchet upgrade workflow.yml

# output to a different path
ratchet upgrade -out workflow-compiled.yml workflow.yml

Note

Performs an update if the constraint ref is for a branch.

Check

The check command checks if all versions are pinned, exiting with a non-zero error code when entries are not pinned:

ratchet check workflow.yml

Examples

CI/CD workflow

Ratchet is distributed as a very small container, so you can use it as a step inside CI/CD jobs. Here is a GitHub Actions example:

jobs:
  my_job:
    runs-on: 'ubuntu-latest'
    name: 'ratchet'
    steps:
      - uses: 'actions/checkout@755da8c3cf115ac066823e79a1e1788f8940201b' # ratchet:actions/checkout@v3

      # Example of pinning:
      - uses: 'docker://ghcr.io/sethvargo/ratchet:latest'
        with:
          args: 'pin .github/workflows/my-workflow.yml'

      # Example of checking versions are pinned:
      - uses: 'docker://ghcr.io/sethvargo/ratchet:latest'
        with:
          args: 'check .github/workflows/my-workflow.yml'

This same pattern can be extended to other CI/CD systems that support container-based runtimes. For non-container-based runtimes, download the ratchet binary from GitHub Releases.

Runnable container CLI

Ratchet can run directly from a container on your local system:

docker run -it --rm -v "${PWD}:${PWD}" -w "${PWD}" ghcr.io/sethvargo/ratchet:latest COMMAND

Create a shell alias to make this easier:

function ratchet {
  docker run -it --rm -v "${PWD}:${PWD}" -w "${PWD}" ghcr.io/sethvargo/ratchet:latest "$@"
}

Auth

• The container resolver uses default "keychain" auth, which looks for local system auth, similar to the Docker and gcloud CLIs.

• The GitHub resolver defaults to public github.com. Provide an oauth access token with appropriate permissions via the GITHUB_TOKEN environment variable. To use a GitHub Enterprise installation, set the ACTIONS_BASE_URL and ACTIONS_UPLOAD_URL environment variables to point your instance.

Excluding

There may be instances in which you want to exclude a particular reference from being pinned. You can use the ratchet:exclude annotation as a line comment and ratchet will not process that reference:

uses: 'actions/checkout@v3' # ratchet:exclude

There cannot be any spaces in the exclusion string, and the exclusion string only applies to the line on which it appears.

Terminology

• Unpinned version - An unpinned version is a non-absolute reference to a floating tag or label, such as actions/checkout@v4 or ubuntu:22.04.

• Pinned version - A pinned version is an absolute hashed reference, such as actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b or ubuntu@sha256:82becede498899ec668628e7cb0ad87b6e1c371cb8a1e597d83a47fac21d6af3.

Known issues

• Indentation is always set to 2 spaces. The upstream YAML library does not capture pre-parsing indentation. Thus, all files will be saved with 2 spaces for indentation.

• Does not support resolving values in anchors or aliases. This is technically possible, but most CI systems also don't support these advanced YAML features.

  Similarly, Ratchet does not support matrix-style expansion, since those values cannot be guaranteed to be known at compile time. For example, Ratchet will error on the following GitHub Actions workflow:

  jobs:
    my_job:
      strategy:
        matrix:
          version:
          - '1'
          - '2'
  
      steps:
        - uses: 'actions/checkout@v${{ matrix.version }}'