Go supply chain

Needs: Docker

A Go program released the way supply-chain guidance now asks for: built for four platforms, described by a software bill of materials (SBOM), checked for known vulnerabilities, and signed, with one command. Go, Syft, Grype and cosign all run in containers, so none of them is installed on your machine, and CI runs exactly the same steps.

Try it right now

You need Lask and Docker:

git clone https://github.com/lask-task-runner/lask.git
cd lask/example/01-projects/05-go-supply-chain
lask sync                                          # one-time, needs network: tools module and images
export COSIGN_PASSWORD='choose-a-passphrase'
lask run keygen                                    # one-time: writes cosign.key and cosign.pub
lask eval release --version v1.0.0

["dist/hello_v1.0.0_linux_amd64","dist/hello_v1.0.0_linux_arm64","dist/hello_v1.0.0_darwin_arm64",
 "dist/hello_v1.0.0_windows_amd64.exe","dist/hello_v1.0.0.spdx.json","dist/checksums.txt","dist/checksums.txt.bundle"]

The binaries are real, so run the one for your machine: ./dist/hello_v1.0.0_darwin_arm64 --name Lask.

The first release takes a couple of minutes, mostly Grype downloading its vulnerability database. The database and Go's caches are kept in Docker volumes (lask-grype-cache, lask-go-cache), so later runs are quick.

cosign.key must stay private; cosign.pub is the half you would publish. This example's .gitignore leaves out both, so each reader makes their own.

What release does

main.lask runs these steps in order. Each one is also a task you can run on its own:

Step	Task	Runs in
go vet and go test, at the same time	test	golang
Build for linux/amd64, linux/arm64, darwin/arm64 and windows/amd64, all at once	build_all, or build <os> <arch>	golang, one container per platform
Write an SPDX SBOM from what Go embedded in each binary	sbom	Syft
Fail on any vulnerability of --fail-on severity or worse (default high), while the next two steps run	scan <sbom>	Grype
Write checksums.txt over every file	checksums	coreutils
Sign checksums.txt, and so everything it lists	sign	cosign
Check the signature, then every checksum	verify	cosign, coreutils

The cross-compilation target belongs to the environment, not the command. build asks the tools module for a Go environment with GOOS and GOARCH set, and build_all starts one per platform with async:

build(os: String, arch: String, --version: String = "dev"): String = do {
  ext = os == "windows" ? ".exe" : ""
  out = "dist/hello_#{version}_#{os}_#{arch}#{ext}"
  target = tools.go.env(goos = os, goarch = arch, cgo_enabled = "0", cache_dir = go_cache)
  $[target] go build -trimpath -ldflags "-s -w -X main.version=#{version}" -o #{out} ./cmd/hello
  out
}

build_all(--version: String = "dev"): Array<String> =
  all(map(platforms, \(p: Platform) -> async build(p.os, p.arch, version = version)))

The scan does not hold up signing. It is started with async and awaited before verify, so a vulnerability still fails the release:

scanned = async scan(sbom_file, fail_on = fail_on)
checksums()
sign(password = password)
await scanned

The key's password is a !! parameter, read from COSIGN_PASSWORD by default. It reaches cosign only through the container's environment, and Lask prints it as *** wherever it would appear in the log.

The images

Every image is pinned in lask.lock.json. Go, Syft, Grype and coreutils come from lask-module-tools, declared in lask.json. cosign's official image has no shell for a command to run in, so this project builds its own from a short recipe, tools/cosign.Dockerfile. The recipe is named where the environment is written:

cosign_image = #./tools/cosign.Dockerfile

lask sync builds it. The lock pins it by the hash of the recipe, so an edited Dockerfile is found the next time lask sync --frozen runs in CI.

Signing without a transparency log

To run offline and without an account, sign keeps the signature local (--tlog-upload=false), and verify accordingly passes --insecure-ignore-tlog=true. A public project would normally sign keyless through Sigstore, where the signature is recorded in the Rekor transparency log and tied to a CI identity instead of a key file. That change is confined to the sign and verify tasks.

Check it without running anything

lask check          # names, arguments and types; nothing runs
lask envs list      # every image, what requires it, and its pin
lask run --help     # every task, from its own comments

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The whole project is on GitHub: example/01-projects/05-go-supply-chain.