GitHub Action
Generate Generic Attestations
Generate signed attestations for workflow artifacts. Internally powered by the @actions/attest package.
Attestations bind some subject (a named artifact along with its digest) to a predicate (some assertion about that subject) using the in-toto format. Predicates consist of a type URI and a JSON object containing type-dependent parameters.
A verifiable signature is generated for the attestation using a short-lived Sigstore-issued signing certificate. If the repository initiating the GitHub Actions workflow is public, the public-good instance of Sigstore will be used to generate the attestation signature. If the repository is private/internal, it will use the GitHub private Sigstore instance.
Once the attestation has been created and signed, it will be uploaded to the GH attestations API and associated with the repository from which the workflow was initiated.
Attestations can be verified using the attestation
command in the GitHub
CLI.
See Using artifact attestations to establish provenance for builds for more information on artifact attestations.
Within the GitHub Actions workflow which builds some artifact you would like to attest:
-
Ensure that the following permissions are set:
permissions: id-token: write attestations: write
The
id-token
permission gives the action the ability to mint the OIDC token necessary to request a Sigstore signing certificate. Theattestations
permission is necessary to persist the attestation. -
Add the following to your workflow after your artifact has been built:
- uses: actions/attest@v1 with: subject-path: '<PATH TO ARTIFACT>' predicate-type: '<PREDICATE URI>' predicate-path: '<PATH TO PREDICATE>'
The
subject-path
parameter should identify the artifact for which you want to generate an attestation. Thepredicate-type
can be any of the the vetted predicate types or a custom value. Thepredicate-path
identifies a file containg the JSON-encoded predicate parameters.
See action.yml
- uses: actions/attest@v1
with:
# Path to the artifact serving as the subject of the attestation. Must
# specify exactly one of "subject-path" or "subject-digest". May contain
# a glob pattern or list of paths (total subject count cannot exceed 2500).
subject-path:
# SHA256 digest of the subject for the attestation. Must be in the form
# "sha256:hex_digest" (e.g. "sha256:abc123..."). Must specify exactly one
# of "subject-path" or "subject-digest".
subject-digest:
# Subject name as it should appear in the attestation. Required unless
# "subject-path" is specified, in which case it will be inferred from the
# path.
subject-name:
# URI identifying the type of the predicate.
predicate-type:
# String containing the value for the attestation predicate. String length
# cannot exceed 16MB. Must supply exactly one of "predicate-path" or
# "predicate".
predicate:
# Path to the file which contains the content for the attestation predicate.
# File size cannot exceed 16MB. Must supply exactly one of "predicate-path"
# or "predicate".
predicate-path:
# Whether to push the attestation to the image registry. Requires that the
# "subject-name" parameter specify the fully-qualified image name and that
# the "subject-digest" parameter be specified. Defaults to false.
push-to-registry:
# Whether to attach a list of generated attestations to the workflow run
# summary page. Defaults to true.
show-summary:
# The GitHub token used to make authenticated API requests. Default is
# ${{ github.token }}
github-token:
Name | Description | Example |
---|---|---|
bundle-path |
Absolute path to the file containing the generated attestation | /tmp/attestation.jsonl |
Attestations are saved in the JSON-serialized Sigstore bundle format.
If multiple subjects are being attested at the same time, a single attestation will be created with references to each of the supplied subjects.
No more than 1024 subjects can be attested at the same time.
Whether supplied via the predicate
or predicatePath
input, the predicate
string cannot exceed 16MB.
For the basic use case, simply add the attest
action to your workflow and
supply the path to the artifact for which you want to generate attestation.
name: build-attest
on:
workflow_dispatch:
jobs:
build:
permissions:
id-token: write
contents: read
attestations: write
steps:
- name: Checkout
uses: actions/checkout@v4
- name: Build artifact
run: make my-app
- name: Attest
uses: actions/attest@v1
with:
subject-path: '${{ github.workspace }}/my-app'
predicate-type: 'https://example.com/predicate/v1'
predicate: '{}'
If you are generating multiple artifacts, you can generate an attestation for
each by using a wildcard in the subject-path
input.
- uses: actions/attest@v1
with:
subject-path: 'dist/**/my-bin-*'
predicate-type: 'https://example.com/predicate/v1'
predicate: '{}'
For supported wildcards along with behavior and documentation, see @actions/glob which is used internally to search for files.
Alternatively, you can explicitly list multiple subjects with either a comma or newline delimited list:
- uses: actions/attest@v1
with:
subject-path: 'dist/foo, dist/bar'
- uses: actions/attest@v1
with:
subject-path: |
dist/foo
dist/bar
When working with container images you can invoke the action with the
subject-name
and subject-digest
inputs.
If you want to publish the attestation to the container registry with the
push-to-registry
option, it is important that the subject-name
specify the
fully-qualified image name (e.g. "ghcr.io/user/app" or
"acme.azurecr.io/user/app"). Do NOT include a tag as part of the image name --
the specific image being attested is identified by the supplied digest.
NOTE: When pushing to Docker Hub, please use "docker.io" as the registry portion of the image name.
name: build-attested-image
on:
push:
branches: [main]
jobs:
build:
runs-on: ubuntu-latest
permissions:
id-token: write
packages: write
contents: read
attestations: write
env:
REGISTRY: ghcr.io
IMAGE_NAME: ${{ github.repository }}
steps:
- name: Checkout
uses: actions/checkout@v4
- name: Login to GitHub Container Registry
uses: docker/login-action@v3
with:
registry: ${{ env.REGISTRY }}
username: ${{ github.actor }}
password: ${{ secrets.GITHUB_TOKEN }}
- name: Build and push image
id: push
uses: docker/[email protected]
with:
context: .
push: true
tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
- name: Attest
uses: actions/attest@v1
id: attest
with:
subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
subject-digest: ${{ steps.push.outputs.digest }}
predicate-type: 'https://in-toto.io/attestation/release/v0.1'
predicate: '{"purl":"pkg:oci/..."}'
push-to-registry: true