273 lines
7.7 KiB
Markdown
273 lines
7.7 KiB
Markdown
# attest
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GitHub Action to sign and upload [in-toto Attestation Predicates][0] for
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artifacts as part of a workflow.
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## Usage
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Within the GitHub Actions workflow which builds some artifact you would like to
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attest,
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1. Ensure that the following permissions are set:
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```yaml
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permissions:
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id-token: write
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contents: write
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```
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The `id-token` permission gives the action the ability to mint the OIDC token
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necessary to request a Sigstore signing certificate. The `contents`
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permission is necessary to persist the attestation.
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> **NOTE**: The set of required permissions will be refined in a future
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> release.
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1. After your artifact build step, add the following:
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```yaml
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- uses: actions/attest@main
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with:
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predicate-path: './predicate.json'
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predicate-type: 'https://in-toto.io/attestation/release/v0.1'
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subject-path: '${{ github.workspace }}/PATH_TO_FILE'
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```
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The `subject-path` parameter should identity the artifact for which you want
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to generate an attestation.
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### What is being attested?
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The generated attestation is based on the inputs of `predicate-path` and `predicate-type`
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```json
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{
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"_type": "https://in-toto.io/Statement/v1",
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"subject": [
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{
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"name": "subject",
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"digest": {
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"sha256": "7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32"
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}
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}
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],
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"predicateType": $predicateType,
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"predicate": {
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...
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}
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}
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```
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The predicate statement is signed with a short-lived, [Sigstore][1]-issued
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certificate.
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If the repository initiating the GitHub Actions workflow is public, the public
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instance of Sigstore will be used to generate the attestation signature. If the
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repository is private, it will use the GitHub private Sigstore instance.
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### Where does the attestation go?
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On the actions summary page for a repository you'll see an "Attestations" link
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which will take you to a list of all the attestations generated by workflows in
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that repository.
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### How are attestations verified?
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Attestations can be verified using the [gh-attestation][2] extension for the
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[GitHub CLI][3].
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## Customization
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See [action.yml](action.yml)
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### Inputs
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- `predicate` - String containing the value for the attestation predicate.
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Must supply exactly one of "predicate-path" or "predicate".
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- `predicate-path` - Path to the file which contains the content for the
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attestation predicate.
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Must supply exactly one of "predicate-path" or "predicate".
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- `predicate-type` - URI identifying the type of the predicate.
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- `subject-path` - Path to the artifact for which the predicate statement will be
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generated.
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Must specify exactly one of `subject-path` or `subject-digest`. Wildcards can
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be used to identify more than one artifact.
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- `subject-digest` - Digest of the subject for which the predicate statement
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will be generated.
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Only SHA-256 digests are accepted and the supplied value must be in the form
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"sha256:\<hex-encoded-digest\>". Must specify exactly one of `subject-path` or
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`subject-digest`.
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- `subject-name` - Subject name as it should appear in the predicate statement.
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Required when the subject is identified by the `subject-digest` parameter.
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When attesting container images, the name should be the fully qualified image
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name.
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- `push-to-registry` - If true, the signed attestation is pushed to the
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container registry identified by the `subject-name`. Default: `false`.
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- `github-token` - Token used to make authenticated requests to the GitHub API.
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Default: `${{ github.token }}`.
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The supplied token must have the permissions necessary to write attestations
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to the repository.
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### Outputs
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- `bundle-path` - The file path of JSON-serialized [Sigstore bundle][4]
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containing the attestation and related verification material.
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## Sample Workflows
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### Identify Artifact by Path
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For the basic use case, simply add the `attest` action to
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your workflow and supply the path to the artifact for which you want to generate
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attestation.
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```yaml
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name: attest
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on:
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workflow_dispatch:
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jobs:
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build:
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permissions:
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id-token: write
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contents: write
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steps:
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- name: Checkout
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uses: actions/checkout@v4
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- name: Build artifact
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run: make some-app
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- name: Attest
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uses: actions/attest@main
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with:
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predicate: |
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'{ "purl": $YOUR_PURL, "releaseId": $YOUR_RELEASE_ID }'
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predicate-type: 'https://in-toto.io/attestation/release/v0.1'
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subject-path: '${{ github.workspace }}/some-app'
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```
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### Identify Artifacts by Wildcard
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If you are generating multiple artifacts, you can generate attest for
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each artifact by using a wildcard in the `subject-path` input.
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```yaml
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name: build-wildcard-with-attest
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on:
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workflow_dispatch:
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jobs:
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build:
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permissions:
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id-token: write
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contents: write
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steps:
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- name: Checkout
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uses: actions/checkout@v4
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- name: Set up Go
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uses: actions/setup-go@v4
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- name: Run GoReleaser
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uses: goreleaser/goreleaser-action@v5
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with:
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distribution: goreleaser
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version: latest
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args: release --clean
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env:
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GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
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- name: Attest artifact
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uses: actions/attest@main
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with:
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predicate: |
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'{ "purl": $YOUR_PURL, "releaseId": $YOUR_RELEASE_ID }'
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predicate-type: 'https://in-toto.io/attestation/release/v0.1'
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subject-path: 'dist/**/my-bin-*'
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```
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For supported wildcards along with behavior and documentation, see
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[@actions/glob][5] which is used internally to search for files.
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### Container Image
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When working with container images you may not have a `subject-path` value you
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can supply. In this case you can invoke the action with the `subject-name` and
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`subject-digest` inputs.
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If you want to publish the attestation to the container registry with the
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`push-to-registry` option, it is important that the `subject-name` specify the
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fully-qualified image name (e.g. "ghcr.io/user/app" or
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"acme.azurecr.io/user/app"). Do NOT include a tag as part of the image name --
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the specific image being attested is identified by the supplied digest.
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> **NOTE**: When pushing to Docker Hub, please use "index.docker.io" as the
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> registry portion of the image name.
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```yaml
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name: build-image-with-attest
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on:
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push:
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branches: [main]
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jobs:
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build:
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runs-on: ubuntu-latest
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permissions:
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id-token: write
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packages: write
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contents: write
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env:
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REGISTRY: ghcr.io
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IMAGE_NAME: ${{ github.repository }}
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steps:
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- name: Checkout
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uses: actions/checkout@v4
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- name: Login to GitHub Container Registry
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uses: docker/login-action@v3
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with:
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registry: ${{ env.REGISTRY }}
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username: ${{ github.actor }}
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password: ${{ secrets.GITHUB_TOKEN }}
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- name: Build and push image
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id: push
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uses: docker/[email protected]
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with:
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context: .
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push: true
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tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
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- name: Attest
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uses: actions/attest@main
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id: attest
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with:
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subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
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subject-digest: ${{ steps.push.outputs.digest }}
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predicate: |
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'{ "purl": $YOUR_PURL, "releaseId": $YOUR_RELEASE_ID }'
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predicate-type: 'https://in-toto.io/attestation/release/v0.1'
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```
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[0]: https://github.com/in-toto/attestation/blob/main/spec/predicates/README.md
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[1]: https://www.sigstore.dev/
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[2]: https://github.com/github-early-access/gh-attestation
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[3]: https://cli.github.com/
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[4]: https://github.com/sigstore/protobuf-specs/blob/main/protos/sigstore_bundle.proto
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[5]: https://github.com/actions/toolkit/tree/main/packages/glob#patterns
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