メニュー
Sign and verify container image provenance using Sigstore Cosign with keyless OIDC-based signing, attestations, and Kubernetes admission enforcement.
デフォルトでは、最初にソースを確認する Prompt が選択されています。直接コマンドに切り替えるか、ローカルコピーをダウンロードすることもできます。
インストールを決める前に、SKILL.md と SkillsMP に表示されている付属ファイルをお読みください。
SOC 職業分類に基づく
Codex または Claude でインストール この Prompt をコピーして Codex、Claude、または他のアシスタントに貼り付けると、Skill ページを確認してインストールできます。
直接コマンドでは確認用 Prompt が省略されます。実行前にソースを確認してください。
npx skills add https://github.com/xalgord/xalgorix --skill implementing-image-provenance-verification-with-cosignコマンドは1行のまま表示されます。コピー前に横へスクロールして全体を確認してください。
ローカルで確認しますか？SkillsMP が現在取得できるファイルをダウンロードできます。
SKILL.md を表示中
Detecting and exploiting HTTP request smuggling vulnerabilities caused by Content-Length and Transfer-Encoding parsing discrepancies between front-end and back-end servers.
Identifying and exploiting OAuth 2.0 and OpenID Connect misconfigurations including redirect URI manipulation, token leakage, and authorization code theft during security assessments.
Identifying and exploiting dangling DNS records pointing to unclaimed cloud services, enabling subdomain takeover for phishing, cookie stealing, and authentication bypass during authorized penetration tests.
| name | implementing-image-provenance-verification-with-cosign |
| description | Sign and verify container image provenance using Sigstore Cosign with keyless OIDC-based signing, attestations, and Kubernetes admission enforcement. |
| domain | cybersecurity |
| subdomain | container-security |
| tags | ["cosign","sigstore","image-signing","supply-chain","provenance","keyless","slsa"] |
| version | 1.0 |
| author | mahipal |
| license | Apache-2.0 |
| nist_csf | ["PR.PS-01","PR.IR-01","ID.AM-08","DE.CM-01"] |
Cosign is a Sigstore tool for signing, verifying, and attaching metadata to container images and OCI artifacts. It supports both key-based and keyless (OIDC) signing, integrates with Fulcio (certificate authority) and Rekor (transparency log), and enables supply chain security for container images.
cosign verify in CI but not gated at admission: signing in the pipeline proves nothing at runtime if the cluster will still pull unsigned images. Enforce with the Sigstore policy-controller ClusterImagePolicy or a Kyverno verifyImages rule, and confirm it is active (not just installed).validationFailureAction: Audit (Kyverno) or a permissive ClusterImagePolicy only logs. Set Kyverno to Enforce; verify an unsigned pod is rejected: kubectl run bad --image=ghcr.io/myorg/unsigned:latest should fail admission.cosign verify ...:v1.0.0 is subject to tag re-push (TOCTOU). Verify and admit by @sha256: digest.--certificate-identity-regexp=".*" or omitting --certificate-oidc-issuer accepts signatures from any Fulcio identity. Pin --certificate-identity=<exact> (or a tight regex) and --certificate-oidc-issuer=https://token.actions.githubusercontent.com.ClusterImagePolicy images.glob: "ghcr.io/myorg/**" silently skips images pulled from a mirror/proxy or a different registry path - they admit unverified.cosign verify should confirm signature + Fulcio certificate + Rekor inclusion; check rekor-cli search --email <id> returns the entry.# Install via Go
go install github.com/sigstore/cosign/v2/cmd/cosign@latest
# Install via Homebrew
brew install cosign
# Install via script
curl -O -L "https://github.com/sigstore/cosign/releases/latest/download/cosign-linux-amd64"
sudo mv cosign-linux-amd64 /usr/local/bin/cosign
sudo chmod +x /usr/local/bin/cosign
# Verify installation
cosign version
# Generate cosign key pair (creates cosign.key and cosign.pub)
cosign generate-key-pair
# Generate key pair stored in KMS
cosign generate-key-pair --kms awskms:///alias/cosign-key
cosign generate-key-pair --kms gcpkms://projects/PROJECT/locations/LOCATION/keyRings/KEYRING/cryptoKeys/KEY
cosign generate-key-pair --kms hashivault://transit/keys/cosign
# Sign an image
cosign sign --key cosign.key ghcr.io/myorg/myapp:v1.0.0
# Sign with annotations
cosign sign --key cosign.key \
-a "build-id=12345" \
-a "git-sha=$(git rev-parse HEAD)" \
ghcr.io/myorg/myapp:v1.0.0
# Verify signature
cosign verify --key cosign.pub ghcr.io/myorg/myapp:v1.0.0
# Verify with annotation check
cosign verify --key cosign.pub \
-a "build-id=12345" \
ghcr.io/myorg/myapp:v1.0.0
# Keyless sign - opens browser for OIDC auth
cosign sign ghcr.io/myorg/myapp:v1.0.0
# The signature, certificate, and Rekor entry are created automatically
# GitHub Actions (uses OIDC token automatically)
cosign sign ghcr.io/myorg/myapp:v1.0.0 \
--yes
# With explicit identity token
cosign sign ghcr.io/myorg/myapp:v1.0.0 \
--identity-token=$(cat /var/run/sigstore/cosign/oidc-token) \
--yes
# Verify by email identity
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity=builder@example.com \
--certificate-oidc-issuer=https://accounts.google.com
# Verify by GitHub Actions workflow
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity=https://github.com/myorg/myrepo/.github/workflows/build.yml@refs/heads/main \
--certificate-oidc-issuer=https://token.actions.githubusercontent.com
# Verify with regex matching
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity-regexp=".*@example.com" \
--certificate-oidc-issuer=https://accounts.google.com
# Generate SBOM
syft ghcr.io/myorg/myapp:v1.0.0 -o cyclonedx-json > sbom.cdx.json
# Attach SBOM as attestation
cosign attest --key cosign.key \
--type cyclonedx \
--predicate sbom.cdx.json \
ghcr.io/myorg/myapp:v1.0.0
# Verify attestation
cosign verify-attestation --key cosign.pub \
--type cyclonedx \
ghcr.io/myorg/myapp:v1.0.0
# Run scan and save results
grype ghcr.io/myorg/myapp:v1.0.0 -o json > vuln-scan.json
# Attach scan results as attestation
cosign attest --key cosign.key \
--type vuln \
--predicate vuln-scan.json \
ghcr.io/myorg/myapp:v1.0.0
# Attach SLSA provenance
cosign attest --key cosign.key \
--type slsaprovenance \
--predicate provenance.json \
ghcr.io/myorg/myapp:v1.0.0
# Verify SLSA provenance
cosign verify-attestation --key cosign.pub \
--type slsaprovenance \
ghcr.io/myorg/myapp:v1.0.0
name: Sign and Publish
on:
push:
tags: ['v*']
permissions:
contents: read
packages: write
id-token: write # Required for keyless signing
jobs:
build-sign:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: sigstore/cosign-installer@v3
- name: Login to GHCR
uses: docker/login-action@v3
with:
registry: ghcr.io
username: ${{ github.actor }}
password: ${{ secrets.GITHUB_TOKEN }}
- name: Build and push
id: build
uses: docker/build-push-action@v5
with:
push: true
tags: ghcr.io/${{ github.repository }}:${{ github.ref_name }}
- name: Sign image (keyless)
run: |
cosign sign --yes \
ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }}
- name: Generate and attach SBOM
run: |
syft ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }} -o cyclonedx-json > sbom.json
cosign attest --yes \
--type cyclonedx \
--predicate sbom.json \
ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }}
# Install policy-controller
helm repo add sigstore https://sigstore.github.io/helm-charts
helm install policy-controller sigstore/policy-controller \
--namespace cosign-system --create-namespace
# Enforce signed images in namespace
apiVersion: policy.sigstore.dev/v1beta1
kind: ClusterImagePolicy
metadata:
name: require-signed-images
spec:
images:
- glob: "ghcr.io/myorg/**"
authorities:
- keyless:
url: https://fulcio.sigstore.dev
identities:
- issuer: https://token.actions.githubusercontent.com
subjectRegExp: "https://github.com/myorg/.*"
ctlog:
url: https://rekor.sigstore.dev
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
name: verify-image-signature
spec:
validationFailureAction: Enforce
rules:
- name: verify-cosign-signature
match:
any:
- resources:
kinds: ["Pod"]
verifyImages:
- imageReferences:
- "ghcr.io/myorg/*"
attestors:
- entries:
- keyless:
subject: "https://github.com/myorg/*"
issuer: "https://token.actions.githubusercontent.com"
rekor:
url: https://rekor.sigstore.dev
# Search Rekor for image signatures
rekor-cli search --email builder@example.com
# Get specific entry
rekor-cli get --uuid <entry-uuid>
# Verify entry inclusion
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity=builder@example.com \
--certificate-oidc-issuer=https://accounts.google.com