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implementing-image-provenance-verification-with-cosign Sign and verify container image provenance using Sigstore Cosign with keyless OIDC-based signing, attestations, and Kubernetes admission enforcement. Use when working with implementing image provenance verification with cosign.
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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. Use when working with implementing image provenance verification with cosign. domain cybersecurity subdomain container-security tags ["cosign","sigstore","image-signing","supply-chain","provenance","keyless","slsa"] version 1.0 author oyi77 license Apache-2.0 nist_csf ["PR.PS-01","PR.IR-01","ID.AM-08","DE.CM-01"]
Implementing Image Provenance Verification with Cosign
Overview
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.
When to Use
Trigger phrases:
"implementing image provenance verification with cosign"
"Sign and verify container image provenance using Sigstore Cosign with keyless OI"
When deploying or configuring implementing image provenance verification with cosign capabilities in your environment
When establishing security controls aligned to compliance requirements
When building or improving security architecture for this domain
When conducting security assessments that require this implementation
Prerequisites
Cosign CLI installed
Docker or Podman for building images
OCI-compliant container registry (Docker Hub, GHCR, GCR, ECR)
OIDC provider account (GitHub, Google, Microsoft) for keyless signing
Installing Cosign
go install github.com/sigstore/cosign/v2/cmd/cosign@latest
brew install cosign
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
cosign version
Key-Based Signing
This section covers key-based signing for implementing image provenance verification with cosign.
Ensure all prerequisites are met before proceeding
Follow the documented workflow steps in sequence
Record results and any anomalies encountered during this phase
Generate Key Pair
cosign generate-key-pair
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 Image with Key
cosign sign --key cosign.key ghcr.io/myorg/myapp:v1.0.0
cosign sign --key cosign.key \
-a "build-id=12345" \
-a "git-sha=$(git rev-parse HEAD) " \
ghcr.io/myorg/myapp:v1.0.0
Verify Image with Key
cosign verify --key cosign.pub ghcr.io/myorg/myapp:v1.0.0
cosign verify --key cosign.pub \
-a "build-id=12345" \
ghcr.io/myorg/myapp:v1.0.0
Keyless Signing (OIDC) This section covers keyless signing (oidc) for implementing image provenance verification with cosign.
Ensure all prerequisites are met before proceeding
Follow the documented workflow steps in sequence
Record results and any anomalies encountered during this phase
Sign with Keyless (Interactive)
cosign sign ghcr.io/myorg/myapp:v1.0.0
Sign with Keyless (CI/CD - Non-Interactive)
cosign sign ghcr.io/myorg/myapp:v1.0.0 \
--yes
cosign sign ghcr.io/myorg/myapp:v1.0.0 \
--identity-token=$(cat /var/run/sigstore/cosign/oidc-token) \
--yes
Verify Keyless Signature
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity=builder@example.com \
--certificate-oidc-issuer=https://accounts.google.com
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
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity-regexp=".*@example.com" \
--certificate-oidc-issuer=https://accounts.google.com
Attestations (SLSA Provenance) This section covers attestations (slsa provenance) for implementing image provenance verification with cosign.
Ensure all prerequisites are met before proceeding
Follow the documented workflow steps in sequence
Record results and any anomalies encountered during this phase
Attach SBOM Attestation
syft ghcr.io/myorg/myapp:v1.0.0 -o cyclonedx-json > sbom.cdx.json
cosign attest --key cosign.key \
--type cyclonedx \
--predicate sbom.cdx.json \
ghcr.io/myorg/myapp:v1.0.0
cosign verify-attestation --key cosign.pub \
--type cyclonedx \
ghcr.io/myorg/myapp:v1.0.0
Attach Vulnerability Scan Attestation
grype ghcr.io/myorg/myapp:v1.0.0 -o json > vuln-scan.json
cosign attest --key cosign.key \
--type vuln \
--predicate vuln-scan.json \
ghcr.io/myorg/myapp:v1.0.0
SLSA Provenance Attestation
cosign attest --key cosign.key \
--type slsaprovenance \
--predicate provenance.json \
ghcr.io/myorg/myapp:v1.0.0
cosign verify-attestation --key cosign.pub \
--type slsaprovenance \
ghcr.io/myorg/myapp:v1.0.0
CI/CD Integration This section covers ci/cd integration for implementing image provenance verification with cosign.
Ensure all prerequisites are met before proceeding
Follow the documented workflow steps in sequence
Record results and any anomalies encountered during this phase
GitHub Actions name: Sign and Publish
on:
push:
tags: ['v*' ]
permissions:
contents: read
packages: write
id-token: write
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 }}
Kubernetes Admission Enforcement This section covers kubernetes admission enforcement for implementing image provenance verification with cosign.
Ensure all prerequisites are met before proceeding
Follow the documented workflow steps in sequence
Record results and any anomalies encountered during this phase
Policy Controller (Sigstore)
helm repo add sigstore https://sigstore.github.io/helm-charts
helm install policy-controller sigstore/policy-controller \
--namespace cosign-system --create-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
Kyverno Integration 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
Transparency Log (Rekor)
rekor-cli search --email builder@example.com
rekor-cli get --uuid <entry-uuid>
cosign verify ghcr.io/myorg/myapp:v1.0.0 \
--certificate-identity=builder@example.com \
--certificate-oidc-issuer=https://accounts.google.com
Best Practices
Use keyless signing in CI/CD for automated pipelinesSign by digest not by tag for immutable referencesAttach SBOM attestations alongside signaturesEnforce signatures at admission with policy-controller or KyvernoUse OIDC identity verification instead of just key verificationStore keys in KMS (AWS KMS, GCP KMS, HashiCorp Vault) for key-based signingVerify the full chain : signature + certificate + Rekor inclusionInclude build metadata as annotations on signatures
When NOT to Use
You need to test the implementation (use performing-* skills)
Task is about configuring existing tools (use configuring-* skills)
You need to analyze security events (use analyzing-* skills)
Task is about building detection rules (use building-* skills)
You don't have access to the target environment
Task requires vendor-specific expertise (consult vendor docs)
Red Flags
Performing actions without explicit written authorization from the asset owner
Testing against production systems without a defined scope and rules of engagement
Failing to use write-blockers when acquiring forensic evidence
Not verifying hash integrity before and after imaging
Modifying original evidence during analysis
Verification
All steps executed successfully against a test environment before production use
Output documented with screenshots or logs demonstrating expected behavior
Hash values computed and verified match between source and image
Chain of custody log complete with timestamps and examiner names
Analysis tools and versions documented for reproducibility
Process
Analyze the task requirements
Apply domain expertise
Verify output quality
Anti-Rationalization Table Rationalization Reality "We are too small to be targeted" Automated attacks target everyone. Size does not matter. "Security slows us down" A breach slows you down 100x more. Build security in from the start. "We will fix it after launch" Vulnerabilities in production are exploited within hours. Fix before deploy.
