implementing-image-provenance-verification-with-cosign

name	implementing-image-provenance-verification-with-cosign
description	Signs and verifies container image provenance using Sigstore Cosign, covering key-based and keyless OIDC-based signing (Fulcio, Rekor transparency log), SLSA attestations, and enforcing signature verification via Kubernetes admission control. Use when signing container images for supply chain security, setting up keyless OIDC signing, attaching attestations, or enforcing verified-image-only policies at admission in a Kubernetes cluster.
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"]
mitre_attack	["T1610","T1611","T1609","T1525","T1195"]

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

• 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

# 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

Key-Based Signing

Generate Key Pair

# 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 Image with Key

# 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