Securing Container Registry Images

When to Use

• When establishing security controls for container image registries (ECR, ACR, GCR, Docker Hub)
• When building CI/CD pipelines that enforce vulnerability scanning before image promotion
• When implementing image signing and verification to prevent supply chain attacks
• When auditing existing registries for vulnerable, unscanned, or unsigned images
• When compliance requires software bill of materials (SBOM) for deployed container images

Do not use for runtime container security (use Falco or Sysdig), for Kubernetes admission control (use OPA Gatekeeper or Kyverno after establishing registry controls), or for host-level vulnerability scanning (use Amazon Inspector or Qualys).

Prerequisites

• Trivy installed (brew install trivy or apt install trivy)
• Grype installed (curl -sSfL https://raw.githubusercontent.com/anchore/grype/main/install.sh | sh)
• Cosign installed for image signing (go install github.com/sigstore/cosign/v2/cmd/cosign@latest)
• Syft installed for SBOM generation (curl -sSfL https://raw.githubusercontent.com/anchore/syft/main/install.sh | sh)
• Container registry access (ECR, ACR, GCR, or private registry)

Workflow

Step 1: Scan Images for Vulnerabilities with Trivy

Run comprehensive vulnerability scans against container images before and after pushing to the registry.

# Scan a local image for vulnerabilities
trivy image --severity HIGH,CRITICAL myapp:latest

# Scan a remote registry image
trivy image --severity HIGH,CRITICAL 123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

# Scan with JSON output for CI/CD processing
trivy image --format json --output trivy-results.json myapp:latest

# Scan for vulnerabilities AND misconfigurations
trivy image --scanners vuln,misconfig,secret myapp:latest

# Scan a specific image with SBOM output
trivy image --format spdx-json --output sbom.json myapp:latest

# Fail CI/CD if critical vulnerabilities found
trivy image --exit-code 1 --severity CRITICAL myapp:latest

Step 2: Scan with Grype for Additional Coverage

Use Grype as a complementary scanner for broader vulnerability database coverage.

# Scan image with Grype
grype myapp:latest

# Scan with severity threshold
grype myapp:latest --fail-on critical

# Output in JSON for processing
grype myapp:latest -o json > grype-results.json

# Scan an SBOM instead of the image directly
syft myapp:latest -o spdx-json > sbom.json
grype sbom:sbom.json

# Scan a directory-based image export
grype dir:/path/to/image-rootfs

Step 3: Generate Software Bill of Materials (SBOM)

Create SBOMs for all images to maintain an inventory of software components and dependencies.

# Generate SBOM with Syft in SPDX format
syft myapp:latest -o spdx-json > sbom-spdx.json

# Generate SBOM in CycloneDX format
syft myapp:latest -o cyclonedx-json > sbom-cyclonedx.json

# Attach SBOM to the image as an OCI artifact
cosign attach sbom --sbom sbom-spdx.json \
  123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

# Verify SBOM contents
syft myapp:latest -o table | head -50

Step 4: Sign Images with Cosign and Sigstore

Implement image signing to ensure image integrity and authenticity in the supply chain.

# Generate a key pair for signing
cosign generate-key-pair

# Sign an image in the registry
cosign sign --key cosign.key \
  123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

# Sign using keyless signing with Sigstore (OIDC-based)
cosign sign --yes \
  123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

# Verify image signature
cosign verify --key cosign.pub \
  123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

# Verify keyless signature
cosign verify \
  --certificate-identity developer@company.com \
  --certificate-oidc-issuer https://accounts.google.com \
  123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

# Add attestation with scan results
cosign attest --predicate trivy-results.json \
  --key cosign.key \
  123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

Step 5: Configure Registry-Level Security Controls

Set up registry-specific security features for ECR, ACR, and GCR.

# AWS ECR: Enable image scanning on push
aws ecr put-image-scanning-configuration \
  --repository-name myapp \
  --image-scanning-configuration scanOnPush=true

# ECR: Set image tag immutability (prevent tag overwrites)
aws ecr put-image-tag-mutability \

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