SBOM & Supply Chain Security

Improve release trust with reproducible metadata and verification gates.

When to Use This Skill

Use this skill when:

• Producing SBOMs for container images or application builds
• Verifying dependencies before deploy
• Enforcing signed artifact and provenance policies
• Preparing for SOC2, ISO 27001, or customer security reviews
• Implementing SLSA framework requirements
• Responding to supply chain vulnerabilities (e.g., Log4Shell-style events)

Prerequisites

• syft installed for SBOM generation
• cdxgen installed for CycloneDX SBOM generation
• grype for vulnerability matching against SBOMs
• cosign v2+ for signing and attestation
• Container registry with OCI artifact support
• CI/CD pipeline with OIDC identity for keyless signing

SBOM Formats

CycloneDX vs SPDX Comparison

comparison:
  cyclonedx:
    standard: "OWASP CycloneDX"
    focus: "Application security, vulnerability tracking"
    formats: ["JSON", "XML", "Protocol Buffers"]
    strengths:
      - Vulnerability references (VEX support)
      - Service and API dependency tracking
      - Hardware BOM support
    best_for: "Security-focused SBOM, vulnerability management"

  spdx:
    standard: "Linux Foundation SPDX (ISO/IEC 5962:2021)"
    focus: "License compliance, legal review"
    formats: ["JSON", "RDF/XML", "Tag-Value", "YAML"]
    strengths:
      - ISO standard
      - License expression language
      - Relationship modeling
    best_for: "License compliance, regulatory requirements"

Syft SBOM Generation

# Generate SBOM for a container image (CycloneDX JSON)
syft ghcr.io/acme/api:v1.2.3 -o cyclonedx-json > sbom-cyclonedx.json

# Generate SBOM in SPDX format
syft ghcr.io/acme/api:v1.2.3 -o spdx-json > sbom-spdx.json

# Generate SBOM from a local directory (source code)
syft dir:. -o cyclonedx-json > sbom-source.json

# Generate SBOM from a Dockerfile/built image
syft docker:my-local-image:latest -o cyclonedx-json > sbom-local.json

# Generate SBOM for a specific package ecosystem
syft dir:. --catalogers python -o cyclonedx-json > sbom-python.json

# Include file hashes for deeper analysis
syft ghcr.io/acme/api:v1.2.3 -o cyclonedx-json --file-metadata > sbom-with-hashes.json

# Multiple output formats simultaneously
syft ghcr.io/acme/api:v1.2.3 \
  -o cyclonedx-json=sbom-cdx.json \
  -o spdx-json=sbom-spdx.json \
  -o table=sbom-summary.txt

cdxgen SBOM Generation

# Install cdxgen
npm install -g @cyclonedx/cdxgen

# Generate CycloneDX SBOM for a project directory
cdxgen -o sbom.json .

# Specify project type
cdxgen -t python -o sbom-python.json .
cdxgen -t java -o sbom-java.json .
cdxgen -t node -o sbom-node.json .
cdxgen -t go -o sbom-go.json .

# Generate SBOM with evidence (call stacks, file occurrences)
cdxgen --evidence -o sbom-with-evidence.json .

# Generate for a container image
cdxgen -t docker -o sbom-container.json ghcr.io/acme/api:v1.2.3

# Generate with deep analysis (slower but more accurate)
cdxgen --deep -o sbom-deep.json .

# Output in different formats
cdxgen -o sbom.xml --format xml .

Vulnerability Matching

# Scan SBOM for vulnerabilities with Grype
grype sbom:sbom-cyclonedx.json

# Fail on critical/high vulnerabilities
grype sbom:sbom-cyclonedx.json --fail-on high

# Output as JSON for CI processing
grype sbom:sbom-cyclonedx.json -o json > vulnerability-report.json

# Scan container image directly
grype ghcr.io/acme/api:v1.2.3

# Use Trivy with SBOM input
trivy sbom sbom-cyclonedx.json

# Trivy scan with severity filter
trivy sbom sbom-cyclonedx.json --severity CRITICAL,HIGH --exit-code 1

Cosign Signing and Attestation

Image Signing

# Keyless signing (recommended - uses OIDC identity from CI)
cosign sign ghcr.io/acme/api@sha256:abc123...

# Sign with a key pair
cosign generate-key-pair
cosign sign --key cosign.key ghcr.io/acme/api@sha256:abc123...

# Verify keyless signature
cosign verify \
  --certificate-identity=https://github.com/acme/api/.github/workflows/build.yml@refs/heads/main \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  ghcr.io/acme/api@sha256:abc123...

# Verify with key
cosign verify --key cosign.pub ghcr.io/acme/api@sha256:abc123...

SBOM Attestation

# Attach SBOM as an in-toto attestation to a container image
cosign attest --predicate sbom-cyclonedx.json \
  --type cyclonedx \
  ghcr.io/acme/api@sha256:abc123...


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