Sbom Supply Chain Agent Skill

Generate, sign, and verify SBOMs and provenance attestations to secure the software supply chain. Use when implementing SLSA controls, artifact trust policies, or compliance evidence for releases.

3k tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

511

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/BagelHole/DevOps-Security-Agent-Skills --skill sbom-supply-chain

The instruction itself

19 sections, as written by the author

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...

# Attach SPDX SBOM
cosign attest --predicate sbom-spdx.json \
  --type spdx \
  ghcr.io/acme/api@sha256:abc123...

# Verify SBOM attestation
cosign verify-attestation \
  --type cyclonedx \
  --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...

# Extract the SBOM from attestation
cosign verify-attestation --type cyclonedx \
  --certificate-identity=... --certificate-oidc-issuer=... \
  ghcr.io/acme/api@sha256:abc123... | jq -r '.payload' | base64 -d | jq '.predicate'

In-toto Provenance Attestation

# Create a custom provenance attestation
cat > provenance.json << 'EOF'
{
  "buildType": "https://github.com/acme/build-system@v1",
  "builder": {
    "id": "https://github.com/acme/api/.github/workflows/build.yml@refs/heads/main"
  },
  "invocation": {
    "configSource": {
      "uri": "git+https://github.com/acme/api@refs/heads/main",
      "digest": { "sha1": "abc123def456" },
      "entryPoint": ".github/workflows/build.yml"
    }
  },
  "metadata": {
    "buildStartedOn": "2025-01-15T10:00:00Z",
    "buildFinishedOn": "2025-01-15T10:05:00Z",
    "completeness": {
      "parameters": true,
      "environment": true,
      "materials": true
    }
  },
  "materials": [
    {
      "uri": "git+https://github.com/acme/api@refs/heads/main",
      "digest": { "sha1": "abc123def456" }
    },
    {
      "uri": "pkg:docker/[email protected]",
      "digest": { "sha256": "def456..." }
    }
  ]
}
EOF

# Attach provenance attestation
cosign attest --predicate provenance.json \
  --type slsaprovenance \
  ghcr.io/acme/api@sha256:abc123...

CI/CD Pipeline Integration

# .github/workflows/sbom-supply-chain.yml
name: Build with SBOM and Signing
on:
  push:
    tags: ['v*']

permissions:
  contents: read
  packages: write
  id-token: write  # Required for keyless signing

jobs:
  build-sign-attest:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@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 image
        id: build
        uses: docker/build-push-action@v5
        with:
          push: true
          tags: ghcr.io/${{ github.repository }}:${{ github.ref_name }}

      - name: Install tools
        run: |
          curl -sSfL https://raw.githubusercontent.com/anchore/syft/main/install.sh | sh -s -- -b /usr/local/bin
          curl -sSfL https://raw.githubusercontent.com/anchore/grype/main/install.sh | sh -s -- -b /usr/local/bin

      - name: Generate SBOM
        run: |
          syft ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }} \
            -o cyclonedx-json=sbom-cdx.json \
            -o spdx-json=sbom-spdx.json

      - name: Scan SBOM for vulnerabilities
        run: |
          grype sbom:sbom-cdx.json --fail-on critical -o json > vuln-report.json

      - name: Install cosign
        uses: sigstore/cosign-installer@v3

      - name: Sign image (keyless)
        run: |
          cosign sign ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }}

      - name: Attach SBOM attestation
        run: |
          cosign attest --predicate sbom-cdx.json \
            --type cyclonedx \
            ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }}

      - name: Upload artifacts
        uses: actions/upload-artifact@v4
        with:
          name: sbom-and-reports
          path: |
            sbom-cdx.json
            sbom-spdx.json
            vuln-report.json

Policy Enforcement

Kyverno Policy: Require Signed Images with SBOM

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-signed-images-with-sbom
spec:
  validationFailureAction: Enforce
  webhookTimeoutSeconds: 30
  rules:
    - name: verify-signature
      match:
        any:
          - resources:
              kinds: ["Pod"]
      verifyImages:
        - imageReferences: ["ghcr.io/acme/*"]
          attestors:
            - entries:
                - keyless:
                    subject: "https://github.com/acme/*"
                    issuer: "https://token.actions.githubusercontent.com"
                    rekor:
                      url: "https://rekor.sigstore.dev"
          attestations:
            - type: cyclonedx
              conditions:
                - all:
                    - key: "{{ components[].name }}"
                      operator: AllNotIn
                      value: ["log4j-core"]

OPA Policy: Verify SBOM Before Deploy

package sbom.verify

import rego.v1

default allow := false

allow if {
    sbom_present
    no_critical_vulns
    signed_by_ci
}

sbom_present if {
    input.attestations.cyclonedx != null
    count(input.attestations.cyclonedx.components) > 0
}

no_critical_vulns if {
    not any_critical
}

any_critical if {
    some vuln in input.vulnerability_report.matches
    vuln.vulnerability.severity == "Critical"
    vuln.vulnerability.fix.state == "fixed"
}

signed_by_ci if {
    input.signature.issuer == "https://token.actions.githubusercontent.com"
    startswith(input.signature.subject, "https://github.com/acme/")
}

Troubleshooting

| Problem | Cause | Solution |

|---------|-------|----------|

| Syft misses dependencies | Unsupported package manager or format | Check syft catalogers list; use cdxgen for deeper analysis; contribute upstream |

| Cosign sign fails with "no identity token" | Missing OIDC provider in CI | Ensure id-token: write permission in GitHub Actions; check OIDC provider config |

| Grype reports false positives | Package version detection incorrect | Verify SBOM accuracy; report to grype GitHub; add ignore rules for confirmed FPs |

| SBOM attestation too large | Large image with many dependencies | Compress SBOM; use SPDX compact format; consider splitting per layer |

| Verification fails in admission controller | Wrong identity or issuer URL | Check exact --certificate-identity and --certificate-oidc-issuer values |

| cdxgen produces empty SBOM | Project type not detected | Specify type explicitly with -t; ensure manifest files (package.json, etc.) exist |

Best Practices

Generate SBOMs in both CycloneDX and SPDX for maximum compatibility
Sign all release artifacts with keyless signing (Sigstore/Fulcio)
Attach SBOMs as in-toto attestations to container images
Scan SBOMs for vulnerabilities in CI and block on critical findings
Archive SBOMs for every release for audit and incident response
Enforce signature verification in admission controllers (Kyverno, OPA)
Monitor for new CVEs against stored SBOMs continuously
Include SBOM generation in every build pipeline, not just releases
Track SBOM completeness metrics (percentage of deps captured)
Establish a VEX (Vulnerability Exploitability eXchange) process for false positives

dependency-scanning - Library vulnerability triage
container-scanning - Container CVE scanning
policy-as-code - Policy enforcement
model-supply-chain-security - ML artifact trust

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How to use it

Copy the folder

Take bagelhole/sbom-supply-chain from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

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Install what it needs

The instructions reference npm. Without those the skill loads but fails at the first command.

Sbom Supply Chain Agent Skill

Install

The instruction itself

SBOM & Supply Chain Security

When to Use This Skill

Prerequisites

SBOM Formats

CycloneDX vs SPDX Comparison

Syft SBOM Generation

cdxgen SBOM Generation

Vulnerability Matching

Cosign Signing and Attestation

Image Signing

SBOM Attestation

In-toto Provenance Attestation

CI/CD Pipeline Integration

Policy Enforcement

Kyverno Policy: Require Signed Images with SBOM

OPA Policy: Verify SBOM Before Deploy

Troubleshooting

Best Practices

Related Skills

Other skills for the same job

How to use it