implementing-supply-chain-security-with-in-toto

Implement software supply chain integrity verification for container builds using the in-toto framework, covering signing-key generation, defining a supply chain layout, recording pipeline steps as signed link metadata, verifying before deployment, Kubernetes admission control, and SLSA integration. Use when generating in-toto attestations for CI/CD pipeline steps, verifying that a container image followed an approved build process, or enforcing supply chain provenance at admission time.

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Repository: mukul975/Anthropic-Cybersecurity-Skills
Last source activity: August 2, 2026 at 16:32
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name	implementing-supply-chain-security-with-in-toto
description	Implement software supply chain integrity verification for container builds using the in-toto framework, covering signing-key generation, defining a supply chain layout, recording pipeline steps as signed link metadata, verifying before deployment, Kubernetes admission control, and SLSA integration. Use when generating in-toto attestations for CI/CD pipeline steps, verifying that a container image followed an approved build process, or enforcing supply chain provenance at admission time.
domain	cybersecurity
subdomain	container-security
tags	["in-toto","supply-chain-security","attestation","slsa","sigstore","container-security","cncf","provenance","sbom"]
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 Supply Chain Security with in-toto

Overview

in-toto is a CNCF graduated project that ensures the integrity of software supply chains from initiation to end-user installation. It creates a verifiable record of the entire software development lifecycle by generating cryptographically signed attestations (called "link metadata") at each step, proving what happened, who performed it, and what artifacts were produced. For container environments, in-toto verifies that images deployed to Kubernetes followed approved build processes and have not been tampered with.

When to Use

When deploying or configuring implementing supply chain security with in toto 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

Python 3.8+ or Go runtime for in-toto client libraries
GPG or Ed25519 keys for signing attestations
Container build pipeline (Docker, Buildah, or Kaniko)
Container registry (Docker Hub, ECR, GCR, or Harbor)
Kubernetes cluster for deployment verification

Core Concepts

Supply Chain Layout

The layout is the central policy document that defines:

Steps: Ordered operations in the supply chain (clone, build, test, package, push)
Functionaries: Authorized entities (people or CI systems) that perform each step
Inspections: Client-side verification checks performed at verification time
Expected artifacts: Input/output relationships between steps

from in_toto.models.layout import Layout, Step, Inspection
from securesystemslib.interface import import_ed25519_privatekey_from_file

# Create the supply chain layout
layout = Layout()
layout.set_relative_expiration(months=3)

# Define the code clone step
step_clone = Step(name="clone")
step_clone.expected_materials = []
step_clone.expected_products = [["CREATE", "src/*"]]
step_clone.pubkeys = [clone_functionary_keyid]
step_clone.expected_command = ["git", ]
step_clone.threshold = 


step_build = Step(name=)
step_build.expected_materials = [[, , , , , ]]
step_build.expected_products = [[, ]]
step_build.pubkeys = [build_functionary_keyid]
step_build.expected_command = [, ]
step_build.threshold = 


step_scan = Step(name=)
step_scan.expected_materials = [[, , , , , ]]
step_scan.expected_products = [[, ]]
step_scan.pubkeys = [scan_functionary_keyid]
step_scan.threshold = 

layout.steps = [step_clone, step_build, step_scan]

# Generate Ed25519 key pairs for each functionary
mkdir -p keys

# Project owner key (signs the layout)
in-toto-keygen --type ed25519 keys/owner

# CI builder key
in-toto-keygen --type ed25519 keys/builder

# Security scanner key
in-toto-keygen --type ed25519 keys/scanner

#!/usr/bin/env python3
"""Generate in-toto supply chain layout for container builds."""

from in_toto.models.layout import Layout, Step, Inspection
from in_toto.models.metadata import Envelope
from securesystemslib.signer import CryptoSigner
from securesystemslib.interface import import_ed25519_publickey_from_file

def create_container_build_layout():
    layout = Layout()
    layout.set_relative_expiration(months=6)

    # Load functionary public keys
    builder_key = import_ed25519_publickey_from_file("keys/builder.pub")
    scanner_key = import_ed25519_publickey_from_file("keys/scanner.pub")

    layout.keys = {
        builder_key["keyid"]: builder_key,
        scanner_key["keyid"]: scanner_key,
    }

    # Step 1: Source code checkout
    checkout = Step(name="checkout")
    checkout.expected_materials = []
    checkout.expected_products = [
        ["CREATE", "Dockerfile"],
        ["CREATE", "src/*"],
        ["CREATE", "requirements.txt"],
    ]
    checkout.pubkeys = [builder_key["keyid"]]
    checkout.threshold = 1

    # Step 2: Build container image
    build = Step(name="build")
    build.expected_materials = [
        ["MATCH", "Dockerfile", "WITH", "PRODUCTS", "FROM", "checkout"],
        ["MATCH", "src/*", "WITH", "PRODUCTS", "FROM", "checkout"],
    ]
    build.expected_products = [["CREATE", "image-digest.txt"]]
    build.pubkeys = [builder_key["keyid"]]
    build.threshold = 1

    # Step 3: Security scan
    scan = Step(name="scan")
    scan.expected_materials = [
        ["MATCH", "image-digest.txt", "WITH", "PRODUCTS", "FROM", "build"]
    ]
    scan.expected_products = [
        ["CREATE", "vulnerability-report.json"],
        ["CREATE", "sbom.json"],
    ]
    scan.pubkeys = [scanner_key["keyid"]]
    scan.threshold = 1

    # Inspection: Verify no critical vulnerabilities
    inspect_vulns = Inspection(name="verify-no-critical-vulns")
    inspect_vulns.expected_materials = [
        ["MATCH", "vulnerability-report.json", "WITH", "PRODUCTS", "FROM", "scan"]
    ]
    inspect_vulns.run = [
        "python", "-c",
        "import json,sys; r=json.load(open('vulnerability-report.json')); "
        "sys.exit(1) if any(v['severity']=='CRITICAL' for v in r.get('vulnerabilities',[])) else sys.exit(0)"
    ]

    layout.steps = [checkout, build, scan]
    layout.inspect = [inspect_vulns]

    return layout

if __name__ == "__main__":
    layout = create_container_build_layout()
    # Sign with owner key and save
    owner_signer = CryptoSigner.from_priv_key_uri("file:keys/owner")
    envelope = Envelope.from_signable(layout)
    envelope.create_signature(owner_signer)
    envelope.dump("root.layout")
    print("Layout created and signed: root.layout")

# In CI/CD pipeline - record each step

# Step 1: Checkout
in-toto-run --step-name checkout \
  --key keys/builder \
  --products Dockerfile src/* requirements.txt \
  -- git clone https://github.com/org/app.git .

# Step 2: Build
in-toto-run --step-name build \
  --key keys/builder \
  --materials Dockerfile src/* \
  --products image-digest.txt \
  -- bash -c "docker build -t app:latest . && docker inspect --format='{{.Id}}' app:latest > image-digest.txt"

# Step 3: Scan
in-toto-run --step-name scan \
  --key keys/scanner \
  --materials image-digest.txt \
  --products vulnerability-report.json sbom.json \
  -- bash -c "trivy image --format json app:latest > vulnerability-report.json && syft app:latest -o json > sbom.json"

# Verify the entire supply chain
in-toto-verify --layout root.layout \
  --layout-key keys/owner.pub \
  --link-dir ./link-metadata/

# If verification passes, proceed with deployment
if [ $? -eq 0 ]; then
  kubectl apply -f deployment.yaml
  echo "Supply chain verification passed - deploying"
else
  echo "SUPPLY CHAIN VERIFICATION FAILED - blocking deployment"
  exit 1
fi

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingWebhookConfiguration
metadata:
  name: in-toto-verifier
webhooks:
  - name: verify.in-toto.io
    rules:
      - apiGroups: ["apps"]
        resources: ["deployments"]
        operations: ["CREATE", "UPDATE"]
    clientConfig:
      service:
        name: in-toto-webhook
        namespace: security
        path: /verify
    failurePolicy: Fail
    sideEffects: None
    admissionReviewVersions: ["v1"]

SLSA Level	in-toto Requirement
Level 1	Build process documented (layout exists)
Level 2	Signed attestations from hosted build service
Level 3	Hardened build platform, non-falsifiable provenance
Level 4	Two-party review, hermetic builds