Implementing Code Signing for Artifacts

Ne Zaman Kullanılır

• establishing yaparken: artifact integrity verification to prevent supply chain tampering
• compliance yaparken: requires cryptographic proof that build artifacts are authentic and unmodified
• distributing yaparken software to customers who need to verify publisher identity
• implementing yaparken zero-trust Dağıt:ment pipelines that reject unsigned artifacts
• meeting yaparken: SLSA Level 2+ requirements for provenance and integrity

Kullanma: for encrypting artifacts (signing provides integrity, not confidentiality), for container image signing specifically (use cosign), or for source code authentication (use commit signing).

Ön Gereksinimler

• GPG key pair for traditional signing or Sigstore account for keyless signing
• Code signing certificate from a Certificate Authority for public distribution
• CI/CD pipeline with Erişim: signing keys or identity provider
• Verification infrastructure in Dağıt:ment pipelines

İş Akışı

Adım 1: Şunu üret:nd Manage Signing Keys

gpg --full-generate-key --batch <<EOF
Key-Type: eddsa
Key-Curve: ed25519
Subkey-Type: eddsa
Subkey-Curve: ed25519
Name-Real: CI Build System
Name-Email: ci-signing@company.com
Expire-Date: 1y
%no-protection
EOF

gpg --armor --export ci-signing@company.com > signing-key.pub

gpg --armor --export-secret-keys ci-signing@company.com > signing-key.priv

Adım 2: Sign Build Artifacts in CI/CD

name: Build and Sign

on:
  push:
    tags: ['v*']

jobs:
  build-sign:
    runs-on: ubuntu-latest
    permissions:
      contents: write
      id-token: write  # For Sigstore keyless signing
    steps:
      - uses: actions/checkout@v4

      - name: Build artifacts
        run: |
          make build
          sha256sum dist/* > dist/checksums.sha256

      - name: Import GPG Key
        run: |
          echo "${{ secrets.GPG_PRIVATE_KEY }}" | gpg --batch --import
          gpg --list-secret-keys

      - name: Sign artifacts
        run: |
          for file in dist/*; do
            gpg --detach-sign --armor --local-user ci-signing@company.com "$file"
          done

      - name: Install cosign for keyless signing
        uses: sigstore/cosign-installer@v3

      - name: Keyless sign with Sigstore
        run: |
          for file in dist/*.tar.gz; do
            cosign sign-blob "$file" \
              --output-signature "${file}.sig" \
              --output-certificate "${file}.cert" \
              --yes
          done

      - name: Create Release with signed artifacts
        uses: softprops/action-gh-release@v2
        with:
          files: |
            dist/*
            dist/*.asc
            dist/*.sig
            dist/*.cert

Adım 3: Verify Signatures in Dağıt:ment Pipeline

gpg --import signing-key.pub
gpg --verify artifact.tar.gz.asc artifact.tar.gz

cosign verify-blob artifact.tar.gz \
  --signature artifact.tar.gz.sig \
  --certificate artifact.tar.gz.cert \
  --certificate-identity ci-signing@company.com \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

sha256sum --check checksums.sha256

Adım 4: Sign npm Packages with Provenance

{
  "scripts": {
    "prepublishOnly": "npm run build && npm run test"
  },
  "publishConfig": {
    "provenance": true
  }
}

npm publish --provenance

Key Concepts

Term	Definition
Code Signing	Cryptographic process of signing software artifacts to verify publisher identity and artifact integrity
Detached Signature	Signature stored in a separate file from the artifact, allowing independent distribution
Keyless Signing	Sigstore's approach using short-lived certificates tied to OIDC identities instead of long-lived keys
Provenance	Metadata describing how, where, and by whom an artifact was built
Transparency Log	Append-only log (Rekor) that records all signing events for public auditability
Trust Chain	Hierarchical chain from root CA to signing certificate establishing trust in the signer's identity
SLSA	Supply-chain Levels for Software Artifacts — framework defining levels of supply chain security

Tools & Systems

• GPG/PGP: Traditional asymmetric cryptography tool for signing and verifying artifacts
• Sigstore (cosign): Modern keyless signing infrastructure using OIDC identity and transparency logs
• Rekor: Sigstore's transparency log recording all signing events immutably
• Fulcio: Sigstore's certificate authority issuing short-lived certificates bound to OIDC identities
• notation: Microsoft's artifact signing tool for OCI registries (Project Notary v2)

Common Scenarios

Scenario: Establishing Signed Release Pipeline

Context: An open-source project needs to sign release artifacts so users can verify authenticity and tespit etme
tampering.

Approach:

1. Use Sigstore keyless signing in GitHub Actions (no key management overhead)
2. Sign all release binaries with cosign sign-blob using OIDC identity
3. Şunu üret:nd sign checksums file for bulk verification
4. Upload signatures, certificates, and checksums alongside release artifacts
5. Document verification instructions in the project README
6. Add verification step to the Homebrew formula or apt repository

Pitfalls: GPG key compromise requires revoking and re-signing all artifacts. Sigstore keyless signing avoids this by using ephemeral keys. Long-lived signing keys in CI/CD secrets are a supply chain risk if the CI system is compromised.

Output Format

Artifact Signing Report
========================
Pipeline: Build and Sign v2.3.0
Date: 2026-02-23
Signing Method: Sigstore Keyless + GPG

SIGNED ARTIFACTS:
  app-v2.3.0-linux-amd64.tar.gz
    GPG:      PASS (ci-signing@company.com, EdDSA/Ed25519)
    Sigstore: PASS (Rekor entry: 24658135, Fulcio cert issued)
    SHA256:   a1b2c3d4...

  app-v2.3.0-darwin-arm64.tar.gz
    GPG:      PASS
    Sigstore: PASS (Rekor entry: 24658136)
    SHA256:   e5f6g7h8...

  checksums.sha256
    GPG:      PASS (detached signature)

TRANSPARENCY LOG:
  Entries recorded: 3
  Log index range: 24658135-24658137
  Verification: https://search.sigstore.dev

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