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implementing-sigstore-for-software-signing

Implements Sigstore keyless signing and verification for container images and software artifacts.

954|172|Updated Mar 13, 2026
Search Tags:#supply chain security#OIDC#sigstore#rekor#container signing#Cosign#keyless signing
One-click install
npx skills add https://github.com/xalgord/xalgorix --skill implementing-sigstore-for-software-signing
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: implementing-sigstore-for-software-signing
Source: https://github.com/xalgord/xalgorix/tree/main/internal/tools/skills/data/supply-chain-security/implementing-sigstore-for-software-signing
Command: npx skills add https://github.com/xalgord/xalgorix --skill implementing-sigstore-for-software-signing

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill requires sigstore, requests, cryptography.

What problem does it solve?

Teams need to prove that container images and build artifacts came from their own CI pipelines without managing long-lived signing keys, and they need verifiable audit trails of every signing event.

Core Features & Use Cases

  • Keyless Signing with Cosign and Fulcio: Sign container images and blobs using short-lived certificates bound to OIDC identities, eliminating private key management.
  • Rekor Transparency Log Auditing: Query and verify signing events by identity or artifact hash to confirm tamper-evident provenance.
  • CI/CD and Kubernetes Enforcement: Integrate signing into GitHub Actions and enforce signed-image policies at admission with Sigstore Policy Controller or Kyverno.
  • Use Case: A DevOps team signs images in GitHub Actions using the workflow OIDC identity, then configures a ClusterImagePolicy so the Kubernetes cluster rejects any unsigned or wrongly-signed image at deploy time.

Quick Start

Ask the assistant to sign a container image digest with Cosign keyless signing and verify it against a pinned OIDC issuer and identity.

Frequently Asked Questions about implementing-sigstore-for-software-signing

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I sign a container image with Cosign keyless signing?▼

Run cosign sign against the image digest, for example cosign sign myimage@sha256:abc123. Cosign opens an OIDC flow, obtains a short-lived Fulcio certificate, signs the digest, and records the event in Rekor. Always sign the digest, not the tag.

How do I use Cosign signing in GitHub Actions without interactive login?▼

Grant id-token: write permission in the workflow, install Cosign with the sigstore/cosign-installer action, and set SIGSTORE_ID_TOKEN from the GitHub OIDC token endpoint. Cosign then signs non-interactively using the workflow identity.

Why does cosign verify fail even though the image was signed?▼

Common causes are certificate identity or issuer mismatch, an image digest that changed after signing, or a missing Rekor entry. Pin both --certificate-oidc-issuer and a tight --certificate-identity-regexp, and confirm the signed digest matches the deployed image.

Can Sigstore keyless signing work in air-gapped or offline environments?▼

No, keyless signing requires reaching Fulcio and Rekor over the network for OIDC verification and transparency log entries. Air-gapped environments need a private Sigstore instance or traditional key-based signing instead.

How do I enforce that only signed images deploy to Kubernetes?▼

Deploy Sigstore Policy Controller or Kyverno with a ClusterImagePolicy requiring Cosign signatures from your pinned OIDC issuer and identity regex. Test by deploying an unsigned image and one signed by a different identity, confirming both are rejected.

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