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securitycritical PriorityID: sigstore-keyless-ephemeral-workload-attestation-production-standard

Sigstore Keyless Ephemeral Workload Identity Attestation and Verification Standard

Enforces zero-trust supply chain validation by mandating keyless, short-lived OIDC workload identity attestation via Sigstore (Fulcio and Rekor) instead of static long-lived private keys. Requires strict verification of cryptographic transparency log inclusion proofs (SETs) and cryptographic binding of ephemeral X.509 certificates to immutable CI/CD workload identity claims.

Prohibited Anti-Pattern: Persisting static cryptographic signing keys in CI/CD secrets or skipping Rekor log and Fulcio SAN identity validation during artifact verification

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---
description: Sigstore Keyless Ephemeral Workload Identity Attestation and Verification Standard - Enforces zero-trust supply chain validation by mandating keyless, short-lived OIDC workload identity attestation via Sigstore (Fulcio and Rekor) instead of static long-lived private keys. Requires strict verification of cryptographic transparency log inclusion proofs (SETs) and cryptographic binding of ephemeral X.509 certificates to immutable CI/CD workload identity claims.
globs: src/**/*.{ts,tsx,js,mjs}, scripts/**/*.{ts,js,mjs,sh}, .github/workflows/**/*.{yml,yaml}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/sigstore-keyless-ephemeral-workload-attestation-production-standard"
---

# Sigstore Keyless Ephemeral Workload Identity Attestation and Verification Standard

> **Severity**: CRITICAL | **Category**: security
> **Anti-Pattern Warning**: Persisting static cryptographic signing keys in CI/CD secrets or skipping Rekor log and Fulcio SAN identity validation during artifact verification

## System Constraints
You are a Principal Software Architect enforcing the Sigstore Keyless Ephemeral Workload Identity Attestation Pipeline standard. Mandate invariants that eliminate long-lived signing keys, validate workload identity SANs against cryptographic root-of-trust bundles, and require immutable transparency log entry verification.

## Strict Guidelines
- Engineers MUST NEVER provision, inject, or persist static long-lived private cryptographic keys (e.g., COSIGN_KEY, GPG keys) into CI/CD runner secrets or configuration files.
- Engineers MUST ALWAYS leverage ambient OIDC tokens with an audience explicitly scoped to 'sigstore' to obtain ephemeral, short-lived X.509 certificates from Fulcio.
- Verification routines MUST explicitly validate the Subject Alternative Name (SAN) of the leaf certificate, including the issuer URI (e.g., https://token.actions.githubusercontent.com) and the identity URI or subject (e.g., workflow repository path and reference).
- Verification routines MUST validate the Rekor transparency log inclusion proof and Signed Entry Timestamp (SET), verifying artifact existence within the log before the ephemeral certificate expired.
- Build and deployment pipelines MUST reject artifacts accompanied only by unanchored signatures or detached signatures lacking Rekor bundle inclusion proofs.
- Components NEVER accept arbitrary trusted root overrides unless anchored directly to a validated enterprise or public Sigstore TUF (The Update Framework) root.

## Bad vs Good Implementations
### Artifact Attestation Verification with Policy Validation

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: The verification function executes verification without specifying certificate identity policies. It accepts any valid Sigstore certificate, regardless of whether it was issued to a malicious third-party repository or an unauthorized identity, and fails to assert explicit Rekor entry consistency.
```typescript
import { verify } from '@sigstore/verify';
import * as fs from 'fs';

export async function verifyArtifact(artifactPath: string, bundlePath: string): Promise<boolean> {
  const artifact = fs.readFileSync(artifactPath);
  const bundle = JSON.parse(fs.readFileSync(bundlePath, 'utf8'));

  // CRITICAL FLAW: Performs superficial signature check without validating
  // the certificate SAN identity, issuer, or Rekor transparency inclusion.
  // Any entity with any valid certificate issued by Fulcio can pass this check.
  try {
    await verify(bundle, artifact);
    return true;
  } catch (err) {
    return false;
  }
}
```

#### Production Standard (Correct)
> **Standard**: The updated routine strictly binds artifact validation to the expected OIDC issuer and workflow identity URI (SAN). It mandates at least one validated Rekor transparency log proof and Certificate Transparency log proof, rejecting unauthorized builds and forged certificates.
```typescript
import { verify } from '@sigstore/verify';
import * as fs from 'fs';

interface ExpectedIdentity {
  issuer: string;
  identityUri: string;
}

export async function verifyArtifactKeyless(
  artifactPath: string,
  bundlePath: string,
  expected: ExpectedIdentity
): Promise<void> {
  const artifact = fs.readFileSync(artifactPath);
  const rawBundle = fs.readFileSync(bundlePath, 'utf8');
  const bundle = JSON.parse(rawBundle);

  // SECURE: Enforces strict SAN claims, valid OIDC issuer match,
  // and mandatory Rekor transparency log verification via Sigstore TUF root.
  await verify(bundle, artifact, {
    certificateIssuer: expected.issuer,
    certificateIdentityURI: expected.identityUri,
    tlogThreshold: 1,
    ctlogThreshold: 1
  });
}
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

GitHub Actions & OIDC Context Inspector
Inspects and validates repository workflow identity configurations, OIDC token claims, and audience parameters.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Cosign Security CLI
Container signing, verification, and storage in OCI registries using keyless Fulcio and Rekor primitives.
Gitsign Git Commit Attestation
Keyless Git commit signing and verification based on Sigstore ephemeral certificates.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Sigstore Keyless Ephemeral Workload Identity Attestation and Verification Standard

Sigstore Keyless Ephemeral Workload Identity Attestation and Verification Standard defines an industrial-grade behavioral standard for security engineering. Enforces zero-trust supply chain validation by mandating keyless, short-lived OIDC workload identity attestation via Sigstore (Fulcio and Rekor) instead of static long-lived private keys. Requires strict verification of cryptographic transparency log inclusion proofs (SETs) and cryptographic binding of ephemeral X.509 certificates to immutable CI/CD workload identity claims. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Persisting static cryptographic signing keys in CI/CD secrets or skipping Rekor log and Fulcio SAN identity validation during artifact verification Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftPersisting static cryptographic signing keys in CI/CD secrets or skipping Rekor log and Fulcio SAN identity validation during artifact verificationCritical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Engineers MUST NEVER provision, inject, or persist static long-lived private cryptographic keys (e.g., COSIGN_KEY, GPG keys) into CI/CD runner secrets or configuration files.

Engineers MUST NEVER provision, inject, or persist static long-lived private cryptographic keys (e.g., COSIGN_KEY, GPG keys) into CI/CD runner secrets or configuration files.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Engineers MUST ALWAYS leverage ambient OIDC tokens with an audience explicitly scoped to 'sigstore' to obtain ephemeral, short-lived X.509 certificates from Fulcio.

Engineers MUST ALWAYS leverage ambient OIDC tokens with an audience explicitly scoped to 'sigstore' to obtain ephemeral, short-lived X.509 certificates from Fulcio.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Verification routines MUST explicitly validate the Subject Alternative Name (SAN) of the leaf certificate, including the issuer URI (e.g., https

Verification routines MUST explicitly validate the Subject Alternative Name (SAN) of the leaf certificate, including the issuer URI (e.g., https://token.actions.githubusercontent.com) and the identity URI or subject (e.g., workflow repository path and reference).

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Verification routines MUST validate the Rekor transparency log inclusion proof and Signed Entry Timestamp (SET), verifying artifact existence within the log before the ephemeral certificate expired.

Verification routines MUST validate the Rekor transparency log inclusion proof and Signed Entry Timestamp (SET), verifying artifact existence within the log before the ephemeral certificate expired.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

Build and deployment pipelines MUST reject artifacts accompanied only by unanchored signatures or detached signatures lacking Rekor bundle inclusion proofs.

Build and deployment pipelines MUST reject artifacts accompanied only by unanchored signatures or detached signatures lacking Rekor bundle inclusion proofs.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
6

Components NEVER accept arbitrary trusted root overrides unless anchored directly to a validated enterprise or public Sigstore TUF (The Update Framework) root.

Components NEVER accept arbitrary trusted root overrides unless anchored directly to a validated enterprise or public Sigstore TUF (The Update Framework) root.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Sigstore Keyless Ephemeral Workload Identity Attestation and Verification Standard critical for AI coding assistants?

Enforces zero-trust supply chain validation by mandating keyless, short-lived OIDC workload identity attestation via Sigstore (Fulcio and Rekor) instead of static long-lived private keys. Requires strict verification of cryptographic transparency log inclusion proofs (SETs) and cryptographic binding of ephemeral X.509 certificates to immutable CI/CD workload identity claims. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Persisting static cryptographic signing keys in CI/CD secrets or skipping Rekor log and Fulcio SAN identity validation during artifact verification) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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