# configuring-certificate-authority-with-openssl

> Build a two-tier PKI hierarchy (Root CA + Intermediate CA) using OpenSSL and Python, including certificate issuance, CRL distribution, OCSP responder configuration, and certificate policy management.

- Skill: `mukul975/configuring-certificate-authority-with-openssl` (Agent Skill, multi-file: 8 files)
- Install (CLI): `npx skillmds add mukul975/configuring-certificate-authority-with-openssl`
- Raw SKILL.md: https://api.skillmd.com/api/skills/mukul975/configuring-certificate-authority-with-openssl/raw
- Safety review: CAUTION (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security, Coding & Dev Tools, DevOps & Infra, Infrastructure as Code, Secure Coding
- Tags: Certificate Authority, Crl, Ocsp, Openssl, Pki, Python Cryptography, Tls, X509
- License: Apache-2.0
- Author: mukul975 (https://skillmd.com/u/mukul975)
- Updated: 2026-07-06
- Page: https://skillmd.com/skills/mukul975/configuring-certificate-authority-with-openssl

---

# Configuring Certificate Authority with OpenSSL

## Overview

A Certificate Authority (CA) is the trust anchor in a PKI hierarchy, responsible for issuing, signing, and revoking digital certificates. This skill covers building a two-tier CA hierarchy (Root CA + Intermediate CA) using OpenSSL and the Python cryptography library, including CRL distribution, OCSP responder configuration, and certificate policy management.


## When to Use

- When deploying or configuring configuring certificate authority with openssl 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

- Familiarity with cryptography concepts and tools
- Access to a test or lab environment for safe execution
- Python 3.8+ with required dependencies installed
- Appropriate authorization for any testing activities

## Objectives

- Create a Root CA with self-signed certificate
- Create an Intermediate CA signed by the Root CA
- Issue server and client certificates from the Intermediate CA
- Configure Certificate Revocation Lists (CRLs)
- Implement certificate policies and constraints
- Build a complete PKI hierarchy programmatically

## Key Concepts

### CA Hierarchy

```
Root CA (offline, air-gapped)
  |
  +-- Intermediate CA (online, operational)
        |
        +-- Server Certificates
        +-- Client Certificates
        +-- Code Signing Certificates
```

### Certificate Extensions

| Extension | Purpose | Critical |
|-----------|---------|----------|
| basicConstraints | CA:TRUE/FALSE, pathLenConstraint | Yes |
| keyUsage | keyCertSign, cRLSign, digitalSignature | Yes |
| extendedKeyUsage | serverAuth, clientAuth, codeSigning | No |
| subjectKeyIdentifier | Hash of public key | No |
| authorityKeyIdentifier | Issuer's key identifier | No |
| crlDistributionPoints | URL to CRL | No |
| authorityInfoAccess | OCSP responder URL | No |

## Security Considerations

- Root CA private key must be stored offline (air-gapped HSM)
- Use minimum 4096-bit RSA or P-384 ECDSA for CA keys
- Set path length constraints on intermediate CAs
- Implement certificate policies (OIDs)
- Enable CRL and OCSP for revocation checking
- Audit all certificate issuance operations

## Validation Criteria

- [ ] Root CA self-signed certificate is valid
- [ ] Intermediate CA certificate chains to Root CA
- [ ] Issued certificates chain to Intermediate -> Root
- [ ] Path length constraints are enforced
- [ ] CRL is generated and accessible
- [ ] Revoked certificates appear in CRL
- [ ] Certificate policies are correctly embedded