| name | configuring-certificate-authority-with-openssl |
| description | 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 + |
| domain | cybersecurity |
| subdomain | cryptography |
| tags | ["cryptography","pki","certificate-authority","openssl","x509"] |
| version | 1.0 |
| author | mahipal |
| license | Apache-2.0 |
| nist_csf | ["PR.DS-01","PR.DS-02","PR.DS-10"] |
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
Common Misconfigurations & Verification
- No
nameConstraints on the intermediate CA: an unconstrained intermediate can sign a cert for any domain. Add a critical nameConstraints=permitted;DNS:.example.com extension and verify with openssl x509 -text -noout | grep -A2 "Name Constraints".
- Missing
basicConstraints=critical,CA:TRUE,pathlen:0: without pathlen:0 an issuing CA can mint further sub-CAs. Confirm the leaf certs have CA:FALSE.
- Weak signature algorithm: a CA signing with
sha1WithRSAEncryption (or MD5) is trivially forgeable. Force -sha256/-sha384 and reject SHA-1 with openssl x509 -text | grep "Signature Algorithm".
- Root key online / not air-gapped, or RSA <4096 / not P-384: root keys must be offline. Use 4096-bit RSA or P-384 ECDSA.
keyUsage not marked critical or includes too much: CA certs need keyCertSign,cRLSign only; leaf certs must NOT have keyCertSign.- No CRL/OCSP distribution point: revocation is impossible. Verify
crlDistributionPoints and authorityInfoAccess are present.
- Verify the chain end-to-end:
openssl verify -CAfile root.pem -untrusted intermediate.pem leaf.pem must return OK, and a cert signed by an untrusted/rogue CA MUST be rejected. Test that a cert violating a name constraint fails validation, not just that valid ones pass.
Prerequisites
