configuring-certificate-authority-with-openssl

Generate a self-signed Root CA certificate with basicConstraints=critical,CA:TRUE, then create an Intermediate CA signed by the root with pathlen:0. Keep the root key offline and use 4096-bit RSA or P-384 ECDSA for both CA keys.

Create a CSR for the server, then sign it with the Intermediate CA including extendedKeyUsage=serverAuth and a crlDistributionPoints extension. Verify the result chains correctly with openssl verify -CAfile root.pem -untrusted intermediate.pem leaf.pem.

CA keys should use a minimum of 4096-bit RSA or P-384 ECDSA, and the root key must be stored offline or in an air-gapped HSM. Signing algorithms must be SHA-256 or SHA-384; SHA-1 and MD5 signatures are forgeable and must be rejected.

Common causes include missing basicConstraints=critical,CA:TRUE, absent nameConstraints allowing unrestricted signing, or an incomplete chain file. Check extensions with openssl x509 -text -noout and confirm the full chain verifies against the root.

Yes, OpenSSL can generate Certificate Revocation Lists and the CA certificates should embed crlDistributionPoints and authorityInfoAccess extensions pointing to the CRL URL and OCSP responder. Revoked certificates must appear in the published CRL for revocation checking to work.