Advanced OpenSSL: TLS debugging, certificate inspection, and PKI operations.
medium risk
Beyond s_client, OpenSSL handles the full certificate lifecycle: inspecting cert details, verifying chains, checking expiry, generating CSRs, and testing specific TLS ciphers and protocol versions. Essential for TLS troubleshooting.
openssl s_client -connect host:443 -servername host 2>/dev/null | openssl x509 -noout -datesCheck TLS certificate expiry date · explain & risk-check →openssl x509 -in cert.pem -noout -textFull certificate details (SANs, issuer, validity) · explain & risk-check →openssl verify -CAfile ca.pem cert.pemVerify certificate against CA chain · explain & risk-check →openssl req -new -newkey rsa:2048 -nodes -keyout server.key -out server.csrGenerate private key and CSR · explain & risk-check →openssl s_client -connect host:443 -tls1_2 2>/dev/null | grep -i cipherTest specific TLS version and cipher negotiation · explain & risk-check →Use `openssl s_client -connect host:443 2>/dev/null | openssl x509 -noout -enddate` in monitoring scripts to alert on certificate expiry — check daily and alert when < 30 days remain.
Reference text is hand-written and may be incomplete — check man openssl for your version. Test destructive commands on a non-production system first.