Full certificate inspect

Dump all cert fields: subject, issuer, validity, extensions, SANs, key usage

openssl x509 -in cert.pem -noout -text
tool
openssl27 commands
tags
openssltlssecuritydebug

More openssl commands

  • Cert expiry check (CI gate)
    openssl x509 -in cert.pem -noout -checkend 86400 && echo OK || echo EXPIRING

    Exit 0 if cert valid >24h; perfect for monitoring/CI alerts on expiry

  • Inspect live server chain
    openssl s_client -connect <host>:443 -servername <host> -showcerts </dev/null 2>/dev/null

    Fetch full chain with SNI; -servername is mandatory for vhosts/SNI backends

  • Extract SAN list
    openssl x509 -in cert.pem -noout -ext subjectAltName

    Show only SAN entries; modern browsers ignore CN, so SAN is what matters

  • Verify cert against CA chain
    openssl verify -CAfile ca-chain.pem cert.pem

    Validate trust chain; note: -CAfile must hold intermediates+root in order

  • Match cert and private key
    diff <(openssl x509 -in cert.pem -noout -modulus | md5sum) <(openssl rsa -in key.pem -noout -modulus | md5sum)

    Equal modulus hashes prove key matches cert; empty diff = match

all 27 openssl commands