Extract SAN list

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

openssl x509 -in cert.pem -noout -ext subjectAltName
tool
openssl27 commands
tags
openssltlsdnssecurity

More openssl commands

  • 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

  • CSR + key in one shot
    openssl req -new -newkey rsa:2048 -nodes -keyout key.pem -out req.csr -subj "/CN=<host>" -addext "subjectAltName=DNS:<host>"

    Generate key+CSR with SAN inline; -addext avoids editing openssl.cnf

  • Self-signed cert with SAN
    openssl req -x509 -newkey rsa:2048 -nodes -keyout key.pem -out cert.pem -days 365 -subj "/CN=<host>" -addext "subjectAltName=DNS:<host>"

    One-liner self-signed cert valid 1y; SAN required or TLS clients reject it

  • PEM to PKCS12 bundle
    openssl pkcs12 -export -in cert.pem -inkey key.pem -certfile ca-chain.pem -out bundle.p12 -name <name>

    Bundle cert+key+chain into .p12 for Java keystores / Windows imports

all 27 openssl commands