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Show the SHA-256 fingerprint of a certificate

harmlessSSL and certificatesalle
Adjust the values, the command updates live
user@server
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -fingerprint -sha256

Calculates the unique SHA-256 fingerprint of the delivered certificate. Useful after replacing a certificate to determine reliably whether the server already sends the new one or still the old one held in memory by a service that was not reloaded. For comparison, openssl x509 -in datei.pem -noout -fingerprint -sha256 gives the value of the local file.

Also searched as

  • show ssl certificate fingerprint
  • is the new certificate already being served
  • sha256 fingerprint openssl

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All in SSL and certificates

Check the SSL certificate expiration date of a website

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -dates
harmlessSSL and certificates

Check whether a certificate expires within the next days

#openssl x509 -in /etc/letsencrypt/live/example.com/cert.pem -noout -checkend $(( 30 * 86400 )) && echo "noch gültig" || echo "läuft bald ab"
harmlessSSL and certificates

Check whether a private key matches a certificate

#openssl x509 -noout -modulus -in /etc/ssl/certs/example.com.crt | openssl md5 && openssl rsa -noout -modulus -in /etc/ssl/private/example.com.key | openssl md5
harmlessSSL and certificates

Check whether a website's certificate is trusted

$openssl s_client -connect example.com:443 -servername example.com -verify_hostname example.com </dev/null 2>/dev/null | grep "Verify return code"
harmlessSSL and certificates

Create a self-signed certificate for testing

$openssl req -x509 -newkey rsa:2048 -nodes -days 365 -keyout test.key -out test.crt -subj "/CN=test.example.com" -addext "subjectAltName=DNS:test.example.com"
cautionSSL and certificates

Read all domains of a certificate (SAN)

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -ext subjectAltName
harmlessSSL and certificates

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