Openssl check cert

echo "" | openssl s_client -connect google.com:443 2>&1 | grep -A 6 "Certificate cha
in"

Check a certificate:
Check a certificate and return information about it (signing authority, expiration date, etc.)

openssl x509 -in server.crt -text -noout

Check a key:
Check the SSL key and verify the consistency

openssl rsa -in server.key -check

Check a CSR:
Verify the CSR and print CSR data filled in when generating the CSR

openssl req -text -noout -verify -in server.csr