openssl

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

Verify a certificate and key matches
These two commands print out md5 checksums of the certificate and key; the checksums can be compared to verify that the certificate and key match.
openssl x509 -noout -modulus -in server.crt | openssl md5
openssl rsa -noout -modulus -in server.key | openssl md5