How can I verify that an SSL certificate file matches the key file?

Question

I recently received an error that my SSL certificate did not match the private key. How can I validate that the cert matches the key?

Answer 1

You can validate that a CSR, certificate and privatekey match each other by comparing their Modulus values:

Here is the CSR modulus:

openssl req -noout -modulus -in mydomain.com.csr
Modulus=XYZ

Here is the certificate modulus:

openssl x509 -noout -modulus -in mydomain.com.cer
Modulus=XYZ

Here is the privatekey modulus:

openssl rsa -noout -modulus -in mydomain.com.key
Modulus=XYZ