OpenSSL

Check SSL

On domain

openssl s_client -connect www.domain.com:443

Check a Certificate Signing Request (CSR)

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

Check a private key

openssl rsa -in privateKey.key -check

Check a certificate (crt or pem)

openssl x509 -in certificate.crt -text -noout

Check a PKCS#12 file (.pfx or .p12)

openssl pkcs12 -info -in keyStore.p12

Create CSR+Key

Create a CSR

openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key

Create Self-signed

openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt

Verify a CSR matches KEY

Check that MD5 hash of the public key to ensure that it matches with what is in a CSR or private key

openssl x509 -noout -modulus -in certificate.crt | openssl md5
openssl rsa -noout -modulus -in privateKey.key | openssl md5
openssl req -noout -modulus -in CSR.csr | openssl md5

Convert

Convert a DER file (.crt .cer .der) to PEM

openssl x509 -inform der -in certificate.cer -out certificate.pem

Convert a PEM file to DER

openssl x509 -outform der -in certificate.pem -out certificate.der

Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM
You can add -nocerts to only output the private key or add -nokeys to only output the certificates.

openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes

Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)

openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt