FAQ: Common OpenSSL Commands

While PKCS keys can (and often should) be generated  within Sentry,  PKCS private keys cannot be exported out of Sentry. Sentry administrators sometimes need to generate keys outside of Sentry - so that they have a copy of the private key outside of Sentry. 


A helpful tool to generate keys is OpenSSL, which is an open source implementation of the SSL protocol. There are versions of OpenSSL for many operating systems including Windows, Linux, and Mac. OpenSSL is commonly used to create CSRs and private keys. 


Note that Sentry does not utilize OpenSSL for TLS/SSL processing because it is an insecure open source code base.  For more information on why Sentry does not utilize OpenSSL please see: http://www.forumsys.com/tag/openssl/.


General OpenSSL Commands

These commands allow you to generate CSRs, Certificates, Private Keys and do other miscellaneous tasks.

  • Generate a new private key and Certificate Signing Request
    openssl req -sha256 -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key
  • Generate a self-signed certificate
    openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt
  • Generate a certificate signing request (CSR) for an existing private key
    openssl req -out CSR.csr -key privateKey.key -new
  • Generate a certificate signing request based on an existing certificate
    openssl x509 -x509toreq -in certificate.crt -out CSR.csr -signkey privateKey.key
  • Remove a passphrase from a private key
    openssl rsa -in privateKey.pem -out newPrivateKey.pem

Checking Using OpenSSL

If you need to check the information within a Certificate, CSR or Private Key, use these commands. 

  • 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
    openssl x509 -in certificate.crt -text -noout
  • Check a PKCS#12 file (.pfx or .p12)
    openssl pkcs12 -info -in keyStore.p12

Debugging Using OpenSSL

If you are receiving an error that the private doesn't match the certificate or that a certificate that you installed to a site is not trusted, try one of these commands.

  • Check an 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
  • Check an SSL connection. All the certificates (including Intermediates) should be displayed
    openssl s_client -connect www.paypal.com:443

Converting and Combining Using OpenSSL

These commands allow you to convert certificates and keys to different formats to make them compatible with specific types of servers or software. For example, you can convert PEM files into a PKCS#12 file that can be imported into Sentry

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

    You can add -nocerts to only output the private key or add -nokeys to only output the certificates.

  • Combine a PEM certificate file, a CA cert, and a private key to PKCS#12 (.pfx .p12)
    openssl pkcs12 -export -out certificate.p12 -inkey privateKey.key -in certificate.crt -certfile CACert.crt
  • Combine multiple PEM certificates (end user, intermediates, and root CA cert) and a PEM private key to PKCS#12 (.pfx .p12)
    First add all of the pem format certificates (without the private key) into a single PEM file.
  • openssl pkcs12 -export -inkey privatekey.pem -in certificates.pem -out keypair.p12
  • Convert PEM certificate files to PKCS#7 (.p7b)
    openssl crl2pkcs7 -nocrl -certfile certificate.pem -certfile certificate2.pem -out outfile.p7b



Article is closed for comments.