Monday, March 21, 2016

HOWTO - use openssl on linux - a bunch of useful openssl commands to use


Generate CSRs, Certificates, Private Keys and do other miscellaneous tasks:

Generate a new private key and Certificate Signing Request
  • openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key

Generate a self-signed certificate
  • openssl req -x509 -sha256 -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 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 a normal PEM file that would work with Apache to a PFX (PKCS#12) file and use it with Tomcat or IIS.
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.
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

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