(Ruby) Convert Java KeyStore to PKCS12 / PFX

Loads a Java keystore file and saves it as a PKCS12 / PFX. A Java keystore (JKS) can contain two types of entries: (1) trusted root certificates or (2) private keys + cert chains. Usually a JKS will contain all entries of one type or another (and thus a particular JKS serves one purpose or another; meaning that a JKS containing trusted roots is used as a source for verifying pre-trusted roots, and a JKS containing private keys (and cert chains) is used as a secure, encrypted store for private keys).

A PKCS12 / PFX typically contains one or more private keys, along with each private key's certificate chain. Therefore, it typically makes sense to only write the private key entries to a PKCS12 (and the associated certificate chains). If a JKS contains trusted root certificates, it makes more sense to conver it to a PEM file (such as the CA cert bundle in PEM format from mozilla.org).

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# This requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

jks = Chilkat::CkJavaKeyStore.new()

jksPassword = "myJksPassword"

# Load the Java keystore from a file.  The JKS file password is used
# to verify the keyed digest that is found at the very end of the keystore.
# It verifies that the keystore has not been modified.
success = jks.LoadFile(jksPassword,"/someDir/keyStore.jks")
if (success != true)
    print jks.lastErrorText() + "\n";
    exit
end

# To convert, we'll access the private key entries
# from the JKS, add each to the PKCS12, and then save the PKCS12.
pkcs12 = Chilkat::CkPfx.new()

numPrivateKeys = jks.get_NumPrivateKeys()

# For each private key entry, get the private key and
# the associated certificate chain.
# Each private key is password protected.  Usually it is the same
# password as used for the keyed digest of the entire JKS.  
# However, this does not have to be.  The password is passed
# here to handle the possibility of each private key requiring
# a different password.
i = 0
while i < numPrivateKeys
    # privKey is a CkPrivateKey
    privKey = jks.GetPrivateKey(jksPassword,i)
    print jks.getPrivateKeyAlias(i) + "\n";
    # certChain is a CkCertChain
    certChain = jks.GetCertChain(i)

    # Add the private key and it's associated certificate chain to the PKCS12.
    success = pkcs12.AddPrivateKey(privKey,certChain)
    if (success != true)
        print pkcs12.lastErrorText() + "\n";

        exit
    end

    i = i + 1
end

# Save the PKCS12 / PFX to a file.
# The password can be the same as the JKS password, or something new.
# (With the PKCS12 format, there is a single password for the entire contents
# of the file.  With the JKS format, there is flexibility in allowing each private key
# to have it's own password.)
pkcs12Password = "myNewPassword"
success = pkcs12.ToFile(pkcs12Password,"/pkcs12_files/myPfx.p12")
if (success != true)
    print pkcs12.lastErrorText() + "\n";
else
    print "Successfully saved to PKCS12 format." + "\n";
end