Ruby code for doing P12 to PEM conversion via command line. Supports MRI/JRuby/Rubinius

gistfile1.rb

require 'tempfile'
require 'openssl'
require 'escape' # gem install escape

class CommandFailError < StandardError; end

def p12_to_pem_text(p12, pass='')
  pass = '' if pass.nil?

  # Use shell command for JRuby (see https://github.com/jruby/jruby-ossl/issues/8)
  if RUBY_PLATFORM == 'java'
    tf_p12 = Tempfile.new 'tf_p12'
    tf_p12.write p12
    tf_p12.close

    tf_pem = Tempfile.new 'tf_pem'
    tf_pem.close

    cmd = Escape.shell_command(['openssl', 'pkcs12', '-in', tf_p12.path, '-out', tf_pem.path, 
                                '-nodes', '-clcerts', '-password', 'pass:'+pass]).to_s + ' &> /dev/null'

    begin
      result = system cmd
      raise CommandFailError if result.nil? || result == false
      pem = File.read tf_pem.path
    ensure
      tf_pem.unlink
      tf_p12.unlink
    end

    pem
  else
    # Use PKCS12 class for everything else (works in MRI/Rubinius)
    pkcs12 = OpenSSL::PKCS12.new p12, pass
    pkcs12.certificate.to_s + pkcs12.key.to_s
  end
end