gistfile1.rb

@key = OpenSSL::PKey::RSA.new 2048

# Generate CSR
csr = OpenSSL::X509::Request.new
csr.version = 0 
csr.subject = OpenSSL::X509::Name.new([
  ['CN', "PEM", OpenSSL::ASN1::UTF8STRING]
])
csr.public_key = @key.public_key
csr.sign @key, OpenSSL::Digest::SHA1.new

path = File.join(TMP_FOLDER, 'PEMCertificateSigningRequest.certSigningRequest')
open path, 'w' do |io|
  io.write csr.to_pem
end