require 'openssl'

# find first SEQUENCE of SEQUENCE in TBSCertificate
# tag == 16 is a SEQUENCE chunk
def spki_sha1_hash(cert)
  spki = OpenSSL::ASN1.decode(cert).value[0].find { |e|
    e.tag == 16 && e.value[0].tag == 16
  }
  return unless spki
  ["sha1", [OpenSSL::Digest::SHA1.digest(spki.to_der)].pack('m*').chomp].join("/")
end

if $0 == __FILE__
  ARGV.each do |file|
    cert = OpenSSL::X509::Certificate.new(File.read(file))
    spkihash = spki_sha1_hash(cert.to_der)
    sha1, b64 = spkihash.split('/')
    puts '=='
    puts 'Subject: ' + cert.subject.to_s
    puts 'Issuer: ' + cert.issuer.to_s
    puts spkihash
    puts b64.unpack('m*')[0].each_byte.map { |e| sprintf("%02x", e) }.join
  end
end