Question

Does anyone know if ruby implements something similar to the openssl_seal function from PHP? I’d like to be able to interact with a server running a modified implementation of this answer. The PHP solution is pretty simple and it’d be great if I could find something for Ruby to do the same.

Somebody was looking for the same for python a year ago, but didn’t find anything.

Answer 1

EVP_Seal does simple wrapping with RSA so you can do it manually with OpenSSL features.

Here’s a PHP script that does seal with 1 cert:

<?php
$pubkey = openssl_pkey_get_public(file_get_contents('selfcert.pem'));

$message = 'hello,world';
$cipher_text = NULL;

$keys = NULL;
openssl_seal($message, $cipher_text, $keys, array($pubkey));

$file = fopen('wrapped.bin', 'wb');
fwrite($file, $keys[0]);
fclose($file);

$file = fopen('data.bin', 'wb');
fwrite($file, $cipher_text);
fclose($file);
?>

and a Ruby script that unseal it:

require 'openssl'

wrapped = File.read('wrapped.bin')
cipher_text = File.read('data.bin')

privkey = OpenSSL::PKey::RSA.new(File.read('privkey.pem'))
key = privkey.private_decrypt(wrapped)

cipher = OpenSSL::Cipher.new('rc4')
cipher.decrypt
cipher.key = key

p cipher.update(cipher_text) + cipher.final

You can do ‘seal’ with Ruby as well but creating secure session key (RC4 key for this example) is rather difficult so you’d better not try to do by yourself.