Encrypted using openssl executable, decrypting with ruby's OpenSSL module?

ruby-talk
1

I have some files on my system that have been encrypted using the "openssl"
executable (via "openssl rc4 -e"), and I would like to decrypt them using
the "OpenSSL" ruby module.

I know that the salt and iv values are stored in the files that are encrypted
by the openssl executable, but I haven't been able to properly extract that
information from these files so that I can use this salt and iv with the ruby
OpenSSL decryption functions.

Can anyone point me to a ruby example for extracting this salt and iv
info from an openssl-encrypted file, so I can then decrypt it via ruby's
OpenSSL module?

Thanks in advance.

···

--
Lloyd Zusman
ljz@asfast.com
God bless you.

2

[ ... ]

Can anyone point me to a ruby example for extracting this salt and iv
info from an openssl-encrypted file, so I can then decrypt it via ruby's
OpenSSL module?

Well, I figured it out. First of all, I need the key size and iv size
for the encryption scheme. According to the chart in Table 15.6 at
this
site, codeidol.com - codeidol Resources and Information.,
these values are 16 and 0,
respectively, for the RC4 encryption scheme. Armed with these values,
I
came up with the following ruby code (more error checking is needed):

#!/usr/bin/
ruby

require 'openssl'
require 'digest/md5'

def decrypt_from_openssl_encrypted(file, password, scheme, keysize,
ivsize)
  encrypted_data = nil
  begin
    File.open(file, 'r') {
      >f>
      encrypted_data = f.read
    }
  rescue
    return nil
  end
  if encrypted_data.nil? or
     encrypted_data.length < 16 or
     encrypted_data[0, 8] != 'Salted__'
    return nil
  end
  salt = encrypted_data[8, 8]
  encrypted_data = encrypted_data[16..-1]
  totsize = keysize + ivsize
  keyivdata = ''
  temp = ''
  while keyivdata.length < totsize do
    temp = Digest::MD5.digest(temp + password + salt);
    keyivdata << temp
  end
  key = keyivdata[0, keysize]
  iv = keyivdata[keysize, ivsize]
  c = OpenSSL::Cipher::Cipher.new(scheme)
  c.decrypt
  c.key = key
  c.iv = iv
  result = c.update(encrypted_data)
  result << c.final
  return result
end

file = 'encrypted.file'
password = '???'
scheme = 'rc4'
keysize = 16
ivsize = 0

decrypted = decrypt_from_openssl_encrypted(file,
                                           password,
                                           scheme,
                                           keysize,
                                           ivsize)

if decrypted.nil?
  puts 'unable to decrypt'
else
  puts decrypted
end

···

On Jul 28, 3:05 am, Lloyd Zusman <l...@asfast.com> wrote:

--
Lloyd Zusman
ljz@asfast.com
God bless you.