Ruby OpenSSL DES encoding "wrong final block length"

Question

I have the following encryption/decryption using OpenSSL (under Linux in my example):

$ echo test | openssl des -a -K 79616d7379616d73 -iv 1234567890ABCDEF
+ax5NT+Pjh0=

$ echo +ax5NT+Pjh0= | openssl des -a -d -K 79616d7379616d73 -iv 1234567890ABCDEF
test

All good. I need to translate it in Ruby code. As far as I did:

#!/usr/bin/env ruby

require 'openssl'

key = "\x79\x61\x6d\x73\x79\x61\x6d\x73"
iv = "\x12\x34\x56\x78\x90\xAB\xCD\xEF"
todecode = "+ax5NT+Pjh0="

def decode(encryptedString, key, iv)
    decrypt = OpenSSL::Cipher::Cipher.new('des-cbc')
    decrypt.decrypt
    decrypt.key = key
    decrypt.iv = iv
    decrypt.update(encryptedString) + decrypt.final
end

decoded = decode(todecode, key, iv)

puts decoded

It throws me the following error:

decode.rb:14:in `final': wrong final block length (OpenSSL::Cipher::CipherError)`

What am I doing wrong? Did I select the wrong encryption or wrong use of key/iv?

Small nit... Use echo -n, not echo (unless you want the new line). But it probably is not the cause of your problem. — jww
– jww, Commented May 28, 2017 at 23:22

bsteo · Accepted Answer · 2017-05-28 14:07:54Z

1

Seems I forgot to base64_decode the string.

todecode = Base64::decode64("+ax5NT+Pjh0=")

answered May 28, 2017 at 14:07

bsteo

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