Encrypt file with Ruby OpenSSL and decrypt with command line - ruby

Question

I am automating an OpenSSL file encryption process using Ruby. The files encrypted this way need to be able to be decrypted using OpenSSL on linux command line.
I can encrypt the file using the following Ruby method:
def encrypt_file
cipher = OpenSSL::Cipher.new('aes-256-cbc')
cipher.encrypt
cipher.key = "somelongkeystring"
buf = ""
File.open("file.enc", "wb") do |outf|
File.open("file.zip", "rb") do |inf|
while inf.read(4096, buf)
outf << cipher.update(buf)
end
outf << cipher.final
end
end
end
I need to be able to decrypt the file (file.enc) using the following command:
$ openssl aes-256-cbc -d -in file.enc -out file.zip
However, when I run this I get an error for bad magic number after I type the key from above.
Since I cannot change the decrypt approach (meaning it uses only a password and is entered on linux command line) how can I change my Ruby method to encrypt the file so it can be decrypted this way?

Answer 1

With the help of a similar question in stackoverflow, Im able to achieve it in ruby.
First u've to add an iv thing into ur cipher object, like this
cipher = OpenSSL::Cipher.new('aes-256-cbc')
cipher.encrypt
cipher.iv = "0"*16
cipher.key = "somelongkeystring"
While decryption u've to pass -K and -iv values
openssl aes-256-cbc -d -in file.enc -out file.zip -K <key_hex_code> -iv <iv_hex_code>
U can generate hex codes in ruby like this "string".unpack('H*'). There must be some way to generate hex codes in cli as well.

Answer 2

A solution based on Sumit's answer:
require 'openssl'
class Crypto
def initialize(key, iv, data, cipher='aes-256-cbc')
#key = key
#iv = iv
#cipher = cipher
#data = data
end
def encrypt
c = OpenSSL::Cipher.new(#cipher).encrypt
c.iv = #iv
c.key = #key
c.update(#data) + c.final
end
def decrypt
c = OpenSSL::Cipher.new(#cipher).decrypt
c.iv = #iv
c.key = #key
c.update(#data) + c.final
end
end
iv = '0'*16
key = '1'*32
message = 'My Message'
encrypted = Crypto.new(key,iv,message).encrypt
puts Crypto.new(key,iv,encrypted).decrypt
puts `echo -n '#{encrypted}' | openssl aes-256-cbc -d -K #{key.unpack('H*').first} -iv #{iv.unpack('H*').first}`
# My Message
# My Message
This solutions works for strings, can easily be adapted to files.

Answer 3

I got this to work though not using the Ruby OpenSSL implementation (which I would prefer). If you use the -k flag you can specify a password as the next argument then you don't need to pass anything and can use system to call it.
system("openssl aes-256-cbc -k '#{key}' -in file.zip -out file.enc")
If anyone has an approach using the Ruby OpenSSL implementation I would appreciate it.