[ruby-core:84579] [Ruby trunk Bug#14265] Possible bug in OpenSSL library

Issue #14265 has been reported by careta (Dumb Thomas).

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Bug #14265: Possible bug in OpenSSL library
https://bugs.ruby-lang.org/issues/14265

* Author: careta (Dumb Thomas)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.3.3p222 (2016-11-21) [x86_64-linux-gnu] (Debian Stable)
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
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Hi, 

I'm not sure if this is a bug or not, but there is a difference between Ruby and
Python when using Blowfish encryption in ECB mode. Using the same algorithm parameters, and the same input, the encrypted output is completely different.

Behold these two code samples:

RUBY==================
require 'digest'
require 'openssl'

cleartext = 'whatevs'

md5 = Digest::MD5.new
md5.update(cleartext)

payload = (md5.digest + cleartext).ljust(0x80, "\x00")

puts "plaintext: " + payload.unpack('H*')[0]

secret_key = "supersecretsupersecret"

cipher = OpenSSL::Cipher::Cipher.new("bf-ecb").send :encrypt
cipher.key = secret_key
cipher.padding = 0
binary_data = (cipher.update(payload) << cipher.final)

puts "ciphertext: " + binary_data.unpack('H*')[0]

cipher = OpenSSL::Cipher::Cipher.new("bf-ecb").send :decrypt
cipher.key = secret_key
cipher.padding = 0
str = (cipher.update(binary_data) << cipher.final)

puts "decrypted: " + str.unpack('H*')[0]
RUBY==================


PYTHON================
from Crypto.Cipher import Blowfish
from Crypto.Hash import MD5
import binascii

cleartext = 'whatevs'
md5_key = MD5.new(cleartext).digest()
payload = (md5_key + cleartext).ljust(0x80, "\x00")
print "plaintext: " + binascii.hexlify(payload)
secret_key = "supersecretsupersecret"

ciphertext = Blowfish.new(secret_key, Blowfish.MODE_ECB).encrypt(payload)

print "ciphertext: " + binascii.hexlify(ciphertext)

print "decrypted: " + binascii.hexlify(Blowfish.new(secret_key,
1).decrypt(ciphertext))
PYTHON================


It seems that the Ruby OpenSSL makes some assumptions with regards to
key length - I'm not sure if this is a bug or not. The fix for the code
I pasted before was very simple: when initializing the cipher, I have to
specify the key_len before setting the key:

cipher = OpenSSL::Cipher::Cipher.new("bf-ecb").send :encrypt
cipher.key_len = secret_key.length
cipher.key = secret_key
cipher.padding = 0
binary_data = (cipher.update(payload) << cipher.final)

This makes it work correctly and match the Python output.



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