ArgumentError: key must be 32 bytes

[darrenboyd]

I'm using encryptor via attr-encrypted in a Rails 5 application. While evaluating an upgrade to Ruby 2.4.0, I came across the following error coming out of this gem. Not sure if this is a bug, or something I'm doing wrong, or some change related to Ruby 2.4.0 that requires some effort on my part.

From Ruby 2.4.0

[7] pry(main)> RUBY_VERSION
=> "2.4.0"
[8] pry(main)> secret_key = SecureRandom.random_bytes(64)
=> "\xF3\xA6\xE9\x91\xFD\x94\xCB\xBDH\xA9|\xDF\x04\xBF\xAC\x13+0\xB5\xAF`[\b\xE6\xEDw\xCDD\x97\x19\"\xD1\xB1\xFB\x8A\x8Cn\x84N\x05\xDCp\x1C\xA0o3\x9D\t\xFA\x1F\xC1\x1C&F\xFC\xB0,\xDB\xBE\xE1\x8E9\xD4\xA6"
[9] pry(main)> iv = SecureRandom.random_bytes(12)
=> "\xD5\x00\xB1Q.>)\xAE\xF0x\xBB\xA1"
[10] pry(main)> encrypted_value = Encryptor.encrypt(value: 'some string to encrypt', key: secret_key, iv: iv)
ArgumentError: key must be 32 bytes
from /home/darren/.gem/ruby/2.4.0/gems/encryptor-3.0.0/lib/encryptor.rb:72:in `key='

Previous behavior from Ruby 2.3.3

[1] pry(main)> RUBY_VERSION
=> "2.3.3"
[2] pry(main)> secret_key = SecureRandom.random_bytes(64)
=> "A\xFD\xBC\xA5\x1A\x8E\xD7\x17W\x00r5\x8CHv|\xA7\xFB6\xB8N\x9Fb\x93\xA4\x9Aw\x8E\bq\xBA\xFC\xEF\xA3\x9E\xE2\xED\xB1\b\xBC\xE3\xDA\xEA\xDB\xF2\xAC0\xDAh\xCE\x88/(\x16\xC9\xDDs9\xD11\xE5\xE9\t\\"
[3] pry(main)> iv = SecureRandom.random_bytes(12)
=> "\xC8\xE3\xBE\x91y\x95sF\xE6\x89\x8C\""
[4] pry(main)> encrypted_value = Encryptor.encrypt(value: 'some string to encrypt', key: secret_key, iv: iv)
=> "\x12\x9A\x81*U\xCFT\x91\xB7;\xAF\xF2I]\x9C@L\xD5\xB8;\x00\x87\xF3\x82yS(r\x90\xC8\x86\xBB\x13\x92\xA83$O"

These are both using encryptor 3.0.0.

[spdawson]

This is affecting my Rails 5.0.1 application too, following an upgrade to Ruby 2.4

[zuzannast]

Same issue for me when upgrading to Ruby 2.4.0.

[consti]

I don't think that the issue really comes from Encryptor;
afaik this is the change in the OpenSSL library that causes the error: ruby/ruby@ce63526

We've solved it by generating keys that are the correct size length;
if OpenSSL requires 32 bytes, make sure you generate it with SecureRandom.random_bytes(32).

If you plan to store the keys in a YML file (or similar), you will probably have to resort to using Base64.

We did this:

namespace :openssl do
  desc "Generate Base64 encoded bytes for application.yml"
  task generate: :environment do
    {
      ENCRYPT_SECRET_KEY: 32,
      ENCRYPT_IV: 12,
      ENCRYPT_SALT: 128
    }.each do |k, length|
      value = Base64.encode64(SecureRandom.random_bytes(length)).delete("\n")
      puts "#{k}: '#{value}'"
    end
  end
end

Then in initializers/encryptor.rb:

# frozen_string_literal: true
Encryptor.default_options.merge!(
  algorithm: 'aes-256-gcm',
  key: Base64.decode64(ENV['ENCRYPT_SECRET_KEY']),
  iv: Base64.decode64(ENV['ENCRYPT_IV']),
  salt: Base64.decode64(ENV['ENCRYPT_SALT'])
)

[anaumov]

Hi there! Could you tell me how I can migrate from 128 byte key to 32 byte key in production?

[darrenboyd]

@anaumov We were able to simply truncate our keys from their longer length to 32 bytes. It seems that while the Ruby SSL implementation allowed for keys longer than 32 bytes, it truncated them. The recent change is to raise an error for keys that aren't exactly 32 bytes.

Obviously, you should test this to make sure it's works for you :).

[spdawson]

A simple key truncation also worked in our case.

[saboyutaka]

Hi there, I got a error like almost same thing, but iv not key.
Since on openssl is merged, key must be 32 bytes and iv must be 12 bytes in Ruby 2.4.0. before 2.4.0, these are truncated.

Hi there, I also encountered the same kind of error but IV not key.
Since this change of openssl have been merged, in Ruby2.4.0, key must be 32 bytes, IV must be 12 bytes.
I tryed to change iv to 12 bytes. And it works
But I think good to fix the number of bytes of ArgumentError in this gem.

[danielricecodes]

This is a really frustrating issue. It would be great if someone could post their solution to this problem. I've tried the Base64 encode/decode method to no avail. I also arrived here because I'm using the attr_encrypted gem, not this gem specifically.

[saghaulor]

@danielricecodes people have posted their solution. Use the correct sized key and iv. You can trim the extra bytes and it should work.

However, I'm not certain how the IV was handled in Ruby < 2.4. If it was similarly ignored like the extra bytes in the key, then you should be able to simply trim the IV.

[danielricecodes]

Here's a way I figured out can generate a 32 character key without using SecureRandom...

Just run this in rails console

  `rake secret`[0..31]

It will spit out a 32 byte string - just without all the random garbage SecureRandom will throw in there. You don't have to Base64 encode that value either.

[saghaulor]

@danielricecodes I don't recommend doing that, but you're welcome to do whatever you like.