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Sysrandom

Secure random number generation for Ruby using system RNG facilities e.g. /dev/urandom, getrandom(2)

Why?

System/OS-level random number generators like /dev/urandom and getrandom(2) provide the best option for generating cryptographically secure random numbers.

Ruby's built-in SecureRandom does not provide this, but instead uses OpenSSL's userspace RNG. This has been a source of vulnerabilities in Ruby, and this Ruby bug ticket contains more discussion on the issue.

This gem aims to solve the problem.

Description

In cryptography circles, the prevailing advice is to use OS RNG functionality, namely /dev/urandom or equivalent calls which use an OS-level CSPRNG to produce random numbers.

This gem provides an easy-to-install repackaging of the randombytes functionality from libsodium for the purpose of generating secure random numbers trustworthy for use in cryptographic contexts, such as generating cryptographic keys, initialization vectors, or nonces.

The following random number generators are utilized:

Platform	RNG
Linux	getrandom(2) if available, otherwise /dev/urandom
Windows	RtlGenRandom CryptGenRandom without CryptoAPI deps
OpenBSD	arc4random(3) with ChaCha20 CSPRNG (not RC4)
JRuby	NativePRNGNonBlocking on Java 8, otherwise SHA1PRNG
Others	/dev/urandom

Supported Platforms

Sysrandom is tested on the following Ruby implementations:

Ruby (MRI) 2.0, 2.1, 2.2, 2.3
JRuby 9.1.1.0

Installation

Add this line to your application's Gemfile:

gem 'sysrandom'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sysrandom

Usage

Sysrandom aims to be API-compatible with Ruby's built-in SecureRandom class, but always prefers OS-level RNG wherever it's available:

>> Sysrandom.random_number(42)
=> 15
>> Sysrandom.random_bytes(32)
=> "\xD6J\xB3\xD2\x8B\x7F*9D\xB7\xF9\xEA\xE2\\\xAAH\tV#\xEC\x84\xE3E\r\x97\xB9\b\xFCH\x17\xA0\v"
>> Sysrandom.base64(32)
=> "WXPkxfAuLRpnI6Z4zFb4E+MIenx6w6vKhe01+rMPuIQ="
>> Sysrandom.urlsafe_base64(32)
=> "37rsMfR4X8g7Bb-uDJEekRHnB3r_7nO03cv52ilaWqE="
>> Sysrandom.hex(32)
=> "c950496ce200abf7d18eb1414e9206c6335f971a37d0394114f56439b59831ba"
>> Sysrandom.uuid
=> "391c6f52-8017-4838-9790-131a9b979c63"

SecureRandom API docs

Patching SecureRandom with Sysrandom

Since Sysrandom is SecureRandom-compatible, it can be patched in-place of SecureRandom if you prefer its RNG behavior.

To do this, require sysrandom/securerandom:

>> SecureRandom
=> SecureRandom
>> require "sysrandom/securerandom"
=> true
>> SecureRandom
=> Sysrandom
>> SecureRandom.hex(32)
=> "d1bbe8c1ab78fc2fe514c5623d913a27ffd2dcdc9e002f3b358bb01a996962f1"

Contributing

Fork this repository on Github
Make your changes and send a pull request
If your changes look good, we'll merge them