[ruby-core:75452] [Ruby trunk Bug#9569] SecureRandom should try /dev/urandom first

Issue #9569 has been updated by Tony Arcieri.


George Koehler: you're missing the point: the OS RNG should be used instead of OpenSSL's. That isn't necessarily /dev/urandom on every platform. Clearly /dev/urandom is a poor candidate for Windows (CryptGenRandom or RtlGenRandom should be used)

Again, I'll point to libsodium's randombytes implementation (and take the opportunity to say it's available today via the RbNaCl gem). 

https://github.com/jedisct1/libsodium/blob/master/src/libsodium/randombytes/sysrandom/randombytes_sysrandom.c

This implementation uses arc4random() on OpenBSD:

https://github.com/jedisct1/libsodium/blob/master/src/libsodium/randombytes/sysrandom/randombytes_sysrandom.c#L36

Specifically it checks for a "safe" arc4random(). On OpenBSD, despite the name arc4random() doesn't use RC4 internally, but instead uses the ChaCha20 stream cipher, which is modern and secure.

If you rerun your benchmarks using arc4random, I expect you will probably see equal or better performance than OpenSSL.

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Bug #9569: SecureRandom should try /dev/urandom first
https://bugs.ruby-lang.org/issues/9569#change-58571

* Author: Corey Csuhta
* Status: Rejected
* Priority: Normal
* Assignee: ruby-core
* ruby -v: 
* Backport: 
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Right now, `SecureRandom.random_bytes` tries to detect an OpenSSL to use before it tries to detect `/dev/urandom`. I think it should be the other way around. In both cases, you just need random bytes to unpack, so SecureRandom could skip the middleman (and [second point of failure](http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/)) and just talk to `/dev/urandom` directly if it's available.

Is this a case of just re-ordering the two code chunks so that `/dev/urandom` is tried first?

Relevant lines: https://github.com/ruby/ruby/blob/trunk/lib/securerandom.rb#L59-L90



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