[ruby-core:75314] [Ruby trunk Bug#9569] SecureRandom should try /dev/urandom first

Issue #9569 has been updated by Corey Csuhta.


The Linux man page keeps getting mentioned, but what the current fallback code is actually doing is simply looking for any device named `/dev/urandom` on the host system:

https://github.com/ruby/ruby/blob/62b6e90d583e0a1c2be538a42640d69600608747/random.c#L459

The man page for `random(4)` on OS X, OpenBSD, and other UNIX-y OSes does not match the Linux man page. Every version of UNIX or Linux can have different text in their man pages. The actual code that implements /dev/urandom also varies across OSes.

If the man pages are the source of truth in this argument, you should be detecting the specific operating system to do what they say with their specific random device.

But of course, that is silly. I don't actually want Ruby to do that. I want Ruby to drop the use of OpenSSL for this operation. It was just worth noting this discrepancy.

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Bug #9569: SecureRandom should try /dev/urandom first
https://bugs.ruby-lang.org/issues/9569#change-58441

* 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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