Preload digest/sha2 to avoid thread safe error.

[frodsan]

Summary

I got this error in production using Puma in multi-threaded mode:

RuntimeError: Digest::Base cannot be directly inherited in Ruby
from active_support/security_utils.rb:23:in `variable_size_secure_compare'
from active_support/security_utils.rb:23:in `hexdigest'
from active_support/security_utils.rb:23:in `digest'

Looks like Digest uses const_missing to load Digest::SHA256 (https://github.com/ruby/ruby/blob/trunk/ext/digest/lib/digest.rb#L8)

Other information

• https://bugs.ruby-lang.org/issues/9494
• ruby/ruby@c02fa39

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[matthewd]

Let's fix

rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

Line 5 in f8e4c83

require "digest"

(any others?) at the same time.

[frodsan]

@matthewd cool! I was wondering if it's better to use OpenSSL implementation? Like:
https://github.com/rails/rails/blob/master/actionpack/lib/action_controller/metal/request_forgery_protection.rb#L395

[matthewd]

I don't think there's any advantage to using the OpenSSL one. (Whereas I assume it's used there because it's being passed to OpenSSL HMAC, not called directly.)