Make -devrandom option a no-op?

[rfjakob]

Commit f3c777d added the -devrandom option:

commit f3c777d5eaa682d878c638192311e52f9c204294
Author: @slackner 
Date:   Sun Nov 19 13:30:04 2017 +0100

main: Add '-devrandom' commandline option

Allows to use /dev/random for generating the master key instead of the
default Go implementation. When the kernel random generator has been
properly initialized both are considered equally secure, however:

* Versions of Go prior to 1.9 just fall back to /dev/urandom if the
  getrandom() syscall would be blocking (Go Bug #19274)

* Kernel versions prior to 3.17 do not support getrandom(), and there
  is no check if the random generator has been properly initialized
  before reading from /dev/urandom

This is especially useful for embedded hardware with low-entroy. Please
note that generation of the master key might block indefinitely if the
kernel cannot harvest enough entropy.

• We now require Go 1.13 (a5f88e8)

• However, it looks like kernel 3.16 is still alive with the last commit only a year ago: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/log/?h=linux-3.16.y

@slackner do you think -devrandom is still useful?

[slackner]

I don't mind if it is removed / replaced with a no-op, at least for me it is no longer that relevant (due to the newer Go version and modern Linux kernels used).

Note that Linux now also generates entropy instead of returning low quality randomness to usermode right after startup: https://lwn.net/Articles/802360/.

Best regards,
Sebastian

[rfjakob]

Done in 61ef6b0