linux-kernel - Re: [PATCH 1/5] random: fix crng

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Message-ID: <1699469.KmO53oa8XU@tauon.chronox.de>
Date:   Fri, 13 Apr 2018 07:38:30 +0200
From:   Stephan Mueller <smueller@...onox.de>
To:     Theodore Ts'o <tytso@....edu>
Cc:     linux-crypto@...r.kernel.org,
        Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
        stable@...nel.org
Subject: Re: [PATCH 1/5] random: fix crng_ready() test

Am Freitag, 13. April 2018, 03:30:42 CEST schrieb Theodore Ts'o:

Hi Theodore,

> The crng_init variable has three states:
> 
> 0: The CRNG is not initialized at all
> 1: The CRNG has a small amount of entropy, hopefully good enough for
>    early-boot, non-cryptographical use cases
> 2: The CRNG is fully initialized and we are sure it is safe for
>    cryptographic use cases.
> 
> The crng_ready() function should only return true once we are in the
> last state.
> 
Do I see that correctly that getrandom(2) will now unblock after the 
input_pool has obtained 128 bits of entropy? Similarly for 
get_random_bytes_wait.

As this seems to be the only real use case for crng_ready (apart from 
logging), what is the purpose of crng_init == 1?

Ciao
Stephan