mix_pool_bytes() has numerous problems, as discussed in prior emails.
Do we still want to be putting so much effort into a development dead
end?
-Michael
On Thu, Mar 31, 2022 at 8:28 AM Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
>
> Prior, the "input_pool_data" array needed no real initialization, and so
> it was easy to mark it with __latent_entropy to populate it during
> compile-time. In switching to using a hash function, this required us to
> specifically initialize it to some specific state, which means we
> dropped the __latent_entropy attribute. An unfortunate side effect was
> this meant the pool was no longer seeded using compile-time random data.
> In order to bring this back, we declare an array in rand_initialize()
> with __latent_entropy and call mix_pool_bytes() on that at init, which
> accomplishes the same thing as before. We make this __initconst, so that
> it doesn't take up space at runtime after init.
>
> Fixes: 6e8ec2552c7d ("random: use computational hash for entropy extraction")
> Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> ---
> Changes v1->v2:
> - Use __initconst.
>
> drivers/char/random.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 40107f8b9e9e..1d8242969751 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -975,6 +975,11 @@ int __init rand_initialize(void)
> bool arch_init = true;
> unsigned long rv;
>
> +#if defined(LATENT_ENTROPY_PLUGIN)
> + static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
> + _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
> +#endif
> +
> for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) {
> if (!arch_get_random_seed_long_early(&rv) &&
> !arch_get_random_long_early(&rv)) {
> --
> 2.35.1
>
