From: Dominik Brodowski <linux@dominikbrodowski.net>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
tytso@mit.edu, ebiggers@kernel.org,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH v2 7/9] random: use simpler fast key erasure flow on per-cpu keys
Date: Wed, 9 Feb 2022 09:30:16 +0100 [thread overview]
Message-ID: <YgN7mOTtQ03etVJX@owl.dominikbrodowski.net> (raw)
In-Reply-To: <20220209011919.493762-8-Jason@zx2c4.com>
Nice work, just a few minor queries:
> -static void extract_crng(u8 out[CHACHA_BLOCK_SIZE])
> +/*
> + * The general form here is based on a "fast key erasure RNG" from
> + * <https://blog.cr.yp.to/20170723-random.html>. It generates a ChaCha
> + * block using the provided key, and then immediately overwites that
> + * key with half the block. It returns the resultant ChaCha state to the
> + * user, along with the second half of the block containing 32 bytes of
> + * random data that may be used; random_data_len may not be greater than
> + * 32.
> + */
> +static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE],
> + u32 chacha_state[CHACHA_STATE_WORDS],
> + u8 *random_data, size_t random_data_len)
> {
> - unsigned long flags, init_time;
> + u8 first_block[CHACHA_BLOCK_SIZE];
Do we need a BUG_ON(random_data_len > 32) here?
>
> - if (crng_ready()) {
> - init_time = READ_ONCE(primary_crng.init_time);
> - if (time_after(jiffies, init_time + CRNG_RESEED_INTERVAL))
> - crng_reseed();
> - }
> - spin_lock_irqsave(&primary_crng.lock, flags);
> - chacha20_block(&primary_crng.state[0], out);
> - if (primary_crng.state[12] == 0)
> - primary_crng.state[13]++;
> - spin_unlock_irqrestore(&primary_crng.lock, flags);
> + chacha_init_consts(chacha_state);
> + memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE);
> + memset(&chacha_state[12], 0, sizeof(u32) * 4);
No IV, no generation counter here? As you already have a generation counter
in use for other purposes, why not use it here as well as some non-zero
starting point?
Otherwise, it looks really nice.
Thanks,
Dominik
next prev parent reply other threads:[~2022-02-09 8:37 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 1:19 [PATCH v2 0/9] random: cleanups around per-cpu crng & rdrand Jason A. Donenfeld
2022-02-09 1:19 ` [PATCH v2 1/9] random: use RDSEED instead of RDRAND in entropy extraction Jason A. Donenfeld
2022-02-09 6:18 ` Dominik Brodowski
2022-02-09 1:19 ` [PATCH v2 2/9] random: get rid of secondary crngs Jason A. Donenfeld
2022-02-09 8:22 ` Dominik Brodowski
2022-02-09 10:26 ` Jason A. Donenfeld
2022-02-21 2:38 ` Eric Biggers
2022-02-09 1:19 ` [PATCH v2 3/9] random: inline leaves of rand_initialize() Jason A. Donenfeld
2022-02-09 8:22 ` Dominik Brodowski
2022-02-09 10:27 ` Jason A. Donenfeld
2022-02-09 1:19 ` [PATCH v2 4/9] random: ensure early RDSEED goes through mixer on init Jason A. Donenfeld
2022-02-09 8:23 ` Dominik Brodowski
2022-02-09 10:37 ` Jason A. Donenfeld
2022-02-09 1:19 ` [PATCH v2 5/9] random: do not xor RDRAND when writing into /dev/random Jason A. Donenfeld
2022-02-09 8:28 ` Dominik Brodowski
2022-02-09 10:40 ` Jason A. Donenfeld
2022-02-09 1:19 ` [PATCH v2 6/9] random: absorb fast pool into input pool after fast load Jason A. Donenfeld
2022-02-09 8:29 ` Dominik Brodowski
2022-02-09 10:45 ` Jason A. Donenfeld
2022-02-15 21:13 ` [PATCH v3] " Jason A. Donenfeld
2022-02-21 2:47 ` Eric Biggers
2022-02-21 14:57 ` Jason A. Donenfeld
2022-02-21 14:58 ` [PATCH v4] " Jason A. Donenfeld
2022-02-21 19:08 ` Eric Biggers
2022-02-09 1:19 ` [PATCH v2 7/9] random: use simpler fast key erasure flow on per-cpu keys Jason A. Donenfeld
2022-02-09 8:30 ` Dominik Brodowski [this message]
2022-02-09 10:54 ` Jason A. Donenfeld
2022-02-14 18:46 ` [PATCH v3] " Jason A. Donenfeld
2022-02-16 23:21 ` [PATCH v4] " Jason A. Donenfeld
2022-02-21 3:37 ` Eric Biggers
2022-02-21 14:42 ` Jason A. Donenfeld
2022-02-09 1:19 ` [PATCH v2 8/9] random: use hash function for crng_slow_load() Jason A. Donenfeld
2022-02-09 8:30 ` Dominik Brodowski
2022-02-21 3:40 ` Eric Biggers
2022-02-09 1:19 ` [PATCH v2 9/9] random: remove outdated INT_MAX >> 6 check in urandom_read() Jason A. Donenfeld
2022-02-21 3:56 ` Eric Biggers
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