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    Subject[PATCH 5.10 037/163] random: early initialization of ChaCha constants
    Date
    From: Dominik Brodowski <linux@dominikbrodowski.net>

    commit 96562f286884e2db89c74215b199a1084b5fb7f7 upstream.

    Previously, the ChaCha constants for the primary pool were only
    initialized in crng_initialize_primary(), called by rand_initialize().
    However, some randomness is actually extracted from the primary pool
    beforehand, e.g. by kmem_cache_create(). Therefore, statically
    initialize the ChaCha constants for the primary pool.

    Cc: Herbert Xu <herbert@gondor.apana.org.au>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: <linux-crypto@vger.kernel.org>
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/char/random.c | 5 ++++-
    include/crypto/chacha.h | 15 +++++++++++----
    2 files changed, 15 insertions(+), 5 deletions(-)

    --- a/drivers/char/random.c
    +++ b/drivers/char/random.c
    @@ -457,6 +457,10 @@ struct crng_state {

    static struct crng_state primary_crng = {
    .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
    + .state[0] = CHACHA_CONSTANT_EXPA,
    + .state[1] = CHACHA_CONSTANT_ND_3,
    + .state[2] = CHACHA_CONSTANT_2_BY,
    + .state[3] = CHACHA_CONSTANT_TE_K,
    };

    /*
    @@ -823,7 +827,6 @@ static void crng_initialize_secondary(st

    static void __init crng_initialize_primary(struct crng_state *crng)
    {
    - chacha_init_consts(crng->state);
    _extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
    if (crng_init_try_arch_early(crng) && trust_cpu && crng_init < 2) {
    invalidate_batched_entropy();
    --- a/include/crypto/chacha.h
    +++ b/include/crypto/chacha.h
    @@ -47,12 +47,19 @@ static inline void hchacha_block(const u
    hchacha_block_generic(state, out, nrounds);
    }

    +enum chacha_constants { /* expand 32-byte k */
    + CHACHA_CONSTANT_EXPA = 0x61707865U,
    + CHACHA_CONSTANT_ND_3 = 0x3320646eU,
    + CHACHA_CONSTANT_2_BY = 0x79622d32U,
    + CHACHA_CONSTANT_TE_K = 0x6b206574U
    +};
    +
    static inline void chacha_init_consts(u32 *state)
    {
    - state[0] = 0x61707865; /* "expa" */
    - state[1] = 0x3320646e; /* "nd 3" */
    - state[2] = 0x79622d32; /* "2-by" */
    - state[3] = 0x6b206574; /* "te k" */
    + state[0] = CHACHA_CONSTANT_EXPA;
    + state[1] = CHACHA_CONSTANT_ND_3;
    + state[2] = CHACHA_CONSTANT_2_BY;
    + state[3] = CHACHA_CONSTANT_TE_K;
    }

    void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);

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