[PATCH 5.4 046/240] random: early initialization of ChaCha constants

Greg Kroah-Hartman
2022-06-20T13:32:53Z

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
@@ -458,6 +458,10 @@ 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,
};

/*
@@ -824,7 +828,6 @@ 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
@@ -51,12 +51,19 @@ int crypto_chacha12_setkey(struct crypto
int crypto_chacha_crypt(struct skcipher_request *req);
int crypto_xchacha_crypt(struct skcipher_request *req);

+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;
}

#endif /* _CRYPTO_CHACHA_H */