random: initialize ChaCha20 constants with correct endianness

commit a181e0fdb2164268274453b5b291589edbb9b22d upstream.

On big endian CPUs, the ChaCha20-based CRNG is using the wrong
endianness for the ChaCha20 constants.

This doesn't matter cryptographically, but technically it means it's not
ChaCha20 anymore.  Fix it to always use the standard constants.

Cc: linux-crypto@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 7057d521695be6fa4156340923c5a6bc5e67409d..2c059987d28fedca2e4bdd0e4231cc96bf102dde 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -817,7 +817,7 @@ static bool __init crng_init_try_arch_early(struct crng_state *crng)
 
 static void crng_initialize_secondary(struct crng_state *crng)
 {
-       memcpy(&crng->state[0], "expand 32-byte k", 16);
+       chacha_init_consts(crng->state);
        _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
        crng_init_try_arch(crng);
        crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
@@ -825,7 +825,7 @@ static void crng_initialize_secondary(struct crng_state *crng)
 
 static void __init crng_initialize_primary(struct crng_state *crng)
 {
-       memcpy(&crng->state[0], "expand 32-byte k", 16);
+       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();

diff --git a/include/crypto/chacha20.h b/include/crypto/chacha20.h
index f76302d99e2bedbdb0be35c202cd8a8b24c3a6a6..da08504e347e59e377858dac6ef312d83f022330 100644 (file)
--- a/include/crypto/chacha20.h
+++ b/include/crypto/chacha20.h
@@ -24,4 +24,12 @@ int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
                           unsigned int keysize);
 int crypto_chacha20_crypt(struct skcipher_request *req);
 
+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" */
+}
+
 #endif