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[RESEND] random: initialize ChaCha20 constants with correct endianness

Message ID 20210322051347.266831-1-ebiggers@kernel.org
State New
Headers show
Series [RESEND] random: initialize ChaCha20 constants with correct endianness | expand

Commit Message

Eric Biggers March 22, 2021, 5:13 a.m. UTC 
From: Eric Biggers <ebiggers@google.com>

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: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/char/random.c   | 4 ++--
 include/crypto/chacha.h | 9 +++++++--
 2 files changed, 9 insertions(+), 4 deletions(-)

Comments

Herbert Xu April 2, 2021, 9:03 a.m. UTC | #1 
On Sun, Mar 21, 2021 at 10:13:47PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>

> 

> 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: Herbert Xu <herbert@gondor.apana.org.au>

> Acked-by: Ard Biesheuvel <ardb@kernel.org>

> Signed-off-by: Eric Biggers <ebiggers@google.com>

> ---

>  drivers/char/random.c   | 4 ++--

>  include/crypto/chacha.h | 9 +++++++--

>  2 files changed, 9 insertions(+), 4 deletions(-)


Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
diff mbox series

Patch

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0fe9e200e4c84..5d6acfecd919b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -819,7 +819,7 @@  static bool __init crng_init_try_arch_early(struct crng_state *crng)
 
 static void __maybe_unused 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;
@@ -827,7 +827,7 @@  static void __maybe_unused 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) {
 		invalidate_batched_entropy();
diff --git a/include/crypto/chacha.h b/include/crypto/chacha.h
index 3a1c72fdb7cf5..dabaee6987186 100644
--- a/include/crypto/chacha.h
+++ b/include/crypto/chacha.h
@@ -47,13 +47,18 @@  static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
 		hchacha_block_generic(state, out, nrounds);
 }
 
-void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
-static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
+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" */
+}
+
+void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
+static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
+{
+	chacha_init_consts(state);
 	state[4]  = key[0];
 	state[5]  = key[1];
 	state[6]  = key[2];