linux-kernel - [PATCH 5.10 082/299] random: initialize ChaCha20 constants with correct endianness

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Message-Id: <20210510102007.633969883@linuxfoundation.org>
Date:   Mon, 10 May 2021 12:17:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, linux-crypto@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Jann Horn <jannh@...gle.com>, Theodore Tso <tytso@....edu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 082/299] random: initialize ChaCha20 constants with correct endianness

From: Eric Biggers <ebiggers@...gle.com>

[ Upstream commit a181e0fdb2164268274453b5b291589edbb9b22d ]

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@...r.kernel.org
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Jann Horn <jannh@...gle.com>
Cc: Theodore Ts'o <tytso@....edu>
Acked-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/char/random.c   | 4 ++--
 include/crypto/chacha.h | 9 +++++++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index f462b9d2f5a5..340ad21491e2 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 3a1c72fdb7cf..dabaee698718 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];
-- 
2.30.2