* [PATCH] crypto: x86/aes-gcm - simplify GCM hash subkey derivation
@ 2024-04-20 6:00 Eric Biggers
2024-04-20 18:19 ` Eric Biggers
0 siblings, 1 reply; 3+ messages in thread
From: Eric Biggers @ 2024-04-20 6:00 UTC (permalink / raw
To: linux-crypto; +Cc: x86
From: Eric Biggers <ebiggers@google.com>
Remove a redundant expansion of the AES key, and utilize the zero page.
Also rename rfc4106_set_hash_subkey() to aes_gcm_derive_hash_subkey()
because it's used for both versions of AES-GCM, not just RFC4106.
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
arch/x86/crypto/aesni-intel_glue.c | 26 +++++++-------------------
1 file changed, 7 insertions(+), 19 deletions(-)
diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c
index 110b3282a1f2..b4058c3d410d 100644
--- a/arch/x86/crypto/aesni-intel_glue.c
+++ b/arch/x86/crypto/aesni-intel_glue.c
@@ -38,11 +38,10 @@
#define AESNI_ALIGN 16
#define AESNI_ALIGN_ATTR __attribute__ ((__aligned__(AESNI_ALIGN)))
#define AES_BLOCK_MASK (~(AES_BLOCK_SIZE - 1))
-#define RFC4106_HASH_SUBKEY_SIZE 16
#define AESNI_ALIGN_EXTRA ((AESNI_ALIGN - 1) & ~(CRYPTO_MINALIGN - 1))
#define CRYPTO_AES_CTX_SIZE (sizeof(struct crypto_aes_ctx) + AESNI_ALIGN_EXTRA)
#define XTS_AES_CTX_SIZE (sizeof(struct aesni_xts_ctx) + AESNI_ALIGN_EXTRA)
/* This data is stored at the end of the crypto_tfm struct.
@@ -588,27 +587,14 @@ static int xctr_crypt(struct skcipher_request *req)
err = skcipher_walk_done(&walk, nbytes);
}
return err;
}
-static int
-rfc4106_set_hash_subkey(u8 *hash_subkey, const u8 *key, unsigned int key_len)
+static int aes_gcm_derive_hash_subkey(const struct crypto_aes_ctx *aes_key,
+ u8 hash_subkey[AES_BLOCK_SIZE])
{
- struct crypto_aes_ctx ctx;
- int ret;
-
- ret = aes_expandkey(&ctx, key, key_len);
- if (ret)
- return ret;
-
- /* Clear the data in the hash sub key container to zero.*/
- /* We want to cipher all zeros to create the hash sub key. */
- memset(hash_subkey, 0, RFC4106_HASH_SUBKEY_SIZE);
-
- aes_encrypt(&ctx, hash_subkey, hash_subkey);
-
- memzero_explicit(&ctx, sizeof(ctx));
+ aes_encrypt(aes_key, hash_subkey, page_address(ZERO_PAGE(0)));
return 0;
}
static int common_rfc4106_set_key(struct crypto_aead *aead, const u8 *key,
unsigned int key_len)
@@ -622,11 +608,12 @@ static int common_rfc4106_set_key(struct crypto_aead *aead, const u8 *key,
key_len -= 4;
memcpy(ctx->nonce, key + key_len, sizeof(ctx->nonce));
return aes_set_key_common(&ctx->aes_key_expanded, key, key_len) ?:
- rfc4106_set_hash_subkey(ctx->hash_subkey, key, key_len);
+ aes_gcm_derive_hash_subkey(&ctx->aes_key_expanded,
+ ctx->hash_subkey);
}
/* This is the Integrity Check Value (aka the authentication tag) length and can
* be 8, 12 or 16 bytes long. */
static int common_rfc4106_set_authsize(struct crypto_aead *aead,
@@ -1328,11 +1315,12 @@ static int generic_gcmaes_set_key(struct crypto_aead *aead, const u8 *key,
unsigned int key_len)
{
struct generic_gcmaes_ctx *ctx = generic_gcmaes_ctx_get(aead);
return aes_set_key_common(&ctx->aes_key_expanded, key, key_len) ?:
- rfc4106_set_hash_subkey(ctx->hash_subkey, key, key_len);
+ aes_gcm_derive_hash_subkey(&ctx->aes_key_expanded,
+ ctx->hash_subkey);
}
static int generic_gcmaes_encrypt(struct aead_request *req)
{
struct crypto_aead *tfm = crypto_aead_reqtfm(req);
base-commit: 543ea178fbfadeaf79e15766ac989f3351349f02
--
2.44.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] crypto: x86/aes-gcm - simplify GCM hash subkey derivation
2024-04-20 6:00 [PATCH] crypto: x86/aes-gcm - simplify GCM hash subkey derivation Eric Biggers
@ 2024-04-20 18:19 ` Eric Biggers
2024-04-26 9:39 ` Herbert Xu
0 siblings, 1 reply; 3+ messages in thread
From: Eric Biggers @ 2024-04-20 18:19 UTC (permalink / raw
To: linux-crypto; +Cc: x86
On Fri, Apr 19, 2024 at 11:00:37PM -0700, Eric Biggers wrote:
> + aes_encrypt(aes_key, hash_subkey, page_address(ZERO_PAGE(0)));
Actually, page_address(ZERO_PAGE(0)) expands into a surprisingly large number of
instructions. Using empty_zero_page directly would avoid this, but there's
little precedent for doing that. For now, I think just using something like
'static const u8 zeroes[16]' is the way to go for small buffers like this.
- Eric
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] crypto: x86/aes-gcm - simplify GCM hash subkey derivation
2024-04-20 18:19 ` Eric Biggers
@ 2024-04-26 9:39 ` Herbert Xu
0 siblings, 0 replies; 3+ messages in thread
From: Herbert Xu @ 2024-04-26 9:39 UTC (permalink / raw
To: Eric Biggers; +Cc: linux-crypto, x86
Eric Biggers <ebiggers@kernel.org> wrote:
> On Fri, Apr 19, 2024 at 11:00:37PM -0700, Eric Biggers wrote:
>> + aes_encrypt(aes_key, hash_subkey, page_address(ZERO_PAGE(0)));
>
> Actually, page_address(ZERO_PAGE(0)) expands into a surprisingly large number of
> instructions. Using empty_zero_page directly would avoid this, but there's
> little precedent for doing that. For now, I think just using something like
> 'static const u8 zeroes[16]' is the way to go for small buffers like this.
Yes it's not worth the effort given the small size. But still it
looks like lib/raid6 could benefit from using a shared zero page
too.
Cheers,
--
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-04-20 6:00 [PATCH] crypto: x86/aes-gcm - simplify GCM hash subkey derivation Eric Biggers
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