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authorArvind Sankar <nivedita@alum.mit.edu>2020-10-25 10:31:17 -0400
committerHerbert Xu <herbert@gondor.apana.org.au>2020-10-30 17:35:03 +1100
commitb8399819b2dd6f29195ed7535217b66c01b1e57d (patch)
tree5c7ef309f029a74a63ed469a3dc2d45e0116e2c9 /lib/crypto
parent7a4295f6c9d54e082474667e552a227606b4a085 (diff)
crypto: lib/sha256 - Clear W[] in sha256_update() instead of sha256_transform()
The temporary W[] array is currently zeroed out once every call to sha256_transform(), i.e. once every 64 bytes of input data. Moving it to sha256_update() instead so that it is cleared only once per update can save about 2-3% of the total time taken to compute the digest, with a reasonable memset() implementation, and considerably more (~20%) with a bad one (eg the x86 purgatory currently uses a memset() coded in C). Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'lib/crypto')
-rw-r--r--lib/crypto/sha256.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
index 099cd11f83c1..c6bfeacc5b81 100644
--- a/lib/crypto/sha256.c
+++ b/lib/crypto/sha256.c
@@ -43,10 +43,9 @@ static inline void BLEND_OP(int I, u32 *W)
W[I] = s1(W[I-2]) + W[I-7] + s0(W[I-15]) + W[I-16];
}
-static void sha256_transform(u32 *state, const u8 *input)
+static void sha256_transform(u32 *state, const u8 *input, u32 *W)
{
u32 a, b, c, d, e, f, g, h, t1, t2;
- u32 W[64];
int i;
/* load the input */
@@ -200,15 +199,13 @@ static void sha256_transform(u32 *state, const u8 *input)
state[0] += a; state[1] += b; state[2] += c; state[3] += d;
state[4] += e; state[5] += f; state[6] += g; state[7] += h;
-
- /* clear any sensitive info... */
- memzero_explicit(W, 64 * sizeof(u32));
}
void sha256_update(struct sha256_state *sctx, const u8 *data, unsigned int len)
{
unsigned int partial, done;
const u8 *src;
+ u32 W[64];
partial = sctx->count & 0x3f;
sctx->count += len;
@@ -223,11 +220,13 @@ void sha256_update(struct sha256_state *sctx, const u8 *data, unsigned int len)
}
do {
- sha256_transform(sctx->state, src);
+ sha256_transform(sctx->state, src, W);
done += 64;
src = data + done;
} while (done + 63 < len);
+ memzero_explicit(W, sizeof(W));
+
partial = 0;
}
memcpy(sctx->buf + partial, src, len - done);