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| author | Arvind Sankar <nivedita@alum.mit.edu> | 2020-10-25 10:31:17 -0400 |
|---|---|---|
| committer | Herbert Xu <herbert@gondor.apana.org.au> | 2020-10-30 17:35:03 +1100 |
| commit | b8399819b2dd6f29195ed7535217b66c01b1e57d (patch) | |
| tree | 5c7ef309f029a74a63ed469a3dc2d45e0116e2c9 /lib/crypto | |
| parent | 7a4295f6c9d54e082474667e552a227606b4a085 (diff) | |
| download | linux-b8399819b2dd6f29195ed7535217b66c01b1e57d.tar.bz2 | |
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.c | 11 |
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); |