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*_Update of length zero is legal.

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We can slightly simplify tls1_P_hash. (Confirmed md32_common.h emits
code with the check.)

Change-Id: I0293ceaaee261a7ac775b42a639f7a9f67705456
Reviewed-on: https://boringssl-review.googlesource.com/6647
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2015-12-06 21:04:36 -05:00 committed by Adam Langley
parent d9f0671bbe
commit 871fff076b
1 changed files with 12 additions and 16 deletions
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28
ssl/t1_enc.c
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@ -159,40 +159,36 @@ static int tls1_P_hash(uint8_t *out, size_t out_len, const EVP_MD *md,
const uint8_t *seed1, size_t seed1_len,
const uint8_t *seed2, size_t seed2_len,
const uint8_t *seed3, size_t seed3_len) {
size_t chunk;
HMAC_CTX ctx, ctx_tmp, ctx_init;
uint8_t A1[EVP_MAX_MD_SIZE];
unsigned A1_len;
int ret = 0;
chunk = EVP_MD_size(md);
size_t chunk = EVP_MD_size(md);
HMAC_CTX_init(&ctx);
HMAC_CTX_init(&ctx_tmp);
HMAC_CTX_init(&ctx_init);
if (!HMAC_Init_ex(&ctx_init, secret, secret_len, md, NULL) ||
!HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
(seed1_len && !HMAC_Update(&ctx, seed1, seed1_len)) ||
(seed2_len && !HMAC_Update(&ctx, seed2, seed2_len)) ||
(seed3_len && !HMAC_Update(&ctx, seed3, seed3_len)) ||
!HMAC_Update(&ctx, seed1, seed1_len) ||
!HMAC_Update(&ctx, seed2, seed2_len) ||
!HMAC_Update(&ctx, seed3, seed3_len) ||
!HMAC_Final(&ctx, A1, &A1_len)) {
goto err;
}
for (;;) {
/* Reinit mac contexts. */
if (!HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
!HMAC_Update(&ctx, A1, A1_len) ||
(out_len > chunk && !HMAC_CTX_copy_ex(&ctx_tmp, &ctx)) ||
(seed1_len && !HMAC_Update(&ctx, seed1, seed1_len)) ||
(seed2_len && !HMAC_Update(&ctx, seed2, seed2_len)) ||
(seed3_len && !HMAC_Update(&ctx, seed3, seed3_len))) {
goto err;
}
unsigned len;
uint8_t hmac[EVP_MAX_MD_SIZE];
if (!HMAC_Final(&ctx, hmac, &len)) {
if (!HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
!HMAC_Update(&ctx, A1, A1_len) ||
/* Save a copy of |ctx| to compute the next A1 value below. */
(out_len > chunk && !HMAC_CTX_copy_ex(&ctx_tmp, &ctx)) ||
!HMAC_Update(&ctx, seed1, seed1_len) ||
!HMAC_Update(&ctx, seed2, seed2_len) ||
!HMAC_Update(&ctx, seed3, seed3_len) ||
!HMAC_Final(&ctx, hmac, &len)) {
goto err;
}
assert(len == chunk);