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Avoid fragile aliasing of SHA224/384 update/final

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This is purported to save a few cycles, but makes the code less
obvious and more brittle, and in fact breaks on platforms where for
ABI continuity reasons there is a SHA2 implementation in libc, and
so EVP needs to call those to avoid conflicts.

A sufficiently good optimizer could simply generate the same entry
points for:

        foo(...) { ... }
    and
        bar(...) { return foo(...); }

but, even without that, the different is negligible, with the
"winner" varying from run to run (openssl speed -evp sha384):

    Old:
    type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes 16384 bytes
    sha384           28864.28k   117362.62k   266469.21k   483258.03k   635144.87k 649123.16k

    New:
    type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes 16384 bytes
    sha384           30055.18k   120725.98k   272057.26k   482847.40k   634585.09k 650308.27k

Reviewed-by: Rich Salz <rsalz@openssl.org>
This commit is contained in:
Viktor Dukhovni 2018-02-13 22:43:15 -05:00
parent 7296027956
commit babab8e7c9
1 changed files with 24 additions and 9 deletions
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33
crypto/evp/m_sha1.c
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@ -116,16 +116,21 @@ static int init224(EVP_MD_CTX *ctx)
return SHA224_Init(EVP_MD_CTX_md_data(ctx));
}
static int update224(EVP_MD_CTX *ctx, const void *data, size_t count)
{
return SHA224_Update(EVP_MD_CTX_md_data(ctx), data, count);
}
static int final224(EVP_MD_CTX *ctx, unsigned char *md)
{
return SHA224_Final(md, EVP_MD_CTX_md_data(ctx));
}
static int init256(EVP_MD_CTX *ctx)
{
return SHA256_Init(EVP_MD_CTX_md_data(ctx));
}
/*
* Even though there're separate SHA224_[Update|Final], we call
* SHA256 functions even in SHA224 context. This is what happens
* there anyway, so we can spare few CPU cycles:-)
*/
static int update256(EVP_MD_CTX *ctx, const void *data, size_t count)
{
return SHA256_Update(EVP_MD_CTX_md_data(ctx), data, count);
@ -142,8 +147,8 @@ static const EVP_MD sha224_md = {
SHA224_DIGEST_LENGTH,
EVP_MD_FLAG_DIGALGID_ABSENT,
init224,
update256,
final256,
update224,
final224,
NULL,
NULL,
SHA256_CBLOCK,
@ -189,6 +194,16 @@ static int init384(EVP_MD_CTX *ctx)
return SHA384_Init(EVP_MD_CTX_md_data(ctx));
}
static int update384(EVP_MD_CTX *ctx, const void *data, size_t count)
{
return SHA384_Update(EVP_MD_CTX_md_data(ctx), data, count);
}
static int final384(EVP_MD_CTX *ctx, unsigned char *md)
{
return SHA384_Final(md, EVP_MD_CTX_md_data(ctx));
}
static int init512(EVP_MD_CTX *ctx)
{
return SHA512_Init(EVP_MD_CTX_md_data(ctx));
@ -249,8 +264,8 @@ static const EVP_MD sha384_md = {
SHA384_DIGEST_LENGTH,
EVP_MD_FLAG_DIGALGID_ABSENT,
init384,
update512,
final512,
update384,
final384,
NULL,
NULL,
SHA512_CBLOCK,