Commit babab8e7 authored by Viktor Dukhovni's avatar Viktor Dukhovni
Browse files

Avoid fragile aliasing of SHA224/384 update/final 



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: default avatarRich Salz <rsalz@openssl.org>
parent 72960279

crypto/evp/m_sha1.c

+24 −9
Original line number Diff line number Diff line
@@ -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,