[PATCH v4 5/8] lib: sha256: add feature sha256_hmac

[Philippe REYNES]

Hi Raymond,


Le 13/12/2024 à 17:49, Raymond Mao a écrit :
>
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>
> Hi Philippe,
>
> On Thu, 12 Dec 2024 at 08:37, Philippe Reynes 
> <philippe.reynes at softathome.com> wrote:
>
>     Adds the support of the hmac based on sha256.
>     This implementation is based on rfc2104.
>
>     Signed-off-by: Philippe Reynes <philippe.reynes at softathome.com>
>     ---
>      include/u-boot/sha256.h |  4 ++++
>      lib/sha256_common.c     | 48
>     +++++++++++++++++++++++++++++++++++++++++
>      2 files changed, 52 insertions(+)
>
>     diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
>     index 44a9b528b48..2f12275b703 100644
>     --- a/include/u-boot/sha256.h
>     +++ b/include/u-boot/sha256.h
>     @@ -45,4 +45,8 @@ void sha256_finish(sha256_context * ctx, uint8_t
>     digest[SHA256_SUM_LEN]);
>      void sha256_csum_wd(const unsigned char *input, unsigned int ilen,
>                     unsigned char *output, unsigned int chunk_sz);
>
>     +void sha256_hmac(const unsigned char *key, int keylen,
>     +                const unsigned char *input, unsigned int ilen,
>     +                unsigned char *output);
>     +
>      #endif /* _SHA256_H */
>     diff --git a/lib/sha256_common.c b/lib/sha256_common.c
>     index 7041abd26d9..46262ea99a2 100644
>     --- a/lib/sha256_common.c
>     +++ b/lib/sha256_common.c
>     @@ -48,3 +48,51 @@ void sha256_csum_wd(const unsigned char *input,
>     unsigned int ilen,
>
>             sha256_finish(&ctx, output);
>      }
>     +
>     +void sha256_hmac(const unsigned char *key, int keylen,
>     +                const unsigned char *input, unsigned int ilen,
>     +                unsigned char *output)
>     +{
>     +       int i;
>     +       sha256_context ctx;
>     +       unsigned char keybuf[64];
>     +       unsigned char k_ipad[64];
>     +       unsigned char k_opad[64];
>     +       unsigned char tmpbuf[32];
>     +       int keybuf_len;
>     +
>     +       if (keylen > 64) {
>     +               sha256_starts(&ctx);
>     +               sha256_update(&ctx, key, keylen);
>     +               sha256_finish(&ctx, keybuf);
>     +
>     +               keybuf_len = 32;
>     +       } else {
>     +               memcpy(keybuf, key, keylen);
>     +               keybuf_len = keylen;
>     +       }
>     +
>     +       memset(k_ipad, 0x36, 64);
>     +       memset(k_opad, 0x5C, 64);
>     +
>     +       for (i = 0; i < keybuf_len; i++) {
>     +               k_ipad[i] ^= keybuf[i];
>     +               k_opad[i] ^= keybuf[i];
>     +       }
>     +
>     +       sha256_starts(&ctx);
>     +       sha256_update(&ctx, k_ipad, sizeof(k_ipad));
>     +       sha256_update(&ctx, input, ilen);
>     +       sha256_finish(&ctx, tmpbuf);
>     +
>     +       sha256_starts(&ctx);
>     +       sha256_update(&ctx, k_opad, sizeof(k_opad));
>     +       sha256_update(&ctx, tmpbuf, sizeof(tmpbuf));
>     +       sha256_finish(&ctx, output);
>     +
>     +       memset(k_ipad, 0, sizeof(k_ipad));
>     +       memset(k_opad, 0, sizeof(k_opad));
>     +       memset(tmpbuf, 0, sizeof(tmpbuf));
>     +       memset(keybuf, 0, sizeof(keybuf));
>     +       memset(&ctx, 0, sizeof(sha256_context));
>     +}
>     -- 
>     2.25.1
>
> The sha256 hmac common implementation now sounds good.
> Do you have a comparison of performance with the MbedTLS high-level API
> mbedtls_md_hmac()?
> I am wondering if it is worth using this API specially when MbedTLS is 
> enabled,
> since it significantly simplifies the implementation.
>
I have done some test, and the legacy implementation is the fastest.
To do my test, I have run 1 000 000 times the unit test for hmac.
here the result:
common + legacy => 7 seconds
common + mbedtls => 17 seconds
mbedtls => 17 seconds

I have kept common + mbedtls for the v5.
But I may use a pure mbedtls if you prefer.


> Regards,
> Raymond


Regards,

Philippe