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

[Philippe REYNES]

Hi Raymond,



Le 16/12/2024 à 16:01, Raymond Mao a écrit :
> Hi Philippe,
>
> On Mon, 16 Dec 2024 at 07:48, Philippe REYNES 
> <philippe.reynes at softathome.com> wrote:
>
>     Hi Raymond,
>
>
>     Le 13/12/2024 à 17:49, Raymond Mao a écrit :
>>
>>     *This Mail comes from Outside of SoftAtHome: *Do not answer,
>>     click links or open attachments unless you recognize the sender
>>     and know the content is safe.
>>
>>     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.
>
>
> If my understanding is correct, "common + mbedtls => 17 seconds" means 
> mbedtls enabled and with your patch,
> while "mbedtls => 17 seconds" means using mbedtls_md_hmac(), right?
>

Correct


> If this is the case, I would prefer to use mbedtls_md_hmac() since it 
> brings more simplicity.
>

Ok, I do the change.

Thanks for this fast answer.


> Regards,
> Raymond


Regards,

Philippe