Re: [PATCH 1/4] lib: sha256: add feature sha256_hmac

Hi Philippe,

It might be useful to have a cover letter explaining what the plans for this code are, great that there are tests but adding code in without it being used isn't always a feature so a cover letter with some details often helps with the context.

Also if you're not aware there's work to integrate MBedTLS [1] and I'm not sure if that also may provide the functionality.

Peter

[1] https://lists.denx.de/pipermail/u-boot/2024-July/557832.html

On Tue, 16 Jul 2024 at 16:16, Philippe Reynes philippe.reynes@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@softathome.com

include/u-boot/sha256.h | 4 ++++ lib/sha256.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+)

diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h index a4fe176c0b4..7aa4c54d0d4 100644 --- a/include/u-boot/sha256.h +++ b/include/u-boot/sha256.h @@ -24,4 +24,8 @@ 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.c b/lib/sha256.c index 665ba6f152e..64f6b48974b 100644 --- a/lib/sha256.c +++ b/lib/sha256.c @@ -298,3 +298,43 @@ void sha256_csum_wd(const unsigned char *input, unsigned int ilen,

    sha256_finish(&ctx, output);

}

+/*

• • Output = HMAC-SHA-256( input buffer, hmac key )
• */

+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 k_ipad[64];
  

•   unsigned char k_opad[64];
  

•   unsigned char tmpbuf[32];
  

•   memset(k_ipad, 0x36, 64);
  

•   memset(k_opad, 0x5C, 64);
  

•   for (i = 0; i < keylen; i++) {
  

•           if (i >= 64)
  

•                   break;
  

•           k_ipad[i] ^= key[i];
  

•           k_opad[i] ^= key[i];
  

•   }
  

•   sha256_starts(&ctx);
  

•   sha256_update(&ctx, k_ipad, 64);
  

•   sha256_update(&ctx, input, ilen);
  

•   sha256_finish(&ctx, tmpbuf);
  

•   sha256_starts(&ctx);
  

•   sha256_update(&ctx, k_opad, 64);
  

•   sha256_update(&ctx, tmpbuf, 32);
  

•   sha256_finish(&ctx, output);
  

•   memset(k_ipad, 0, 64);
  

•   memset(k_opad, 0, 64);
  

•   memset(tmpbuf, 0, 32);
  

•   memset(&ctx, 0, sizeof(sha256_context));
  

+}

2.25.1