[PATCH v5 5/9] lib: sha256: add feature sha256_hmac

[Philippe REYNES]

Hi Raymond,


Le 17/12/2024 à 15:54, Raymond Mao a écrit :
>
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>
> Hi Philippe,
>
> On Tue, 17 Dec 2024 at 03:32, 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/mbedtls/sha256.c    | 15 +++++++++++++
>      lib/sha256.c            | 50
>     +++++++++++++++++++++++++++++++++++++++++
>      3 files changed, 69 insertions(+)
>
>     diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
>     index 44a9b528b48..99cf78e204c 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);
>
>     +int 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/mbedtls/sha256.c b/lib/mbedtls/sha256.c
>     index 2128e598834..7d456a82017 100644
>     --- a/lib/mbedtls/sha256.c
>     +++ b/lib/mbedtls/sha256.c
>     @@ -10,6 +10,8 @@
>      #endif /* USE_HOSTCC */
>      #include <u-boot/sha256.h>
>
>     +#include <mbedtls/md.h>
>     +
>      const u8 sha256_der_prefix[SHA256_DER_LEN] = {
>             0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
>             0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
>     @@ -33,3 +35,16 @@ void sha256_finish(sha256_context *ctx, uint8_t
>     digest[SHA256_SUM_LEN])
>             mbedtls_sha256_finish(ctx, digest);
>             mbedtls_sha256_free(ctx);
>      }
>     +
>     +int sha256_hmac(const unsigned char *key, int keylen,
>     +               const unsigned char *input, unsigned int ilen,
>     +               unsigned char *output)
>     +{
>     +       const mbedtls_md_info_t *md;
>     +
>     +       md = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
>     +       if (!md)
>     +               return MBEDTLS_ERR_MD_FEATURE_UNAVAILABLE;
>     +
>     +       return mbedtls_md_hmac(md, key, keylen, input, ilen, output);
>     +}
>     diff --git a/lib/sha256.c b/lib/sha256.c
>     index 827bd9a872b..a18aec3928b 100644
>     --- a/lib/sha256.c
>     +++ b/lib/sha256.c
>     @@ -264,3 +264,53 @@ void sha256_finish(sha256_context * ctx,
>     uint8_t digest[32])
>             PUT_UINT32_BE(ctx->state[6], digest, 24);
>             PUT_UINT32_BE(ctx->state[7], digest, 28);
>      }
>     +
>     +int 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;
>
>
> All looks fine but keys shorter than 64 bytes are copied as is, 
> without explicit zero-padding, this might be an issue.


You're right, I have fixed that in v6.


>
>     +       }
>     +
>     +       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));
>     +
>     +       return 0;
>     +}
>     -- 
>     2.25.1
>
>
> Regards,
> Raymond


Regards,

Philippe