[PATCH v3 4/5] lib: mbedtls: sha256: add support of key derivation

[Philippe REYNES]

Hi Raymond,


Le 09/12/2024 à 17:28, Raymond Mao a écrit :
>
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>
> Hi Philippe,
>
> On Mon, 9 Dec 2024 at 04:42, Philippe Reynes 
> <philippe.reynes at softathome.com> wrote:
>
>     Adds the support of key derivation using the scheme hkdf.
>     This scheme is defined in rfc5869.
>
>     Signed-off-by: Philippe Reynes <philippe.reynes at softathome.com>
>     ---
>      include/u-boot/sha256.h |  7 +++++++
>      lib/mbedtls/sha256.c    | 22 ++++++++++++++++++++++
>      2 files changed, 29 insertions(+)
>
>     diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
>     index 2f12275b703..5643efcb85c 100644
>     --- a/include/u-boot/sha256.h
>     +++ b/include/u-boot/sha256.h
>     @@ -49,4 +49,11 @@ void sha256_hmac(const unsigned char *key, int
>     keylen,
>                      const unsigned char *input, unsigned int ilen,
>                      unsigned char *output);
>
>     +#if defined(CONFIG_HKDF_MBEDTLS)
>     +int sha256_hkdf(const unsigned char *salt, int saltlen,
>     +               const unsigned char *ikm, int ikmlen,
>     +               const unsigned char *info, int infolen,
>     +               unsigned char *output, int outputlen);
>     +#endif
>     +
>
>
> I think this will be better:
> #if CONFIG_IS_ENABLED(HKDF_MBEDTLS)
> int sha256_hkdf(const unsigned char *salt, int saltlen,
>                  const unsigned char *ikm, int ikmlen,
>                  const unsigned char *info, int infolen,
>                  unsigned char *output, int outputlen);
> #else
> static inline int sha256_hkdf(const unsigned char __always_unused *salt,
>                 int __always_unused saltlen,
>                 const unsigned char __always_unused *ikm,
>                 int __always_unused ikmlen,
>                 const unsigned char __always_unused *info,
>                 int __always_unused infolen,
>                 unsigned char __always_unused *output,
>                 int __always_unused outputlen) {
>         return -EOPNOTSUPP;
> }
> #endif


I have done this change in the v4


>      #endif /* _SHA256_H */
>     diff --git a/lib/mbedtls/sha256.c b/lib/mbedtls/sha256.c
>     index 1b9fc1a8503..6e9659d31bb 100644
>     --- a/lib/mbedtls/sha256.c
>     +++ b/lib/mbedtls/sha256.c
>     @@ -11,6 +11,11 @@
>      #include <string.h>
>      #include <u-boot/sha256.h>
>
>     +#if CONFIG_IS_ENABLED(HKDF_MBEDTLS)
>     +#include <mbedtls/md.h>
>     +#include <mbedtls/hkdf.h>
>     +#endif
>     +
>      const u8 sha256_der_prefix[SHA256_DER_LEN] = {
>             0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
>             0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
>     @@ -98,3 +103,20 @@ void sha256_hmac(const unsigned char *key, int
>     keylen,
>             memset(tmpbuf, 0, sizeof(tmpbuf));
>             memset(&ctx, 0, sizeof(sha256_context));
>      }
>     +
>     +#if CONFIG_IS_ENABLED(HKDF_MBEDTLS)
>     +int sha256_hkdf(const unsigned char *salt, int saltlen,
>     +               const unsigned char *ikm, int ikmlen,
>     +               const unsigned char *info, int infolen,
>     +               unsigned char *output, int outputlen)
>     +{
>     +       const mbedtls_md_info_t *md;
>     +
>     +       md = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
>     +
>     +       return mbedtls_hkdf(md, salt, saltlen,
>     +                           ikm, ikmlen,
>     +                           info, infolen,
>     +                           output, outputlen);
>     +}
>     +#endif
>     -- 
>     2.25.1
>
Regards,
Philippe