[PATCH v2 2/5] lib: sha256: add feature sha256_hmac

[Philippe Reynes]

Adds the support of the hmac based on sha256.
This implementation is based on rfc2104.

Signed-off-by: Philippe Reynes <philippe.rey...@softathome.com>
---
 include/u-boot/sha256.h |  4 ++++
 lib/mbedtls/sha256.c    | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
index b58d5b58d39..77dbcd4553a 100644
--- a/include/u-boot/sha256.h
+++ b/include/u-boot/sha256.h
@@ -44,4 +44,8 @@ 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/mbedtls/sha256.c b/lib/mbedtls/sha256.c
index 24aa58fa674..1b9fc1a8503 100644
--- a/lib/mbedtls/sha256.c
+++ b/lib/mbedtls/sha256.c
@@ -8,6 +8,7 @@
 #ifndef USE_HOSTCC
 #include <cyclic.h>
 #endif /* USE_HOSTCC */
+#include <string.h>
 #include <u-boot/sha256.h>
 
 const u8 sha256_der_prefix[SHA256_DER_LEN] = {
@@ -60,3 +61,40 @@ 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 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, 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(&ctx, 0, sizeof(sha256_context));
+}
-- 
2.25.1