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

[Philippe Reynes <philippe.reynes@softathome.com>]

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