[PATCH v4 5/8] 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.reynes at softathome.com>
---
 include/u-boot/sha256.h |  4 ++++
 lib/sha256_common.c     | 48 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
index 44a9b528b48..2f12275b703 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);
 
+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_common.c b/lib/sha256_common.c
index 7041abd26d9..46262ea99a2 100644
--- a/lib/sha256_common.c
+++ b/lib/sha256_common.c
@@ -48,3 +48,51 @@ 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 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;
+	}
+
+	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));
+}
-- 
2.25.1