[PATCH v6 5/9] 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/mbedtls/sha256.c    | 15 ++++++++++++
 lib/sha256.c            | 51 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 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..c2e77c854b9 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -264,3 +264,54 @@ 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 {
+		memset(keybuf, 0, sizeof(keybuf));
+		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));
+
+	return 0;
+}
-- 
2.25.1