1 files changed, 63 insertions, 0 deletions
diff --git a/chip/g/dcrypto/hmac.c b/chip/g/dcrypto/hmac.c
new file mode 100644
index 0000000000..7cc45a03ba
--- /dev/null
+++ b/chip/g/dcrypto/hmac.c
@@ -0,0 +1,63 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "internal.h"
+#include "dcrypto.h"
+
+#include <stdint.h>
+
+#include "cryptoc/sha256.h"
+#include "cryptoc/util.h"
+
+/* TODO(sukhomlinov): add support for hardware hmac. */
+static void hmac_sha256_init(LITE_HMAC_CTX *ctx, const void *key,
+			     unsigned int len)
+{
+	unsigned int i;
+
+	BUILD_ASSERT(sizeof(ctx->opad) >= SHA256_BLOCK_SIZE);
+
+	memset(&ctx->opad[0], 0, SHA256_BLOCK_SIZE);
+
+	if (len > SHA256_BLOCK_SIZE) {
+		DCRYPTO_SHA256_init(&ctx->hash, 0);
+		HASH_update(&ctx->hash, key, len);
+		memcpy(&ctx->opad[0], HASH_final(&ctx->hash),
+		       HASH_size(&ctx->hash));
+	} else {
+		memcpy(&ctx->opad[0], key, len);
+	}
+
+	for (i = 0; i < SHA256_BLOCK_SIZE; ++i)
+		ctx->opad[i] ^= 0x36;
+
+	DCRYPTO_SHA256_init(&ctx->hash, 0);
+	/* hash ipad */
+	HASH_update(&ctx->hash, ctx->opad, SHA256_BLOCK_SIZE);
+
+	for (i = 0; i < SHA256_BLOCK_SIZE; ++i)
+		ctx->opad[i] ^= (0x36 ^ 0x5c);
+}
+
+void DCRYPTO_HMAC_SHA256_init(LITE_HMAC_CTX *ctx, const void *key,
+			      unsigned int len)
+{
+	hmac_sha256_init(ctx, key, len);
+}
+
+const uint8_t *DCRYPTO_HMAC_final(LITE_HMAC_CTX *ctx)
+{
+	uint8_t digest[SHA256_DIGEST_SIZE]; /* up to SHA256 */
+
+	memcpy(digest, HASH_final(&ctx->hash),
+	       (HASH_size(&ctx->hash) <= sizeof(digest) ?
+			HASH_size(&ctx->hash) :
+			sizeof(digest)));
+	DCRYPTO_SHA256_init(&ctx->hash, 0);
+	HASH_update(&ctx->hash, ctx->opad, SHA256_BLOCK_SIZE);
+	HASH_update(&ctx->hash, digest, HASH_size(&ctx->hash));
+	always_memset(&ctx->opad[0], 0, SHA256_BLOCK_SIZE); /* wipe key */
+	return HASH_final(&ctx->hash);
+}