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/* 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"
/* TODO(ngm): add support for hardware hmac. */
static void HMAC_init(LITE_HMAC_CTX *ctx, const void *key, unsigned int len)
{
unsigned int i;
memset(&ctx->opad[0], 0, sizeof(ctx->opad));
if (len > sizeof(ctx->opad)) {
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 < sizeof(ctx->opad); ++i)
ctx->opad[i] ^= 0x36;
DCRYPTO_SHA256_init(&ctx->hash, 0);
/* hash ipad */
HASH_update(&ctx->hash, ctx->opad, sizeof(ctx->opad));
for (i = 0; i < sizeof(ctx->opad); ++i)
ctx->opad[i] ^= (0x36 ^ 0x5c);
}
void DCRYPTO_HMAC_SHA256_init(LITE_HMAC_CTX *ctx, const void *key,
unsigned int len)
{
DCRYPTO_SHA256_init(&ctx->hash, 0);
HMAC_init(ctx, key, len);
}
const uint8_t *DCRYPTO_HMAC_final(LITE_HMAC_CTX *ctx)
{
uint8_t digest[SHA_DIGEST_MAX_BYTES]; /* upto SHA2 */
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, sizeof(ctx->opad));
HASH_update(&ctx->hash, digest, HASH_size(&ctx->hash));
memset(&ctx->opad[0], 0, sizeof(ctx->opad)); /* wipe key */
return HASH_final(&ctx->hash);
}
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