--- /dev/null
+/* hmac-sha256.c */
+/*
+ This file is part of the AVR-Crypto-Lib.
+ Copyright (C) 2008 Daniel Otte (daniel.otte@rub.de)
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ *
+ * implementation of HMAC as described in RFC2104
+ * Author: Daniel Otte
+ * email: daniel.otte@rub.de
+ * License: GPLv3 or later
+ **/
+
+/*
+ * hmac = hash ( k^opad , hash( k^ipad , msg))
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include "config.h"
+#include "sha256.h"
+#include "hmac-sha256.h"
+
+#define IPAD 0x36
+#define OPAD 0x5C
+
+#ifndef HMAC_SHA256_SHORTONLY
+
+void hmac_sha256_init(hmac_sha256_ctx_t *s, const void* key, uint16_t keylength_b){
+ uint8_t buffer[HMAC_SHA256_BLOCK_BYTES];
+ uint8_t i;
+
+ memset(buffer, 0, HMAC_SHA256_BLOCK_BYTES);
+ if (keylength_b > HMAC_SHA256_BLOCK_BITS){
+ sha256((void*)buffer, key, keylength_b);
+ } else {
+ memcpy(buffer, key, (keylength_b+7)/8);
+ }
+
+ for (i=0; i<HMAC_SHA256_BLOCK_BYTES; ++i){
+ buffer[i] ^= IPAD;
+ }
+
+ sha256_init(&(s->a));
+ sha256_nextBlock(&(s->a), buffer);
+
+ for (i=0; i<HMAC_SHA256_BLOCK_BYTES; ++i){
+ buffer[i] ^= IPAD^OPAD;
+ }
+ sha256_init(&(s->b));
+ sha256_nextBlock(&(s->b), buffer);
+
+#if defined SECURE_WIPE_BUFFER
+ memset(buffer, 0, SHA256_BLOCK_BYTES);
+#endif
+}
+
+void hmac_sha256_nextBlock(hmac_sha256_ctx_t *s, const void* block){
+ sha256_nextBlock(&(s->a), block);
+}
+
+void hmac_sha256_lastBlock(hmac_sha256_ctx_t *s, const void* block, uint16_t length_b){
+/* while(length_b>=SHA256_BLOCK_BITS){
+ sha256_nextBlock(&(s->a), block);
+ block = (uint8_t*)block + SHA256_BLOCK_BYTES;
+ length_b -= SHA256_BLOCK_BITS;
+ }
+*/ sha256_lastBlock(&(s->a), block, length_b);
+}
+
+void hmac_sha256_final(void* dest, hmac_sha256_ctx_t *s){
+ sha256_ctx2hash((sha256_hash_t*)dest, &(s->a));
+ sha256_lastBlock(&(s->b), dest, SHA256_HASH_BITS);
+ sha256_ctx2hash((sha256_hash_t*)dest, &(s->b));
+}
+
+#endif
+
+/*
+ * keylength in bits!
+ * message length in bits!
+ */
+void hmac_sha256(void* dest, const void* key, uint16_t keylength_b, const void* msg, uint32_t msglength_b){ /* a one-shot*/
+ sha256_ctx_t s;
+ uint8_t i;
+ uint8_t buffer[HMAC_SHA256_BLOCK_BYTES];
+
+ memset(buffer, 0, HMAC_SHA256_BLOCK_BYTES);
+
+ /* if key is larger than a block we have to hash it*/
+ if (keylength_b > SHA256_BLOCK_BITS){
+ sha256((void*)buffer, key, keylength_b);
+ } else {
+ memcpy(buffer, key, (keylength_b+7)/8);
+ }
+
+ for (i=0; i<SHA256_BLOCK_BYTES; ++i){
+ buffer[i] ^= IPAD;
+ }
+ sha256_init(&s);
+ sha256_nextBlock(&s, buffer);
+ while (msglength_b >= HMAC_SHA256_BLOCK_BITS){
+ sha256_nextBlock(&s, msg);
+ msg = (uint8_t*)msg + HMAC_SHA256_BLOCK_BYTES;
+ msglength_b -= HMAC_SHA256_BLOCK_BITS;
+ }
+ sha256_lastBlock(&s, msg, msglength_b);
+ /* since buffer still contains key xor ipad we can do ... */
+ for (i=0; i<HMAC_SHA256_BLOCK_BYTES; ++i){
+ buffer[i] ^= IPAD ^ OPAD;
+ }
+ sha256_ctx2hash(dest, &s); /* save inner hash temporary to dest */
+ sha256_init(&s);
+ sha256_nextBlock(&s, buffer);
+ sha256_lastBlock(&s, dest, SHA256_HASH_BITS);
+ sha256_ctx2hash(dest, &s);
+}