contiki/core/lib/ccm-star.c

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/*
* Copyright (c) 2013, Hasso-Plattner-Institut.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
*/
/**
* \file
* AES_128-based CCM* implementation.
* \author
* Original: Konrad Krentz <konrad.krentz@gmail.com>
* Generified version: Justin King-Lacroix <justin.kinglacroix@gmail.com>
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*/
#include "ccm-star.h"
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#include "lib/aes-128.h"
#include <string.h>
/* see RFC 3610 */
#define CCM_STAR_AUTH_FLAGS(Adata, M) ((Adata ? (1u << 6) : 0) | (((M - 2u) >> 1) << 3) | 1u)
#define CCM_STAR_ENCRYPTION_FLAGS 1
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/*---------------------------------------------------------------------------*/
static void
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set_iv(uint8_t *iv,
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uint8_t flags,
const uint8_t *nonce,
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uint8_t counter)
{
iv[0] = flags;
memcpy(iv + 1, nonce, CCM_STAR_NONCE_LENGTH);
iv[14] = 0;
iv[15] = counter;
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}
/*---------------------------------------------------------------------------*/
/* XORs the block m[pos] ... m[pos + 15] with K_{counter} */
static void
ctr_step(const uint8_t *nonce,
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uint8_t pos,
uint8_t *m_and_result,
uint8_t m_len,
uint8_t counter)
{
uint8_t a[AES_128_BLOCK_SIZE];
uint8_t i;
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set_iv(a, CCM_STAR_ENCRYPTION_FLAGS, nonce, counter);
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AES_128.encrypt(a);
for(i = 0; (pos + i < m_len) && (i < AES_128_BLOCK_SIZE); i++) {
m_and_result[pos + i] ^= a[i];
}
}
/*---------------------------------------------------------------------------*/
static void
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mic(const uint8_t *nonce,
const uint8_t *m, uint8_t m_len,
const uint8_t *a, uint8_t a_len,
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uint8_t *result,
uint8_t mic_len)
{
uint8_t x[AES_128_BLOCK_SIZE];
uint8_t pos;
uint8_t i;
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set_iv(x, CCM_STAR_AUTH_FLAGS(a_len, mic_len), nonce, m_len);
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AES_128.encrypt(x);
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if(a_len) {
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x[1] = x[1] ^ a_len;
for(i = 2; (i - 2 < a_len) && (i < AES_128_BLOCK_SIZE); i++) {
x[i] ^= a[i - 2];
}
AES_128.encrypt(x);
pos = 14;
while(pos < a_len) {
for(i = 0; (pos + i < a_len) && (i < AES_128_BLOCK_SIZE); i++) {
x[i] ^= a[pos + i];
}
pos += AES_128_BLOCK_SIZE;
AES_128.encrypt(x);
}
}
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if(m_len) {
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pos = 0;
while(pos < m_len) {
for(i = 0; (pos + i < m_len) && (i < AES_128_BLOCK_SIZE); i++) {
x[i] ^= m[pos + i];
}
pos += AES_128_BLOCK_SIZE;
AES_128.encrypt(x);
}
}
ctr_step(nonce, 0, x, AES_128_BLOCK_SIZE, 0);
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memcpy(result, x, mic_len);
}
/*---------------------------------------------------------------------------*/
static void
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ctr(const uint8_t *nonce, uint8_t *m, uint8_t m_len)
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{
uint8_t pos;
uint8_t counter;
pos = 0;
counter = 1;
while(pos < m_len) {
ctr_step(nonce, pos, m, m_len, counter++);
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pos += AES_128_BLOCK_SIZE;
}
}
/*---------------------------------------------------------------------------*/
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static void
set_key(const uint8_t *key)
{
AES_128.set_key(key);
}
/*---------------------------------------------------------------------------*/
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static void
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aead(const uint8_t* nonce,
uint8_t* m, uint8_t m_len,
const uint8_t* a, uint8_t a_len,
uint8_t *result, uint8_t mic_len,
int forward)
{
if(!forward) {
/* decrypt */
ctr(nonce, m, m_len);
}
mic(nonce,
m, m_len,
a, a_len,
result,
mic_len);
if(forward) {
/* encrypt */
ctr(nonce, m, m_len);
}
}
/*---------------------------------------------------------------------------*/
const struct ccm_star_driver ccm_star_driver = {
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set_key,
aead
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};
/*---------------------------------------------------------------------------*/