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sys/hashes: add AES-CMAC implementation

master
José Alamos 5 years ago committed by Alexandre Abadie
parent
commit
5dc146269d
  1. 113
      sys/hashes/cmac.c
  2. 85
      sys/include/hashes/cmac.h

113
sys/hashes/cmac.c

@ -0,0 +1,113 @@
/*
* Copyright (C) 2016 Fundación Inria Chile
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup sys_hashes_cmac
* @{
*
* @file
* @brief AES_CMAC implementation
*
* @author José Ignacio Alamos <jose.alamos@inria.cl>
*
* @}
*/
#include <inttypes.h>
#include <stdio.h>
#include <string.h>
#include "crypto/ciphers.h"
#include "hashes/cmac.h"
#define MIN(a, b) a < b ? a : b
static void _xor128(uint8_t *x, uint8_t *y)
{
for (unsigned i = 0; i < 16; i++) {
y[i] = x[i] ^ y[i];
}
}
static void _leftshift(uint8_t *x, uint8_t *y)
{
for (unsigned i = 0; i < 15; i++) {
y[i] = (x[i] << 1) | (x[i + 1] >> 7);
}
y[15] = x[15] << 1;
}
int cmac_init(cmac_context_t *ctx, const uint8_t *key, uint8_t key_size)
{
if (key_size != CMAC_BLOCK_SIZE) {
return CIPHER_ERR_INVALID_KEY_SIZE;
}
memset(ctx, 0, sizeof(cmac_context_t));
return cipher_init(&(ctx->aes_ctx), CIPHER_AES_128, key, key_size);
}
void cmac_update(cmac_context_t *ctx, const void *data, size_t len)
{
uint8_t d[16];
while (len) {
uint8_t c;
if (ctx->M_n == 16) {
ctx->M_n = 0;
_xor128(ctx->M_last, ctx->X);
cipher_encrypt(&ctx->aes_ctx, ctx->X, d);
memcpy(ctx->X, d, CMAC_BLOCK_SIZE);
}
c = MIN(CMAC_BLOCK_SIZE - ctx->M_n, len);
memcpy(ctx->M_last + ctx->M_n, data, c);
ctx->M_n += c;
len -= c;
data = (void *) (((uint8_t *) data) + c);
if (ctx->M_n < CMAC_BLOCK_SIZE) {
break;
}
}
}
void cmac_final(cmac_context_t *ctx, void *digest)
{
/* Generate subkeys */
uint8_t K[CMAC_BLOCK_SIZE];
uint8_t L[CMAC_BLOCK_SIZE];
memset(K, 0, CMAC_BLOCK_SIZE);
cipher_encrypt(&ctx->aes_ctx, K, L);
if (L[0] & 0x80) {
_leftshift(L, K);
K[15] ^= 0x87;
}
else {
_leftshift(L, K);
}
if (ctx->M_n != 16) {
/* Generate K2 */
if (K[0] & 0x80) {
_leftshift(K, K);
K[15] ^= 0x87;
}
else {
_leftshift(K, K);
}
/* Padding */
memset(ctx->M_last + ctx->M_n, 0, CMAC_BLOCK_SIZE - ctx->M_n);
ctx->M_last[ctx->M_n] = 0x80;
}
_xor128(K, ctx->M_last);
_xor128(ctx->M_last, ctx->X);
cipher_encrypt(&ctx->aes_ctx, ctx->X, L);
memcpy(digest, L, CMAC_BLOCK_SIZE);
}

85
sys/include/hashes/cmac.h

@ -0,0 +1,85 @@
/*
* Copyright (C) 2016 Fundación Inria Chile
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup sys_hashes_cmac AES_CMAC
* @ingroup sys_hashes
* @brief Implementation of the AES CMAC hashing function
* @{
*
* @file
* @brief AES_CMAC interface definition
*
* @author José Ignacio Alamos <jose.alamos@inria.cl>
*/
#ifndef HASHES_CMAC_H
#define HASHES_CMAC_H
#include <stdio.h>
#include "crypto/ciphers.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Length of AES_CMAC block in bytes
*/
#define CMAC_BLOCK_SIZE 16
/**
* @brief AES_CMAC calculation context
*/
typedef struct {
/** AES128 context */
cipher_t aes_ctx;
/** auxiliar array for CMAC calculations **/
uint8_t X[CMAC_BLOCK_SIZE];
/** current last block **/
uint8_t M_last[CMAC_BLOCK_SIZE];
/** last byte in last block */
uint32_t M_n;
} cmac_context_t;
/**
* @brief Initialize CMAC message digest context
*
* @param[in] ctx Pointer to the CMAC context to initialize
* @param[in] key Key to be set
* @param[in] key_size Size of the key
*
* @return CIPHER_INIT_SUCCESS if the initialization was successful.
* CIPHER_ERR_INVALID_KEY_SIZE if the key size is not valid.
*/
int cmac_init(cmac_context_t *ctx, const uint8_t *key, uint8_t key_size);
/**
* @brief Update the CMAC context with a portion of the message being hashed
*
* @param[in] ctx Pointer to the CMAC context to update
* @param[in] data Input data
* @param[in] len Length of @p data
*/
void cmac_update(cmac_context_t *ctx, const void *data, size_t len);
/**
* @brief Finalizes the CMAC message digest
*
* @param[in] ctx Pointer to the CMAC context
* @param[out] digest Result location
*/
void cmac_final(cmac_context_t *ctx, void *digest);
#ifdef __cplusplus
}
#endif
#endif /* HASHES_CMAC_H */
/** @} */
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