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/*
* One-key CBC MAC (OMAC1) hash with AES-128
*
* Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "aes.h"
#include "aes_wrap.h"
static void gf_mulx(u8 *pad)
{
int i, carry;
carry = pad[0] & 0x80;
for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
pad[AES_BLOCK_SIZE - 1] <<= 1;
if (carry)
pad[AES_BLOCK_SIZE - 1] ^= 0x87;
}
/**
* omac1_aes_128_vector - One-Key CBC MAC (OMAC1) hash with AES-128
* @key: 128-bit key for the hash operation
* @num_elem: Number of elements in the data vector
* @addr: Pointers to the data areas
* @len: Lengths of the data blocks
* @mac: Buffer for MAC (128 bits, i.e., 16 bytes)
* Returns: 0 on success, -1 on failure
*
* This is a mode for using block cipher (AES in this case) for authentication.
* OMAC1 was standardized with the name CMAC by NIST in a Special Publication
* (SP) 800-38B.
*/
int omac1_aes_128_vector(const u8 *key, size_t num_elem,
const u8 *addr[], const size_t *len, u8 *mac)
{
void *ctx;
u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
const u8 *pos, *end;
size_t i, e, left, total_len;
ctx = aes_encrypt_init(key, 16);
if (ctx == NULL)
return -1;
os_memset(cbc, 0, AES_BLOCK_SIZE);
total_len = 0;
for (e = 0; e < num_elem; e++)
total_len += len[e];
left = total_len;
e = 0;
pos = addr[0];
end = pos + len[0];
while (left >= AES_BLOCK_SIZE) {
for (i = 0; i < AES_BLOCK_SIZE; i++) {
cbc[i] ^= *pos++;
if (pos >= end) {
e++;
pos = addr[e];
end = pos + len[e];
}
}
if (left > AES_BLOCK_SIZE)
aes_encrypt(ctx, cbc, cbc);
left -= AES_BLOCK_SIZE;
}
os_memset(pad, 0, AES_BLOCK_SIZE);
aes_encrypt(ctx, pad, pad);
gf_mulx(pad);
if (left || total_len == 0) {
for (i = 0; i < left; i++) {
cbc[i] ^= *pos++;
if (pos >= end) {
e++;
pos = addr[e];
end = pos + len[e];
}
}
cbc[left] ^= 0x80;
gf_mulx(pad);
}
for (i = 0; i < AES_BLOCK_SIZE; i++)
pad[i] ^= cbc[i];
aes_encrypt(ctx, pad, mac);
aes_encrypt_deinit(ctx);
return 0;
}
/**
* omac1_aes_128 - One-Key CBC MAC (OMAC1) hash with AES-128 (aka AES-CMAC)
* @key: 128-bit key for the hash operation
* @data: Data buffer for which a MAC is determined
* @data_len: Length of data buffer in bytes
* @mac: Buffer for MAC (128 bits, i.e., 16 bytes)
* Returns: 0 on success, -1 on failure
*
* This is a mode for using block cipher (AES in this case) for authentication.
* OMAC1 was standardized with the name CMAC by NIST in a Special Publication
* (SP) 800-38B.
*/
int omac1_aes_128(const u8 *key, const u8 *data, size_t data_len, u8 *mac)
{
return omac1_aes_128_vector(key, 1, &data, &data_len, mac);
}