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/*
AES-CMAC-128 (rfc 4493)
Copyright (C) Stefan Metzmacher 2012
Copyright (C) Jeremy Allison 2012
Copyright (C) Michael Adam 2012
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/>.
*/
#include "replace.h"
#include "lib/crypto/aes.h"
#include "lib/crypto/aes_cmac_128.h"
static const uint8_t const_Zero[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
static const uint8_t const_Rb[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87
};
#define _MSB(x) (((x)[0] & 0x80)?1:0)
void aes_cmac_128_init(struct aes_cmac_128_context *ctx,
const uint8_t K[AES_BLOCK_SIZE])
{
ZERO_STRUCTP(ctx);
AES_set_encrypt_key(K, 128, &ctx->aes_key);
/* step 1 - generate subkeys k1 and k2 */
AES_encrypt(const_Zero, ctx->L, &ctx->aes_key);
if (_MSB(ctx->L) == 0) {
aes_block_lshift(ctx->L, ctx->K1);
} else {
aes_block_lshift(ctx->L, ctx->tmp);
aes_block_xor(ctx->tmp, const_Rb, ctx->K1);
}
if (_MSB(ctx->K1) == 0) {
aes_block_lshift(ctx->K1, ctx->K2);
} else {
aes_block_lshift(ctx->K1, ctx->tmp);
aes_block_xor(ctx->tmp, const_Rb, ctx->K2);
}
}
void aes_cmac_128_update(struct aes_cmac_128_context *ctx,
const uint8_t *msg, size_t msg_len)
{
/*
* check if we expand the block
*/
if (ctx->last_len < AES_BLOCK_SIZE) {
size_t len = MIN(AES_BLOCK_SIZE - ctx->last_len, msg_len);
if (len > 0) {
memcpy(&ctx->last[ctx->last_len], msg, len);
msg += len;
msg_len -= len;
ctx->last_len += len;
}
}
if (msg_len == 0) {
/* if it is still the last block, we are done */
return;
}
/*
* now checksum everything but the last block
*/
aes_block_xor(ctx->X, ctx->last, ctx->Y);
AES_encrypt(ctx->Y, ctx->X, &ctx->aes_key);
while (msg_len > AES_BLOCK_SIZE) {
aes_block_xor(ctx->X, msg, ctx->Y);
AES_encrypt(ctx->Y, ctx->X, &ctx->aes_key);
msg += AES_BLOCK_SIZE;
msg_len -= AES_BLOCK_SIZE;
}
/*
* copy the last block, it will be processed in
* aes_cmac_128_final().
*/
ZERO_STRUCT(ctx->last);
memcpy(ctx->last, msg, msg_len);
ctx->last_len = msg_len;
}
void aes_cmac_128_final(struct aes_cmac_128_context *ctx,
uint8_t T[AES_BLOCK_SIZE])
{
if (ctx->last_len < AES_BLOCK_SIZE) {
ctx->last[ctx->last_len] = 0x80;
aes_block_xor(ctx->last, ctx->K2, ctx->tmp);
} else {
aes_block_xor(ctx->last, ctx->K1, ctx->tmp);
}
aes_block_xor(ctx->tmp, ctx->X, ctx->Y);
AES_encrypt(ctx->Y, T, &ctx->aes_key);
ZERO_STRUCTP(ctx);
}
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