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/*
* AES-128-CMAC with TLen 16 for IEEE 802.11w BIP
* Copyright 2008, Jouni Malinen <j@w1.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <net/mac80211.h>
#include "key.h"
#include "aes_cmac.h"
#define AES_BLOCK_SIZE 16
#define AES_CMAC_KEY_LEN 16
#define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
#define AAD_LEN 20
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;
}
static void aes_128_cmac_vector(struct crypto_cipher *tfm, u8 *scratch,
size_t num_elem,
const u8 *addr[], const size_t *len, u8 *mac)
{
u8 *cbc, *pad;
const u8 *pos, *end;
size_t i, e, left, total_len;
cbc = scratch;
pad = scratch + AES_BLOCK_SIZE;
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)
crypto_cipher_encrypt_one(tfm, cbc, cbc);
left -= AES_BLOCK_SIZE;
}
memset(pad, 0, AES_BLOCK_SIZE);
crypto_cipher_encrypt_one(tfm, 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];
crypto_cipher_encrypt_one(tfm, pad, pad);
memcpy(mac, pad, CMAC_TLEN);
}
void ieee80211_aes_cmac(struct crypto_cipher *tfm, u8 *scratch, const u8 *aad,
const u8 *data, size_t data_len, u8 *mic)
{
const u8 *addr[3];
size_t len[3];
u8 zero[CMAC_TLEN];
memset(zero, 0, CMAC_TLEN);
addr[0] = aad;
len[0] = AAD_LEN;
addr[1] = data;
len[1] = data_len - CMAC_TLEN;
addr[2] = zero;
len[2] = CMAC_TLEN;
aes_128_cmac_vector(tfm, scratch, 3, addr, len, mic);
}
struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[])
{
struct crypto_cipher *tfm;
tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(tfm))
return NULL;
crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN);
return tfm;
}
void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
{
if (tfm)
crypto_free_cipher(tfm);
}
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