aes_ccm.c
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/*
* Copyright 2003-2004, Instant802 Networks, Inc.
* Copyright 2005-2006, Devicescape Software, Inc.
*
* 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 "ieee80211_key.h"
#include "aes_ccm.h"
static void ieee80211_aes_encrypt(struct crypto_cipher *tfm,
const u8 pt[16], u8 ct[16])
{
crypto_cipher_encrypt_one(tfm, ct, pt);
}
static inline void aes_ccm_prepare(struct crypto_cipher *tfm, u8 *b_0, u8 *aad,
u8 *b, u8 *s_0, u8 *a)
{
int i;
ieee80211_aes_encrypt(tfm, b_0, b);
/* Extra Authenticate-only data (always two AES blocks) */
for (i = 0; i < AES_BLOCK_LEN; i++)
aad[i] ^= b[i];
ieee80211_aes_encrypt(tfm, aad, b);
aad += AES_BLOCK_LEN;
for (i = 0; i < AES_BLOCK_LEN; i++)
aad[i] ^= b[i];
ieee80211_aes_encrypt(tfm, aad, a);
/* Mask out bits from auth-only-b_0 */
b_0[0] &= 0x07;
/* S_0 is used to encrypt T (= MIC) */
b_0[14] = 0;
b_0[15] = 0;
ieee80211_aes_encrypt(tfm, b_0, s_0);
}
void ieee80211_aes_ccm_encrypt(struct crypto_cipher *tfm, u8 *scratch,
u8 *b_0, u8 *aad, u8 *data, size_t data_len,
u8 *cdata, u8 *mic)
{
int i, j, last_len, num_blocks;
u8 *pos, *cpos, *b, *s_0, *e;
b = scratch;
s_0 = scratch + AES_BLOCK_LEN;
e = scratch + 2 * AES_BLOCK_LEN;
num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
last_len = data_len % AES_BLOCK_LEN;
aes_ccm_prepare(tfm, b_0, aad, b, s_0, b);
/* Process payload blocks */
pos = data;
cpos = cdata;
for (j = 1; j <= num_blocks; j++) {
int blen = (j == num_blocks && last_len) ?
last_len : AES_BLOCK_LEN;
/* Authentication followed by encryption */
for (i = 0; i < blen; i++)
b[i] ^= pos[i];
ieee80211_aes_encrypt(tfm, b, b);
b_0[14] = (j >> 8) & 0xff;
b_0[15] = j & 0xff;
ieee80211_aes_encrypt(tfm, b_0, e);
for (i = 0; i < blen; i++)
*cpos++ = *pos++ ^ e[i];
}
for (i = 0; i < CCMP_MIC_LEN; i++)
mic[i] = b[i] ^ s_0[i];
}
int ieee80211_aes_ccm_decrypt(struct crypto_cipher *tfm, u8 *scratch,
u8 *b_0, u8 *aad, u8 *cdata, size_t data_len,
u8 *mic, u8 *data)
{
int i, j, last_len, num_blocks;
u8 *pos, *cpos, *b, *s_0, *a;
b = scratch;
s_0 = scratch + AES_BLOCK_LEN;
a = scratch + 2 * AES_BLOCK_LEN;
num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
last_len = data_len % AES_BLOCK_LEN;
aes_ccm_prepare(tfm, b_0, aad, b, s_0, a);
/* Process payload blocks */
cpos = cdata;
pos = data;
for (j = 1; j <= num_blocks; j++) {
int blen = (j == num_blocks && last_len) ?
last_len : AES_BLOCK_LEN;
/* Decryption followed by authentication */
b_0[14] = (j >> 8) & 0xff;
b_0[15] = j & 0xff;
ieee80211_aes_encrypt(tfm, b_0, b);
for (i = 0; i < blen; i++) {
*pos = *cpos++ ^ b[i];
a[i] ^= *pos++;
}
ieee80211_aes_encrypt(tfm, a, a);
}
for (i = 0; i < CCMP_MIC_LEN; i++) {
if ((mic[i] ^ s_0[i]) != a[i])
return -1;
}
return 0;
}
struct crypto_cipher * ieee80211_aes_key_setup_encrypt(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, ALG_CCMP_KEY_LEN);
return tfm;
}
void ieee80211_aes_key_free(struct crypto_cipher *tfm)
{
if (tfm)
crypto_free_cipher(tfm);
}