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Jouni Malinen765cb462009-01-08 13:32:01 +02001/*
2 * AES-128-CMAC with TLen 16 for IEEE 802.11w BIP
3 * Copyright 2008, Jouni Malinen <j@w1.fi>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10#include <linux/kernel.h>
11#include <linux/types.h>
12#include <linux/crypto.h>
13#include <linux/err.h>
Johannes Berg0cd20a22011-07-06 22:02:14 +020014#include <crypto/aes.h>
Jouni Malinen765cb462009-01-08 13:32:01 +020015
16#include <net/mac80211.h>
17#include "key.h"
18#include "aes_cmac.h"
19
Jouni Malinen765cb462009-01-08 13:32:01 +020020#define AES_CMAC_KEY_LEN 16
21#define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
22#define AAD_LEN 20
23
24
25static void gf_mulx(u8 *pad)
26{
27 int i, carry;
28
29 carry = pad[0] & 0x80;
30 for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
31 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
32 pad[AES_BLOCK_SIZE - 1] <<= 1;
33 if (carry)
34 pad[AES_BLOCK_SIZE - 1] ^= 0x87;
35}
36
37
Johannes Berg75396ae2011-07-06 22:00:35 +020038static void aes_128_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
Jouni Malinen765cb462009-01-08 13:32:01 +020039 const u8 *addr[], const size_t *len, u8 *mac)
40{
Johannes Berg75396ae2011-07-06 22:00:35 +020041 u8 scratch[2 * AES_BLOCK_SIZE];
Jouni Malinen765cb462009-01-08 13:32:01 +020042 u8 *cbc, *pad;
43 const u8 *pos, *end;
44 size_t i, e, left, total_len;
45
46 cbc = scratch;
47 pad = scratch + AES_BLOCK_SIZE;
48
49 memset(cbc, 0, AES_BLOCK_SIZE);
50
51 total_len = 0;
52 for (e = 0; e < num_elem; e++)
53 total_len += len[e];
54 left = total_len;
55
56 e = 0;
57 pos = addr[0];
58 end = pos + len[0];
59
60 while (left >= AES_BLOCK_SIZE) {
61 for (i = 0; i < AES_BLOCK_SIZE; i++) {
62 cbc[i] ^= *pos++;
63 if (pos >= end) {
64 e++;
65 pos = addr[e];
66 end = pos + len[e];
67 }
68 }
69 if (left > AES_BLOCK_SIZE)
70 crypto_cipher_encrypt_one(tfm, cbc, cbc);
71 left -= AES_BLOCK_SIZE;
72 }
73
74 memset(pad, 0, AES_BLOCK_SIZE);
75 crypto_cipher_encrypt_one(tfm, pad, pad);
76 gf_mulx(pad);
77
78 if (left || total_len == 0) {
79 for (i = 0; i < left; i++) {
80 cbc[i] ^= *pos++;
81 if (pos >= end) {
82 e++;
83 pos = addr[e];
84 end = pos + len[e];
85 }
86 }
87 cbc[left] ^= 0x80;
88 gf_mulx(pad);
89 }
90
91 for (i = 0; i < AES_BLOCK_SIZE; i++)
92 pad[i] ^= cbc[i];
93 crypto_cipher_encrypt_one(tfm, pad, pad);
94 memcpy(mac, pad, CMAC_TLEN);
95}
96
97
Johannes Berg75396ae2011-07-06 22:00:35 +020098void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,
Jouni Malinen765cb462009-01-08 13:32:01 +020099 const u8 *data, size_t data_len, u8 *mic)
100{
101 const u8 *addr[3];
102 size_t len[3];
103 u8 zero[CMAC_TLEN];
104
105 memset(zero, 0, CMAC_TLEN);
106 addr[0] = aad;
107 len[0] = AAD_LEN;
108 addr[1] = data;
109 len[1] = data_len - CMAC_TLEN;
110 addr[2] = zero;
111 len[2] = CMAC_TLEN;
112
Johannes Berg75396ae2011-07-06 22:00:35 +0200113 aes_128_cmac_vector(tfm, 3, addr, len, mic);
Jouni Malinen765cb462009-01-08 13:32:01 +0200114}
115
116
117struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[])
118{
119 struct crypto_cipher *tfm;
120
121 tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
Ben Hutchings1ac62ba2010-08-01 17:37:03 +0100122 if (!IS_ERR(tfm))
123 crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN);
Jouni Malinen765cb462009-01-08 13:32:01 +0200124
125 return tfm;
126}
127
128
129void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
130{
Jesper Juhlffa56e542010-11-04 22:59:56 +0100131 crypto_free_cipher(tfm);
Jouni Malinen765cb462009-01-08 13:32:01 +0200132}