1/*
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/export.h>
14#include <linux/err.h>
15#include <crypto/aes.h>
16
17#include <net/mac80211.h>
18#include "key.h"
19#include "aes_cmac.h"
20
21#define AES_CMAC_KEY_LEN 16
22#define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
23#define AAD_LEN 20
24
25
26static void gf_mulx(u8 *pad)
27{
28	int i, carry;
29
30	carry = pad[0] & 0x80;
31	for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
32		pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
33	pad[AES_BLOCK_SIZE - 1] <<= 1;
34	if (carry)
35		pad[AES_BLOCK_SIZE - 1] ^= 0x87;
36}
37
38
39static void aes_128_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
40				const u8 *addr[], const size_t *len, u8 *mac)
41{
42	u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
43	const u8 *pos, *end;
44	size_t i, e, left, total_len;
45
46	memset(cbc, 0, AES_BLOCK_SIZE);
47
48	total_len = 0;
49	for (e = 0; e < num_elem; e++)
50		total_len += len[e];
51	left = total_len;
52
53	e = 0;
54	pos = addr[0];
55	end = pos + len[0];
56
57	while (left >= AES_BLOCK_SIZE) {
58		for (i = 0; i < AES_BLOCK_SIZE; i++) {
59			cbc[i] ^= *pos++;
60			if (pos >= end) {
61				e++;
62				pos = addr[e];
63				end = pos + len[e];
64			}
65		}
66		if (left > AES_BLOCK_SIZE)
67			crypto_cipher_encrypt_one(tfm, cbc, cbc);
68		left -= AES_BLOCK_SIZE;
69	}
70
71	memset(pad, 0, AES_BLOCK_SIZE);
72	crypto_cipher_encrypt_one(tfm, pad, pad);
73	gf_mulx(pad);
74
75	if (left || total_len == 0) {
76		for (i = 0; i < left; i++) {
77			cbc[i] ^= *pos++;
78			if (pos >= end) {
79				e++;
80				pos = addr[e];
81				end = pos + len[e];
82			}
83		}
84		cbc[left] ^= 0x80;
85		gf_mulx(pad);
86	}
87
88	for (i = 0; i < AES_BLOCK_SIZE; i++)
89		pad[i] ^= cbc[i];
90	crypto_cipher_encrypt_one(tfm, pad, pad);
91	memcpy(mac, pad, CMAC_TLEN);
92}
93
94
95void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,
96			const u8 *data, size_t data_len, u8 *mic)
97{
98	const u8 *addr[3];
99	size_t len[3];
100	u8 zero[CMAC_TLEN];
101
102	memset(zero, 0, CMAC_TLEN);
103	addr[0] = aad;
104	len[0] = AAD_LEN;
105	addr[1] = data;
106	len[1] = data_len - CMAC_TLEN;
107	addr[2] = zero;
108	len[2] = CMAC_TLEN;
109
110	aes_128_cmac_vector(tfm, 3, addr, len, mic);
111}
112
113
114struct crypto_cipher *ieee80211_aes_cmac_key_setup(const u8 key[])
115{
116	struct crypto_cipher *tfm;
117
118	tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
119	if (!IS_ERR(tfm))
120		crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN);
121
122	return tfm;
123}
124
125
126void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
127{
128	crypto_free_cipher(tfm);
129}
130
131void ieee80211_aes_cmac_calculate_k1_k2(struct ieee80211_key_conf *keyconf,
132					u8 *k1, u8 *k2)
133{
134	u8 l[AES_BLOCK_SIZE] = {};
135	struct ieee80211_key *key =
136		container_of(keyconf, struct ieee80211_key, conf);
137
138	crypto_cipher_encrypt_one(key->u.aes_cmac.tfm, l, l);
139
140	memcpy(k1, l, AES_BLOCK_SIZE);
141	gf_mulx(k1);
142
143	memcpy(k2, k1, AES_BLOCK_SIZE);
144	gf_mulx(k2);
145}
146EXPORT_SYMBOL(ieee80211_aes_cmac_calculate_k1_k2);
147