xref: /openbmc/linux/net/mac80211/aes_cmac.c (revision 12eb4683)
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 
26 static 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 
39 static 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 
95 void 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 
114 struct 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 
126 void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
127 {
128 	crypto_free_cipher(tfm);
129 }
130 
131 void 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 }
146 EXPORT_SYMBOL(ieee80211_aes_cmac_calculate_k1_k2);
147