1 /*
2 * Copyright 2003-2004, Instant802 Networks, Inc.
3 * Copyright 2005-2006, Devicescape Software, Inc.
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>
14
15 #include <net/mac80211.h>
16 #include "key.h"
17 #include "aes_ccm.h"
18
aes_ccm_prepare(struct crypto_cipher * tfm,u8 * scratch,u8 * a)19 static void aes_ccm_prepare(struct crypto_cipher *tfm, u8 *scratch, u8 *a)
20 {
21 int i;
22 u8 *b_0, *aad, *b, *s_0;
23
24 b_0 = scratch + 3 * AES_BLOCK_LEN;
25 aad = scratch + 4 * AES_BLOCK_LEN;
26 b = scratch;
27 s_0 = scratch + AES_BLOCK_LEN;
28
29 crypto_cipher_encrypt_one(tfm, b, b_0);
30
31 /* Extra Authenticate-only data (always two AES blocks) */
32 for (i = 0; i < AES_BLOCK_LEN; i++)
33 aad[i] ^= b[i];
34 crypto_cipher_encrypt_one(tfm, b, aad);
35
36 aad += AES_BLOCK_LEN;
37
38 for (i = 0; i < AES_BLOCK_LEN; i++)
39 aad[i] ^= b[i];
40 crypto_cipher_encrypt_one(tfm, a, aad);
41
42 /* Mask out bits from auth-only-b_0 */
43 b_0[0] &= 0x07;
44
45 /* S_0 is used to encrypt T (= MIC) */
46 b_0[14] = 0;
47 b_0[15] = 0;
48 crypto_cipher_encrypt_one(tfm, s_0, b_0);
49 }
50
51
ieee80211_aes_ccm_encrypt(struct crypto_cipher * tfm,u8 * scratch,u8 * data,size_t data_len,u8 * cdata,u8 * mic)52 void ieee80211_aes_ccm_encrypt(struct crypto_cipher *tfm, u8 *scratch,
53 u8 *data, size_t data_len,
54 u8 *cdata, u8 *mic)
55 {
56 int i, j, last_len, num_blocks;
57 u8 *pos, *cpos, *b, *s_0, *e, *b_0, *aad;
58
59 b = scratch;
60 s_0 = scratch + AES_BLOCK_LEN;
61 e = scratch + 2 * AES_BLOCK_LEN;
62 b_0 = scratch + 3 * AES_BLOCK_LEN;
63 aad = scratch + 4 * AES_BLOCK_LEN;
64
65 num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
66 last_len = data_len % AES_BLOCK_LEN;
67 aes_ccm_prepare(tfm, scratch, b);
68
69 /* Process payload blocks */
70 pos = data;
71 cpos = cdata;
72 for (j = 1; j <= num_blocks; j++) {
73 int blen = (j == num_blocks && last_len) ?
74 last_len : AES_BLOCK_LEN;
75
76 /* Authentication followed by encryption */
77 for (i = 0; i < blen; i++)
78 b[i] ^= pos[i];
79 crypto_cipher_encrypt_one(tfm, b, b);
80
81 b_0[14] = (j >> 8) & 0xff;
82 b_0[15] = j & 0xff;
83 crypto_cipher_encrypt_one(tfm, e, b_0);
84 for (i = 0; i < blen; i++)
85 *cpos++ = *pos++ ^ e[i];
86 }
87
88 for (i = 0; i < CCMP_MIC_LEN; i++)
89 mic[i] = b[i] ^ s_0[i];
90 }
91
92
ieee80211_aes_ccm_decrypt(struct crypto_cipher * tfm,u8 * scratch,u8 * cdata,size_t data_len,u8 * mic,u8 * data)93 int ieee80211_aes_ccm_decrypt(struct crypto_cipher *tfm, u8 *scratch,
94 u8 *cdata, size_t data_len, u8 *mic, u8 *data)
95 {
96 int i, j, last_len, num_blocks;
97 u8 *pos, *cpos, *b, *s_0, *a, *b_0, *aad;
98
99 b = scratch;
100 s_0 = scratch + AES_BLOCK_LEN;
101 a = scratch + 2 * AES_BLOCK_LEN;
102 b_0 = scratch + 3 * AES_BLOCK_LEN;
103 aad = scratch + 4 * AES_BLOCK_LEN;
104
105 num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
106 last_len = data_len % AES_BLOCK_LEN;
107 aes_ccm_prepare(tfm, scratch, a);
108
109 /* Process payload blocks */
110 cpos = cdata;
111 pos = data;
112 for (j = 1; j <= num_blocks; j++) {
113 int blen = (j == num_blocks && last_len) ?
114 last_len : AES_BLOCK_LEN;
115
116 /* Decryption followed by authentication */
117 b_0[14] = (j >> 8) & 0xff;
118 b_0[15] = j & 0xff;
119 crypto_cipher_encrypt_one(tfm, b, b_0);
120 for (i = 0; i < blen; i++) {
121 *pos = *cpos++ ^ b[i];
122 a[i] ^= *pos++;
123 }
124 crypto_cipher_encrypt_one(tfm, a, a);
125 }
126
127 for (i = 0; i < CCMP_MIC_LEN; i++) {
128 if ((mic[i] ^ s_0[i]) != a[i])
129 return -1;
130 }
131
132 return 0;
133 }
134
135
ieee80211_aes_key_setup_encrypt(const u8 key[])136 struct crypto_cipher *ieee80211_aes_key_setup_encrypt(const u8 key[])
137 {
138 struct crypto_cipher *tfm;
139
140 tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
141 if (!IS_ERR(tfm))
142 crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
143
144 return tfm;
145 }
146
147
ieee80211_aes_key_free(struct crypto_cipher * tfm)148 void ieee80211_aes_key_free(struct crypto_cipher *tfm)
149 {
150 crypto_free_cipher(tfm);
151 }
152