1 /*
2 * Cryptographic API
3 *
4 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
5 *
6 * Copyright (c) 2004 Jouni Malinen <jkmaline@cc.hut.fi>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12
13 #include <linux/init.h>
14 #include <linux/module.h>
15 #include <linux/string.h>
16 #include <linux/crypto.h>
17
18
19 struct michael_mic_ctx {
20 u8 pending[4];
21 size_t pending_len;
22
23 u32 l, r;
24 };
25
26
rotl(u32 val,int bits)27 static inline u32 rotl(u32 val, int bits)
28 {
29 return (val << bits) | (val >> (32 - bits));
30 }
31
32
rotr(u32 val,int bits)33 static inline u32 rotr(u32 val, int bits)
34 {
35 return (val >> bits) | (val << (32 - bits));
36 }
37
38
xswap(u32 val)39 static inline u32 xswap(u32 val)
40 {
41 return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
42 }
43
44
45 #define michael_block(l, r) \
46 do { \
47 r ^= rotl(l, 17); \
48 l += r; \
49 r ^= xswap(l); \
50 l += r; \
51 r ^= rotl(l, 3); \
52 l += r; \
53 r ^= rotr(l, 2); \
54 l += r; \
55 } while (0)
56
57
get_le32(const u8 * p)58 static inline u32 get_le32(const u8 *p)
59 {
60 return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
61 }
62
63
put_le32(u8 * p,u32 v)64 static inline void put_le32(u8 *p, u32 v)
65 {
66 p[0] = v;
67 p[1] = v >> 8;
68 p[2] = v >> 16;
69 p[3] = v >> 24;
70 }
71
72
michael_init(void * ctx)73 static void michael_init(void *ctx)
74 {
75 struct michael_mic_ctx *mctx = ctx;
76 mctx->pending_len = 0;
77 }
78
79
michael_update(void * ctx,const u8 * data,unsigned int len)80 static void michael_update(void *ctx, const u8 *data, unsigned int len)
81 {
82 struct michael_mic_ctx *mctx = ctx;
83
84 if (mctx->pending_len) {
85 int flen = 4 - mctx->pending_len;
86 if (flen > len)
87 flen = len;
88 memcpy(&mctx->pending[mctx->pending_len], data, flen);
89 mctx->pending_len += flen;
90 data += flen;
91 len -= flen;
92
93 if (mctx->pending_len < 4)
94 return;
95
96 mctx->l ^= get_le32(mctx->pending);
97 michael_block(mctx->l, mctx->r);
98 mctx->pending_len = 0;
99 }
100
101 while (len >= 4) {
102 mctx->l ^= get_le32(data);
103 michael_block(mctx->l, mctx->r);
104 data += 4;
105 len -= 4;
106 }
107
108 if (len > 0) {
109 mctx->pending_len = len;
110 memcpy(mctx->pending, data, len);
111 }
112 }
113
114
michael_final(void * ctx,u8 * out)115 static void michael_final(void *ctx, u8 *out)
116 {
117 struct michael_mic_ctx *mctx = ctx;
118 u8 *data = mctx->pending;
119
120 /* Last block and padding (0x5a, 4..7 x 0) */
121 switch (mctx->pending_len) {
122 case 0:
123 mctx->l ^= 0x5a;
124 break;
125 case 1:
126 mctx->l ^= data[0] | 0x5a00;
127 break;
128 case 2:
129 mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
130 break;
131 case 3:
132 mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
133 0x5a000000;
134 break;
135 }
136 michael_block(mctx->l, mctx->r);
137 /* l ^= 0; */
138 michael_block(mctx->l, mctx->r);
139
140 put_le32(out, mctx->l);
141 put_le32(out + 4, mctx->r);
142 }
143
144
michael_setkey(void * ctx,const u8 * key,unsigned int keylen,u32 * flags)145 static int michael_setkey(void *ctx, const u8 *key, unsigned int keylen,
146 u32 *flags)
147 {
148 struct michael_mic_ctx *mctx = ctx;
149 if (keylen != 8) {
150 if (flags)
151 *flags = CRYPTO_TFM_RES_BAD_KEY_LEN;
152 return -EINVAL;
153 }
154 mctx->l = get_le32(key);
155 mctx->r = get_le32(key + 4);
156 return 0;
157 }
158
159
160 static struct crypto_alg michael_mic_alg = {
161 .cra_name = "michael_mic",
162 .cra_flags = CRYPTO_ALG_TYPE_DIGEST,
163 .cra_blocksize = 8,
164 .cra_ctxsize = sizeof(struct michael_mic_ctx),
165 .cra_module = THIS_MODULE,
166 .cra_list = LIST_HEAD_INIT(michael_mic_alg.cra_list),
167 .cra_u = { .digest = {
168 .dia_digestsize = 8,
169 .dia_init = michael_init,
170 .dia_update = michael_update,
171 .dia_final = michael_final,
172 .dia_setkey = michael_setkey } }
173 };
174
175
michael_mic_init(void)176 static int __init michael_mic_init(void)
177 {
178 return crypto_register_alg(&michael_mic_alg);
179 }
180
181
michael_mic_exit(void)182 static void __exit michael_mic_exit(void)
183 {
184 crypto_unregister_alg(&michael_mic_alg);
185 }
186
187
188 module_init(michael_mic_init);
189 module_exit(michael_mic_exit);
190
191 MODULE_LICENSE("GPL v2");
192 MODULE_DESCRIPTION("Michael MIC");
193 MODULE_AUTHOR("Jouni Malinen <jkmaline@cc.hut.fi>");
194