Root/crypto/michael_mic.c

1/*
2 * Cryptographic API
3 *
4 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
5 *
6 * Copyright (c) 2004 Jouni Malinen <j@w1.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#include <crypto/internal/hash.h>
13#include <asm/byteorder.h>
14#include <linux/init.h>
15#include <linux/module.h>
16#include <linux/string.h>
17#include <linux/types.h>
18
19
20struct michael_mic_ctx {
21    u32 l, r;
22};
23
24struct michael_mic_desc_ctx {
25    u8 pending[4];
26    size_t pending_len;
27
28    u32 l, r;
29};
30
31static inline u32 xswap(u32 val)
32{
33    return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
34}
35
36
37#define michael_block(l, r) \
38do { \
39    r ^= rol32(l, 17); \
40    l += r; \
41    r ^= xswap(l); \
42    l += r; \
43    r ^= rol32(l, 3); \
44    l += r; \
45    r ^= ror32(l, 2); \
46    l += r; \
47} while (0)
48
49
50static int michael_init(struct shash_desc *desc)
51{
52    struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
53    struct michael_mic_ctx *ctx = crypto_shash_ctx(desc->tfm);
54    mctx->pending_len = 0;
55    mctx->l = ctx->l;
56    mctx->r = ctx->r;
57
58    return 0;
59}
60
61
62static int michael_update(struct shash_desc *desc, const u8 *data,
63               unsigned int len)
64{
65    struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
66    const __le32 *src;
67
68    if (mctx->pending_len) {
69        int flen = 4 - mctx->pending_len;
70        if (flen > len)
71            flen = len;
72        memcpy(&mctx->pending[mctx->pending_len], data, flen);
73        mctx->pending_len += flen;
74        data += flen;
75        len -= flen;
76
77        if (mctx->pending_len < 4)
78            return 0;
79
80        src = (const __le32 *)mctx->pending;
81        mctx->l ^= le32_to_cpup(src);
82        michael_block(mctx->l, mctx->r);
83        mctx->pending_len = 0;
84    }
85
86    src = (const __le32 *)data;
87
88    while (len >= 4) {
89        mctx->l ^= le32_to_cpup(src++);
90        michael_block(mctx->l, mctx->r);
91        len -= 4;
92    }
93
94    if (len > 0) {
95        mctx->pending_len = len;
96        memcpy(mctx->pending, src, len);
97    }
98
99    return 0;
100}
101
102
103static int michael_final(struct shash_desc *desc, u8 *out)
104{
105    struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
106    u8 *data = mctx->pending;
107    __le32 *dst = (__le32 *)out;
108
109    /* Last block and padding (0x5a, 4..7 x 0) */
110    switch (mctx->pending_len) {
111    case 0:
112        mctx->l ^= 0x5a;
113        break;
114    case 1:
115        mctx->l ^= data[0] | 0x5a00;
116        break;
117    case 2:
118        mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
119        break;
120    case 3:
121        mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
122            0x5a000000;
123        break;
124    }
125    michael_block(mctx->l, mctx->r);
126    /* l ^= 0; */
127    michael_block(mctx->l, mctx->r);
128
129    dst[0] = cpu_to_le32(mctx->l);
130    dst[1] = cpu_to_le32(mctx->r);
131
132    return 0;
133}
134
135
136static int michael_setkey(struct crypto_shash *tfm, const u8 *key,
137              unsigned int keylen)
138{
139    struct michael_mic_ctx *mctx = crypto_shash_ctx(tfm);
140
141    const __le32 *data = (const __le32 *)key;
142
143    if (keylen != 8) {
144        crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
145        return -EINVAL;
146    }
147
148    mctx->l = le32_to_cpu(data[0]);
149    mctx->r = le32_to_cpu(data[1]);
150    return 0;
151}
152
153static struct shash_alg alg = {
154    .digestsize = 8,
155    .setkey = michael_setkey,
156    .init = michael_init,
157    .update = michael_update,
158    .final = michael_final,
159    .descsize = sizeof(struct michael_mic_desc_ctx),
160    .base = {
161        .cra_name = "michael_mic",
162        .cra_blocksize = 8,
163        .cra_alignmask = 3,
164        .cra_ctxsize = sizeof(struct michael_mic_ctx),
165        .cra_module = THIS_MODULE,
166    }
167};
168
169static int __init michael_mic_init(void)
170{
171    return crypto_register_shash(&alg);
172}
173
174
175static void __exit michael_mic_exit(void)
176{
177    crypto_unregister_shash(&alg);
178}
179
180
181module_init(michael_mic_init);
182module_exit(michael_mic_exit);
183
184MODULE_LICENSE("GPL v2");
185MODULE_DESCRIPTION("Michael MIC");
186MODULE_AUTHOR("Jouni Malinen <j@w1.fi>");
187

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