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