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