1/*
2 * Michael MIC implementation - optimized for TKIP MIC operations
3 * Copyright 2002-2003, Instant802 Networks, 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/types.h>
11
12#include "michael.h"
13
14static inline u32 rotr(u32 val, int bits)
15{
16	return (val >> bits) | (val << (32 - bits));
17}
18
19
20static inline u32 rotl(u32 val, int bits)
21{
22	return (val << bits) | (val >> (32 - bits));
23}
24
25
26static inline u32 xswap(u32 val)
27{
28	return ((val & 0xff00ff00) >> 8) | ((val & 0x00ff00ff) << 8);
29}
30
31
32#define michael_block(l, r) \
33do { \
34	r ^= rotl(l, 17); \
35	l += r; \
36	r ^= xswap(l); \
37	l += r; \
38	r ^= rotl(l, 3); \
39	l += r; \
40	r ^= rotr(l, 2); \
41	l += r; \
42} while (0)
43
44
45static inline u32 michael_get32(u8 *data)
46{
47	return data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
48}
49
50
51static inline void michael_put32(u32 val, u8 *data)
52{
53	data[0] = val & 0xff;
54	data[1] = (val >> 8) & 0xff;
55	data[2] = (val >> 16) & 0xff;
56	data[3] = (val >> 24) & 0xff;
57}
58
59
60void michael_mic(u8 *key, u8 *da, u8 *sa, u8 priority,
61		 u8 *data, size_t data_len, u8 *mic)
62{
63	u32 l, r, val;
64	size_t block, blocks, left;
65
66	l = michael_get32(key);
67	r = michael_get32(key + 4);
68
69	/* A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC
70	 * calculation, but it is _not_ transmitted */
71	l ^= michael_get32(da);
72	michael_block(l, r);
73	l ^= da[4] | (da[5] << 8) | (sa[0] << 16) | (sa[1] << 24);
74	michael_block(l, r);
75	l ^= michael_get32(&sa[2]);
76	michael_block(l, r);
77	l ^= priority;
78	michael_block(l, r);
79
80	/* Real data */
81	blocks = data_len / 4;
82	left = data_len % 4;
83
84	for (block = 0; block < blocks; block++) {
85		l ^= michael_get32(&data[block * 4]);
86		michael_block(l, r);
87	}
88
89	/* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make
90	 * total length a multiple of 4. */
91	val = 0x5a;
92	while (left > 0) {
93		val <<= 8;
94		left--;
95		val |= data[blocks * 4 + left];
96	}
97	l ^= val;
98	michael_block(l, r);
99	/* last block is zero, so l ^ 0 = l */
100	michael_block(l, r);
101
102	michael_put32(l, mic);
103	michael_put32(r, mic + 4);
104}
105