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 14 static inline u32 rotr(u32 val, int bits) 15 { 16 return (val >> bits) | (val << (32 - bits)); 17 } 18 19 20 static inline u32 rotl(u32 val, int bits) 21 { 22 return (val << bits) | (val >> (32 - bits)); 23 } 24 25 26 static inline u32 xswap(u32 val) 27 { 28 return ((val & 0xff00ff00) >> 8) | ((val & 0x00ff00ff) << 8); 29 } 30 31 32 #define michael_block(l, r) \ 33 do { \ 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 45 static inline u32 michael_get32(u8 *data) 46 { 47 return data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24); 48 } 49 50 51 static 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 60 void 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