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 #include <linux/types.h> 10 #include <linux/bitops.h> 11 #include <linux/ieee80211.h> 12 #include <asm/unaligned.h> 13 14 #include "michael.h" 15 16 static void michael_block(struct michael_mic_ctx *mctx, u32 val) 17 { 18 mctx->l ^= val; 19 mctx->r ^= rol32(mctx->l, 17); 20 mctx->l += mctx->r; 21 mctx->r ^= ((mctx->l & 0xff00ff00) >> 8) | 22 ((mctx->l & 0x00ff00ff) << 8); 23 mctx->l += mctx->r; 24 mctx->r ^= rol32(mctx->l, 3); 25 mctx->l += mctx->r; 26 mctx->r ^= ror32(mctx->l, 2); 27 mctx->l += mctx->r; 28 } 29 30 static void michael_mic_hdr(struct michael_mic_ctx *mctx, const u8 *key, 31 struct ieee80211_hdr *hdr) 32 { 33 u8 *da, *sa, tid; 34 35 da = ieee80211_get_DA(hdr); 36 sa = ieee80211_get_SA(hdr); 37 if (ieee80211_is_data_qos(hdr->frame_control)) 38 tid = ieee80211_get_tid(hdr); 39 else 40 tid = 0; 41 42 mctx->l = get_unaligned_le32(key); 43 mctx->r = get_unaligned_le32(key + 4); 44 45 /* 46 * A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC 47 * calculation, but it is _not_ transmitted 48 */ 49 michael_block(mctx, get_unaligned_le32(da)); 50 michael_block(mctx, get_unaligned_le16(&da[4]) | 51 (get_unaligned_le16(sa) << 16)); 52 michael_block(mctx, get_unaligned_le32(&sa[2])); 53 michael_block(mctx, tid); 54 } 55 56 void michael_mic(const u8 *key, struct ieee80211_hdr *hdr, 57 const u8 *data, size_t data_len, u8 *mic) 58 { 59 u32 val; 60 size_t block, blocks, left; 61 struct michael_mic_ctx mctx; 62 63 michael_mic_hdr(&mctx, key, hdr); 64 65 /* Real data */ 66 blocks = data_len / 4; 67 left = data_len % 4; 68 69 for (block = 0; block < blocks; block++) 70 michael_block(&mctx, get_unaligned_le32(&data[block * 4])); 71 72 /* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make 73 * total length a multiple of 4. */ 74 val = 0x5a; 75 while (left > 0) { 76 val <<= 8; 77 left--; 78 val |= data[blocks * 4 + left]; 79 } 80 81 michael_block(&mctx, val); 82 michael_block(&mctx, 0); 83 84 put_unaligned_le32(mctx.l, mic); 85 put_unaligned_le32(mctx.r, mic + 4); 86 } 87