michael.c
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/*
* Michael MIC implementation - optimized for TKIP MIC operations
* Copyright 2002-2003, Instant802 Networks, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/types.h>
#include <linux/bitops.h>
#include <linux/ieee80211.h>
#include <asm/unaligned.h>
#include "michael.h"
static void michael_block(struct michael_mic_ctx *mctx, u32 val)
{
mctx->l ^= val;
mctx->r ^= rol32(mctx->l, 17);
mctx->l += mctx->r;
mctx->r ^= ((mctx->l & 0xff00ff00) >> 8) |
((mctx->l & 0x00ff00ff) << 8);
mctx->l += mctx->r;
mctx->r ^= rol32(mctx->l, 3);
mctx->l += mctx->r;
mctx->r ^= ror32(mctx->l, 2);
mctx->l += mctx->r;
}
static void michael_mic_hdr(struct michael_mic_ctx *mctx, const u8 *key,
struct ieee80211_hdr *hdr)
{
u8 *da, *sa, tid;
da = ieee80211_get_DA(hdr);
sa = ieee80211_get_SA(hdr);
if (ieee80211_is_data_qos(hdr->frame_control))
tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
else
tid = 0;
mctx->l = get_unaligned_le32(key);
mctx->r = get_unaligned_le32(key + 4);
/*
* A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC
* calculation, but it is _not_ transmitted
*/
michael_block(mctx, get_unaligned_le32(da));
michael_block(mctx, get_unaligned_le16(&da[4]) |
(get_unaligned_le16(sa) << 16));
michael_block(mctx, get_unaligned_le32(&sa[2]));
michael_block(mctx, tid);
}
void michael_mic(const u8 *key, struct ieee80211_hdr *hdr,
const u8 *data, size_t data_len, u8 *mic)
{
u32 val;
size_t block, blocks, left;
struct michael_mic_ctx mctx;
michael_mic_hdr(&mctx, key, hdr);
/* Real data */
blocks = data_len / 4;
left = data_len % 4;
for (block = 0; block < blocks; block++)
michael_block(&mctx, get_unaligned_le32(&data[block * 4]));
/* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make
* total length a multiple of 4. */
val = 0x5a;
while (left > 0) {
val <<= 8;
left--;
val |= data[blocks * 4 + left];
}
michael_block(&mctx, val);
michael_block(&mctx, 0);
put_unaligned_le32(mctx.l, mic);
put_unaligned_le32(mctx.r, mic + 4);
}