1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Michael MIC implementation - optimized for TKIP MIC operations
4  * Copyright 2002-2003, Instant802 Networks, Inc.
5  */
6 #include <linux/types.h>
7 #include <linux/bitops.h>
8 #include <linux/ieee80211.h>
9 #include <asm/unaligned.h>
10 
11 #include "michael.h"
12 
michael_block(struct michael_mic_ctx * mctx,u32 val)13 static void michael_block(struct michael_mic_ctx *mctx, u32 val)
14 {
15 	mctx->l ^= val;
16 	mctx->r ^= rol32(mctx->l, 17);
17 	mctx->l += mctx->r;
18 	mctx->r ^= ((mctx->l & 0xff00ff00) >> 8) |
19 		   ((mctx->l & 0x00ff00ff) << 8);
20 	mctx->l += mctx->r;
21 	mctx->r ^= rol32(mctx->l, 3);
22 	mctx->l += mctx->r;
23 	mctx->r ^= ror32(mctx->l, 2);
24 	mctx->l += mctx->r;
25 }
26 
michael_mic_hdr(struct michael_mic_ctx * mctx,const u8 * key,struct ieee80211_hdr * hdr)27 static void michael_mic_hdr(struct michael_mic_ctx *mctx, const u8 *key,
28 			    struct ieee80211_hdr *hdr)
29 {
30 	u8 *da, *sa, tid;
31 
32 	da = ieee80211_get_DA(hdr);
33 	sa = ieee80211_get_SA(hdr);
34 	if (ieee80211_is_data_qos(hdr->frame_control))
35 		tid = ieee80211_get_tid(hdr);
36 	else
37 		tid = 0;
38 
39 	mctx->l = get_unaligned_le32(key);
40 	mctx->r = get_unaligned_le32(key + 4);
41 
42 	/*
43 	 * A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC
44 	 * calculation, but it is _not_ transmitted
45 	 */
46 	michael_block(mctx, get_unaligned_le32(da));
47 	michael_block(mctx, get_unaligned_le16(&da[4]) |
48 			    (get_unaligned_le16(sa) << 16));
49 	michael_block(mctx, get_unaligned_le32(&sa[2]));
50 	michael_block(mctx, tid);
51 }
52 
michael_mic(const u8 * key,struct ieee80211_hdr * hdr,const u8 * data,size_t data_len,u8 * mic)53 void michael_mic(const u8 *key, struct ieee80211_hdr *hdr,
54 		 const u8 *data, size_t data_len, u8 *mic)
55 {
56 	u32 val;
57 	size_t block, blocks, left;
58 	struct michael_mic_ctx mctx;
59 
60 	michael_mic_hdr(&mctx, key, hdr);
61 
62 	/* Real data */
63 	blocks = data_len / 4;
64 	left = data_len % 4;
65 
66 	for (block = 0; block < blocks; block++)
67 		michael_block(&mctx, get_unaligned_le32(&data[block * 4]));
68 
69 	/* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make
70 	 * total length a multiple of 4. */
71 	val = 0x5a;
72 	while (left > 0) {
73 		val <<= 8;
74 		left--;
75 		val |= data[blocks * 4 + left];
76 	}
77 
78 	michael_block(&mctx, val);
79 	michael_block(&mctx, 0);
80 
81 	put_unaligned_le32(mctx.l, mic);
82 	put_unaligned_le32(mctx.r, mic + 4);
83 }
84