1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
|
/* $OpenBSD: ieee80211_crypto_bip.c,v 1.6 2014/12/23 03:24:08 tedu Exp $ */
/*-
* Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This code implements the Broadcast/Multicast Integrity Protocol (BIP)
* defined in IEEE P802.11w/D7.0 section 8.3.4.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/socket.h>
#include <sys/endian.h>
#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_media.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <net80211/ieee80211_var.h>
#include <net80211/ieee80211_crypto.h>
#include <net80211/ieee80211_priv.h>
#include <crypto/rijndael.h>
#include <crypto/cmac.h>
/* BIP software crypto context */
struct ieee80211_bip_ctx {
AES_CMAC_CTX cmac;
};
/*
* Initialize software crypto context. This function can be overridden
* by drivers doing hardware crypto.
*/
int
ieee80211_bip_set_key(struct ieee80211com *ic, struct ieee80211_key *k)
{
struct ieee80211_bip_ctx *ctx;
ctx = malloc(sizeof(*ctx), M_DEVBUF, M_NOWAIT | M_ZERO);
if (ctx == NULL)
return ENOMEM;
AES_CMAC_SetKey(&ctx->cmac, k->k_key);
k->k_priv = ctx;
return 0;
}
void
ieee80211_bip_delete_key(struct ieee80211com *ic, struct ieee80211_key *k)
{
if (k->k_priv != NULL)
free(k->k_priv, M_DEVBUF, 0);
k->k_priv = NULL;
}
/* pseudo-header used for BIP MIC computation */
struct ieee80211_bip_frame {
u_int8_t i_fc[2];
u_int8_t i_addr1[IEEE80211_ADDR_LEN];
u_int8_t i_addr2[IEEE80211_ADDR_LEN];
u_int8_t i_addr3[IEEE80211_ADDR_LEN];
} __packed;
struct mbuf *
ieee80211_bip_encap(struct ieee80211com *ic, struct mbuf *m0,
struct ieee80211_key *k)
{
struct ieee80211_bip_ctx *ctx = k->k_priv;
struct ieee80211_bip_frame aad;
struct ieee80211_frame *wh;
u_int8_t *mmie, mic[AES_CMAC_DIGEST_LENGTH];
struct mbuf *m;
wh = mtod(m0, struct ieee80211_frame *);
KASSERT((wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) ==
IEEE80211_FC0_TYPE_MGT);
/* clear Protected bit from group management frames */
wh->i_fc[1] &= ~IEEE80211_FC1_PROTECTED;
/* construct AAD (additional authenticated data) */
aad.i_fc[0] = wh->i_fc[0];
aad.i_fc[1] = wh->i_fc[1] & ~(IEEE80211_FC1_RETRY |
IEEE80211_FC1_PWR_MGT | IEEE80211_FC1_MORE_DATA);
/* XXX 11n may require clearing the Order bit too */
IEEE80211_ADDR_COPY(aad.i_addr1, wh->i_addr1);
IEEE80211_ADDR_COPY(aad.i_addr2, wh->i_addr2);
IEEE80211_ADDR_COPY(aad.i_addr3, wh->i_addr3);
AES_CMAC_Init(&ctx->cmac);
AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&aad, sizeof aad);
AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&wh[1],
m0->m_len - sizeof(*wh));
m = m0;
/* reserve trailing space for MMIE */
if (M_TRAILINGSPACE(m) < IEEE80211_MMIE_LEN) {
MGET(m->m_next, M_DONTWAIT, m->m_type);
if (m->m_next == NULL)
goto nospace;
m = m->m_next;
m->m_len = 0;
}
/* construct Management MIC IE */
mmie = mtod(m, u_int8_t *) + m->m_len;
mmie[0] = IEEE80211_ELEMID_MMIE;
mmie[1] = 16;
LE_WRITE_2(&mmie[2], k->k_id);
LE_WRITE_6(&mmie[4], k->k_tsc);
memset(&mmie[10], 0, 8); /* MMIE MIC field set to 0 */
AES_CMAC_Update(&ctx->cmac, mmie, IEEE80211_MMIE_LEN);
AES_CMAC_Final(mic, &ctx->cmac);
/* truncate AES-128-CMAC to 64-bit */
memcpy(&mmie[10], mic, 8);
m->m_len += IEEE80211_MMIE_LEN;
m0->m_pkthdr.len += IEEE80211_MMIE_LEN;
k->k_tsc++;
return m0;
nospace:
ic->ic_stats.is_tx_nombuf++;
m_freem(m0);
return NULL;
}
struct mbuf *
ieee80211_bip_decap(struct ieee80211com *ic, struct mbuf *m0,
struct ieee80211_key *k)
{
struct ieee80211_bip_ctx *ctx = k->k_priv;
struct ieee80211_frame *wh;
struct ieee80211_bip_frame aad;
u_int8_t *mmie, mic0[8], mic[AES_CMAC_DIGEST_LENGTH];
u_int64_t ipn;
wh = mtod(m0, struct ieee80211_frame *);
KASSERT((wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) ==
IEEE80211_FC0_TYPE_MGT);
/*
* It is assumed that management frames are contiguous and that
* the mbuf length has already been checked to contain at least
* a header and a MMIE (checked in ieee80211_decrypt()).
*/
KASSERT(m0->m_len >= sizeof(*wh) + IEEE80211_MMIE_LEN);
mmie = mtod(m0, u_int8_t *) + m0->m_len - IEEE80211_MMIE_LEN;
ipn = LE_READ_6(&mmie[4]);
if (ipn <= k->k_mgmt_rsc) {
/* replayed frame, discard */
ic->ic_stats.is_cmac_replays++;
m_freem(m0);
return NULL;
}
/* save and mask MMIE MIC field to 0 */
memcpy(mic0, &mmie[10], 8);
memset(&mmie[10], 0, 8);
/* construct AAD (additional authenticated data) */
aad.i_fc[0] = wh->i_fc[0];
aad.i_fc[1] = wh->i_fc[1] & ~(IEEE80211_FC1_RETRY |
IEEE80211_FC1_PWR_MGT | IEEE80211_FC1_MORE_DATA);
/* XXX 11n may require clearing the Order bit too */
IEEE80211_ADDR_COPY(aad.i_addr1, wh->i_addr1);
IEEE80211_ADDR_COPY(aad.i_addr2, wh->i_addr2);
IEEE80211_ADDR_COPY(aad.i_addr3, wh->i_addr3);
/* compute MIC */
AES_CMAC_Init(&ctx->cmac);
AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&aad, sizeof aad);
AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&wh[1],
m0->m_len - sizeof(*wh));
AES_CMAC_Final(mic, &ctx->cmac);
/* check that MIC matches the one in MMIE */
if (timingsafe_bcmp(mic, mic0, 8) != 0) {
ic->ic_stats.is_cmac_icv_errs++;
m_freem(m0);
return NULL;
}
/*
* There is no need to trim the MMIE from the mbuf since it is
* an information element and will be ignored by upper layers.
* We do it anyway as it is cheap to do it here and because it
* may be confused with fixed fields by upper layers.
*/
m_adj(m0, -IEEE80211_MMIE_LEN);
/* update last seen packet number (MIC is validated) */
k->k_mgmt_rsc = ipn;
return m0;
}
|
