1 /* $OpenBSD: ieee80211_crypto_bip.c,v 1.10 2018/11/09 14:14:31 claudio Exp $ */
2
3 /*-
4 * Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18
19 /*
20 * This code implements the Broadcast/Multicast Integrity Protocol (BIP)
21 * defined in IEEE P802.11w/D7.0 section 8.3.4.
22 */
23
24 #include <sys/param.h>
25 #include <sys/systm.h>
26 #include <sys/mbuf.h>
27 #include <sys/malloc.h>
28 #include <sys/kernel.h>
29 #include <sys/socket.h>
30 #include <sys/endian.h>
31
32 #include <net/if.h>
33 #include <net/if_dl.h>
34 #include <net/if_media.h>
35
36 #include <netinet/in.h>
37 #include <netinet/if_ether.h>
38
39 #include <net80211/ieee80211_var.h>
40 #include <net80211/ieee80211_crypto.h>
41 #include <net80211/ieee80211_priv.h>
42
43 #include <crypto/aes.h>
44 #include <crypto/cmac.h>
45
46 /* BIP software crypto context */
47 struct ieee80211_bip_ctx {
48 AES_CMAC_CTX cmac;
49 };
50
51 /*
52 * Initialize software crypto context. This function can be overridden
53 * by drivers doing hardware crypto.
54 */
55 int
ieee80211_bip_set_key(struct ieee80211com * ic,struct ieee80211_key * k)56 ieee80211_bip_set_key(struct ieee80211com *ic, struct ieee80211_key *k)
57 {
58 struct ieee80211_bip_ctx *ctx;
59
60 ctx = malloc(sizeof(*ctx), M_DEVBUF, M_NOWAIT | M_ZERO);
61 if (ctx == NULL)
62 return ENOMEM;
63 AES_CMAC_SetKey(&ctx->cmac, k->k_key);
64 k->k_priv = ctx;
65 return 0;
66 }
67
68 void
ieee80211_bip_delete_key(struct ieee80211com * ic,struct ieee80211_key * k)69 ieee80211_bip_delete_key(struct ieee80211com *ic, struct ieee80211_key *k)
70 {
71 if (k->k_priv != NULL) {
72 explicit_bzero(k->k_priv, sizeof(struct ieee80211_bip_ctx));
73 free(k->k_priv, M_DEVBUF, sizeof(struct ieee80211_bip_ctx));
74 }
75 k->k_priv = NULL;
76 }
77
78 /* pseudo-header used for BIP MIC computation */
79 struct ieee80211_bip_frame {
80 u_int8_t i_fc[2];
81 u_int8_t i_addr1[IEEE80211_ADDR_LEN];
82 u_int8_t i_addr2[IEEE80211_ADDR_LEN];
83 u_int8_t i_addr3[IEEE80211_ADDR_LEN];
84 } __packed;
85
86 struct mbuf *
ieee80211_bip_encap(struct ieee80211com * ic,struct mbuf * m0,struct ieee80211_key * k)87 ieee80211_bip_encap(struct ieee80211com *ic, struct mbuf *m0,
88 struct ieee80211_key *k)
89 {
90 struct ieee80211_bip_ctx *ctx = k->k_priv;
91 struct ieee80211_bip_frame aad;
92 struct ieee80211_frame *wh;
93 u_int8_t *mmie, mic[AES_CMAC_DIGEST_LENGTH];
94 struct mbuf *m;
95
96 wh = mtod(m0, struct ieee80211_frame *);
97 KASSERT((wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) ==
98 IEEE80211_FC0_TYPE_MGT);
99 /* clear Protected bit from group management frames */
100 wh->i_fc[1] &= ~IEEE80211_FC1_PROTECTED;
101
102 /* construct AAD (additional authenticated data) */
103 aad.i_fc[0] = wh->i_fc[0];
104 aad.i_fc[1] = wh->i_fc[1] & ~(IEEE80211_FC1_RETRY |
105 IEEE80211_FC1_PWR_MGT | IEEE80211_FC1_MORE_DATA);
106 /* XXX 11n may require clearing the Order bit too */
107 IEEE80211_ADDR_COPY(aad.i_addr1, wh->i_addr1);
108 IEEE80211_ADDR_COPY(aad.i_addr2, wh->i_addr2);
109 IEEE80211_ADDR_COPY(aad.i_addr3, wh->i_addr3);
110
111 AES_CMAC_Init(&ctx->cmac);
112 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&aad, sizeof aad);
113 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&wh[1],
114 m0->m_len - sizeof(*wh));
115
116 m = m0;
117 /* reserve trailing space for MMIE */
118 if (m_trailingspace(m) < IEEE80211_MMIE_LEN) {
119 MGET(m->m_next, M_DONTWAIT, m->m_type);
120 if (m->m_next == NULL)
121 goto nospace;
122 m = m->m_next;
123 m->m_len = 0;
124 }
125
126 /* construct Management MIC IE */
127 mmie = mtod(m, u_int8_t *) + m->m_len;
128 mmie[0] = IEEE80211_ELEMID_MMIE;
129 mmie[1] = 16;
130 LE_WRITE_2(&mmie[2], k->k_id);
131 LE_WRITE_6(&mmie[4], k->k_tsc);
132 memset(&mmie[10], 0, 8); /* MMIE MIC field set to 0 */
133
134 AES_CMAC_Update(&ctx->cmac, mmie, IEEE80211_MMIE_LEN);
135 AES_CMAC_Final(mic, &ctx->cmac);
136 /* truncate AES-128-CMAC to 64-bit */
137 memcpy(&mmie[10], mic, 8);
138
139 m->m_len += IEEE80211_MMIE_LEN;
140 m0->m_pkthdr.len += IEEE80211_MMIE_LEN;
141
142 k->k_tsc++;
143
144 return m0;
145 nospace:
146 ic->ic_stats.is_tx_nombuf++;
147 m_freem(m0);
148 return NULL;
149 }
150
151 struct mbuf *
ieee80211_bip_decap(struct ieee80211com * ic,struct mbuf * m0,struct ieee80211_key * k)152 ieee80211_bip_decap(struct ieee80211com *ic, struct mbuf *m0,
153 struct ieee80211_key *k)
154 {
155 struct ieee80211_bip_ctx *ctx = k->k_priv;
156 struct ieee80211_frame *wh;
157 struct ieee80211_bip_frame aad;
158 u_int8_t *mmie, mic0[8], mic[AES_CMAC_DIGEST_LENGTH];
159 u_int64_t ipn;
160
161 wh = mtod(m0, struct ieee80211_frame *);
162 KASSERT((wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) ==
163 IEEE80211_FC0_TYPE_MGT);
164
165 /*
166 * It is assumed that management frames are contiguous and that
167 * the mbuf length has already been checked to contain at least
168 * a header and a MMIE (checked in ieee80211_decrypt()).
169 */
170 KASSERT(m0->m_len >= sizeof(*wh) + IEEE80211_MMIE_LEN);
171 mmie = mtod(m0, u_int8_t *) + m0->m_len - IEEE80211_MMIE_LEN;
172
173 ipn = LE_READ_6(&mmie[4]);
174 if (ipn <= k->k_mgmt_rsc) {
175 /* replayed frame, discard */
176 ic->ic_stats.is_cmac_replays++;
177 m_freem(m0);
178 return NULL;
179 }
180
181 /* save and mask MMIE MIC field to 0 */
182 memcpy(mic0, &mmie[10], 8);
183 memset(&mmie[10], 0, 8);
184
185 /* construct AAD (additional authenticated data) */
186 aad.i_fc[0] = wh->i_fc[0];
187 aad.i_fc[1] = wh->i_fc[1] & ~(IEEE80211_FC1_RETRY |
188 IEEE80211_FC1_PWR_MGT | IEEE80211_FC1_MORE_DATA);
189 /* XXX 11n may require clearing the Order bit too */
190 IEEE80211_ADDR_COPY(aad.i_addr1, wh->i_addr1);
191 IEEE80211_ADDR_COPY(aad.i_addr2, wh->i_addr2);
192 IEEE80211_ADDR_COPY(aad.i_addr3, wh->i_addr3);
193
194 /* compute MIC */
195 AES_CMAC_Init(&ctx->cmac);
196 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&aad, sizeof aad);
197 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&wh[1],
198 m0->m_len - sizeof(*wh));
199 AES_CMAC_Final(mic, &ctx->cmac);
200
201 /* check that MIC matches the one in MMIE */
202 if (timingsafe_bcmp(mic, mic0, 8) != 0) {
203 ic->ic_stats.is_cmac_icv_errs++;
204 m_freem(m0);
205 return NULL;
206 }
207 /*
208 * There is no need to trim the MMIE from the mbuf since it is
209 * an information element and will be ignored by upper layers.
210 * We do it anyway as it is cheap to do it here and because it
211 * may be confused with fixed fields by upper layers.
212 */
213 m_adj(m0, -IEEE80211_MMIE_LEN);
214
215 /* update last seen packet number (MIC is validated) */
216 k->k_mgmt_rsc = ipn;
217
218 return m0;
219 }
220