1 /* $OpenBSD: ieee80211_crypto_bip.c,v 1.7 2015/11/24 13:45:06 mpi 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/rijndael.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 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 69 ieee80211_bip_delete_key(struct ieee80211com *ic, struct ieee80211_key *k) 70 { 71 if (k->k_priv != NULL) 72 free(k->k_priv, M_DEVBUF, 0); 73 k->k_priv = NULL; 74 } 75 76 /* pseudo-header used for BIP MIC computation */ 77 struct ieee80211_bip_frame { 78 u_int8_t i_fc[2]; 79 u_int8_t i_addr1[IEEE80211_ADDR_LEN]; 80 u_int8_t i_addr2[IEEE80211_ADDR_LEN]; 81 u_int8_t i_addr3[IEEE80211_ADDR_LEN]; 82 } __packed; 83 84 struct mbuf * 85 ieee80211_bip_encap(struct ieee80211com *ic, struct mbuf *m0, 86 struct ieee80211_key *k) 87 { 88 struct ieee80211_bip_ctx *ctx = k->k_priv; 89 struct ieee80211_bip_frame aad; 90 struct ieee80211_frame *wh; 91 u_int8_t *mmie, mic[AES_CMAC_DIGEST_LENGTH]; 92 struct mbuf *m; 93 94 wh = mtod(m0, struct ieee80211_frame *); 95 KASSERT((wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) == 96 IEEE80211_FC0_TYPE_MGT); 97 /* clear Protected bit from group management frames */ 98 wh->i_fc[1] &= ~IEEE80211_FC1_PROTECTED; 99 100 /* construct AAD (additional authenticated data) */ 101 aad.i_fc[0] = wh->i_fc[0]; 102 aad.i_fc[1] = wh->i_fc[1] & ~(IEEE80211_FC1_RETRY | 103 IEEE80211_FC1_PWR_MGT | IEEE80211_FC1_MORE_DATA); 104 /* XXX 11n may require clearing the Order bit too */ 105 IEEE80211_ADDR_COPY(aad.i_addr1, wh->i_addr1); 106 IEEE80211_ADDR_COPY(aad.i_addr2, wh->i_addr2); 107 IEEE80211_ADDR_COPY(aad.i_addr3, wh->i_addr3); 108 109 AES_CMAC_Init(&ctx->cmac); 110 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&aad, sizeof aad); 111 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&wh[1], 112 m0->m_len - sizeof(*wh)); 113 114 m = m0; 115 /* reserve trailing space for MMIE */ 116 if (M_TRAILINGSPACE(m) < IEEE80211_MMIE_LEN) { 117 MGET(m->m_next, M_DONTWAIT, m->m_type); 118 if (m->m_next == NULL) 119 goto nospace; 120 m = m->m_next; 121 m->m_len = 0; 122 } 123 124 /* construct Management MIC IE */ 125 mmie = mtod(m, u_int8_t *) + m->m_len; 126 mmie[0] = IEEE80211_ELEMID_MMIE; 127 mmie[1] = 16; 128 LE_WRITE_2(&mmie[2], k->k_id); 129 LE_WRITE_6(&mmie[4], k->k_tsc); 130 memset(&mmie[10], 0, 8); /* MMIE MIC field set to 0 */ 131 132 AES_CMAC_Update(&ctx->cmac, mmie, IEEE80211_MMIE_LEN); 133 AES_CMAC_Final(mic, &ctx->cmac); 134 /* truncate AES-128-CMAC to 64-bit */ 135 memcpy(&mmie[10], mic, 8); 136 137 m->m_len += IEEE80211_MMIE_LEN; 138 m0->m_pkthdr.len += IEEE80211_MMIE_LEN; 139 140 k->k_tsc++; 141 142 return m0; 143 nospace: 144 ic->ic_stats.is_tx_nombuf++; 145 m_freem(m0); 146 return NULL; 147 } 148 149 struct mbuf * 150 ieee80211_bip_decap(struct ieee80211com *ic, struct mbuf *m0, 151 struct ieee80211_key *k) 152 { 153 struct ieee80211_bip_ctx *ctx = k->k_priv; 154 struct ieee80211_frame *wh; 155 struct ieee80211_bip_frame aad; 156 u_int8_t *mmie, mic0[8], mic[AES_CMAC_DIGEST_LENGTH]; 157 u_int64_t ipn; 158 159 wh = mtod(m0, struct ieee80211_frame *); 160 KASSERT((wh->i_fc[0] & IEEE80211_FC0_TYPE_MASK) == 161 IEEE80211_FC0_TYPE_MGT); 162 163 /* 164 * It is assumed that management frames are contiguous and that 165 * the mbuf length has already been checked to contain at least 166 * a header and a MMIE (checked in ieee80211_decrypt()). 167 */ 168 KASSERT(m0->m_len >= sizeof(*wh) + IEEE80211_MMIE_LEN); 169 mmie = mtod(m0, u_int8_t *) + m0->m_len - IEEE80211_MMIE_LEN; 170 171 ipn = LE_READ_6(&mmie[4]); 172 if (ipn <= k->k_mgmt_rsc) { 173 /* replayed frame, discard */ 174 ic->ic_stats.is_cmac_replays++; 175 m_freem(m0); 176 return NULL; 177 } 178 179 /* save and mask MMIE MIC field to 0 */ 180 memcpy(mic0, &mmie[10], 8); 181 memset(&mmie[10], 0, 8); 182 183 /* construct AAD (additional authenticated data) */ 184 aad.i_fc[0] = wh->i_fc[0]; 185 aad.i_fc[1] = wh->i_fc[1] & ~(IEEE80211_FC1_RETRY | 186 IEEE80211_FC1_PWR_MGT | IEEE80211_FC1_MORE_DATA); 187 /* XXX 11n may require clearing the Order bit too */ 188 IEEE80211_ADDR_COPY(aad.i_addr1, wh->i_addr1); 189 IEEE80211_ADDR_COPY(aad.i_addr2, wh->i_addr2); 190 IEEE80211_ADDR_COPY(aad.i_addr3, wh->i_addr3); 191 192 /* compute MIC */ 193 AES_CMAC_Init(&ctx->cmac); 194 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&aad, sizeof aad); 195 AES_CMAC_Update(&ctx->cmac, (u_int8_t *)&wh[1], 196 m0->m_len - sizeof(*wh)); 197 AES_CMAC_Final(mic, &ctx->cmac); 198 199 /* check that MIC matches the one in MMIE */ 200 if (timingsafe_bcmp(mic, mic0, 8) != 0) { 201 ic->ic_stats.is_cmac_icv_errs++; 202 m_freem(m0); 203 return NULL; 204 } 205 /* 206 * There is no need to trim the MMIE from the mbuf since it is 207 * an information element and will be ignored by upper layers. 208 * We do it anyway as it is cheap to do it here and because it 209 * may be confused with fixed fields by upper layers. 210 */ 211 m_adj(m0, -IEEE80211_MMIE_LEN); 212 213 /* update last seen packet number (MIC is validated) */ 214 k->k_mgmt_rsc = ipn; 215 216 return m0; 217 } 218