/* $OpenBSD: ieee80211_crypto_bip.c,v 1.7 2015/11/24 13:45:06 mpi Exp $ */ /*- * Copyright (c) 2008 Damien Bergamini * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* 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; }