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/* $OpenBSD: ieee80211_crypto_bip.c,v 1.9 2017/05/02 17:07:06 mikeb 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 <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/aes.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) {
explicit_bzero(k->k_priv, sizeof(struct ieee80211_bip_ctx));
free(k->k_priv, M_DEVBUF, sizeof(struct ieee80211_bip_ctx));
}
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;
}
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