/*      $OpenBSD: ieee80211_crypto_bip.c,v 1.10 2018/11/09 14:14:31 claudio 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;
}