Adapt 802.11 generic layer to support hardware crypto other than ath(4).

[dragonfly/vkernel-mp.git] / sys / netproto / 802_11 / wlan_ccmp / ieee80211_crypto_ccmp.c

/*
 * Copyright (c) 2002-2005 Sam Leffler, Errno Consulting
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/net80211/ieee80211_crypto_ccmp.c,v 1.7.2.1 2005/12/22 19:02:08 sam Exp $
 * $DragonFly: src/sys/netproto/802_11/wlan_ccmp/ieee80211_crypto_ccmp.c,v 1.5 2007/05/07 14:12:16 sephe Exp $
 */

/*
 * IEEE 802.11i AES-CCMP crypto support.
 *
 * Part of this module is derived from similar code in the Host
 * AP driver. The code is used with the consent of the author and
 * it's license is included below.
 */
#include <sys/param.h>
#include <sys/systm.h> 
#include <sys/mbuf.h>   
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/module.h>

#include <sys/socket.h>

#include <net/if.h>
#include <net/if_arp.h>
#include <net/if_media.h>
#include <net/ethernet.h>

#include <netproto/802_11/ieee80211_var.h>

#include <opencrypto/rijndael.h>

#define AES_BLOCK_LEN 16

struct ccmp_ctx {
        struct ieee80211com *cc_ic;     /* for diagnostics */
        rijndael_ctx         cc_aes;
};

static  void *ccmp_attach(struct ieee80211com *, struct ieee80211_key *);
static  void ccmp_detach(struct ieee80211_key *);
static  int ccmp_setkey(struct ieee80211_key *);
static  int ccmp_encap(struct ieee80211_key *k, struct mbuf *, uint8_t keyid);
static  int ccmp_decap(struct ieee80211_key *, struct mbuf *, int);
static  int ccmp_enmic(struct ieee80211_key *, struct mbuf *, int);
static  int ccmp_demic(struct ieee80211_key *, struct mbuf *, int);
static  int ccmp_getiv(struct ieee80211_key *, struct ieee80211_crypto_iv *,
                uint8_t);
static  int ccmp_update(struct ieee80211_key *,
                const struct ieee80211_crypto_iv *,
                const struct ieee80211_frame *);

static const struct ieee80211_cipher ccmp = {
        .ic_name        = "AES-CCM",
        .ic_cipher      = IEEE80211_CIPHER_AES_CCM,
        .ic_header      = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN +
                          IEEE80211_WEP_EXTIVLEN,
        .ic_trailer     = IEEE80211_WEP_MICLEN,
        .ic_miclen      = 0,
        .ic_attach      = ccmp_attach,
        .ic_detach      = ccmp_detach,
        .ic_setkey      = ccmp_setkey,
        .ic_encap       = ccmp_encap,
        .ic_decap       = ccmp_decap,
        .ic_enmic       = ccmp_enmic,
        .ic_demic       = ccmp_demic,
        .ic_getiv       = ccmp_getiv,
        .ic_update      = ccmp_update
};

static  int ccmp_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
static  int ccmp_decrypt(struct ieee80211_key *, uint64_t pn,
                struct mbuf *, int hdrlen);

/* number of references from net80211 layer */
static  int nrefs = 0;

static void *
ccmp_attach(struct ieee80211com *ic, struct ieee80211_key *k)
{
        struct ccmp_ctx *ctx;

        ctx = kmalloc(sizeof(struct ccmp_ctx), M_DEVBUF, M_NOWAIT | M_ZERO);
        if (ctx == NULL) {
                ic->ic_stats.is_crypto_nomem++;
                return NULL;
        }
        ctx->cc_ic = ic;
        nrefs++;                        /* NB: we assume caller locking */
        return ctx;
}

static void
ccmp_detach(struct ieee80211_key *k)
{
        struct ccmp_ctx *ctx = k->wk_private;

        kfree(ctx, M_DEVBUF);
        KASSERT(nrefs > 0, ("imbalanced attach/detach"));
        nrefs--;                        /* NB: we assume caller locking */
}

static int
ccmp_setkey(struct ieee80211_key *k)
{
        struct ccmp_ctx *ctx = k->wk_private;

        if (k->wk_keylen != (128/NBBY)) {
                IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
                        "%s: Invalid key length %u, expecting %u\n",
                        __func__, k->wk_keylen, 128/NBBY);
                return 0;
        }
        if (k->wk_flags & IEEE80211_KEY_SWCRYPT) {
                rijndael_set_key(&ctx->cc_aes, k->wk_key, k->wk_keylen * NBBY,
                                 1);
        }
        return 1;
}

/*
 * Add privacy headers appropriate for the specified key.
 */
static int
ccmp_encap(struct ieee80211_key *k, struct mbuf *m, uint8_t keyid)
{
        struct ccmp_ctx *ctx = k->wk_private;
        struct ieee80211com *ic = ctx->cc_ic;
        uint8_t *ivp;
        int hdrlen;

        hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));

        /*
         * Copy down 802.11 header and add the IV, KeyID, and ExtIV.
         */
        M_PREPEND(m, ccmp.ic_header, MB_DONTWAIT);
        if (m == NULL)
                return 0;
        ivp = mtod(m, uint8_t *);
        ovbcopy(ivp + ccmp.ic_header, ivp, hdrlen);
        ivp += hdrlen;

        k->wk_keytsc++;         /* XXX wrap at 48 bits */
        ivp[0] = k->wk_keytsc >> 0;             /* PN0 */
        ivp[1] = k->wk_keytsc >> 8;             /* PN1 */
        ivp[2] = 0;                             /* Reserved */
        ivp[3] = keyid | IEEE80211_WEP_EXTIV;   /* KeyID | ExtID */
        ivp[4] = k->wk_keytsc >> 16;            /* PN2 */
        ivp[5] = k->wk_keytsc >> 24;            /* PN3 */
        ivp[6] = k->wk_keytsc >> 32;            /* PN4 */
        ivp[7] = k->wk_keytsc >> 40;            /* PN5 */

        /*
         * Finally, do software encrypt if neeed.
         */
        if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) &&
            !ccmp_encrypt(k, m, hdrlen))
                return 0;

        return 1;
}

static int
ccmp_getiv(struct ieee80211_key *k, struct ieee80211_crypto_iv *iv,
        uint8_t keyid)
{
        uint8_t *ivp = (uint8_t *)iv;

        k->wk_keytsc++;         /* XXX wrap at 48 bits */
        ivp[0] = k->wk_keytsc >> 0;             /* PN0 */
        ivp[1] = k->wk_keytsc >> 8;             /* PN1 */
        ivp[2] = 0;                             /* Reserved */
        ivp[3] = keyid | IEEE80211_WEP_EXTIV;   /* KeyID | ExtID */
        ivp[4] = k->wk_keytsc >> 16;            /* PN2 */
        ivp[5] = k->wk_keytsc >> 24;            /* PN3 */
        ivp[6] = k->wk_keytsc >> 32;            /* PN4 */
        ivp[7] = k->wk_keytsc >> 40;            /* PN5 */

        return 1;
}

/*
 * Add MIC to the frame as needed.
 */
static int
ccmp_enmic(struct ieee80211_key *k, struct mbuf *m, int force)
{
        return 1;
}

static __inline uint64_t
READ_6(uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5)
{
        uint32_t iv32 = (b0 << 0) | (b1 << 8) | (b2 << 16) | (b3 << 24);
        uint16_t iv16 = (b4 << 0) | (b5 << 8);
        return (((uint64_t)iv16) << 32) | iv32;
}

/*
 * Validate and strip privacy headers (and trailer) for a
 * received frame. The specified key should be correct but
 * is also verified.
 */
static int
ccmp_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen)
{
        struct ccmp_ctx *ctx = k->wk_private;
        struct ieee80211_frame *wh;
        uint8_t *ivp;
        uint64_t pn;

        /*
         * Header should have extended IV and sequence number;
         * verify the former and validate the latter.
         */
        wh = mtod(m, struct ieee80211_frame *);
        ivp = mtod(m, uint8_t *) + hdrlen;
        if ((ivp[IEEE80211_WEP_IVLEN] & IEEE80211_WEP_EXTIV) == 0) {
                /*
                 * No extended IV; discard frame.
                 */
                IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
                        "[%6D] Missing ExtIV for AES-CCM cipher\n",
                        wh->i_addr2, ":");
                ctx->cc_ic->ic_stats.is_rx_ccmpformat++;
                return 0;
        }
        pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
        if (pn <= k->wk_keyrsc) {
                /*
                 * Replay violation.
                 */
                ieee80211_notify_replay_failure(ctx->cc_ic, wh, k, pn);
                ctx->cc_ic->ic_stats.is_rx_ccmpreplay++;
                return 0;
        }

        /*
         * Check if the device handled the decrypt in hardware.
         * If so we just strip the header; otherwise we need to
         * handle the decrypt in software.  Note that for the
         * latter we leave the header in place for use in the
         * decryption work.
         */
        if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) &&
            !ccmp_decrypt(k, pn, m, hdrlen))
                return 0;

        /*
         * Copy up 802.11 header and strip crypto bits.
         */
        ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + ccmp.ic_header, hdrlen);
        m_adj(m, ccmp.ic_header);
        m_adj(m, -ccmp.ic_trailer);

        /*
         * Ok to update rsc now.
         */
        k->wk_keyrsc = pn;

        return 1;
}

static int
ccmp_update(struct ieee80211_key *k, const struct ieee80211_crypto_iv *iv,
        const struct ieee80211_frame *wh)
{
        struct ccmp_ctx *ctx = k->wk_private;
        const uint8_t *ivp = (const uint8_t *)iv;
        uint64_t pn;

        /*
         * Header should have extended IV and sequence number;
         * verify the former and validate the latter.
         */
        if ((ivp[IEEE80211_WEP_IVLEN] & IEEE80211_WEP_EXTIV) == 0) {
                /*
                 * No extended IV; discard frame.
                 */
                IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
                        "[%6D] Missing ExtIV for AES-CCM cipher\n",
                        wh->i_addr2, ":");
                ctx->cc_ic->ic_stats.is_rx_ccmpformat++;
                return 0;
        }
        pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
        if (pn <= k->wk_keyrsc) {
                /*
                 * Replay violation.
                 */
                ieee80211_notify_replay_failure(ctx->cc_ic, wh, k, pn);
                ctx->cc_ic->ic_stats.is_rx_ccmpreplay++;
                return 0;
        }

        /*
         * Ok to update rsc now.
         */
        k->wk_keyrsc = pn;
        return 1;
}

/*
 * Verify and strip MIC from the frame.
 */
static int
ccmp_demic(struct ieee80211_key *k, struct mbuf *m, int force)
{
        return 1;
}

static __inline void
xor_block(uint8_t *b, const uint8_t *a, size_t len)
{
        int i;
        for (i = 0; i < len; i++)
                b[i] ^= a[i];
}

/*
 * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
 *
 * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation. See README and COPYING for
 * more details.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 */

static void
ccmp_init_blocks(rijndael_ctx *ctx, struct ieee80211_frame *wh,
        uint64_t pn, size_t dlen,
        uint8_t b0[AES_BLOCK_LEN], uint8_t aad[2 * AES_BLOCK_LEN],
        uint8_t auth[AES_BLOCK_LEN], uint8_t s0[AES_BLOCK_LEN])
{
#define IS_4ADDRESS(wh) \
        ((wh->i_fc[1] & IEEE80211_FC1_DIR_MASK) == IEEE80211_FC1_DIR_DSTODS)
#define IS_QOS_DATA(wh) IEEE80211_QOS_HAS_SEQ(wh)

        /* CCM Initial Block:
         * Flag (Include authentication header, M=3 (8-octet MIC),
         *       L=1 (2-octet Dlen))
         * Nonce: 0x00 | A2 | PN
         * Dlen */
        b0[0] = 0x59;
        /* NB: b0[1] set below */
        IEEE80211_ADDR_COPY(b0 + 2, wh->i_addr2);
        b0[8] = pn >> 40;
        b0[9] = pn >> 32;
        b0[10] = pn >> 24;
        b0[11] = pn >> 16;
        b0[12] = pn >> 8;
        b0[13] = pn >> 0;
        b0[14] = (dlen >> 8) & 0xff;
        b0[15] = dlen & 0xff;

        /* AAD:
         * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
         * A1 | A2 | A3
         * SC with bits 4..15 (seq#) masked to zero
         * A4 (if present)
         * QC (if present)
         */
        aad[0] = 0;     /* AAD length >> 8 */
        /* NB: aad[1] set below */
        aad[2] = wh->i_fc[0] & 0x8f;    /* XXX magic #s */
        aad[3] = wh->i_fc[1] & 0xc7;    /* XXX magic #s */
        /* NB: we know 3 addresses are contiguous */
        memcpy(aad + 4, wh->i_addr1, 3 * IEEE80211_ADDR_LEN);
        aad[22] = wh->i_seq[0] & IEEE80211_SEQ_FRAG_MASK;
        aad[23] = 0; /* all bits masked */
        /*
         * Construct variable-length portion of AAD based
         * on whether this is a 4-address frame/QOS frame.
         * We always zero-pad to 32 bytes before running it
         * through the cipher.
         *
         * We also fill in the priority bits of the CCM
         * initial block as we know whether or not we have
         * a QOS frame.
         */
        if (IS_4ADDRESS(wh)) {
                IEEE80211_ADDR_COPY(aad + 24,
                        ((struct ieee80211_frame_addr4 *)wh)->i_addr4);
                if (IS_QOS_DATA(wh)) {
                        struct ieee80211_qosframe_addr4 *qwh4 =
                                (struct ieee80211_qosframe_addr4 *) wh;
                        aad[30] = qwh4->i_qos[0] & 0x0f;/* just priority bits */
                        aad[31] = 0;
                        b0[1] = aad[30];
                        aad[1] = 22 + IEEE80211_ADDR_LEN + 2;
                } else {
                        *(uint16_t *)&aad[30] = 0;
                        b0[1] = 0;
                        aad[1] = 22 + IEEE80211_ADDR_LEN;
                }
        } else {
                if (IS_QOS_DATA(wh)) {
                        struct ieee80211_qosframe *qwh =
                                (struct ieee80211_qosframe*) wh;
                        aad[24] = qwh->i_qos[0] & 0x0f; /* just priority bits */
                        aad[25] = 0;
                        b0[1] = aad[24];
                        aad[1] = 22 + 2;
                } else {
                        *(uint16_t *)&aad[24] = 0;
                        b0[1] = 0;
                        aad[1] = 22;
                }
                *(uint16_t *)&aad[26] = 0;
                *(uint32_t *)&aad[28] = 0;
        }

        /* Start with the first block and AAD */
        rijndael_encrypt(ctx, b0, auth);
        xor_block(auth, aad, AES_BLOCK_LEN);
        rijndael_encrypt(ctx, auth, auth);
        xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
        rijndael_encrypt(ctx, auth, auth);
        b0[0] &= 0x07;
        b0[14] = b0[15] = 0;
        rijndael_encrypt(ctx, b0, s0);
#undef  IS_QOS_DATA
#undef  IS_4ADDRESS
}

#define CCMP_ENCRYPT(_i, _b, _b0, _pos, _e, _len) do {  \
        /* Authentication */                            \
        xor_block(_b, _pos, _len);                      \
        rijndael_encrypt(&ctx->cc_aes, _b, _b);         \
        /* Encryption, with counter */                  \
        _b0[14] = (_i >> 8) & 0xff;                     \
        _b0[15] = _i & 0xff;                            \
        rijndael_encrypt(&ctx->cc_aes, _b0, _e);        \
        xor_block(_pos, _e, _len);                      \
} while (0)

static int
ccmp_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
{
        struct ccmp_ctx *ctx = key->wk_private;
        struct ieee80211_frame *wh;
        struct mbuf *m = m0;
        int data_len, i, space;
        uint8_t aad[2 * AES_BLOCK_LEN], b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN],
                e[AES_BLOCK_LEN], s0[AES_BLOCK_LEN];
        uint8_t *pos;

        ctx->cc_ic->ic_stats.is_crypto_ccmp++;

        wh = mtod(m, struct ieee80211_frame *);
        data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header);
        ccmp_init_blocks(&ctx->cc_aes, wh, key->wk_keytsc,
                data_len, b0, aad, b, s0);

        i = 1;
        pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
        /* NB: assumes header is entirely in first mbuf */
        space = m->m_len - (hdrlen + ccmp.ic_header);
        for (;;) {
                if (space > data_len)
                        space = data_len;
                /*
                 * Do full blocks.
                 */
                while (space >= AES_BLOCK_LEN) {
                        CCMP_ENCRYPT(i, b, b0, pos, e, AES_BLOCK_LEN);
                        pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
                        data_len -= AES_BLOCK_LEN;
                        i++;
                }
                if (data_len <= 0)              /* no more data */
                        break;
                m = m->m_next;
                if (m == NULL) {                /* last buffer */
                        if (space != 0) {
                                /*
                                 * Short last block.
                                 */
                                CCMP_ENCRYPT(i, b, b0, pos, e, space);
                        }
                        break;
                }
                if (space != 0) {
                        uint8_t *pos_next;
                        int space_next;
                        int len, dl, sp;
                        struct mbuf *n;

                        /*
                         * Block straddles one or more mbufs, gather data
                         * into the block buffer b, apply the cipher, then
                         * scatter the results back into the mbuf chain.
                         * The buffer will automatically get space bytes
                         * of data at offset 0 copied in+out by the
                         * CCMP_ENCRYPT request so we must take care of
                         * the remaining data.
                         */
                        n = m;
                        dl = data_len;
                        sp = space;
                        for (;;) {
                                pos_next = mtod(n, uint8_t *);
                                len = min(dl, AES_BLOCK_LEN);
                                space_next = len > sp ? len - sp : 0;
                                if (n->m_len >= space_next) {
                                        /*
                                         * This mbuf has enough data; just grab
                                         * what we need and stop.
                                         */
                                        xor_block(b+sp, pos_next, space_next);
                                        break;
                                }
                                /*
                                 * This mbuf's contents are insufficient,
                                 * take 'em all and prepare to advance to
                                 * the next mbuf.
                                 */
                                xor_block(b+sp, pos_next, n->m_len);
                                sp += n->m_len, dl -= n->m_len;
                                n = n->m_next;
                                if (n == NULL)
                                        break;
                        }

                        CCMP_ENCRYPT(i, b, b0, pos, e, space);

                        /* NB: just like above, but scatter data to mbufs */
                        dl = data_len;
                        sp = space;
                        for (;;) {
                                pos_next = mtod(m, uint8_t *);
                                len = min(dl, AES_BLOCK_LEN);
                                space_next = len > sp ? len - sp : 0;
                                if (m->m_len >= space_next) {
                                        xor_block(pos_next, e+sp, space_next);
                                        break;
                                }
                                xor_block(pos_next, e+sp, m->m_len);
                                sp += m->m_len, dl -= m->m_len;
                                m = m->m_next;
                                if (m == NULL)
                                        goto done;
                        }
                        /*
                         * Do bookkeeping.  m now points to the last mbuf
                         * we grabbed data from.  We know we consumed a
                         * full block of data as otherwise we'd have hit
                         * the end of the mbuf chain, so deduct from data_len.
                         * Otherwise advance the block number (i) and setup
                         * pos+space to reflect contents of the new mbuf.
                         */
                        data_len -= AES_BLOCK_LEN;
                        i++;
                        pos = pos_next + space_next;
                        space = m->m_len - space_next;
                } else {
                        /*
                         * Setup for next buffer.
                         */
                        pos = mtod(m, uint8_t *);
                        space = m->m_len;
                }
        }
done:
        /* tack on MIC */
        xor_block(b, s0, ccmp.ic_trailer);
        return ieee80211_mbuf_append(m0, ccmp.ic_trailer, b);
}
#undef CCMP_ENCRYPT

#define CCMP_DECRYPT(_i, _b, _b0, _pos, _a, _len) do {  \
        /* Decrypt, with counter */                     \
        _b0[14] = (_i >> 8) & 0xff;                     \
        _b0[15] = _i & 0xff;                            \
        rijndael_encrypt(&ctx->cc_aes, _b0, _b);        \
        xor_block(_pos, _b, _len);                      \
        /* Authentication */                            \
        xor_block(_a, _pos, _len);                      \
        rijndael_encrypt(&ctx->cc_aes, _a, _a);         \
} while (0)

static int
ccmp_decrypt(struct ieee80211_key *key, uint64_t pn, struct mbuf *m, int hdrlen)
{
        struct ccmp_ctx *ctx = key->wk_private;
        struct ieee80211_frame *wh;
        uint8_t aad[2 * AES_BLOCK_LEN];
        uint8_t b0[AES_BLOCK_LEN], b[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
        uint8_t mic[AES_BLOCK_LEN];
        size_t data_len;
        int i;
        uint8_t *pos;
        u_int space;

        ctx->cc_ic->ic_stats.is_crypto_ccmp++;

        wh = mtod(m, struct ieee80211_frame *);
        data_len = m->m_pkthdr.len - (hdrlen + ccmp.ic_header + ccmp.ic_trailer);
        ccmp_init_blocks(&ctx->cc_aes, wh, pn, data_len, b0, aad, a, b);
        m_copydata(m, m->m_pkthdr.len - ccmp.ic_trailer, ccmp.ic_trailer, mic);
        xor_block(mic, b, ccmp.ic_trailer);

        i = 1;
        pos = mtod(m, uint8_t *) + hdrlen + ccmp.ic_header;
        space = m->m_len - (hdrlen + ccmp.ic_header);
        for (;;) {
                if (space > data_len)
                        space = data_len;
                while (space >= AES_BLOCK_LEN) {
                        CCMP_DECRYPT(i, b, b0, pos, a, AES_BLOCK_LEN);
                        pos += AES_BLOCK_LEN, space -= AES_BLOCK_LEN;
                        data_len -= AES_BLOCK_LEN;
                        i++;
                }
                if (data_len <= 0)              /* no more data */
                        break;
                m = m->m_next;
                if (m == NULL) {                /* last buffer */
                        if (space != 0)         /* short last block */
                                CCMP_DECRYPT(i, b, b0, pos, a, space);
                        break;
                }
                if (space != 0) {
                        uint8_t *pos_next;
                        u_int space_next;
                        u_int len;

                        /*
                         * Block straddles buffers, split references.  We
                         * do not handle splits that require >2 buffers
                         * since rx'd frames are never badly fragmented
                         * because drivers typically recv in clusters.
                         */
                        pos_next = mtod(m, uint8_t *);
                        len = min(data_len, AES_BLOCK_LEN);
                        space_next = len > space ? len - space : 0;
                        KASSERT(m->m_len >= space_next,
                                ("not enough data in following buffer, "
                                "m_len %u need %u\n", m->m_len, space_next));

                        xor_block(b+space, pos_next, space_next);
                        CCMP_DECRYPT(i, b, b0, pos, a, space);
                        xor_block(pos_next, b+space, space_next);
                        data_len -= len;
                        i++;

                        pos = pos_next + space_next;
                        space = m->m_len - space_next;
                } else {
                        /*
                         * Setup for next buffer.
                         */
                        pos = mtod(m, uint8_t *);
                        space = m->m_len;
                }
        }
        if (memcmp(mic, a, ccmp.ic_trailer) != 0) {
                IEEE80211_DPRINTF(ctx->cc_ic, IEEE80211_MSG_CRYPTO,
                        "[%6D] AES-CCM decrypt failed; MIC mismatch\n",
                        wh->i_addr2, ":");
                ctx->cc_ic->ic_stats.is_rx_ccmpmic++;
                return 0;
        }
        return 1;
}
#undef CCMP_DECRYPT

/*
 * Module glue.
 */
static int
ccmp_modevent(module_t mod, int type, void *unused)
{
        switch (type) {
        case MOD_LOAD:
                ieee80211_crypto_register(&ccmp);
                return 0;
        case MOD_UNLOAD:
                if (nrefs) {
                        kprintf("wlan_ccmp: still in use (%u dynamic refs)\n",
                                nrefs);
                        return EBUSY;
                }
                ieee80211_crypto_unregister(&ccmp);
                return 0;
        }
        return EINVAL;
}

static moduledata_t ccmp_mod = {
        "wlan_ccmp",
        ccmp_modevent,
        0
};
DECLARE_MODULE(wlan_ccmp, ccmp_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
MODULE_VERSION(wlan_ccmp, 1);
MODULE_DEPEND(wlan_ccmp, wlan, 1, 1, 1);