/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2002-2008 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.
 *
 * 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.
 */

#include <sys/cdefs.h>
/*
 * 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 "opt_wlan.h"

#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_media.h>
#include <net/ethernet.h>

#include <net80211/ieee80211_var.h>

#include <crypto/rijndael/rijndael.h>

#define AES_BLOCK_LEN 16

#define CCMP_128_MIC_LEN                8
#define CCMP_256_MIC_LEN                16

struct ccmp_ctx {
        struct ieee80211vap *cc_vap;    /* for diagnostics+statistics */
        struct ieee80211com *cc_ic;
        rijndael_ctx         cc_aes;
};

static  void *ccmp_attach(struct ieee80211vap *, struct ieee80211_key *);
static  void ccmp_detach(struct ieee80211_key *);
static  int ccmp_setkey(struct ieee80211_key *);
static  void ccmp_setiv(struct ieee80211_key *, uint8_t *);
static  int ccmp_encap(struct ieee80211_key *, struct mbuf *);
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 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     = CCMP_128_MIC_LEN,
        .ic_miclen      = 0,
        .ic_attach      = ccmp_attach,
        .ic_detach      = ccmp_detach,
        .ic_setkey      = ccmp_setkey,
        .ic_setiv       = ccmp_setiv,
        .ic_encap       = ccmp_encap,
        .ic_decap       = ccmp_decap,
        .ic_enmic       = ccmp_enmic,
        .ic_demic       = ccmp_demic,
};

static const struct ieee80211_cipher ccmp_256 = {
        .ic_name        = "AES-CCM-256",
        .ic_cipher      = IEEE80211_CIPHER_AES_CCM_256,
        .ic_header      = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN +
                            IEEE80211_WEP_EXTIVLEN,
        .ic_trailer     = CCMP_256_MIC_LEN,
        .ic_miclen      = 0,
        .ic_attach      = ccmp_attach,
        .ic_detach      = ccmp_detach,
        .ic_setkey      = ccmp_setkey,
        .ic_setiv       = ccmp_setiv,
        .ic_encap       = ccmp_encap,
        .ic_decap       = ccmp_decap,
        .ic_enmic       = ccmp_enmic,
        .ic_demic       = ccmp_demic,
};

static  int ccmp_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
static  int ccmp_decrypt(struct ieee80211_key *, u_int64_t pn,
                struct mbuf *, int hdrlen);

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

static void *
ccmp_attach(struct ieee80211vap *vap, struct ieee80211_key *k)
{
        struct ccmp_ctx *ctx;

        ctx = (struct ccmp_ctx *) IEEE80211_MALLOC(sizeof(struct ccmp_ctx),
                M_80211_CRYPTO, IEEE80211_M_NOWAIT | IEEE80211_M_ZERO);
        if (ctx == NULL) {
                vap->iv_stats.is_crypto_nomem++;
                return NULL;
        }
        ctx->cc_vap = vap;
        ctx->cc_ic = vap->iv_ic;
        nrefs++;                        /* NB: we assume caller locking */
        return ctx;
}

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

        IEEE80211_FREE(ctx, M_80211_CRYPTO);
        KASSERT(nrefs > 0, ("imbalanced attach/detach"));
        nrefs--;                        /* NB: we assume caller locking */
}

static int
ccmp_get_trailer_len(struct ieee80211_key *k)
{
        return (k->wk_cipher->ic_trailer);
}

static int
ccmp_get_header_len(struct ieee80211_key *k)
{
        return (k->wk_cipher->ic_header);
}

/**
 * @brief Return the M parameter to use for CCMP block0 initialisation.
 *
 * M is defined as the number of bytes in the authentication
 * field.
 *
 * See RFC3610, Section 2 (CCM Mode Specification) for more
 * information.
 *
 * The MIC size is defined in 802.11-2020 12.5.3
 * (CTR with CBC-MAC Protocol (CCMP)).
 *
 * CCM-128 - M=8, MIC is 8 octets.
 * CCM-256 - M=16, MIC is 16 octets.
 *
 * @param key   ieee80211_key to calculate M for
 * @retval the number of bytes in the authentication field
 */
static int
ccmp_get_ccm_m(struct ieee80211_key *k)
{
        if (k->wk_cipher->ic_cipher == IEEE80211_CIPHER_AES_CCM)
                return (8);
        if (k->wk_cipher->ic_cipher == IEEE80211_CIPHER_AES_CCM_256)
                return (16);
        return (8); /* XXX default */
}

static int
ccmp_setkey(struct ieee80211_key *k)
{
        uint32_t keylen;
        struct ccmp_ctx *ctx = k->wk_private;

        switch (k->wk_cipher->ic_cipher) {
        case IEEE80211_CIPHER_AES_CCM:
                keylen = 128;
                break;
        case IEEE80211_CIPHER_AES_CCM_256:
                keylen = 256;
                break;
        default:
                IEEE80211_DPRINTF(ctx->cc_vap, IEEE80211_MSG_CRYPTO,
                    "%s: Unexpected cipher (%u)",
                    __func__, k->wk_cipher->ic_cipher);
                return (0);
        }

        if (k->wk_keylen != (keylen/NBBY)) {
                IEEE80211_DPRINTF(ctx->cc_vap, IEEE80211_MSG_CRYPTO,
                        "%s: Invalid key length %u, expecting %u\n",
                        __func__, k->wk_keylen, keylen/NBBY);
                return 0;
        }
        if (k->wk_flags & IEEE80211_KEY_SWENCRYPT)
                rijndael_set_key(&ctx->cc_aes, k->wk_key, k->wk_keylen*NBBY);
        return 1;
}

static void
ccmp_setiv(struct ieee80211_key *k, uint8_t *ivp)
{
        struct ccmp_ctx *ctx = k->wk_private;
        struct ieee80211vap *vap = ctx->cc_vap;
        uint8_t keyid;

        keyid = ieee80211_crypto_get_keyid(vap, k) << 6;

        k->wk_keytsc++;
        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 */
}

/*
 * Add privacy headers appropriate for the specified key.
 */
static int
ccmp_encap(struct ieee80211_key *k, struct mbuf *m)
{
        const struct ieee80211_frame *wh;
        struct ccmp_ctx *ctx = k->wk_private;
        struct ieee80211com *ic = ctx->cc_ic;
        uint8_t *ivp;
        int hdrlen;
        int is_mgmt;

        hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));
        wh = mtod(m, const struct ieee80211_frame *);
        is_mgmt = IEEE80211_IS_MGMT(wh);

        /*
         * Check to see if we need to insert IV/MIC.
         *
         * Some offload devices don't require the IV to be inserted
         * as part of the hardware encryption.
         */
        if (is_mgmt && (k->wk_flags & IEEE80211_KEY_NOIVMGT))
                return 1;
        if ((! is_mgmt) && (k->wk_flags & IEEE80211_KEY_NOIV))
                return 1;

        /*
         * Copy down 802.11 header and add the IV, KeyID, and ExtIV.
         */
        M_PREPEND(m, ccmp_get_header_len(k), IEEE80211_M_NOWAIT);
        if (m == NULL)
                return 0;
        ivp = mtod(m, uint8_t *);
        ovbcopy(ivp + ccmp_get_header_len(k), ivp, hdrlen);
        ivp += hdrlen;

        ccmp_setiv(k, ivp);

        /*
         * Finally, do software encrypt if needed.
         */
        if ((k->wk_flags & IEEE80211_KEY_SWENCRYPT) &&
            !ccmp_encrypt(k, m, hdrlen))
                return 0;

        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)
{
        const struct ieee80211_rx_stats *rxs;
        struct ccmp_ctx *ctx = k->wk_private;
        struct ieee80211vap *vap = ctx->cc_vap;
        struct ieee80211_frame *wh;
        uint8_t *ivp, tid;
        uint64_t pn;
        bool noreplaycheck;

        rxs = ieee80211_get_rx_params_ptr(m);

        if ((rxs != NULL) && (rxs->c_pktflags & IEEE80211_RX_F_IV_STRIP) != 0)
                goto finish;

        /*
         * 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_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
                        "%s", "missing ExtIV for AES-CCM cipher");
                vap->iv_stats.is_rx_ccmpformat++;
                return 0;
        }
        tid = ieee80211_gettid(wh);
        pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);

        noreplaycheck = (k->wk_flags & IEEE80211_KEY_NOREPLAY) != 0;
        noreplaycheck |= (rxs != NULL) && (rxs->c_pktflags & IEEE80211_RX_F_PN_VALIDATED) != 0;
        if (pn <= k->wk_keyrsc[tid] && !noreplaycheck) {
                /*
                 * Replay violation.
                 */
                ieee80211_notify_replay_failure(vap, wh, k, pn, tid);
                vap->iv_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_SWDECRYPT) &&
            !ccmp_decrypt(k, pn, m, hdrlen))
                return 0;

finish:
        /*
         * Copy up 802.11 header and strip crypto bits.
         */
        if (! ((rxs != NULL) && (rxs->c_pktflags & IEEE80211_RX_F_IV_STRIP))) {
                ovbcopy(mtod(m, void *),
                    mtod(m, uint8_t *) + ccmp_get_header_len(k),
                    hdrlen);
                m_adj(m, ccmp_get_header_len(k));
        }

        if ((rxs == NULL) || (rxs->c_pktflags & IEEE80211_RX_F_MIC_STRIP) == 0)
                m_adj(m, -ccmp_get_trailer_len(k));

        /*
         * Ok to update rsc now.
         */
        if ((rxs == NULL) || (rxs->c_pktflags & IEEE80211_RX_F_IV_STRIP) == 0) {
                /*
                 * Do not go backwards in the IEEE80211_KEY_NOREPLAY cases
                 * or in case hardware has checked but frames are arriving
                 * reordered (e.g., LinuxKPI drivers doing RSS which we are
                 * not prepared for at all).
                 */
                if (pn > k->wk_keyrsc[tid])
                        k->wk_keyrsc[tid] = 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];
}

/**
 * @brief Initialise the AES-CCM nonce flag field in the b0 CCMP block.
 *
 * The B_0 block is defined in RFC 3610 section 2.2 (Authentication).
 * b0[0] is the CCM flags field, so the nonce used for B_0 starts at
 * b0[1].  Amusingly, b0[1] is also flags, but it's the 802.11 AES-CCM
 * nonce flags field, NOT the CCM flags field.
 *
 * The AES-CCM nonce flags field is defined in 802.11-2020 12.5.3.3.4
 * (Construct CCM nonce).
 *
 * TODO: net80211 currently doesn't support MFP (management frame protection)
 * and so bit 4 is never set.  This routine and ccmp_init_blocks() will
 * need a pointer to the ieee80211_node or a flag that explicitly states
 * the frame will be sent w/ MFP encryption / received w/ MFP decryption.
 *
 * @param wh    the 802.11 header to populate
 * @param b0    the CCM nonce to update (remembering b0[0] is the CCM
 *              nonce flags, and b0[1] is the AES-CCM nonce flags).
 */
static void
ieee80211_crypto_ccmp_init_nonce_flags(const struct ieee80211_frame *wh,
    char *b0)
{
        if (IEEE80211_IS_DSTODS(wh)) {
                /*
                 * 802.11-2020 12.5.33.3.4 (Construct CCM nonce) mentions
                 * that the low four bits of this byte are the "MPDU priority."
                 * This is defined in 5.1.1.2 (Determination of UP) and
                 * 5.1.1.3 (Interpretation of Priority Parameter in MAC
                 * service primitives).
                 *
                 * The former says "The QoS facility supports eight priority
                 * values, referred to as UPs. The values a UP may take are
                 * the integer values from 0 to 7 and are identical to the
                 * 802.11D priority tags."
                 *
                 * The latter specifically calls out that "Priority parameter
                 * and TID subfield values 0 to 7 are interpreted aas UPs for
                 * the MSDUs" .. and " .. TID subfield values 8 to 15 specify
                 * TIDs that are TS identifiers (TSIDs)" which are used for
                 * TSPEC.  There's a bunch of extra work to be done with frames
                 * received in TIDs 8..15 with no TSPEC, "then the MSDU shall
                 * be sent with priority parameter set to 0."
                 *
                 * All QoS frames (not just QoS data) have TID fields and
                 * thus priorities.  However, the code straight up
                 * copies the 4 bit TID field, rather than a 3 bit MPDU
                 * priority value.  For now, as net80211 doesn't specifically
                 * support TSPEC negotiation, this likely never gets checked.
                 * However as part of any future TSPEC work, this will likely
                 * need to be looked at and checked with interoperability
                 * with other stacks.
                 */
                if (IEEE80211_IS_QOS_ANY(wh)) {
                        const struct ieee80211_qosframe_addr4 *qwh4 =
                            (const struct ieee80211_qosframe_addr4 *) wh;
                        b0[1] = qwh4->i_qos[0] & 0x0f;  /* prio bits */
                } else {
                        b0[1] = 0;
                }
        } else {
                if (IEEE80211_IS_QOS_ANY(wh)) {
                        const struct ieee80211_qosframe *qwh =
                            (const struct ieee80211_qosframe *) wh;
                        b0[1] = qwh->i_qos[0] & 0x0f;   /* prio bits */
                } else {
                        b0[1] = 0;
                }
        }
        /* TODO: populate MFP flag */
}

/*
 * 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,
        uint32_t m, u_int64_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])
{
        /*
         * Map M parameter to encoding
         * RFC3610, Section 2 (CCM Mode Specification)
         */
        m = (m - 2) / 2;

        /* CCM Initial Block:
         *
         * Flag (Include authentication header,
         *    M=3 or 7 (8 or 16 octet auth field),
         *    L=1 (2-octet Dlen))
         *    Adata=1 (one or more auth blocks present)
         * Nonce: 0x00 | A2 | PN
         * Dlen
         */
        b0[0] = 0x40 | 0x01 | (m << 3);
        /* Init b0[1] (CCM nonce flags) */
        ieee80211_crypto_ccmp_init_nonce_flags(wh, b0);
        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;

        /* Init AAD */
        (void) ieee80211_crypto_init_aad(wh, aad, 2 * AES_BLOCK_LEN);

        /* 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);
}

#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_vap->iv_stats.is_crypto_ccmp++;

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

        i = 1;
        pos = mtod(m, uint8_t *) + hdrlen + ccmp_get_header_len(key);
        /* NB: assumes header is entirely in first mbuf */
        space = m->m_len - (hdrlen + ccmp_get_header_len(key));
        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_get_trailer_len(key));
        return m_append(m0, ccmp_get_trailer_len(key), 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, u_int64_t pn, struct mbuf *m, int hdrlen)
{
        const struct ieee80211_rx_stats *rxs;
        struct ccmp_ctx *ctx = key->wk_private;
        struct ieee80211vap *vap = ctx->cc_vap;
        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;

        rxs = ieee80211_get_rx_params_ptr(m);
        if ((rxs != NULL) && (rxs->c_pktflags & IEEE80211_RX_F_DECRYPTED) != 0)
                return (1);

        ctx->cc_vap->iv_stats.is_crypto_ccmp++;

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

        i = 1;
        pos = mtod(m, uint8_t *) + hdrlen + ccmp_get_header_len(key);
        space = m->m_len - (hdrlen + ccmp_get_header_len(key));
        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 the MIC was stripped by HW/driver we are done.
         */
        if ((rxs != NULL) && (rxs->c_pktflags & IEEE80211_RX_F_MIC_STRIP) != 0)
                return (1);

        if (memcmp(mic, a, ccmp_get_trailer_len(key)) != 0) {
                IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
                    "%s", "AES-CCM decrypt failed; MIC mismatch");
                vap->iv_stats.is_rx_ccmpmic++;
                return 0;
        }
        return 1;
}
#undef CCMP_DECRYPT

/*
 * Module glue.
 */
IEEE80211_CRYPTO_MODULE(ccmp, 1);
IEEE80211_CRYPTO_MODULE_ADD(ccmp_256);