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

[dragonfly/vkernel-mp.git] / sys / netproto / 802_11 / wlan / ieee80211_crypto.c

/*
 * Copyright (c) 2001 Atsushi Onoe
 * 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.c,v 1.10.2.2 2005/09/03 22:40:02 sam Exp $
 * $DragonFly: src/sys/netproto/802_11/wlan/ieee80211_crypto.c,v 1.6 2007/05/07 14:12:16 sephe Exp $
 */

/*
 * IEEE 802.11 generic crypto support.
 */
#include <sys/param.h>
#include <sys/mbuf.h>   

#include <sys/socket.h>

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

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

/*
 * Table of registered cipher modules.
 */
static  const struct ieee80211_cipher *ciphers[IEEE80211_CIPHER_MAX];

static  int _ieee80211_crypto_delkey(struct ieee80211com *,
                struct ieee80211_key *);

/*
 * Default "null" key management routines.
 */
static int
null_key_alloc(struct ieee80211com *ic, const struct ieee80211_key *k,
        ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
{
        if (!(&ic->ic_nw_keys[0] <= k &&
             k < &ic->ic_nw_keys[IEEE80211_WEP_NKID])) {
                /*
                 * Not in the global key table, the driver should handle this
                 * by allocating a slot in the h/w key table/cache.  In
                 * lieu of that return key slot 0 for any unicast key
                 * request.  We disallow the request if this is a group key.
                 * This default policy does the right thing for legacy hardware
                 * with a 4 key table.  It also handles devices that pass
                 * packets through untouched when marked with the WEP bit
                 * and key index 0.
                 */
                if (k->wk_flags & IEEE80211_KEY_GROUP)
                        return 0;
                *keyix = 0;     /* NB: use key index 0 for ucast key */
        } else {
                *keyix = k - ic->ic_nw_keys;
        }
        *rxkeyix = IEEE80211_KEYIX_NONE;        /* XXX maybe *keyix? */
        return 1;
}

static int
null_key_delete(struct ieee80211com *ic, const struct ieee80211_key *k)
{
        return 1;
}

static int
null_key_set(struct ieee80211com *ic, const struct ieee80211_key *k,
             const uint8_t mac[IEEE80211_ADDR_LEN])
{
        return 1;
}

static void null_key_update(struct ieee80211com *ic)
{
}

/*
 * Write-arounds for common operations.
 */
static __inline void
cipher_detach(struct ieee80211_key *key)
{
        key->wk_cipher->ic_detach(key);
}

static __inline void *
cipher_attach(struct ieee80211com *ic, struct ieee80211_key *key)
{
        return key->wk_cipher->ic_attach(ic, key);
}

/* 
 * Wrappers for driver key management methods.
 */
static __inline int
dev_key_alloc(struct ieee80211com *ic,
        const struct ieee80211_key *key,
        ieee80211_keyix *keyix, ieee80211_keyix *rxkeyix)
{
        return ic->ic_crypto.cs_key_alloc(ic, key, keyix, rxkeyix);
}

static __inline int
dev_key_delete(struct ieee80211com *ic,
        const struct ieee80211_key *key)
{
        return ic->ic_crypto.cs_key_delete(ic, key);
}

static __inline int
dev_key_set(struct ieee80211com *ic, const struct ieee80211_key *key,
        const uint8_t mac[IEEE80211_ADDR_LEN])
{
        return ic->ic_crypto.cs_key_set(ic, key, mac);
}

/*
 * Setup crypto support.
 */
void
ieee80211_crypto_attach(struct ieee80211com *ic)
{
        struct ieee80211_crypto_state *cs = &ic->ic_crypto;
        int i;

        /* NB: we assume everything is pre-zero'd */
        cs->cs_def_txkey = IEEE80211_KEYIX_NONE;
        cs->cs_max_keyix = IEEE80211_WEP_NKID;
        ciphers[IEEE80211_CIPHER_NONE] = &ieee80211_cipher_none;
        for (i = 0; i < IEEE80211_WEP_NKID; i++)
                ieee80211_crypto_resetkey(ic, &cs->cs_nw_keys[i],
                        IEEE80211_KEYIX_NONE);
        /*
         * Initialize the driver key support routines to noop entries.
         * This is useful especially for the cipher test modules.
         */
        cs->cs_key_alloc = null_key_alloc;
        cs->cs_key_set = null_key_set;
        cs->cs_key_delete = null_key_delete;
        cs->cs_key_update_begin = null_key_update;
        cs->cs_key_update_end = null_key_update;
}

/*
 * Teardown crypto support.
 */
void
ieee80211_crypto_detach(struct ieee80211com *ic)
{
        ieee80211_crypto_delglobalkeys(ic);
}

/*
 * Register a crypto cipher module.
 */
void
ieee80211_crypto_register(const struct ieee80211_cipher *cip)
{
        if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
                kprintf("%s: cipher %s has an invalid cipher index %u\n",
                        __func__, cip->ic_name, cip->ic_cipher);
                return;
        }
        if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
                kprintf("%s: cipher %s registered with a different template\n",
                        __func__, cip->ic_name);
                return;
        }
        ciphers[cip->ic_cipher] = cip;
}

/*
 * Unregister a crypto cipher module.
 */
void
ieee80211_crypto_unregister(const struct ieee80211_cipher *cip)
{
        if (cip->ic_cipher >= IEEE80211_CIPHER_MAX) {
                kprintf("%s: cipher %s has an invalid cipher index %u\n",
                        __func__, cip->ic_name, cip->ic_cipher);
                return;
        }
        if (ciphers[cip->ic_cipher] != NULL && ciphers[cip->ic_cipher] != cip) {
                kprintf("%s: cipher %s registered with a different template\n",
                        __func__, cip->ic_name);
                return;
        }
        /* NB: don't complain about not being registered */
        /* XXX disallow if references */
        ciphers[cip->ic_cipher] = NULL;
}

int
ieee80211_crypto_available(u_int cipher)
{
        return cipher < IEEE80211_CIPHER_MAX && ciphers[cipher] != NULL;
}

const struct ieee80211_cipher *
ieee80211_crypto_cipher(u_int cipher)
{
        return cipher < IEEE80211_CIPHER_MAX ? ciphers[cipher] : NULL;
}

/* 
 * Reset key state to an unused state.  The crypto
 * key allocation mechanism insures other state (e.g.
 * key data) is properly setup before a key is used.
 */
void
ieee80211_crypto_resetkey(struct ieee80211com *ic,
        struct ieee80211_key *k, ieee80211_keyix ix)
{
        if (k < &ic->ic_nw_keys[IEEE80211_WEP_NKID] &&
            k >= &ic->ic_nw_keys[0])
                k->wk_keyid = k - ic->ic_nw_keys;
        else
                k->wk_keyid = 0;

        k->wk_cipher = &ieee80211_cipher_none;
        k->wk_private = k->wk_cipher->ic_attach(ic, k);
        k->wk_keyix = k->wk_rxkeyix = ix;
        k->wk_flags = IEEE80211_KEY_XMIT | IEEE80211_KEY_RECV;
}

/* XXX well-known names! */
static const char *cipher_modnames[] = {
        "wlan_wep",     /* IEEE80211_CIPHER_WEP */
        "wlan_tkip",    /* IEEE80211_CIPHER_TKIP */
        "wlan_aes_ocb", /* IEEE80211_CIPHER_AES_OCB */
        "wlan_ccmp",    /* IEEE80211_CIPHER_AES_CCM */
        "wlan_ckip",    /* IEEE80211_CIPHER_CKIP */
};

/*
 * Establish a relationship between the specified key and cipher
 * and, if necessary, allocate a hardware index from the driver.
 * Note that when a fixed key index is required it must be specified
 * and we blindly assign it w/o consulting the driver (XXX).
 *
 * This must be the first call applied to a key; all the other key
 * routines assume wk_cipher is setup.
 *
 * Locking must be handled by the caller using:
 *      ieee80211_key_update_begin(ic);
 *      ieee80211_key_update_end(ic);
 */
int
ieee80211_crypto_newkey(struct ieee80211com *ic,
        int cipher, int flags, struct ieee80211_key *key)
{
#define N(a)    (sizeof(a) / sizeof(a[0]))
        const struct ieee80211_cipher *cip;
        ieee80211_keyix keyix, rxkeyix;
        void *keyctx;
        int oflags;

        /*
         * Validate cipher and set reference to cipher routines.
         */
        if (cipher >= IEEE80211_CIPHER_MAX) {
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                        "%s: invalid cipher %u\n", __func__, cipher);
                ic->ic_stats.is_crypto_badcipher++;
                return 0;
        }
        cip = ciphers[cipher];
        if (cip == NULL) {
                /*
                 * Auto-load cipher module if we have a well-known name
                 * for it.  It might be better to use string names rather
                 * than numbers and craft a module name based on the cipher
                 * name; e.g. wlan_cipher_<cipher-name>.
                 */
                if (cipher < N(cipher_modnames)) {
                        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                                "%s: unregistered cipher %u, load module %s\n",
                                __func__, cipher, cipher_modnames[cipher]);
                        ieee80211_load_module(cipher_modnames[cipher]);
                        /*
                         * If cipher module loaded it should immediately
                         * call ieee80211_crypto_register which will fill
                         * in the entry in the ciphers array.
                         */
                        cip = ciphers[cipher];
                }
                if (cip == NULL) {
                        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                                "%s: unable to load cipher %u, module %s\n",
                                __func__, cipher,
                                cipher < N(cipher_modnames) ?
                                        cipher_modnames[cipher] : "<unknown>");
                        ic->ic_stats.is_crypto_nocipher++;
                        return 0;
                }
        }

        oflags = key->wk_flags;
        flags &= IEEE80211_KEY_COMMON;
        /*
         * If the hardware does not support the cipher then
         * fallback to a host-based implementation.
         */
        if ((ic->ic_caps & (1<<cipher)) == 0) {
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                    "%s: no h/w support for cipher %s, falling back to s/w\n",
                    __func__, cip->ic_name);
                flags |= IEEE80211_KEY_SWCRYPT;
        } else if (ic->ic_caps_ext & IEEE80211_CEXT_CRYPTO_HDR) {
                flags |= IEEE80211_KEY_NOHDR;
        }
        /*
         * Hardware TKIP with software MIC is an important
         * combination; we handle it by flagging each key,
         * the cipher modules honor it.
         */
        if (cipher == IEEE80211_CIPHER_TKIP &&
            (ic->ic_caps & IEEE80211_C_TKIPMIC) == 0) {
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                    "%s: no h/w support for TKIP MIC, falling back to s/w\n",
                    __func__);
                flags |= IEEE80211_KEY_SWMIC;
        } else if (ic->ic_caps_ext & IEEE80211_CEXT_STRIP_MIC) {
                flags |= IEEE80211_KEY_NOMIC;
        }

        /*
         * Bind cipher to key instance.  Note we do this
         * after checking the device capabilities so the
         * cipher module can optimize space usage based on
         * whether or not it needs to do the cipher work.
         */
        if (key->wk_cipher != cip || key->wk_flags != flags) {
again:
                /*
                 * Fillin the flags so cipher modules can see s/w
                 * crypto requirements and potentially allocate
                 * different state and/or attach different method
                 * pointers.
                 *
                 * XXX this is not right when s/w crypto fallback
                 *     fails and we try to restore previous state.
                 */
                key->wk_flags = flags;
                keyctx = cip->ic_attach(ic, key); /* attach new cipher */
                if (keyctx == NULL) {
                        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                                "%s: unable to attach cipher %s\n",
                                __func__, cip->ic_name);
                        key->wk_flags = oflags; /* restore old flags */
                        ic->ic_stats.is_crypto_attachfail++;
                        return 0;
                }
                cipher_detach(key);             /* detach old cipher */
                key->wk_cipher = cip;           /* XXX refcnt? */
                key->wk_private = keyctx;
        }
        /*
         * Commit to requested usage so driver can see the flags.
         */
        key->wk_flags = flags;

        /*
         * Ask the driver for a key index if we don't have one.
         * Note that entries in the global key table always have
         * an index; this means it's safe to call this routine
         * for these entries just to setup the reference to the
         * cipher template.  Note also that when using software
         * crypto we also call the driver to give us a key index.
         */
        if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
                if (!dev_key_alloc(ic, key, &keyix, &rxkeyix)) {
                        /*
                         * Driver has no room; fallback to doing crypto
                         * in the host.  We change the flags and start the
                         * procedure over.  If we get back here then there's
                         * no hope and we bail.  Note that this can leave
                         * the key in a inconsistent state if the caller
                         * continues to use it.
                         */
                        if ((key->wk_flags & IEEE80211_KEY_SWCRYPT) == 0) {
                                ic->ic_stats.is_crypto_swfallback++;
                                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                                    "%s: no h/w resources for cipher %s, "
                                    "falling back to s/w\n", __func__,
                                    cip->ic_name);
                                oflags = key->wk_flags;
                                flags &= IEEE80211_KEY_COMMON;
                                flags |= IEEE80211_KEY_SWCRYPT;
                                if (cipher == IEEE80211_CIPHER_TKIP)
                                        flags |= IEEE80211_KEY_SWMIC;
                                goto again;
                        }
                        ic->ic_stats.is_crypto_keyfail++;
                        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                            "%s: unable to setup cipher %s\n",
                            __func__, cip->ic_name);
                        return 0;
                }
                key->wk_keyix = keyix;
                key->wk_rxkeyix = rxkeyix;
        }
        return 1;
#undef N
}

/*
 * Remove the key (no locking, for internal use).
 */
static int
_ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
{
        ieee80211_keyix keyix;

        KASSERT(key->wk_cipher != NULL, ("No cipher!"));

        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
            "%s: %s keyix %u flags 0x%x rsc %ju tsc %ju len %u\n",
            __func__, key->wk_cipher->ic_name,
            key->wk_keyix, key->wk_flags,
            key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);

        keyix = key->wk_keyix;
        if (keyix != IEEE80211_KEYIX_NONE) {
                /*
                 * Remove hardware entry.
                 */
                /* XXX key cache */
                if (!dev_key_delete(ic, key)) {
                        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                            "%s: driver did not delete key index %u\n",
                            __func__, keyix);
                        ic->ic_stats.is_crypto_delkey++;
                        /* XXX recovery? */
                }
        }
        cipher_detach(key);
        memset(key, 0, sizeof(*key));
        ieee80211_crypto_resetkey(ic, key, IEEE80211_KEYIX_NONE);
        return 1;
}

/*
 * Remove the specified key.
 */
int
ieee80211_crypto_delkey(struct ieee80211com *ic, struct ieee80211_key *key)
{
        int status;

        ieee80211_key_update_begin(ic);
        status = _ieee80211_crypto_delkey(ic, key);
        ieee80211_key_update_end(ic);
        return status;
}

/*
 * Clear the global key table.
 */
void
ieee80211_crypto_delglobalkeys(struct ieee80211com *ic)
{
        int i;

        ieee80211_key_update_begin(ic);
        for (i = 0; i < IEEE80211_WEP_NKID; i++)
                _ieee80211_crypto_delkey(ic, &ic->ic_nw_keys[i]);
        ieee80211_key_update_end(ic);
}

/*
 * Set the contents of the specified key.
 *
 * Locking must be handled by the caller using:
 *      ieee80211_key_update_begin(ic);
 *      ieee80211_key_update_end(ic);
 */
int
ieee80211_crypto_setkey(struct ieee80211com *ic, struct ieee80211_key *key,
                const uint8_t macaddr[IEEE80211_ADDR_LEN])
{
        const struct ieee80211_cipher *cip = key->wk_cipher;

        KASSERT(cip != NULL, ("No cipher!"));

        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
            "%s: %s keyix %u flags 0x%x mac %6D rsc %ju tsc %ju len %u\n",
            __func__, cip->ic_name, key->wk_keyix,
            key->wk_flags, macaddr, ":",
            key->wk_keyrsc, key->wk_keytsc, key->wk_keylen);

        /*
         * Give cipher a chance to validate key contents.
         * XXX should happen before modifying state.
         */
        if (!cip->ic_setkey(key)) {
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                    "%s: cipher %s rejected key index %u len %u flags 0x%x\n",
                    __func__, cip->ic_name, key->wk_keyix,
                    key->wk_keylen, key->wk_flags);
                ic->ic_stats.is_crypto_setkey_cipher++;
                return 0;
        }
        if (key->wk_keyix == IEEE80211_KEYIX_NONE) {
                /* XXX nothing allocated, should not happen */
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                    "%s: no key index; should not happen!\n", __func__);
                ic->ic_stats.is_crypto_setkey_nokey++;
                return 0;
        }
        return dev_key_set(ic, key, macaddr);
}

/*
 * Add privacy headers appropriate for the specified key.
 */
struct ieee80211_key *
ieee80211_crypto_encap(struct ieee80211com *ic,
        struct ieee80211_node *ni, struct mbuf *m)
{
        struct ieee80211_key *k;

        k = ieee80211_crypto_findkey(ic, ni, m);
        if (k != NULL)
                k = ieee80211_crypto_encap_withkey(ic, m, k);
        return k;
}

struct ieee80211_key *
ieee80211_crypto_findkey(struct ieee80211com *ic,
        struct ieee80211_node *ni, struct mbuf *m)
{
        struct ieee80211_frame *wh;
        struct ieee80211_key *k;

        /*
         * Multicast traffic always uses the multicast key.
         * Otherwise if a unicast key is set we use that and
         * it is always key index 0.  When no unicast key is
         * set we fall back to the default transmit key.
         */
        wh = mtod(m, struct ieee80211_frame *);
        if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
            ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none) {
                if (ic->ic_def_txkey == IEEE80211_KEYIX_NONE) {
                        IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                            "[%6D] no default transmit key (%s) deftxkey %u\n",
                            wh->i_addr1, ":", __func__,
                            ic->ic_def_txkey);
                        ic->ic_stats.is_tx_nodefkey++;
                        return NULL;
                }
                k = &ic->ic_nw_keys[ic->ic_def_txkey];
                KASSERT(k->wk_keyid == ic->ic_def_txkey,
                        ("keyid mismatch: wk_keyid %d, def_txkey %d\n",
                         k->wk_keyid, ic->ic_def_txkey));
        } else {
                k = &ni->ni_ucastkey;
                KASSERT(k->wk_keyid == 0, ("unicast key keyid is not zero\n"));
        }
        return k;
}

struct ieee80211_key *
ieee80211_crypto_encap_withkey(struct ieee80211com *ic,
        struct mbuf *m, struct ieee80211_key *k)
{
        return (k->wk_cipher->ic_encap(k, m, k->wk_keyid << 6) ? k : NULL);
}

struct ieee80211_key *
ieee80211_crypto_getiv(struct ieee80211com *ic, struct ieee80211_crypto_iv *iv,
                       struct ieee80211_key *k)
{
        memset(iv, 0, sizeof(*iv));
        return (k->wk_cipher->ic_getiv(k, iv, k->wk_keyid << 6) ? k : NULL);
}

/*
 * Validate and strip privacy headers (and trailer) for a
 * received frame that has the WEP/Privacy bit set.
 */
struct ieee80211_key *
ieee80211_crypto_decap(struct ieee80211com *ic,
        struct ieee80211_node *ni, struct mbuf *m, int hdrlen)
{
#define IEEE80211_WEP_HDRLEN    (IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN)
#define IEEE80211_WEP_MINLEN \
        (sizeof(struct ieee80211_frame) + \
        IEEE80211_WEP_HDRLEN + IEEE80211_WEP_CRCLEN)
        struct ieee80211_key *k;
        struct ieee80211_frame *wh;
        const struct ieee80211_cipher *cip;
        const uint8_t *ivp;
        uint8_t keyid;

        /* NB: this minimum size data frame could be bigger */
        if (m->m_pkthdr.len < IEEE80211_WEP_MINLEN) {
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_ANY,
                        "%s: WEP data frame too short, len %u\n",
                        __func__, m->m_pkthdr.len);
                ic->ic_stats.is_rx_tooshort++;  /* XXX need unique stat? */
                return NULL;
        }

        /*
         * Locate the key. If unicast and there is no unicast
         * key then we fall back to the key id in the header.
         * This assumes unicast keys are only configured when
         * the key id in the header is meaningless (typically 0).
         */
        wh = mtod(m, struct ieee80211_frame *);
        ivp = mtod(m, const uint8_t *) + hdrlen;        /* XXX contig */
        keyid = ivp[IEEE80211_WEP_IVLEN];
        if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
            ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none)
                k = &ic->ic_nw_keys[keyid >> 6];
        else
                k = &ni->ni_ucastkey;

        /*
         * Insure crypto header is contiguous for all decap work.
         */
        cip = k->wk_cipher;
        if (m->m_len < hdrlen + cip->ic_header &&
            (m = m_pullup(m, hdrlen + cip->ic_header)) == NULL) {
                IEEE80211_DPRINTF(ic, IEEE80211_MSG_CRYPTO,
                    "[%6D] unable to pullup %s header\n",
                    wh->i_addr2, ":", cip->ic_name);
                ic->ic_stats.is_rx_wepfail++;   /* XXX */
                return 0;
        }

        return (cip->ic_decap(k, m, hdrlen) ? k : NULL);
#undef IEEE80211_WEP_MINLEN
#undef IEEE80211_WEP_HDRLEN
}

struct ieee80211_key *
ieee80211_crypto_update(struct ieee80211com *ic, struct ieee80211_node *ni,
        const struct ieee80211_crypto_iv *iv, const struct ieee80211_frame *wh)
{
        struct ieee80211_key *k;

        /*
         * Locate the key. If unicast and there is no unicast
         * key then we fall back to the key id in the header.
         * This assumes unicast keys are only configured when
         * the key id in the header is meaningless (typically 0).
         */
        if (IEEE80211_IS_MULTICAST(wh->i_addr1) ||
            ni->ni_ucastkey.wk_cipher == &ieee80211_cipher_none) {
                const uint8_t *ivp;
                uint8_t keyid;

                ivp = (const uint8_t *)iv;
                keyid = ivp[IEEE80211_WEP_IVLEN];
                k = &ic->ic_nw_keys[keyid >> 6];
        } else {
                k = &ni->ni_ucastkey;
        }
        return (k->wk_cipher->ic_update(k, iv, wh) ? k : NULL);
}