wpa.c

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/*
 * Copyright 2002-2004, Instant802 Networks, Inc.
 * Copyright 2008, Jouni Malinen <j@w1.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.
 */

#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/compiler.h>
#include <linux/ieee80211.h>
#include <linux/gfp.h>
#include <asm/unaligned.h>
#include <net/mac80211.h>
#include <crypto/aes.h>

#include "ieee80211_i.h"
#include "michael.h"
#include "tkip.h"
#include "aes_ccm.h"
#include "aes_cmac.h"
#include "wpa.h"

ieee80211_tx_result
ieee80211_tx_h_michael_mic_add(struct ieee80211_tx_data *tx)
{
        u8 *data, *key, *mic;
        size_t data_len;
        unsigned int hdrlen;
        struct ieee80211_hdr *hdr;
        struct sk_buff *skb = tx->skb;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        int tail;

        hdr = (struct ieee80211_hdr *)skb->data;
        if (!tx->key || tx->key->conf.cipher != WLAN_CIPHER_SUITE_TKIP ||
            skb->len < 24 || !ieee80211_is_data_present(hdr->frame_control))
                return TX_CONTINUE;

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        if (skb->len < hdrlen)
                return TX_DROP;

        data = skb->data + hdrlen;
        data_len = skb->len - hdrlen;

        if (unlikely(info->flags & IEEE80211_TX_INTFL_TKIP_MIC_FAILURE)) {
                /* Need to use software crypto for the test */
                info->control.hw_key = NULL;
        }

        if (info->control.hw_key &&
            (info->flags & IEEE80211_TX_CTL_DONTFRAG ||
             tx->local->ops->set_frag_threshold) &&
            !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_MMIC)) {
                /* hwaccel - with no need for SW-generated MMIC */
                return TX_CONTINUE;
        }

        tail = MICHAEL_MIC_LEN;
        if (!info->control.hw_key)
                tail += TKIP_ICV_LEN;

        if (WARN_ON(skb_tailroom(skb) < tail ||
                    skb_headroom(skb) < TKIP_IV_LEN))
                return TX_DROP;

        key = &tx->key->conf.key[NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY];
        mic = skb_put(skb, MICHAEL_MIC_LEN);
        michael_mic(key, hdr, data, data_len, mic);
        if (unlikely(info->flags & IEEE80211_TX_INTFL_TKIP_MIC_FAILURE))
                mic[0]++;

        return TX_CONTINUE;
}


ieee80211_rx_result
ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
{
        u8 *data, *key = NULL;
        size_t data_len;
        unsigned int hdrlen;
        u8 mic[MICHAEL_MIC_LEN];
        struct sk_buff *skb = rx->skb;
        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

        /*
         * it makes no sense to check for MIC errors on anything other
         * than data frames.
         */
        if (!ieee80211_is_data_present(hdr->frame_control))
                return RX_CONTINUE;

        /*
         * No way to verify the MIC if the hardware stripped it or
         * the IV with the key index. In this case we have solely rely
         * on the driver to set RX_FLAG_MMIC_ERROR in the event of a
         * MIC failure report.
         */
        if (status->flag & (RX_FLAG_MMIC_STRIPPED | RX_FLAG_IV_STRIPPED)) {
                if (status->flag & RX_FLAG_MMIC_ERROR)
                        goto mic_fail;

                if (!(status->flag & RX_FLAG_IV_STRIPPED) && rx->key)
                        goto update_iv;

                return RX_CONTINUE;
        }

        /*
         * Some hardware seems to generate Michael MIC failure reports; even
         * though, the frame was not encrypted with TKIP and therefore has no
         * MIC. Ignore the flag them to avoid triggering countermeasures.
         */
        if (!rx->key || rx->key->conf.cipher != WLAN_CIPHER_SUITE_TKIP ||
            !(status->flag & RX_FLAG_DECRYPTED))
                return RX_CONTINUE;

        if (rx->sdata->vif.type == NL80211_IFTYPE_AP && rx->key->conf.keyidx) {
                /*
                 * APs with pairwise keys should never receive Michael MIC
                 * errors for non-zero keyidx because these are reserved for
                 * group keys and only the AP is sending real multicast
                 * frames in the BSS. (
                 */
                return RX_DROP_UNUSABLE;
        }

        if (status->flag & RX_FLAG_MMIC_ERROR)
                goto mic_fail;

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        if (skb->len < hdrlen + MICHAEL_MIC_LEN)
                return RX_DROP_UNUSABLE;

        if (skb_linearize(rx->skb))
                return RX_DROP_UNUSABLE;
        hdr = (void *)skb->data;

        data = skb->data + hdrlen;
        data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
        key = &rx->key->conf.key[NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY];
        michael_mic(key, hdr, data, data_len, mic);
        if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0)
                goto mic_fail;

        /* remove Michael MIC from payload */
        skb_trim(skb, skb->len - MICHAEL_MIC_LEN);

update_iv:
        /* update IV in key information to be able to detect replays */
        rx->key->u.tkip.rx[rx->security_idx].iv32 = rx->tkip_iv32;
        rx->key->u.tkip.rx[rx->security_idx].iv16 = rx->tkip_iv16;

        return RX_CONTINUE;

mic_fail:
        /*
         * In some cases the key can be unset - e.g. a multicast packet, in
         * a driver that supports HW encryption. Send up the key idx only if
         * the key is set.
         */
        mac80211_ev_michael_mic_failure(rx->sdata,
                                        rx->key ? rx->key->conf.keyidx : -1,
                                        (void *) skb->data, NULL, GFP_ATOMIC);
        return RX_DROP_UNUSABLE;
}


static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        struct ieee80211_key *key = tx->key;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        unsigned long flags;
        unsigned int hdrlen;
        int len, tail;
        u8 *pos;

        if (info->control.hw_key &&
            !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
            !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
                /* hwaccel - with no need for software-generated IV */
                return 0;
        }

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        len = skb->len - hdrlen;

        if (info->control.hw_key)
                tail = 0;
        else
                tail = TKIP_ICV_LEN;

        if (WARN_ON(skb_tailroom(skb) < tail ||
                    skb_headroom(skb) < TKIP_IV_LEN))
                return -1;

        pos = skb_push(skb, TKIP_IV_LEN);
        memmove(pos, pos + TKIP_IV_LEN, hdrlen);
        skb_set_network_header(skb, skb_network_offset(skb) + TKIP_IV_LEN);
        pos += hdrlen;

        /* the HW only needs room for the IV, but not the actual IV */
        if (info->control.hw_key &&
            (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
                return 0;

        /* Increase IV for the frame */
        spin_lock_irqsave(&key->u.tkip.txlock, flags);
        key->u.tkip.tx.iv16++;
        if (key->u.tkip.tx.iv16 == 0)
                key->u.tkip.tx.iv32++;
        pos = ieee80211_tkip_add_iv(pos, key);
        spin_unlock_irqrestore(&key->u.tkip.txlock, flags);

        /* hwaccel - with software IV */
        if (info->control.hw_key)
                return 0;

        /* Add room for ICV */
        skb_put(skb, TKIP_ICV_LEN);

        return ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
                                           key, skb, pos, len);
}


ieee80211_tx_result
ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
{
        struct sk_buff *skb;

        ieee80211_tx_set_protected(tx);

        skb_queue_walk(&tx->skbs, skb) {
                if (tkip_encrypt_skb(tx, skb) < 0)
                        return TX_DROP;
        }

        return TX_CONTINUE;
}


ieee80211_rx_result
ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
        int hdrlen, res, hwaccel = 0;
        struct ieee80211_key *key = rx->key;
        struct sk_buff *skb = rx->skb;
        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);

        hdrlen = ieee80211_hdrlen(hdr->frame_control);

        if (!ieee80211_is_data(hdr->frame_control))
                return RX_CONTINUE;

        if (!rx->sta || skb->len - hdrlen < 12)
                return RX_DROP_UNUSABLE;

        /* it may be possible to optimize this a bit more */
        if (skb_linearize(rx->skb))
                return RX_DROP_UNUSABLE;
        hdr = (void *)skb->data;

        /*
         * Let TKIP code verify IV, but skip decryption.
         * In the case where hardware checks the IV as well,
         * we don't even get here, see ieee80211_rx_h_decrypt()
         */
        if (status->flag & RX_FLAG_DECRYPTED)
                hwaccel = 1;

        res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
                                          key, skb->data + hdrlen,
                                          skb->len - hdrlen, rx->sta->sta.addr,
                                          hdr->addr1, hwaccel, rx->security_idx,
                                          &rx->tkip_iv32,
                                          &rx->tkip_iv16);
        if (res != TKIP_DECRYPT_OK)
                return RX_DROP_UNUSABLE;

        /* Trim ICV */
        skb_trim(skb, skb->len - TKIP_ICV_LEN);

        /* Remove IV */
        memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
        skb_pull(skb, TKIP_IV_LEN);

        return RX_CONTINUE;
}


static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
                                int encrypted)
{
        __le16 mask_fc;
        int a4_included, mgmt;
        u8 qos_tid;
        u8 *b_0, *aad;
        u16 data_len, len_a;
        unsigned int hdrlen;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

        memset(scratch, 0, 6 * AES_BLOCK_SIZE);

        b_0 = scratch + 3 * AES_BLOCK_SIZE;
        aad = scratch + 4 * AES_BLOCK_SIZE;

        /*
         * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
         * Retry, PwrMgt, MoreData; set Protected
         */
        mgmt = ieee80211_is_mgmt(hdr->frame_control);
        mask_fc = hdr->frame_control;
        mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
                                IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
        if (!mgmt)
                mask_fc &= ~cpu_to_le16(0x0070);
        mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        len_a = hdrlen - 2;
        a4_included = ieee80211_has_a4(hdr->frame_control);

        if (ieee80211_is_data_qos(hdr->frame_control))
                qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
        else
                qos_tid = 0;

        data_len = skb->len - hdrlen - CCMP_HDR_LEN;
        if (encrypted)
                data_len -= CCMP_MIC_LEN;

        /* First block, b_0 */
        b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
        /* Nonce: Nonce Flags | A2 | PN
         * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
         */
        b_0[1] = qos_tid | (mgmt << 4);
        memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
        memcpy(&b_0[8], pn, CCMP_PN_LEN);
        /* l(m) */
        put_unaligned_be16(data_len, &b_0[14]);

        /* AAD (extra authenticate-only data) / masked 802.11 header
         * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
        put_unaligned_be16(len_a, &aad[0]);
        put_unaligned(mask_fc, (__le16 *)&aad[2]);
        memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);

        /* Mask Seq#, leave Frag# */
        aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
        aad[23] = 0;

        if (a4_included) {
                memcpy(&aad[24], hdr->addr4, ETH_ALEN);
                aad[30] = qos_tid;
                aad[31] = 0;
        } else {
                memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
                aad[24] = qos_tid;
        }
}


static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
{
        hdr[0] = pn[5];
        hdr[1] = pn[4];
        hdr[2] = 0;
        hdr[3] = 0x20 | (key_id << 6);
        hdr[4] = pn[3];
        hdr[5] = pn[2];
        hdr[6] = pn[1];
        hdr[7] = pn[0];
}


static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
{
        pn[0] = hdr[7];
        pn[1] = hdr[6];
        pn[2] = hdr[5];
        pn[3] = hdr[4];
        pn[4] = hdr[1];
        pn[5] = hdr[0];
}


static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        struct ieee80211_key *key = tx->key;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        int hdrlen, len, tail;
        u8 *pos;
        u8 pn[6];
        u64 pn64;
        u8 scratch[6 * AES_BLOCK_SIZE];

        if (info->control.hw_key &&
            !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
            !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
                /*
                 * hwaccel has no need for preallocated room for CCMP
                 * header or MIC fields
                 */
                return 0;
        }

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        len = skb->len - hdrlen;

        if (info->control.hw_key)
                tail = 0;
        else
                tail = CCMP_MIC_LEN;

        if (WARN_ON(skb_tailroom(skb) < tail ||
                    skb_headroom(skb) < CCMP_HDR_LEN))
                return -1;

        pos = skb_push(skb, CCMP_HDR_LEN);
        memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
        skb_set_network_header(skb, skb_network_offset(skb) + CCMP_HDR_LEN);

        /* the HW only needs room for the IV, but not the actual IV */
        if (info->control.hw_key &&
            (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
                return 0;

        hdr = (struct ieee80211_hdr *) pos;
        pos += hdrlen;

        pn64 = atomic64_inc_return(&key->u.ccmp.tx_pn);

        pn[5] = pn64;
        pn[4] = pn64 >> 8;
        pn[3] = pn64 >> 16;
        pn[2] = pn64 >> 24;
        pn[1] = pn64 >> 32;
        pn[0] = pn64 >> 40;

        ccmp_pn2hdr(pos, pn, key->conf.keyidx);

        /* hwaccel - with software CCMP header */
        if (info->control.hw_key)
                return 0;

        pos += CCMP_HDR_LEN;
        ccmp_special_blocks(skb, pn, scratch, 0);
        ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, scratch, pos, len,
                                  pos, skb_put(skb, CCMP_MIC_LEN));

        return 0;
}


ieee80211_tx_result
ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
{
        struct sk_buff *skb;

        ieee80211_tx_set_protected(tx);

        skb_queue_walk(&tx->skbs, skb) {
                if (ccmp_encrypt_skb(tx, skb) < 0)
                        return TX_DROP;
        }

        return TX_CONTINUE;
}


ieee80211_rx_result
ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
        int hdrlen;
        struct ieee80211_key *key = rx->key;
        struct sk_buff *skb = rx->skb;
        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
        u8 pn[CCMP_PN_LEN];
        int data_len;
        int queue;

        hdrlen = ieee80211_hdrlen(hdr->frame_control);

        if (!ieee80211_is_data(hdr->frame_control) &&
            !ieee80211_is_robust_mgmt_frame(hdr))
                return RX_CONTINUE;

        data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
        if (!rx->sta || data_len < 0)
                return RX_DROP_UNUSABLE;

        if (status->flag & RX_FLAG_DECRYPTED) {
                if (!pskb_may_pull(rx->skb, hdrlen + CCMP_HDR_LEN))
                        return RX_DROP_UNUSABLE;
        } else {
                if (skb_linearize(rx->skb))
                        return RX_DROP_UNUSABLE;
        }

        ccmp_hdr2pn(pn, skb->data + hdrlen);

        queue = rx->security_idx;

        if (memcmp(pn, key->u.ccmp.rx_pn[queue], CCMP_PN_LEN) <= 0) {
                key->u.ccmp.replays++;
                return RX_DROP_UNUSABLE;
        }

        if (!(status->flag & RX_FLAG_DECRYPTED)) {
                u8 scratch[6 * AES_BLOCK_SIZE];
                /* hardware didn't decrypt/verify MIC */
                ccmp_special_blocks(skb, pn, scratch, 1);

                if (ieee80211_aes_ccm_decrypt(
                            key->u.ccmp.tfm, scratch,
                            skb->data + hdrlen + CCMP_HDR_LEN, data_len,
                            skb->data + skb->len - CCMP_MIC_LEN,
                            skb->data + hdrlen + CCMP_HDR_LEN))
                        return RX_DROP_UNUSABLE;
        }

        memcpy(key->u.ccmp.rx_pn[queue], pn, CCMP_PN_LEN);

        /* Remove CCMP header and MIC */
        if (pskb_trim(skb, skb->len - CCMP_MIC_LEN))
                return RX_DROP_UNUSABLE;
        memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
        skb_pull(skb, CCMP_HDR_LEN);

        return RX_CONTINUE;
}


static void bip_aad(struct sk_buff *skb, u8 *aad)
{
        /* BIP AAD: FC(masked) || A1 || A2 || A3 */

        /* FC type/subtype */
        aad[0] = skb->data[0];
        /* Mask FC Retry, PwrMgt, MoreData flags to zero */
        aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
        /* A1 || A2 || A3 */
        memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
}


static inline void bip_ipn_set64(u8 *d, u64 pn)
{
        *d++ = pn;
        *d++ = pn >> 8;
        *d++ = pn >> 16;
        *d++ = pn >> 24;
        *d++ = pn >> 32;
        *d = pn >> 40;
}

static inline void bip_ipn_swap(u8 *d, const u8 *s)
{
        *d++ = s[5];
        *d++ = s[4];
        *d++ = s[3];
        *d++ = s[2];
        *d++ = s[1];
        *d = s[0];
}


ieee80211_tx_result
ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
{
        struct sk_buff *skb;
        struct ieee80211_tx_info *info;
        struct ieee80211_key *key = tx->key;
        struct ieee80211_mmie *mmie;
        u8 aad[20];
        u64 pn64;

        if (WARN_ON(skb_queue_len(&tx->skbs) != 1))
                return TX_DROP;

        skb = skb_peek(&tx->skbs);

        info = IEEE80211_SKB_CB(skb);

        if (info->control.hw_key)
                return TX_CONTINUE;

        if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
                return TX_DROP;

        mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
        mmie->element_id = WLAN_EID_MMIE;
        mmie->length = sizeof(*mmie) - 2;
        mmie->key_id = cpu_to_le16(key->conf.keyidx);

        /* PN = PN + 1 */
        pn64 = atomic64_inc_return(&key->u.aes_cmac.tx_pn);

        bip_ipn_set64(mmie->sequence_number, pn64);

        bip_aad(skb, aad);

        /*
         * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
         */
        ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
                           skb->data + 24, skb->len - 24, mmie->mic);

        return TX_CONTINUE;
}


ieee80211_rx_result
ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
{
        struct sk_buff *skb = rx->skb;
        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
        struct ieee80211_key *key = rx->key;
        struct ieee80211_mmie *mmie;
        u8 aad[20], mic[8], ipn[6];
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;

        if (!ieee80211_is_mgmt(hdr->frame_control))
                return RX_CONTINUE;

        /* management frames are already linear */

        if (skb->len < 24 + sizeof(*mmie))
                return RX_DROP_UNUSABLE;

        mmie = (struct ieee80211_mmie *)
                (skb->data + skb->len - sizeof(*mmie));
        if (mmie->element_id != WLAN_EID_MMIE ||
            mmie->length != sizeof(*mmie) - 2)
                return RX_DROP_UNUSABLE; /* Invalid MMIE */

        bip_ipn_swap(ipn, mmie->sequence_number);

        if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
                key->u.aes_cmac.replays++;
                return RX_DROP_UNUSABLE;
        }

        if (!(status->flag & RX_FLAG_DECRYPTED)) {
                /* hardware didn't decrypt/verify MIC */
                bip_aad(skb, aad);
                ieee80211_aes_cmac(key->u.aes_cmac.tfm, aad,
                                   skb->data + 24, skb->len - 24, mic);
                if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
                        key->u.aes_cmac.icverrors++;
                        return RX_DROP_UNUSABLE;
                }
        }

        memcpy(key->u.aes_cmac.rx_pn, ipn, 6);

        /* Remove MMIE */
        skb_trim(skb, skb->len - sizeof(*mmie));

        return RX_CONTINUE;
}

ieee80211_tx_result
ieee80211_crypto_hw_encrypt(struct ieee80211_tx_data *tx)
{
        struct sk_buff *skb;
        struct ieee80211_tx_info *info = NULL;

        skb_queue_walk(&tx->skbs, skb) {
                info  = IEEE80211_SKB_CB(skb);

                /* handle hw-only algorithm */
                if (!info->control.hw_key)
                        return TX_DROP;
        }

        ieee80211_tx_set_protected(tx);

        return TX_CONTINUE;
}