linux/net/mac80211/wep.c
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   1/*
   2 * Software WEP encryption implementation
   3 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
   4 * Copyright 2003, Instant802 Networks, Inc.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 */
  10
  11#include <linux/netdevice.h>
  12#include <linux/types.h>
  13#include <linux/random.h>
  14#include <linux/compiler.h>
  15#include <linux/crc32.h>
  16#include <linux/crypto.h>
  17#include <linux/err.h>
  18#include <linux/mm.h>
  19#include <linux/scatterlist.h>
  20#include <linux/slab.h>
  21#include <asm/unaligned.h>
  22
  23#include <net/mac80211.h>
  24#include "ieee80211_i.h"
  25#include "wep.h"
  26
  27
  28int ieee80211_wep_init(struct ieee80211_local *local)
  29{
  30        /* start WEP IV from a random value */
  31        get_random_bytes(&local->wep_iv, WEP_IV_LEN);
  32
  33        local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
  34        if (IS_ERR(local->wep_tx_tfm)) {
  35                local->wep_rx_tfm = ERR_PTR(-EINVAL);
  36                return PTR_ERR(local->wep_tx_tfm);
  37        }
  38
  39        local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
  40        if (IS_ERR(local->wep_rx_tfm)) {
  41                crypto_free_cipher(local->wep_tx_tfm);
  42                local->wep_tx_tfm = ERR_PTR(-EINVAL);
  43                return PTR_ERR(local->wep_rx_tfm);
  44        }
  45
  46        return 0;
  47}
  48
  49void ieee80211_wep_free(struct ieee80211_local *local)
  50{
  51        if (!IS_ERR(local->wep_tx_tfm))
  52                crypto_free_cipher(local->wep_tx_tfm);
  53        if (!IS_ERR(local->wep_rx_tfm))
  54                crypto_free_cipher(local->wep_rx_tfm);
  55}
  56
  57static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
  58{
  59        /*
  60         * Fluhrer, Mantin, and Shamir have reported weaknesses in the
  61         * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  62         * 0xff, N) can be used to speedup attacks, so avoid using them.
  63         */
  64        if ((iv & 0xff00) == 0xff00) {
  65                u8 B = (iv >> 16) & 0xff;
  66                if (B >= 3 && B < 3 + keylen)
  67                        return true;
  68        }
  69        return false;
  70}
  71
  72
  73static void ieee80211_wep_get_iv(struct ieee80211_local *local,
  74                                 int keylen, int keyidx, u8 *iv)
  75{
  76        local->wep_iv++;
  77        if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
  78                local->wep_iv += 0x0100;
  79
  80        if (!iv)
  81                return;
  82
  83        *iv++ = (local->wep_iv >> 16) & 0xff;
  84        *iv++ = (local->wep_iv >> 8) & 0xff;
  85        *iv++ = local->wep_iv & 0xff;
  86        *iv++ = keyidx << 6;
  87}
  88
  89
  90static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
  91                                struct sk_buff *skb,
  92                                int keylen, int keyidx)
  93{
  94        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  95        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  96        unsigned int hdrlen;
  97        u8 *newhdr;
  98
  99        hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 100
 101        if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN ||
 102                    skb_headroom(skb) < WEP_IV_LEN))
 103                return NULL;
 104
 105        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 106        newhdr = skb_push(skb, WEP_IV_LEN);
 107        memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
 108
 109        /* the HW only needs room for the IV, but not the actual IV */
 110        if (info->control.hw_key &&
 111            (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
 112                return newhdr + hdrlen;
 113
 114        skb_set_network_header(skb, skb_network_offset(skb) + WEP_IV_LEN);
 115        ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
 116        return newhdr + hdrlen;
 117}
 118
 119
 120static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
 121                                    struct sk_buff *skb,
 122                                    struct ieee80211_key *key)
 123{
 124        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 125        unsigned int hdrlen;
 126
 127        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 128        memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
 129        skb_pull(skb, WEP_IV_LEN);
 130}
 131
 132
 133/* Perform WEP encryption using given key. data buffer must have tailroom
 134 * for 4-byte ICV. data_len must not include this ICV. Note: this function
 135 * does _not_ add IV. data = RC4(data | CRC32(data)) */
 136int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 137                               size_t klen, u8 *data, size_t data_len)
 138{
 139        __le32 icv;
 140        int i;
 141
 142        if (IS_ERR(tfm))
 143                return -1;
 144
 145        icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 146        put_unaligned(icv, (__le32 *)(data + data_len));
 147
 148        crypto_cipher_setkey(tfm, rc4key, klen);
 149        for (i = 0; i < data_len + WEP_ICV_LEN; i++)
 150                crypto_cipher_encrypt_one(tfm, data + i, data + i);
 151
 152        return 0;
 153}
 154
 155
 156/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 157 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 158 * buffer will be added. Both IV and ICV will be transmitted, so the
 159 * payload length increases with 8 bytes.
 160 *
 161 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 162 */
 163int ieee80211_wep_encrypt(struct ieee80211_local *local,
 164                          struct sk_buff *skb,
 165                          const u8 *key, int keylen, int keyidx)
 166{
 167        u8 *iv;
 168        size_t len;
 169        u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 170
 171        iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 172        if (!iv)
 173                return -1;
 174
 175        len = skb->len - (iv + WEP_IV_LEN - skb->data);
 176
 177        /* Prepend 24-bit IV to RC4 key */
 178        memcpy(rc4key, iv, 3);
 179
 180        /* Copy rest of the WEP key (the secret part) */
 181        memcpy(rc4key + 3, key, keylen);
 182
 183        /* Add room for ICV */
 184        skb_put(skb, WEP_ICV_LEN);
 185
 186        return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
 187                                          iv + WEP_IV_LEN, len);
 188}
 189
 190
 191/* Perform WEP decryption using given key. data buffer includes encrypted
 192 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 193 * Return 0 on success and -1 on ICV mismatch. */
 194int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 195                               size_t klen, u8 *data, size_t data_len)
 196{
 197        __le32 crc;
 198        int i;
 199
 200        if (IS_ERR(tfm))
 201                return -1;
 202
 203        crypto_cipher_setkey(tfm, rc4key, klen);
 204        for (i = 0; i < data_len + WEP_ICV_LEN; i++)
 205                crypto_cipher_decrypt_one(tfm, data + i, data + i);
 206
 207        crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 208        if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
 209                /* ICV mismatch */
 210                return -1;
 211
 212        return 0;
 213}
 214
 215
 216/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 217 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 218 * ICV (4 bytes). skb->len includes both IV and ICV.
 219 *
 220 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 221 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 222 * is moved to the beginning of the skb and skb length will be reduced.
 223 */
 224static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 225                                 struct sk_buff *skb,
 226                                 struct ieee80211_key *key)
 227{
 228        u32 klen;
 229        u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 230        u8 keyidx;
 231        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 232        unsigned int hdrlen;
 233        size_t len;
 234        int ret = 0;
 235
 236        if (!ieee80211_has_protected(hdr->frame_control))
 237                return -1;
 238
 239        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 240        if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN)
 241                return -1;
 242
 243        len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN;
 244
 245        keyidx = skb->data[hdrlen + 3] >> 6;
 246
 247        if (!key || keyidx != key->conf.keyidx)
 248                return -1;
 249
 250        klen = 3 + key->conf.keylen;
 251
 252        /* Prepend 24-bit IV to RC4 key */
 253        memcpy(rc4key, skb->data + hdrlen, 3);
 254
 255        /* Copy rest of the WEP key (the secret part) */
 256        memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 257
 258        if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
 259                                       skb->data + hdrlen + WEP_IV_LEN,
 260                                       len))
 261                ret = -1;
 262
 263        /* Trim ICV */
 264        skb_trim(skb, skb->len - WEP_ICV_LEN);
 265
 266        /* Remove IV */
 267        memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
 268        skb_pull(skb, WEP_IV_LEN);
 269
 270        return ret;
 271}
 272
 273
 274static bool ieee80211_wep_is_weak_iv(struct sk_buff *skb,
 275                                     struct ieee80211_key *key)
 276{
 277        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 278        unsigned int hdrlen;
 279        u8 *ivpos;
 280        u32 iv;
 281
 282        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 283        ivpos = skb->data + hdrlen;
 284        iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
 285
 286        return ieee80211_wep_weak_iv(iv, key->conf.keylen);
 287}
 288
 289ieee80211_rx_result
 290ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 291{
 292        struct sk_buff *skb = rx->skb;
 293        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 294        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 295        __le16 fc = hdr->frame_control;
 296
 297        if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 298                return RX_CONTINUE;
 299
 300        if (!(status->flag & RX_FLAG_DECRYPTED)) {
 301                if (skb_linearize(rx->skb))
 302                        return RX_DROP_UNUSABLE;
 303                if (rx->sta && ieee80211_wep_is_weak_iv(rx->skb, rx->key))
 304                        rx->sta->wep_weak_iv_count++;
 305                if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 306                        return RX_DROP_UNUSABLE;
 307        } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 308                if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + WEP_IV_LEN))
 309                        return RX_DROP_UNUSABLE;
 310                if (rx->sta && ieee80211_wep_is_weak_iv(rx->skb, rx->key))
 311                        rx->sta->wep_weak_iv_count++;
 312                ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 313                /* remove ICV */
 314                if (pskb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN))
 315                        return RX_DROP_UNUSABLE;
 316        }
 317
 318        return RX_CONTINUE;
 319}
 320
 321static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 322{
 323        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 324        struct ieee80211_key_conf *hw_key = info->control.hw_key;
 325
 326        if (!hw_key) {
 327                if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
 328                                          tx->key->conf.keylen,
 329                                          tx->key->conf.keyidx))
 330                        return -1;
 331        } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
 332                   (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
 333                if (!ieee80211_wep_add_iv(tx->local, skb,
 334                                          tx->key->conf.keylen,
 335                                          tx->key->conf.keyidx))
 336                        return -1;
 337        }
 338
 339        return 0;
 340}
 341
 342ieee80211_tx_result
 343ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
 344{
 345        struct sk_buff *skb;
 346
 347        ieee80211_tx_set_protected(tx);
 348
 349        skb_queue_walk(&tx->skbs, skb) {
 350                if (wep_encrypt_skb(tx, skb) < 0) {
 351                        I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 352                        return TX_DROP;
 353                }
 354        }
 355
 356        return TX_CONTINUE;
 357}
 358
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