net/mac80211/wep.c

   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
  28 int 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
  49 void 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
  57 static 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
  73 static 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
  90 static 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
 120 static 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)) */
 136 int 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  */
 163 int 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. */
 194 int 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  */
 224 static 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
 274 static 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
 289 ieee80211_rx_result
 290 ieee80211_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
 321 static 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
 342 ieee80211_tx_result
 343 ieee80211_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 }