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, IEEE80211_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) < IEEE80211_WEP_ICV_LEN ||
 102                     skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
 103                 return NULL;
 104
 105         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 106         newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
 107         memmove(newhdr, newhdr + IEEE80211_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         ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
 115         return newhdr + hdrlen;
 116 }
 117
 118
 119 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
 120                                     struct sk_buff *skb,
 121                                     struct ieee80211_key *key)
 122 {
 123         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 124         unsigned int hdrlen;
 125
 126         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 127         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 128         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 129 }
 130
 131
 132 /* Perform WEP encryption using given key. data buffer must have tailroom
 133  * for 4-byte ICV. data_len must not include this ICV. Note: this function
 134  * does _not_ add IV. data = RC4(data | CRC32(data)) */
 135 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 136                                size_t klen, u8 *data, size_t data_len)
 137 {
 138         __le32 icv;
 139         int i;
 140
 141         if (IS_ERR(tfm))
 142                 return -1;
 143
 144         icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 145         put_unaligned(icv, (__le32 *)(data + data_len));
 146
 147         crypto_cipher_setkey(tfm, rc4key, klen);
 148         for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
 149                 crypto_cipher_encrypt_one(tfm, data + i, data + i);
 150
 151         return 0;
 152 }
 153
 154
 155 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 156  * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 157  * buffer will be added. Both IV and ICV will be transmitted, so the
 158  * payload length increases with 8 bytes.
 159  *
 160  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 161  */
 162 int ieee80211_wep_encrypt(struct ieee80211_local *local,
 163                           struct sk_buff *skb,
 164                           const u8 *key, int keylen, int keyidx)
 165 {
 166         u8 *iv;
 167         size_t len;
 168         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 169
 170         iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 171         if (!iv)
 172                 return -1;
 173
 174         len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
 175
 176         /* Prepend 24-bit IV to RC4 key */
 177         memcpy(rc4key, iv, 3);
 178
 179         /* Copy rest of the WEP key (the secret part) */
 180         memcpy(rc4key + 3, key, keylen);
 181
 182         /* Add room for ICV */
 183         skb_put(skb, IEEE80211_WEP_ICV_LEN);
 184
 185         return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
 186                                           iv + IEEE80211_WEP_IV_LEN, len);
 187 }
 188
 189
 190 /* Perform WEP decryption using given key. data buffer includes encrypted
 191  * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 192  * Return 0 on success and -1 on ICV mismatch. */
 193 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 194                                size_t klen, u8 *data, size_t data_len)
 195 {
 196         __le32 crc;
 197         int i;
 198
 199         if (IS_ERR(tfm))
 200                 return -1;
 201
 202         crypto_cipher_setkey(tfm, rc4key, klen);
 203         for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
 204                 crypto_cipher_decrypt_one(tfm, data + i, data + i);
 205
 206         crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 207         if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
 208                 /* ICV mismatch */
 209                 return -1;
 210
 211         return 0;
 212 }
 213
 214
 215 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 216  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 217  * ICV (4 bytes). skb->len includes both IV and ICV.
 218  *
 219  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 220  * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 221  * is moved to the beginning of the skb and skb length will be reduced.
 222  */
 223 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 224                                  struct sk_buff *skb,
 225                                  struct ieee80211_key *key)
 226 {
 227         u32 klen;
 228         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 229         u8 keyidx;
 230         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 231         unsigned int hdrlen;
 232         size_t len;
 233         int ret = 0;
 234
 235         if (!ieee80211_has_protected(hdr->frame_control))
 236                 return -1;
 237
 238         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 239         if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
 240                 return -1;
 241
 242         len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
 243
 244         keyidx = skb->data[hdrlen + 3] >> 6;
 245
 246         if (!key || keyidx != key->conf.keyidx)
 247                 return -1;
 248
 249         klen = 3 + key->conf.keylen;
 250
 251         /* Prepend 24-bit IV to RC4 key */
 252         memcpy(rc4key, skb->data + hdrlen, 3);
 253
 254         /* Copy rest of the WEP key (the secret part) */
 255         memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 256
 257         if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
 258                                        skb->data + hdrlen +
 259                                        IEEE80211_WEP_IV_LEN, len))
 260                 ret = -1;
 261
 262         /* Trim ICV */
 263         skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
 264
 265         /* Remove IV */
 266         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 267         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 268
 269         return ret;
 270 }
 271
 272 ieee80211_rx_result
 273 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 274 {
 275         struct sk_buff *skb = rx->skb;
 276         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 277         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 278         __le16 fc = hdr->frame_control;
 279
 280         if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 281                 return RX_CONTINUE;
 282
 283         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 284                 if (skb_linearize(rx->skb))
 285                         return RX_DROP_UNUSABLE;
 286                 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 287                         return RX_DROP_UNUSABLE;
 288         } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 289                 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
 290                                             IEEE80211_WEP_IV_LEN))
 291                         return RX_DROP_UNUSABLE;
 292                 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 293                 /* remove ICV */
 294                 if (pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
 295                         return RX_DROP_UNUSABLE;
 296         }
 297
 298         return RX_CONTINUE;
 299 }
 300
 301 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 302 {
 303         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 304         struct ieee80211_key_conf *hw_key = info->control.hw_key;
 305
 306         if (!hw_key) {
 307                 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
 308                                           tx->key->conf.keylen,
 309                                           tx->key->conf.keyidx))
 310                         return -1;
 311         } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
 312                    (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
 313                 if (!ieee80211_wep_add_iv(tx->local, skb,
 314                                           tx->key->conf.keylen,
 315                                           tx->key->conf.keyidx))
 316                         return -1;
 317         }
 318
 319         return 0;
 320 }
 321
 322 ieee80211_tx_result
 323 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
 324 {
 325         struct sk_buff *skb;
 326
 327         ieee80211_tx_set_protected(tx);
 328
 329         skb_queue_walk(&tx->skbs, skb) {
 330                 if (wep_encrypt_skb(tx, skb) < 0) {
 331                         I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 332                         return TX_DROP;
 333                 }
 334         }
 335
 336         return TX_CONTINUE;
 337 }