net/mac80211/wep.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Software WEP encryption implementation
   4  * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
   5  * Copyright 2003, Instant802 Networks, Inc.
   6  */
   7
   8 #include <linux/netdevice.h>
   9 #include <linux/types.h>
  10 #include <linux/random.h>
  11 #include <linux/compiler.h>
  12 #include <linux/crc32.h>
  13 #include <linux/crypto.h>
  14 #include <linux/err.h>
  15 #include <linux/mm.h>
  16 #include <linux/scatterlist.h>
  17 #include <linux/slab.h>
  18 #include <asm/unaligned.h>
  19
  20 #include <net/mac80211.h>
  21 #include "ieee80211_i.h"
  22 #include "wep.h"
  23
  24
  25 int ieee80211_wep_init(struct ieee80211_local *local)
  26 {
  27         /* start WEP IV from a random value */
  28         get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN);
  29
  30         local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, 0);
  31         if (IS_ERR(local->wep_tx_tfm)) {
  32                 local->wep_rx_tfm = ERR_PTR(-EINVAL);
  33                 return PTR_ERR(local->wep_tx_tfm);
  34         }
  35
  36         local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, 0);
  37         if (IS_ERR(local->wep_rx_tfm)) {
  38                 crypto_free_cipher(local->wep_tx_tfm);
  39                 local->wep_tx_tfm = ERR_PTR(-EINVAL);
  40                 return PTR_ERR(local->wep_rx_tfm);
  41         }
  42
  43         return 0;
  44 }
  45
  46 void ieee80211_wep_free(struct ieee80211_local *local)
  47 {
  48         if (!IS_ERR(local->wep_tx_tfm))
  49                 crypto_free_cipher(local->wep_tx_tfm);
  50         if (!IS_ERR(local->wep_rx_tfm))
  51                 crypto_free_cipher(local->wep_rx_tfm);
  52 }
  53
  54 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
  55 {
  56         /*
  57          * Fluhrer, Mantin, and Shamir have reported weaknesses in the
  58          * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  59          * 0xff, N) can be used to speedup attacks, so avoid using them.
  60          */
  61         if ((iv & 0xff00) == 0xff00) {
  62                 u8 B = (iv >> 16) & 0xff;
  63                 if (B >= 3 && B < 3 + keylen)
  64                         return true;
  65         }
  66         return false;
  67 }
  68
  69
  70 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
  71                                  int keylen, int keyidx, u8 *iv)
  72 {
  73         local->wep_iv++;
  74         if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
  75                 local->wep_iv += 0x0100;
  76
  77         if (!iv)
  78                 return;
  79
  80         *iv++ = (local->wep_iv >> 16) & 0xff;
  81         *iv++ = (local->wep_iv >> 8) & 0xff;
  82         *iv++ = local->wep_iv & 0xff;
  83         *iv++ = keyidx << 6;
  84 }
  85
  86
  87 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
  88                                 struct sk_buff *skb,
  89                                 int keylen, int keyidx)
  90 {
  91         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  92         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  93         unsigned int hdrlen;
  94         u8 *newhdr;
  95
  96         hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
  97
  98         if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
  99                 return NULL;
 100
 101         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 102         newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
 103         memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
 104
 105         /* the HW only needs room for the IV, but not the actual IV */
 106         if (info->control.hw_key &&
 107             (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
 108                 return newhdr + hdrlen;
 109
 110         ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
 111         return newhdr + hdrlen;
 112 }
 113
 114
 115 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
 116                                     struct sk_buff *skb,
 117                                     struct ieee80211_key *key)
 118 {
 119         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 120         unsigned int hdrlen;
 121
 122         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 123         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 124         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 125 }
 126
 127
 128 /* Perform WEP encryption using given key. data buffer must have tailroom
 129  * for 4-byte ICV. data_len must not include this ICV. Note: this function
 130  * does _not_ add IV. data = RC4(data | CRC32(data)) */
 131 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 132                                size_t klen, u8 *data, size_t data_len)
 133 {
 134         __le32 icv;
 135         int i;
 136
 137         if (IS_ERR(tfm))
 138                 return -1;
 139
 140         icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 141         put_unaligned(icv, (__le32 *)(data + data_len));
 142
 143         crypto_cipher_setkey(tfm, rc4key, klen);
 144         for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
 145                 crypto_cipher_encrypt_one(tfm, data + i, data + i);
 146
 147         return 0;
 148 }
 149
 150
 151 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 152  * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 153  * buffer will be added. Both IV and ICV will be transmitted, so the
 154  * payload length increases with 8 bytes.
 155  *
 156  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 157  */
 158 int ieee80211_wep_encrypt(struct ieee80211_local *local,
 159                           struct sk_buff *skb,
 160                           const u8 *key, int keylen, int keyidx)
 161 {
 162         u8 *iv;
 163         size_t len;
 164         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 165
 166         if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
 167                 return -1;
 168
 169         iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 170         if (!iv)
 171                 return -1;
 172
 173         len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
 174
 175         /* Prepend 24-bit IV to RC4 key */
 176         memcpy(rc4key, iv, 3);
 177
 178         /* Copy rest of the WEP key (the secret part) */
 179         memcpy(rc4key + 3, key, keylen);
 180
 181         /* Add room for ICV */
 182         skb_put(skb, IEEE80211_WEP_ICV_LEN);
 183
 184         return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
 185                                           iv + IEEE80211_WEP_IV_LEN, len);
 186 }
 187
 188
 189 /* Perform WEP decryption using given key. data buffer includes encrypted
 190  * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 191  * Return 0 on success and -1 on ICV mismatch. */
 192 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 193                                size_t klen, u8 *data, size_t data_len)
 194 {
 195         __le32 crc;
 196         int i;
 197
 198         if (IS_ERR(tfm))
 199                 return -1;
 200
 201         crypto_cipher_setkey(tfm, rc4key, klen);
 202         for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
 203                 crypto_cipher_decrypt_one(tfm, data + i, data + i);
 204
 205         crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 206         if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
 207                 /* ICV mismatch */
 208                 return -1;
 209
 210         return 0;
 211 }
 212
 213
 214 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 215  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 216  * ICV (4 bytes). skb->len includes both IV and ICV.
 217  *
 218  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 219  * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 220  * is moved to the beginning of the skb and skb length will be reduced.
 221  */
 222 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 223                                  struct sk_buff *skb,
 224                                  struct ieee80211_key *key)
 225 {
 226         u32 klen;
 227         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 228         u8 keyidx;
 229         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 230         unsigned int hdrlen;
 231         size_t len;
 232         int ret = 0;
 233
 234         if (!ieee80211_has_protected(hdr->frame_control))
 235                 return -1;
 236
 237         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 238         if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
 239                 return -1;
 240
 241         len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
 242
 243         keyidx = skb->data[hdrlen + 3] >> 6;
 244
 245         if (!key || keyidx != key->conf.keyidx)
 246                 return -1;
 247
 248         klen = 3 + key->conf.keylen;
 249
 250         /* Prepend 24-bit IV to RC4 key */
 251         memcpy(rc4key, skb->data + hdrlen, 3);
 252
 253         /* Copy rest of the WEP key (the secret part) */
 254         memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 255
 256         if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
 257                                        skb->data + hdrlen +
 258                                        IEEE80211_WEP_IV_LEN, len))
 259                 ret = -1;
 260
 261         /* Trim ICV */
 262         skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
 263
 264         /* Remove IV */
 265         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 266         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 267
 268         return ret;
 269 }
 270
 271 ieee80211_rx_result
 272 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 273 {
 274         struct sk_buff *skb = rx->skb;
 275         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 276         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 277         __le16 fc = hdr->frame_control;
 278
 279         if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 280                 return RX_CONTINUE;
 281
 282         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 283                 if (skb_linearize(rx->skb))
 284                         return RX_DROP_UNUSABLE;
 285                 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 286                         return RX_DROP_UNUSABLE;
 287         } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 288                 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
 289                                             IEEE80211_WEP_IV_LEN))
 290                         return RX_DROP_UNUSABLE;
 291                 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 292                 /* remove ICV */
 293                 if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
 294                     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 }