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 void 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
  31 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
  32 {
  33         /*
  34          * Fluhrer, Mantin, and Shamir have reported weaknesses in the
  35          * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  36          * 0xff, N) can be used to speedup attacks, so avoid using them.
  37          */
  38         if ((iv & 0xff00) == 0xff00) {
  39                 u8 B = (iv >> 16) & 0xff;
  40                 if (B >= 3 && B < 3 + keylen)
  41                         return true;
  42         }
  43         return false;
  44 }
  45
  46
  47 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
  48                                  int keylen, int keyidx, u8 *iv)
  49 {
  50         local->wep_iv++;
  51         if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
  52                 local->wep_iv += 0x0100;
  53
  54         if (!iv)
  55                 return;
  56
  57         *iv++ = (local->wep_iv >> 16) & 0xff;
  58         *iv++ = (local->wep_iv >> 8) & 0xff;
  59         *iv++ = local->wep_iv & 0xff;
  60         *iv++ = keyidx << 6;
  61 }
  62
  63
  64 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
  65                                 struct sk_buff *skb,
  66                                 int keylen, int keyidx)
  67 {
  68         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  69         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  70         unsigned int hdrlen;
  71         u8 *newhdr;
  72
  73         hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
  74
  75         if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
  76                 return NULL;
  77
  78         hdrlen = ieee80211_hdrlen(hdr->frame_control);
  79         newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
  80         memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
  81
  82         /* the HW only needs room for the IV, but not the actual IV */
  83         if (info->control.hw_key &&
  84             (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
  85                 return newhdr + hdrlen;
  86
  87         ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
  88         return newhdr + hdrlen;
  89 }
  90
  91
  92 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
  93                                     struct sk_buff *skb,
  94                                     struct ieee80211_key *key)
  95 {
  96         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  97         unsigned int hdrlen;
  98
  99         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 100         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 101         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 102 }
 103
 104
 105 /* Perform WEP encryption using given key. data buffer must have tailroom
 106  * for 4-byte ICV. data_len must not include this ICV. Note: this function
 107  * does _not_ add IV. data = RC4(data | CRC32(data)) */
 108 int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
 109                                size_t klen, u8 *data, size_t data_len)
 110 {
 111         __le32 icv;
 112
 113         icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 114         put_unaligned(icv, (__le32 *)(data + data_len));
 115
 116         arc4_setkey(ctx, rc4key, klen);
 117         arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
 118         memzero_explicit(ctx, sizeof(*ctx));
 119
 120         return 0;
 121 }
 122
 123
 124 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 125  * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 126  * buffer will be added. Both IV and ICV will be transmitted, so the
 127  * payload length increases with 8 bytes.
 128  *
 129  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 130  */
 131 int ieee80211_wep_encrypt(struct ieee80211_local *local,
 132                           struct sk_buff *skb,
 133                           const u8 *key, int keylen, int keyidx)
 134 {
 135         u8 *iv;
 136         size_t len;
 137         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 138
 139         if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
 140                 return -1;
 141
 142         iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 143         if (!iv)
 144                 return -1;
 145
 146         len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
 147
 148         /* Prepend 24-bit IV to RC4 key */
 149         memcpy(rc4key, iv, 3);
 150
 151         /* Copy rest of the WEP key (the secret part) */
 152         memcpy(rc4key + 3, key, keylen);
 153
 154         /* Add room for ICV */
 155         skb_put(skb, IEEE80211_WEP_ICV_LEN);
 156
 157         return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3,
 158                                           iv + IEEE80211_WEP_IV_LEN, len);
 159 }
 160
 161
 162 /* Perform WEP decryption using given key. data buffer includes encrypted
 163  * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 164  * Return 0 on success and -1 on ICV mismatch. */
 165 int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
 166                                size_t klen, u8 *data, size_t data_len)
 167 {
 168         __le32 crc;
 169
 170         arc4_setkey(ctx, rc4key, klen);
 171         arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
 172         memzero_explicit(ctx, sizeof(*ctx));
 173
 174         crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 175         if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
 176                 /* ICV mismatch */
 177                 return -1;
 178
 179         return 0;
 180 }
 181
 182
 183 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 184  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 185  * ICV (4 bytes). skb->len includes both IV and ICV.
 186  *
 187  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 188  * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 189  * is moved to the beginning of the skb and skb length will be reduced.
 190  */
 191 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 192                                  struct sk_buff *skb,
 193                                  struct ieee80211_key *key)
 194 {
 195         u32 klen;
 196         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 197         u8 keyidx;
 198         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 199         unsigned int hdrlen;
 200         size_t len;
 201         int ret = 0;
 202
 203         if (!ieee80211_has_protected(hdr->frame_control))
 204                 return -1;
 205
 206         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 207         if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
 208                 return -1;
 209
 210         len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
 211
 212         keyidx = skb->data[hdrlen + 3] >> 6;
 213
 214         if (!key || keyidx != key->conf.keyidx)
 215                 return -1;
 216
 217         klen = 3 + key->conf.keylen;
 218
 219         /* Prepend 24-bit IV to RC4 key */
 220         memcpy(rc4key, skb->data + hdrlen, 3);
 221
 222         /* Copy rest of the WEP key (the secret part) */
 223         memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 224
 225         if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen,
 226                                        skb->data + hdrlen +
 227                                        IEEE80211_WEP_IV_LEN, len))
 228                 ret = -1;
 229
 230         /* Trim ICV */
 231         skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
 232
 233         /* Remove IV */
 234         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 235         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 236
 237         return ret;
 238 }
 239
 240 ieee80211_rx_result
 241 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 242 {
 243         struct sk_buff *skb = rx->skb;
 244         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 245         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 246         __le16 fc = hdr->frame_control;
 247
 248         if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 249                 return RX_CONTINUE;
 250
 251         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 252                 if (skb_linearize(rx->skb))
 253                         return RX_DROP_UNUSABLE;
 254                 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 255                         return RX_DROP_UNUSABLE;
 256         } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 257                 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
 258                                             IEEE80211_WEP_IV_LEN))
 259                         return RX_DROP_UNUSABLE;
 260                 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 261                 /* remove ICV */
 262                 if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
 263                     pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
 264                         return RX_DROP_UNUSABLE;
 265         }
 266
 267         return RX_CONTINUE;
 268 }
 269
 270 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 271 {
 272         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 273         struct ieee80211_key_conf *hw_key = info->control.hw_key;
 274
 275         if (!hw_key) {
 276                 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
 277                                           tx->key->conf.keylen,
 278                                           tx->key->conf.keyidx))
 279                         return -1;
 280         } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
 281                    (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
 282                 if (!ieee80211_wep_add_iv(tx->local, skb,
 283                                           tx->key->conf.keylen,
 284                                           tx->key->conf.keyidx))
 285                         return -1;
 286         }
 287
 288         return 0;
 289 }
 290
 291 ieee80211_tx_result
 292 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
 293 {
 294         struct sk_buff *skb;
 295
 296         ieee80211_tx_set_protected(tx);
 297
 298         skb_queue_walk(&tx->skbs, skb) {
 299                 if (wep_encrypt_skb(tx, skb) < 0) {
 300                         I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 301                         return TX_DROP;
 302                 }
 303         }
 304
 305         return TX_CONTINUE;
 306 }