root/net/mac80211/wep.c

DEFINITIONS

1. ieee80211_wep_init
2. ieee80211_wep_weak_iv
3. ieee80211_wep_get_iv
4. ieee80211_wep_add_iv
5. ieee80211_wep_remove_iv
6. ieee80211_wep_encrypt_data
7. ieee80211_wep_encrypt
8. ieee80211_wep_decrypt_data
9. ieee80211_wep_decrypt
10. ieee80211_crypto_wep_decrypt
11. wep_encrypt_skb
12. ieee80211_crypto_wep_encrypt

   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         return 0;
  31 }
  32 
  33 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
  34 {
  35         /*
  36          * Fluhrer, Mantin, and Shamir have reported weaknesses in the
  37          * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  38          * 0xff, N) can be used to speedup attacks, so avoid using them.
  39          */
  40         if ((iv & 0xff00) == 0xff00) {
  41                 u8 B = (iv >> 16) & 0xff;
  42                 if (B >= 3 && B < 3 + keylen)
  43                         return true;
  44         }
  45         return false;
  46 }
  47 
  48 
  49 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
  50                                  int keylen, int keyidx, u8 *iv)
  51 {
  52         local->wep_iv++;
  53         if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
  54                 local->wep_iv += 0x0100;
  55 
  56         if (!iv)
  57                 return;
  58 
  59         *iv++ = (local->wep_iv >> 16) & 0xff;
  60         *iv++ = (local->wep_iv >> 8) & 0xff;
  61         *iv++ = local->wep_iv & 0xff;
  62         *iv++ = keyidx << 6;
  63 }
  64 
  65 
  66 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
  67                                 struct sk_buff *skb,
  68                                 int keylen, int keyidx)
  69 {
  70         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  71         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  72         unsigned int hdrlen;
  73         u8 *newhdr;
  74 
  75         hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
  76 
  77         if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
  78                 return NULL;
  79 
  80         hdrlen = ieee80211_hdrlen(hdr->frame_control);
  81         newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
  82         memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
  83 
  84         /* the HW only needs room for the IV, but not the actual IV */
  85         if (info->control.hw_key &&
  86             (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
  87                 return newhdr + hdrlen;
  88 
  89         ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
  90         return newhdr + hdrlen;
  91 }
  92 
  93 
  94 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
  95                                     struct sk_buff *skb,
  96                                     struct ieee80211_key *key)
  97 {
  98         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  99         unsigned int hdrlen;
 100 
 101         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 102         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 103         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 104 }
 105 
 106 
 107 /* Perform WEP encryption using given key. data buffer must have tailroom
 108  * for 4-byte ICV. data_len must not include this ICV. Note: this function
 109  * does _not_ add IV. data = RC4(data | CRC32(data)) */
 110 int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
 111                                size_t klen, u8 *data, size_t data_len)
 112 {
 113         __le32 icv;
 114 
 115         icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 116         put_unaligned(icv, (__le32 *)(data + data_len));
 117 
 118         arc4_setkey(ctx, rc4key, klen);
 119         arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
 120         memzero_explicit(ctx, sizeof(*ctx));
 121 
 122         return 0;
 123 }
 124 
 125 
 126 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 127  * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 128  * buffer will be added. Both IV and ICV will be transmitted, so the
 129  * payload length increases with 8 bytes.
 130  *
 131  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 132  */
 133 int ieee80211_wep_encrypt(struct ieee80211_local *local,
 134                           struct sk_buff *skb,
 135                           const u8 *key, int keylen, int keyidx)
 136 {
 137         u8 *iv;
 138         size_t len;
 139         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 140 
 141         if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
 142                 return -1;
 143 
 144         iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 145         if (!iv)
 146                 return -1;
 147 
 148         len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
 149 
 150         /* Prepend 24-bit IV to RC4 key */
 151         memcpy(rc4key, iv, 3);
 152 
 153         /* Copy rest of the WEP key (the secret part) */
 154         memcpy(rc4key + 3, key, keylen);
 155 
 156         /* Add room for ICV */
 157         skb_put(skb, IEEE80211_WEP_ICV_LEN);
 158 
 159         return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3,
 160                                           iv + IEEE80211_WEP_IV_LEN, len);
 161 }
 162 
 163 
 164 /* Perform WEP decryption using given key. data buffer includes encrypted
 165  * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 166  * Return 0 on success and -1 on ICV mismatch. */
 167 int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
 168                                size_t klen, u8 *data, size_t data_len)
 169 {
 170         __le32 crc;
 171 
 172         arc4_setkey(ctx, rc4key, klen);
 173         arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
 174         memzero_explicit(ctx, sizeof(*ctx));
 175 
 176         crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 177         if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
 178                 /* ICV mismatch */
 179                 return -1;
 180 
 181         return 0;
 182 }
 183 
 184 
 185 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 186  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 187  * ICV (4 bytes). skb->len includes both IV and ICV.
 188  *
 189  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 190  * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 191  * is moved to the beginning of the skb and skb length will be reduced.
 192  */
 193 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 194                                  struct sk_buff *skb,
 195                                  struct ieee80211_key *key)
 196 {
 197         u32 klen;
 198         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 199         u8 keyidx;
 200         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 201         unsigned int hdrlen;
 202         size_t len;
 203         int ret = 0;
 204 
 205         if (!ieee80211_has_protected(hdr->frame_control))
 206                 return -1;
 207 
 208         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 209         if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
 210                 return -1;
 211 
 212         len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
 213 
 214         keyidx = skb->data[hdrlen + 3] >> 6;
 215 
 216         if (!key || keyidx != key->conf.keyidx)
 217                 return -1;
 218 
 219         klen = 3 + key->conf.keylen;
 220 
 221         /* Prepend 24-bit IV to RC4 key */
 222         memcpy(rc4key, skb->data + hdrlen, 3);
 223 
 224         /* Copy rest of the WEP key (the secret part) */
 225         memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 226 
 227         if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen,
 228                                        skb->data + hdrlen +
 229                                        IEEE80211_WEP_IV_LEN, len))
 230                 ret = -1;
 231 
 232         /* Trim ICV */
 233         skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
 234 
 235         /* Remove IV */
 236         memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 237         skb_pull(skb, IEEE80211_WEP_IV_LEN);
 238 
 239         return ret;
 240 }
 241 
 242 ieee80211_rx_result
 243 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 244 {
 245         struct sk_buff *skb = rx->skb;
 246         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 247         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 248         __le16 fc = hdr->frame_control;
 249 
 250         if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 251                 return RX_CONTINUE;
 252 
 253         if (!(status->flag & RX_FLAG_DECRYPTED)) {
 254                 if (skb_linearize(rx->skb))
 255                         return RX_DROP_UNUSABLE;
 256                 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 257                         return RX_DROP_UNUSABLE;
 258         } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 259                 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
 260                                             IEEE80211_WEP_IV_LEN))
 261                         return RX_DROP_UNUSABLE;
 262                 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 263                 /* remove ICV */
 264                 if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
 265                     pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
 266                         return RX_DROP_UNUSABLE;
 267         }
 268 
 269         return RX_CONTINUE;
 270 }
 271 
 272 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 273 {
 274         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 275         struct ieee80211_key_conf *hw_key = info->control.hw_key;
 276 
 277         if (!hw_key) {
 278                 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
 279                                           tx->key->conf.keylen,
 280                                           tx->key->conf.keyidx))
 281                         return -1;
 282         } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
 283                    (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
 284                 if (!ieee80211_wep_add_iv(tx->local, skb,
 285                                           tx->key->conf.keylen,
 286                                           tx->key->conf.keyidx))
 287                         return -1;
 288         }
 289 
 290         return 0;
 291 }
 292 
 293 ieee80211_tx_result
 294 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
 295 {
 296         struct sk_buff *skb;
 297 
 298         ieee80211_tx_set_protected(tx);
 299 
 300         skb_queue_walk(&tx->skbs, skb) {
 301                 if (wep_encrypt_skb(tx, skb) < 0) {
 302                         I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 303                         return TX_DROP;
 304                 }
 305         }
 306 
 307         return TX_CONTINUE;
 308 }