LXR linux/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
  28int 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
  49void 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
  57static 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
  73static 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
  90static 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_headroom(skb) < IEEE80211_WEP_IV_LEN))
 102                return NULL;
 103
 104        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 105        newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
 106        memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
 107
 108        /* the HW only needs room for the IV, but not the actual IV */
 109        if (info->control.hw_key &&
 110            (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
 111                return newhdr + hdrlen;
 112
 113        ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
 114        return newhdr + hdrlen;
 115}
 116
 117
 118static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
 119                                    struct sk_buff *skb,
 120                                    struct ieee80211_key *key)
 121{
 122        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 123        unsigned int hdrlen;
 124
 125        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 126        memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 127        skb_pull(skb, IEEE80211_WEP_IV_LEN);
 128}
 129
 130
 131/* Perform WEP encryption using given key. data buffer must have tailroom
 132 * for 4-byte ICV. data_len must not include this ICV. Note: this function
 133 * does _not_ add IV. data = RC4(data | CRC32(data)) */
 134int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 135                               size_t klen, u8 *data, size_t data_len)
 136{
 137        __le32 icv;
 138        int i;
 139
 140        if (IS_ERR(tfm))
 141                return -1;
 142
 143        icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 144        put_unaligned(icv, (__le32 *)(data + data_len));
 145
 146        crypto_cipher_setkey(tfm, rc4key, klen);
 147        for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
 148                crypto_cipher_encrypt_one(tfm, data + i, data + i);
 149
 150        return 0;
 151}
 152
 153
 154/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 155 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 156 * buffer will be added. Both IV and ICV will be transmitted, so the
 157 * payload length increases with 8 bytes.
 158 *
 159 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 160 */
 161int ieee80211_wep_encrypt(struct ieee80211_local *local,
 162                          struct sk_buff *skb,
 163                          const u8 *key, int keylen, int keyidx)
 164{
 165        u8 *iv;
 166        size_t len;
 167        u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 168
 169        if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
 170                return -1;
 171
 172        iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 173        if (!iv)
 174                return -1;
 175
 176        len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
 177
 178        /* Prepend 24-bit IV to RC4 key */
 179        memcpy(rc4key, iv, 3);
 180
 181        /* Copy rest of the WEP key (the secret part) */
 182        memcpy(rc4key + 3, key, keylen);
 183
 184        /* Add room for ICV */
 185        skb_put(skb, IEEE80211_WEP_ICV_LEN);
 186
 187        return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
 188                                          iv + IEEE80211_WEP_IV_LEN, len);
 189}
 190
 191
 192/* Perform WEP decryption using given key. data buffer includes encrypted
 193 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 194 * Return 0 on success and -1 on ICV mismatch. */
 195int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
 196                               size_t klen, u8 *data, size_t data_len)
 197{
 198        __le32 crc;
 199        int i;
 200
 201        if (IS_ERR(tfm))
 202                return -1;
 203
 204        crypto_cipher_setkey(tfm, rc4key, klen);
 205        for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
 206                crypto_cipher_decrypt_one(tfm, data + i, data + i);
 207
 208        crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 209        if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
 210                /* ICV mismatch */
 211                return -1;
 212
 213        return 0;
 214}
 215
 216
 217/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 218 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 219 * ICV (4 bytes). skb->len includes both IV and ICV.
 220 *
 221 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 222 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 223 * is moved to the beginning of the skb and skb length will be reduced.
 224 */
 225static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 226                                 struct sk_buff *skb,
 227                                 struct ieee80211_key *key)
 228{
 229        u32 klen;
 230        u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 231        u8 keyidx;
 232        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 233        unsigned int hdrlen;
 234        size_t len;
 235        int ret = 0;
 236
 237        if (!ieee80211_has_protected(hdr->frame_control))
 238                return -1;
 239
 240        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 241        if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
 242                return -1;
 243
 244        len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
 245
 246        keyidx = skb->data[hdrlen + 3] >> 6;
 247
 248        if (!key || keyidx != key->conf.keyidx)
 249                return -1;
 250
 251        klen = 3 + key->conf.keylen;
 252
 253        /* Prepend 24-bit IV to RC4 key */
 254        memcpy(rc4key, skb->data + hdrlen, 3);
 255
 256        /* Copy rest of the WEP key (the secret part) */
 257        memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 258
 259        if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
 260                                       skb->data + hdrlen +
 261                                       IEEE80211_WEP_IV_LEN, len))
 262                ret = -1;
 263
 264        /* Trim ICV */
 265        skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
 266
 267        /* Remove IV */
 268        memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 269        skb_pull(skb, IEEE80211_WEP_IV_LEN);
 270
 271        return ret;
 272}
 273
 274ieee80211_rx_result
 275ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 276{
 277        struct sk_buff *skb = rx->skb;
 278        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 279        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 280        __le16 fc = hdr->frame_control;
 281
 282        if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 283                return RX_CONTINUE;
 284
 285        if (!(status->flag & RX_FLAG_DECRYPTED)) {
 286                if (skb_linearize(rx->skb))
 287                        return RX_DROP_UNUSABLE;
 288                if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 289                        return RX_DROP_UNUSABLE;
 290        } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 291                if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
 292                                            IEEE80211_WEP_IV_LEN))
 293                        return RX_DROP_UNUSABLE;
 294                ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 295                /* remove ICV */
 296                if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
 297                    pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
 298                        return RX_DROP_UNUSABLE;
 299        }
 300
 301        return RX_CONTINUE;
 302}
 303
 304static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 305{
 306        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 307        struct ieee80211_key_conf *hw_key = info->control.hw_key;
 308
 309        if (!hw_key) {
 310                if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
 311                                          tx->key->conf.keylen,
 312                                          tx->key->conf.keyidx))
 313                        return -1;
 314        } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
 315                   (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
 316                if (!ieee80211_wep_add_iv(tx->local, skb,
 317                                          tx->key->conf.keylen,
 318                                          tx->key->conf.keyidx))
 319                        return -1;
 320        }
 321
 322        return 0;
 323}
 324
 325ieee80211_tx_result
 326ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
 327{
 328        struct sk_buff *skb;
 329
 330        ieee80211_tx_set_protected(tx);
 331
 332        skb_queue_walk(&tx->skbs, skb) {
 333                if (wep_encrypt_skb(tx, skb) < 0) {
 334                        I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 335                        return TX_DROP;
 336                }
 337        }
 338
 339        return TX_CONTINUE;
 340}
 341