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
  21#include <net/mac80211.h>
  22#include "ieee80211_i.h"
  23#include "wep.h"
  24
  25
  26int ieee80211_wep_init(struct ieee80211_local *local)
  27{
  28        /* start WEP IV from a random value */
  29        get_random_bytes(&local->wep_iv, WEP_IV_LEN);
  30
  31        local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
  32                                                CRYPTO_ALG_ASYNC);
  33        if (IS_ERR(local->wep_tx_tfm))
  34                return -ENOMEM;
  35
  36        local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
  37                                                CRYPTO_ALG_ASYNC);
  38        if (IS_ERR(local->wep_rx_tfm)) {
  39                crypto_free_blkcipher(local->wep_tx_tfm);
  40                return -ENOMEM;
  41        }
  42
  43        return 0;
  44}
  45
  46void ieee80211_wep_free(struct ieee80211_local *local)
  47{
  48        crypto_free_blkcipher(local->wep_tx_tfm);
  49        crypto_free_blkcipher(local->wep_rx_tfm);
  50}
  51
  52static inline int ieee80211_wep_weak_iv(u32 iv, int keylen)
  53{
  54        /* Fluhrer, Mantin, and Shamir have reported weaknesses in the
  55         * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  56         * 0xff, N) can be used to speedup attacks, so avoid using them. */
  57        if ((iv & 0xff00) == 0xff00) {
  58                u8 B = (iv >> 16) & 0xff;
  59                if (B >= 3 && B < 3 + keylen)
  60                        return 1;
  61        }
  62        return 0;
  63}
  64
  65
  66static void ieee80211_wep_get_iv(struct ieee80211_local *local,
  67                                 struct ieee80211_key *key, u8 *iv)
  68{
  69        local->wep_iv++;
  70        if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen))
  71                local->wep_iv += 0x0100;
  72
  73        if (!iv)
  74                return;
  75
  76        *iv++ = (local->wep_iv >> 16) & 0xff;
  77        *iv++ = (local->wep_iv >> 8) & 0xff;
  78        *iv++ = local->wep_iv & 0xff;
  79        *iv++ = key->conf.keyidx << 6;
  80}
  81
  82
  83static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
  84                                struct sk_buff *skb,
  85                                struct ieee80211_key *key)
  86{
  87        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
  88        u16 fc;
  89        int hdrlen;
  90        u8 *newhdr;
  91
  92        fc = le16_to_cpu(hdr->frame_control);
  93        fc |= IEEE80211_FCTL_PROTECTED;
  94        hdr->frame_control = cpu_to_le16(fc);
  95
  96        if ((skb_headroom(skb) < WEP_IV_LEN ||
  97             skb_tailroom(skb) < WEP_ICV_LEN)) {
  98                I802_DEBUG_INC(local->tx_expand_skb_head);
  99                if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN,
 100                                              GFP_ATOMIC)))
 101                        return NULL;
 102        }
 103
 104        hdrlen = ieee80211_get_hdrlen(fc);
 105        newhdr = skb_push(skb, WEP_IV_LEN);
 106        memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
 107        ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
 108        return newhdr + hdrlen;
 109}
 110
 111
 112static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
 113                                    struct sk_buff *skb,
 114                                    struct ieee80211_key *key)
 115{
 116        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 117        u16 fc;
 118        int hdrlen;
 119
 120        fc = le16_to_cpu(hdr->frame_control);
 121        hdrlen = ieee80211_get_hdrlen(fc);
 122        memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
 123        skb_pull(skb, WEP_IV_LEN);
 124}
 125
 126
 127/* Perform WEP encryption using given key. data buffer must have tailroom
 128 * for 4-byte ICV. data_len must not include this ICV. Note: this function
 129 * does _not_ add IV. data = RC4(data | CRC32(data)) */
 130void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
 131                                size_t klen, u8 *data, size_t data_len)
 132{
 133        struct blkcipher_desc desc = { .tfm = tfm };
 134        struct scatterlist sg;
 135        __le32 *icv;
 136
 137        icv = (__le32 *)(data + data_len);
 138        *icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 139
 140        crypto_blkcipher_setkey(tfm, rc4key, klen);
 141        sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
 142        crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
 143}
 144
 145
 146/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 147 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 148 * buffer will be added. Both IV and ICV will be transmitted, so the
 149 * payload length increases with 8 bytes.
 150 *
 151 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 152 */
 153int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
 154                          struct ieee80211_key *key)
 155{
 156        u32 klen;
 157        u8 *rc4key, *iv;
 158        size_t len;
 159
 160        if (!key || key->conf.alg != ALG_WEP)
 161                return -1;
 162
 163        klen = 3 + key->conf.keylen;
 164        rc4key = kmalloc(klen, GFP_ATOMIC);
 165        if (!rc4key)
 166                return -1;
 167
 168        iv = ieee80211_wep_add_iv(local, skb, key);
 169        if (!iv) {
 170                kfree(rc4key);
 171                return -1;
 172        }
 173
 174        len = skb->len - (iv + 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->conf.key, key->conf.keylen);
 181
 182        /* Add room for ICV */
 183        skb_put(skb, WEP_ICV_LEN);
 184
 185        ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
 186                                   iv + WEP_IV_LEN, len);
 187
 188        kfree(rc4key);
 189
 190        return 0;
 191}
 192
 193
 194/* Perform WEP decryption using given key. data buffer includes encrypted
 195 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 196 * Return 0 on success and -1 on ICV mismatch. */
 197int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
 198                               size_t klen, u8 *data, size_t data_len)
 199{
 200        struct blkcipher_desc desc = { .tfm = tfm };
 201        struct scatterlist sg;
 202        __le32 crc;
 203
 204        crypto_blkcipher_setkey(tfm, rc4key, klen);
 205        sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
 206        crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
 207
 208        crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 209        if (memcmp(&crc, data + data_len, 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 */
 225int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
 226                          struct ieee80211_key *key)
 227{
 228        u32 klen;
 229        u8 *rc4key;
 230        u8 keyidx;
 231        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 232        u16 fc;
 233        int hdrlen;
 234        size_t len;
 235        int ret = 0;
 236
 237        fc = le16_to_cpu(hdr->frame_control);
 238        if (!(fc & IEEE80211_FCTL_PROTECTED))
 239                return -1;
 240
 241        hdrlen = ieee80211_get_hdrlen(fc);
 242
 243        if (skb->len < 8 + hdrlen)
 244                return -1;
 245
 246        len = skb->len - hdrlen - 8;
 247
 248        keyidx = skb->data[hdrlen + 3] >> 6;
 249
 250        if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP)
 251                return -1;
 252
 253        klen = 3 + key->conf.keylen;
 254
 255        rc4key = kmalloc(klen, GFP_ATOMIC);
 256        if (!rc4key)
 257                return -1;
 258
 259        /* Prepend 24-bit IV to RC4 key */
 260        memcpy(rc4key, skb->data + hdrlen, 3);
 261
 262        /* Copy rest of the WEP key (the secret part) */
 263        memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 264
 265        if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
 266                                       skb->data + hdrlen + WEP_IV_LEN,
 267                                       len)) {
 268                if (net_ratelimit())
 269                        printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
 270                ret = -1;
 271        }
 272
 273        kfree(rc4key);
 274
 275        /* Trim ICV */
 276        skb_trim(skb, skb->len - WEP_ICV_LEN);
 277
 278        /* Remove IV */
 279        memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
 280        skb_pull(skb, WEP_IV_LEN);
 281
 282        return ret;
 283}
 284
 285
 286u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
 287{
 288        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 289        u16 fc;
 290        int hdrlen;
 291        u8 *ivpos;
 292        u32 iv;
 293
 294        fc = le16_to_cpu(hdr->frame_control);
 295        if (!(fc & IEEE80211_FCTL_PROTECTED))
 296                return NULL;
 297
 298        hdrlen = ieee80211_get_hdrlen(fc);
 299        ivpos = skb->data + hdrlen;
 300        iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
 301
 302        if (ieee80211_wep_weak_iv(iv, key->conf.keylen))
 303                return ivpos;
 304
 305        return NULL;
 306}
 307
 308ieee80211_txrx_result
 309ieee80211_crypto_wep_decrypt(struct ieee80211_txrx_data *rx)
 310{
 311        if ((rx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA &&
 312            ((rx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_MGMT ||
 313             (rx->fc & IEEE80211_FCTL_STYPE) != IEEE80211_STYPE_AUTH))
 314                return TXRX_CONTINUE;
 315
 316        if (!(rx->u.rx.status->flag & RX_FLAG_DECRYPTED)) {
 317                if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) {
 318#ifdef CONFIG_MAC80211_DEBUG
 319                        if (net_ratelimit())
 320                                printk(KERN_DEBUG "%s: RX WEP frame, decrypt "
 321                                       "failed\n", rx->dev->name);
 322#endif /* CONFIG_MAC80211_DEBUG */
 323                        return TXRX_DROP;
 324                }
 325        } else if (!(rx->u.rx.status->flag & RX_FLAG_IV_STRIPPED)) {
 326                ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 327                /* remove ICV */
 328                skb_trim(rx->skb, rx->skb->len - 4);
 329        }
 330
 331        return TXRX_CONTINUE;
 332}
 333
 334static int wep_encrypt_skb(struct ieee80211_txrx_data *tx, struct sk_buff *skb)
 335{
 336        if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) {
 337                if (ieee80211_wep_encrypt(tx->local, skb, tx->key))
 338                        return -1;
 339        } else {
 340                tx->u.tx.control->key_idx = tx->key->conf.hw_key_idx;
 341                if (tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) {
 342                        if (!ieee80211_wep_add_iv(tx->local, skb, tx->key))
 343                                return -1;
 344                }
 345        }
 346        return 0;
 347}
 348
 349ieee80211_txrx_result
 350ieee80211_crypto_wep_encrypt(struct ieee80211_txrx_data *tx)
 351{
 352        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) tx->skb->data;
 353        u16 fc;
 354
 355        fc = le16_to_cpu(hdr->frame_control);
 356
 357        if (((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA &&
 358             ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_MGMT ||
 359              (fc & IEEE80211_FCTL_STYPE) != IEEE80211_STYPE_AUTH)))
 360                return TXRX_CONTINUE;
 361
 362        tx->u.tx.control->iv_len = WEP_IV_LEN;
 363        tx->u.tx.control->icv_len = WEP_ICV_LEN;
 364        ieee80211_tx_set_iswep(tx);
 365
 366        if (wep_encrypt_skb(tx, tx->skb) < 0) {
 367                I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 368                return TXRX_DROP;
 369        }
 370
 371        if (tx->u.tx.extra_frag) {
 372                int i;
 373                for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
 374                        if (wep_encrypt_skb(tx, tx->u.tx.extra_frag[i]) < 0) {
 375                                I802_DEBUG_INC(tx->local->
 376                                               tx_handlers_drop_wep);
 377                                return TXRX_DROP;
 378                        }
 379                }
 380        }
 381
 382        return TXRX_CONTINUE;
 383}
 384