openwrt/target/linux/package/ieee80211-dscape/src/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/config.h>
  12 #include <linux/version.h>
  13 #include <linux/netdevice.h>
  14 #include <linux/types.h>
  15 #include <linux/random.h>
  16 #include <linux/compiler.h>
  17
  18 #include <net/ieee80211.h>
  19 #include "ieee80211_i.h"
  20 #include "wep.h"
  21
  22
  23 static const __u32 crc32_table[256] = {
  24         0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
  25         0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
  26         0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
  27         0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
  28         0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
  29         0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
  30         0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
  31         0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
  32         0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
  33         0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
  34         0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
  35         0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
  36         0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
  37         0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
  38         0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
  39         0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
  40         0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
  41         0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
  42         0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
  43         0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
  44         0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
  45         0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
  46         0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
  47         0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
  48         0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
  49         0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
  50         0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
  51         0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
  52         0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
  53         0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
  54         0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
  55         0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
  56         0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
  57         0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
  58         0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
  59         0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
  60         0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
  61         0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
  62         0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
  63         0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
  64         0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
  65         0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
  66         0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
  67         0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
  68         0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
  69         0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
  70         0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
  71         0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
  72         0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
  73         0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
  74         0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
  75         0x2d02ef8dL
  76 };
  77
  78
  79 void ieee80211_wep_init(struct ieee80211_local *local)
  80 {
  81         /* start WEP IV from a random value */
  82         get_random_bytes(&local->wep_iv, WEP_IV_LEN);
  83 }
  84
  85
  86 static inline int ieee80211_wep_weak_iv(u32 iv, int keylen)
  87 {
  88         /* Fluhrer, Mantin, and Shamir have reported weaknesses in the
  89          * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  90          * 0xff, N) can be used to speedup attacks, so avoid using them. */
  91         if ((iv & 0xff00) == 0xff00) {
  92                 u8 B = (iv >> 16) & 0xff;
  93                 if (B >= 3 && B < 3 + keylen)
  94                         return 1;
  95         }
  96         return 0;
  97 }
  98
  99
 100 void ieee80211_wep_get_iv(struct ieee80211_local *local,
 101                           struct ieee80211_key *key, u8 *iv)
 102 {
 103         local->wep_iv++;
 104         if (ieee80211_wep_weak_iv(local->wep_iv, key->keylen))
 105                 local->wep_iv += 0x0100;
 106
 107         if (iv == NULL)
 108                 return;
 109
 110         *iv++ = (local->wep_iv >> 16) & 0xff;
 111         *iv++ = (local->wep_iv >> 8) & 0xff;
 112         *iv++ = local->wep_iv & 0xff;
 113         *iv++ = key->keyidx << 6;
 114 }
 115
 116
 117 u8 * ieee80211_wep_add_iv(struct ieee80211_local *local,
 118                           struct sk_buff *skb,
 119                           struct ieee80211_key *key)
 120 {
 121         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 122         u16 fc;
 123         int hdrlen;
 124         u8 *newhdr;
 125
 126         fc = le16_to_cpu(hdr->frame_control);
 127         fc |= WLAN_FC_ISWEP;
 128         hdr->frame_control = cpu_to_le16(fc);
 129
 130         if ((skb_headroom(skb) < WEP_IV_LEN ||
 131              skb_tailroom(skb) < WEP_ICV_LEN)) {
 132                 I802_DEBUG_INC(local->tx_expand_skb_head);
 133                 if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN,
 134                                               GFP_ATOMIC)))
 135                         return NULL;
 136         }
 137
 138         hdrlen = ieee80211_get_hdrlen(fc);
 139         newhdr = skb_push(skb, WEP_IV_LEN);
 140         memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
 141         ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
 142         return newhdr + hdrlen;
 143 }
 144
 145
 146 void ieee80211_wep_remove_iv(struct ieee80211_local *local,
 147                              struct sk_buff *skb,
 148                              struct ieee80211_key *key)
 149 {
 150         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 151         u16 fc;
 152         int hdrlen;
 153
 154         fc = le16_to_cpu(hdr->frame_control);
 155         hdrlen = ieee80211_get_hdrlen(fc);
 156         memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
 157         skb_pull(skb, WEP_IV_LEN);
 158 }
 159
 160
 161 /* Perform WEP encryption using given key. data buffer must have tailroom
 162  * for 4-byte ICV. data_len must not include this ICV. Note: this function
 163  * does _not_ add IV. data = RC4(data | CRC32(data)) */
 164 void ieee80211_wep_encrypt_data(u8 *rc4key, size_t klen, u8 *data,
 165                                 size_t data_len)
 166 {
 167         u32 i, j, k, crc;
 168         u8 S[256];
 169         u8 kpos, *pos;
 170 #define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0)
 171
 172         /* Setup RC4 state */
 173         for (i = 0; i < 256; i++)
 174                 S[i] = i;
 175         j = 0;
 176         kpos = 0;
 177         for (i = 0; i < 256; i++) {
 178                 j = (j + S[i] + rc4key[kpos]) & 0xff;
 179                 kpos++;
 180                 if (kpos >= klen)
 181                         kpos = 0;
 182                 S_SWAP(i, j);
 183         }
 184
 185         /* Compute CRC32 over unencrypted data and apply RC4 to data */
 186         pos = data;
 187         crc = ~0;
 188         i = j = 0;
 189         for (k = 0; k < data_len; k++) {
 190                 crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8);
 191                 i = (i + 1) & 0xff;
 192                 j = (j + S[i]) & 0xff;
 193                 S_SWAP(i, j);
 194                 *pos++ ^= S[(S[i] + S[j]) & 0xff];
 195         }
 196         crc = ~crc;
 197
 198         /* Append little-endian CRC32 and encrypt it to produce ICV */
 199         pos[0] = crc;
 200         pos[1] = crc >> 8;
 201         pos[2] = crc >> 16;
 202         pos[3] = crc >> 24;
 203         for (k = 0; k < 4; k++) {
 204                 i = (i + 1) & 0xff;
 205                 j = (j + S[i]) & 0xff;
 206                 S_SWAP(i, j);
 207                 *pos++ ^= S[(S[i] + S[j]) & 0xff];
 208         }
 209 }
 210
 211
 212 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 213  * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 214  * buffer will be added. Both IV and ICV will be transmitted, so the
 215  * payload length increases with 8 bytes.
 216  *
 217  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 218  */
 219 int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
 220                           struct ieee80211_key *key)
 221 {
 222         u32 klen;
 223         u8 *rc4key, *iv;
 224         size_t len;
 225
 226         if (key == NULL || key->alg != ALG_WEP)
 227                 return -1;
 228
 229         klen = 3 + key->keylen;
 230         rc4key = kmalloc(klen, GFP_ATOMIC);
 231         if (rc4key == NULL)
 232                 return -1;
 233
 234         iv = ieee80211_wep_add_iv(local, skb, key);
 235         if (iv == NULL) {
 236                 kfree(rc4key);
 237                 return -1;
 238         }
 239
 240         len = skb->len - (iv + WEP_IV_LEN - skb->data);
 241
 242         /* Prepend 24-bit IV to RC4 key */
 243         memcpy(rc4key, iv, 3);
 244
 245         /* Copy rest of the WEP key (the secret part) */
 246         memcpy(rc4key + 3, key->key, key->keylen);
 247
 248         /* Add room for ICV */
 249         skb_put(skb, WEP_ICV_LEN);
 250
 251         ieee80211_wep_encrypt_data(rc4key, klen, iv + WEP_IV_LEN, len);
 252
 253         kfree(rc4key);
 254
 255         return 0;
 256 }
 257
 258
 259 /* Perform WEP decryption using given key. data buffer includes encrypted
 260  * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 261  * Return 0 on success and -1 on ICV mismatch. */
 262 int ieee80211_wep_decrypt_data(u8 *rc4key, size_t klen, u8 *data,
 263                                size_t data_len)
 264 {
 265         u32 i, j, k, crc;
 266         u8 S[256];
 267         u8 kpos, *pos, crcbuf[WEP_ICV_LEN], *cpos;
 268
 269         /* Setup RC4 state */
 270         for (i = 0; i < 256; i++)
 271                 S[i] = i;
 272         j = 0;
 273         kpos = 0;
 274         for (i = 0; i < 256; i++) {
 275                 j = (j + S[i] + rc4key[kpos]) & 0xff;
 276                 kpos++;
 277                 if (kpos >= klen)
 278                         kpos = 0;
 279                 S_SWAP(i, j);
 280         }
 281
 282         /* Apply RC4 to data and compute CRC32 over decrypted data */
 283         pos = data;
 284         crc = ~0;
 285         i = j = 0;
 286         for (k = 0; k < data_len; k++) {
 287                 i = (i + 1) & 0xff;
 288                 j = (j + S[i]) & 0xff;
 289                 S_SWAP(i, j);
 290                 *pos ^= S[(S[i] + S[j]) & 0xff];
 291                 crc = crc32_table[(crc ^ *pos++) & 0xff] ^ (crc >> 8);
 292         }
 293         crc = ~crc;
 294
 295         /* Decrypt little-endian CRC32 and verify that it matches with the
 296          * received ICV */
 297         cpos = crcbuf;
 298         crcbuf[0] = crc;
 299         crcbuf[1] = crc >> 8;
 300         crcbuf[2] = crc >> 16;
 301         crcbuf[3] = crc >> 24;
 302         for (k = 0; k < WEP_ICV_LEN; k++) {
 303                 i = (i + 1) & 0xff;
 304                 j = (j + S[i]) & 0xff;
 305                 S_SWAP(i, j);
 306                 if (*cpos++ != (*pos++ ^ S[(S[i] + S[j]) & 0xff])) {
 307                         /* ICV mismatch */
 308                         return -1;
 309                 }
 310         }
 311
 312         return 0;
 313 }
 314
 315
 316 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 317  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 318  * ICV (4 bytes). skb->len includes both IV and ICV.
 319  *
 320  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 321  * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 322  * is moved to the beginning of the skb and skb length will be reduced.
 323  */
 324 int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
 325                           struct ieee80211_key *key)
 326 {
 327         u32 klen;
 328         u8 *rc4key;
 329         u8 keyidx;
 330         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 331         u16 fc;
 332         int hdrlen;
 333         size_t len;
 334         int ret = 0;
 335
 336         fc = le16_to_cpu(hdr->frame_control);
 337         if (!(fc & WLAN_FC_ISWEP))
 338                 return -1;
 339
 340         hdrlen = ieee80211_get_hdrlen(fc);
 341
 342         if (skb->len < 8 + hdrlen)
 343                 return -1;
 344
 345         len = skb->len - hdrlen - 8;
 346
 347         keyidx = skb->data[hdrlen + 3] >> 6;
 348
 349         if (key == NULL || keyidx != key->keyidx || key->alg != ALG_WEP)
 350                 return -1;
 351
 352         klen = 3 + key->keylen;
 353
 354         rc4key = kmalloc(klen, GFP_ATOMIC);
 355         if (rc4key == NULL)
 356                 return -1;
 357
 358         /* Prepend 24-bit IV to RC4 key */
 359         memcpy(rc4key, skb->data + hdrlen, 3);
 360
 361         /* Copy rest of the WEP key (the secret part) */
 362         memcpy(rc4key + 3, key->key, key->keylen);
 363
 364         if (ieee80211_wep_decrypt_data(rc4key, klen,
 365                                        skb->data + hdrlen + WEP_IV_LEN,
 366                                        len)) {
 367                 printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
 368                 ret = -1;
 369         }
 370
 371         kfree(rc4key);
 372
 373         /* Trim ICV */
 374         skb_trim(skb, skb->len - WEP_ICV_LEN);
 375
 376         /* Remove IV */
 377         memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
 378         skb_pull(skb, WEP_IV_LEN);
 379
 380         return ret;
 381 }
 382
 383
 384 int ieee80211_wep_get_keyidx(struct sk_buff *skb)
 385 {
 386         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 387         u16 fc;
 388         int hdrlen;
 389
 390         fc = le16_to_cpu(hdr->frame_control);
 391         if (!(fc & WLAN_FC_ISWEP))
 392                 return -1;
 393
 394         hdrlen = ieee80211_get_hdrlen(fc);
 395
 396         if (skb->len < 8 + hdrlen)
 397                 return -1;
 398
 399         return skb->data[hdrlen + 3] >> 6;
 400 }
 401
 402
 403 u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
 404 {
 405         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 406         u16 fc;
 407         int hdrlen;
 408         u8 *ivpos;
 409         u32 iv;
 410
 411         fc = le16_to_cpu(hdr->frame_control);
 412         if (!(fc & WLAN_FC_ISWEP))
 413                 return NULL;
 414
 415         hdrlen = ieee80211_get_hdrlen(fc);
 416         ivpos = skb->data + hdrlen;
 417         iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
 418
 419         if (ieee80211_wep_weak_iv(iv, key->keylen))
 420                 return ivpos;
 421
 422         return NULL;
 423 }