1 /*- 2 * Copyright (c) 2002-2005 Sam Leffler, Errno Consulting 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * Alternatively, this software may be distributed under the terms of the 17 * GNU General Public License ("GPL") version 2 as published by the Free 18 * Software Foundation. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 /* 36 * IEEE 802.11 WEP crypto support. 37 */ 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/mbuf.h> 41 #include <sys/malloc.h> 42 #include <sys/kernel.h> 43 #include <sys/module.h> 44 #include <sys/endian.h> 45 46 #include <sys/socket.h> 47 48 #include <net/if.h> 49 #include <net/if_media.h> 50 #include <net/ethernet.h> 51 52 #include <net80211/ieee80211_var.h> 53 54 static void *wep_attach(struct ieee80211com *, struct ieee80211_key *); 55 static void wep_detach(struct ieee80211_key *); 56 static int wep_setkey(struct ieee80211_key *); 57 static int wep_encap(struct ieee80211_key *, struct mbuf *, u_int8_t keyid); 58 static int wep_decap(struct ieee80211_key *, struct mbuf *, int hdrlen); 59 static int wep_enmic(struct ieee80211_key *, struct mbuf *, int); 60 static int wep_demic(struct ieee80211_key *, struct mbuf *, int); 61 62 static const struct ieee80211_cipher wep = { 63 .ic_name = "WEP", 64 .ic_cipher = IEEE80211_CIPHER_WEP, 65 .ic_header = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN, 66 .ic_trailer = IEEE80211_WEP_CRCLEN, 67 .ic_miclen = 0, 68 .ic_attach = wep_attach, 69 .ic_detach = wep_detach, 70 .ic_setkey = wep_setkey, 71 .ic_encap = wep_encap, 72 .ic_decap = wep_decap, 73 .ic_enmic = wep_enmic, 74 .ic_demic = wep_demic, 75 }; 76 77 static int wep_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen); 78 static int wep_decrypt(struct ieee80211_key *, struct mbuf *, int hdrlen); 79 80 struct wep_ctx { 81 struct ieee80211com *wc_ic; /* for diagnostics */ 82 u_int32_t wc_iv; /* initial vector for crypto */ 83 }; 84 85 /* number of references from net80211 layer */ 86 static int nrefs = 0; 87 88 static void * 89 wep_attach(struct ieee80211com *ic, struct ieee80211_key *k) 90 { 91 struct wep_ctx *ctx; 92 93 MALLOC(ctx, struct wep_ctx *, sizeof(struct wep_ctx), 94 M_DEVBUF, M_NOWAIT | M_ZERO); 95 if (ctx == NULL) { 96 ic->ic_stats.is_crypto_nomem++; 97 return NULL; 98 } 99 100 ctx->wc_ic = ic; 101 get_random_bytes(&ctx->wc_iv, sizeof(ctx->wc_iv)); 102 nrefs++; /* NB: we assume caller locking */ 103 return ctx; 104 } 105 106 static void 107 wep_detach(struct ieee80211_key *k) 108 { 109 struct wep_ctx *ctx = k->wk_private; 110 111 FREE(ctx, M_DEVBUF); 112 KASSERT(nrefs > 0, ("imbalanced attach/detach")); 113 nrefs--; /* NB: we assume caller locking */ 114 } 115 116 static int 117 wep_setkey(struct ieee80211_key *k) 118 { 119 return k->wk_keylen >= 40/NBBY; 120 } 121 122 /* 123 * Add privacy headers appropriate for the specified key. 124 */ 125 static int 126 wep_encap(struct ieee80211_key *k, struct mbuf *m, u_int8_t keyid) 127 { 128 struct wep_ctx *ctx = k->wk_private; 129 struct ieee80211com *ic = ctx->wc_ic; 130 u_int32_t iv; 131 u_int8_t *ivp; 132 int hdrlen; 133 134 hdrlen = ieee80211_hdrspace(ic, mtod(m, void *)); 135 136 /* 137 * Copy down 802.11 header and add the IV + KeyID. 138 */ 139 M_PREPEND(m, wep.ic_header, M_NOWAIT); 140 if (m == NULL) 141 return 0; 142 ivp = mtod(m, u_int8_t *); 143 ovbcopy(ivp + wep.ic_header, ivp, hdrlen); 144 ivp += hdrlen; 145 146 /* 147 * XXX 148 * IV must not duplicate during the lifetime of the key. 149 * But no mechanism to renew keys is defined in IEEE 802.11 150 * for WEP. And the IV may be duplicated at other stations 151 * because the session key itself is shared. So we use a 152 * pseudo random IV for now, though it is not the right way. 153 * 154 * NB: Rather than use a strictly random IV we select a 155 * random one to start and then increment the value for 156 * each frame. This is an explicit tradeoff between 157 * overhead and security. Given the basic insecurity of 158 * WEP this seems worthwhile. 159 */ 160 161 /* 162 * Skip 'bad' IVs from Fluhrer/Mantin/Shamir: 163 * (B, 255, N) with 3 <= B < 16 and 0 <= N <= 255 164 */ 165 iv = ctx->wc_iv; 166 if ((iv & 0xff00) == 0xff00) { 167 int B = (iv & 0xff0000) >> 16; 168 if (3 <= B && B < 16) 169 iv += 0x0100; 170 } 171 ctx->wc_iv = iv + 1; 172 173 /* 174 * NB: Preserve byte order of IV for packet 175 * sniffers; it doesn't matter otherwise. 176 */ 177 #if _BYTE_ORDER == _BIG_ENDIAN 178 ivp[0] = iv >> 0; 179 ivp[1] = iv >> 8; 180 ivp[2] = iv >> 16; 181 #else 182 ivp[2] = iv >> 0; 183 ivp[1] = iv >> 8; 184 ivp[0] = iv >> 16; 185 #endif 186 ivp[3] = keyid; 187 188 /* 189 * Finally, do software encrypt if neeed. 190 */ 191 if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) && 192 !wep_encrypt(k, m, hdrlen)) 193 return 0; 194 195 return 1; 196 } 197 198 /* 199 * Add MIC to the frame as needed. 200 */ 201 static int 202 wep_enmic(struct ieee80211_key *k, struct mbuf *m, int force) 203 { 204 205 return 1; 206 } 207 208 /* 209 * Validate and strip privacy headers (and trailer) for a 210 * received frame. If necessary, decrypt the frame using 211 * the specified key. 212 */ 213 static int 214 wep_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen) 215 { 216 struct wep_ctx *ctx = k->wk_private; 217 struct ieee80211_frame *wh; 218 219 wh = mtod(m, struct ieee80211_frame *); 220 221 /* 222 * Check if the device handled the decrypt in hardware. 223 * If so we just strip the header; otherwise we need to 224 * handle the decrypt in software. 225 */ 226 if ((k->wk_flags & IEEE80211_KEY_SWCRYPT) && 227 !wep_decrypt(k, m, hdrlen)) { 228 IEEE80211_DPRINTF(ctx->wc_ic, IEEE80211_MSG_CRYPTO, 229 "[%s] WEP ICV mismatch on decrypt\n", 230 ether_sprintf(wh->i_addr2)); 231 ctx->wc_ic->ic_stats.is_rx_wepfail++; 232 return 0; 233 } 234 235 /* 236 * Copy up 802.11 header and strip crypto bits. 237 */ 238 ovbcopy(mtod(m, void *), mtod(m, u_int8_t *) + wep.ic_header, hdrlen); 239 m_adj(m, wep.ic_header); 240 m_adj(m, -wep.ic_trailer); 241 242 return 1; 243 } 244 245 /* 246 * Verify and strip MIC from the frame. 247 */ 248 static int 249 wep_demic(struct ieee80211_key *k, struct mbuf *skb, int force) 250 { 251 return 1; 252 } 253 254 static const uint32_t crc32_table[256] = { 255 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 256 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L, 257 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 258 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 259 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L, 260 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 261 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 262 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL, 263 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L, 264 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL, 265 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 266 0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 267 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L, 268 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL, 269 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 270 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L, 271 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 272 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L, 273 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 274 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L, 275 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL, 276 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 277 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 278 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL, 279 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L, 280 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L, 281 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L, 282 0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L, 283 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L, 284 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL, 285 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 286 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L, 287 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L, 288 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL, 289 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 290 0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 291 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL, 292 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L, 293 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 294 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L, 295 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL, 296 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L, 297 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 298 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL, 299 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L, 300 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 301 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 302 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L, 303 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L, 304 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L, 305 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 306 0x2d02ef8dL 307 }; 308 309 static int 310 wep_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen) 311 { 312 #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 313 struct wep_ctx *ctx = key->wk_private; 314 struct mbuf *m = m0; 315 u_int8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE]; 316 uint8_t icv[IEEE80211_WEP_CRCLEN]; 317 uint32_t i, j, k, crc; 318 size_t buflen, data_len; 319 uint8_t S[256]; 320 uint8_t *pos; 321 u_int off, keylen; 322 323 ctx->wc_ic->ic_stats.is_crypto_wep++; 324 325 /* NB: this assumes the header was pulled up */ 326 memcpy(rc4key, mtod(m, u_int8_t *) + hdrlen, IEEE80211_WEP_IVLEN); 327 memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen); 328 329 /* Setup RC4 state */ 330 for (i = 0; i < 256; i++) 331 S[i] = i; 332 j = 0; 333 keylen = key->wk_keylen + IEEE80211_WEP_IVLEN; 334 for (i = 0; i < 256; i++) { 335 j = (j + S[i] + rc4key[i % keylen]) & 0xff; 336 S_SWAP(i, j); 337 } 338 339 off = hdrlen + wep.ic_header; 340 data_len = m->m_pkthdr.len - off; 341 342 /* Compute CRC32 over unencrypted data and apply RC4 to data */ 343 crc = ~0; 344 i = j = 0; 345 pos = mtod(m, uint8_t *) + off; 346 buflen = m->m_len - off; 347 for (;;) { 348 if (buflen > data_len) 349 buflen = data_len; 350 data_len -= buflen; 351 for (k = 0; k < buflen; k++) { 352 crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8); 353 i = (i + 1) & 0xff; 354 j = (j + S[i]) & 0xff; 355 S_SWAP(i, j); 356 *pos++ ^= S[(S[i] + S[j]) & 0xff]; 357 } 358 if (m->m_next == NULL) { 359 if (data_len != 0) { /* out of data */ 360 IEEE80211_DPRINTF(ctx->wc_ic, 361 IEEE80211_MSG_CRYPTO, 362 "[%s] out of data for WEP (data_len %zu)\n", 363 ether_sprintf(mtod(m0, 364 struct ieee80211_frame *)->i_addr2), 365 data_len); 366 return 0; 367 } 368 break; 369 } 370 m = m->m_next; 371 pos = mtod(m, uint8_t *); 372 buflen = m->m_len; 373 } 374 crc = ~crc; 375 376 /* Append little-endian CRC32 and encrypt it to produce ICV */ 377 icv[0] = crc; 378 icv[1] = crc >> 8; 379 icv[2] = crc >> 16; 380 icv[3] = crc >> 24; 381 for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) { 382 i = (i + 1) & 0xff; 383 j = (j + S[i]) & 0xff; 384 S_SWAP(i, j); 385 icv[k] ^= S[(S[i] + S[j]) & 0xff]; 386 } 387 return m_append(m0, IEEE80211_WEP_CRCLEN, icv); 388 #undef S_SWAP 389 } 390 391 static int 392 wep_decrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen) 393 { 394 #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 395 struct wep_ctx *ctx = key->wk_private; 396 struct mbuf *m = m0; 397 u_int8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE]; 398 uint8_t icv[IEEE80211_WEP_CRCLEN]; 399 uint32_t i, j, k, crc; 400 size_t buflen, data_len; 401 uint8_t S[256]; 402 uint8_t *pos; 403 u_int off, keylen; 404 405 ctx->wc_ic->ic_stats.is_crypto_wep++; 406 407 /* NB: this assumes the header was pulled up */ 408 memcpy(rc4key, mtod(m, u_int8_t *) + hdrlen, IEEE80211_WEP_IVLEN); 409 memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen); 410 411 /* Setup RC4 state */ 412 for (i = 0; i < 256; i++) 413 S[i] = i; 414 j = 0; 415 keylen = key->wk_keylen + IEEE80211_WEP_IVLEN; 416 for (i = 0; i < 256; i++) { 417 j = (j + S[i] + rc4key[i % keylen]) & 0xff; 418 S_SWAP(i, j); 419 } 420 421 off = hdrlen + wep.ic_header; 422 data_len = m->m_pkthdr.len - (off + wep.ic_trailer), 423 424 /* Compute CRC32 over unencrypted data and apply RC4 to data */ 425 crc = ~0; 426 i = j = 0; 427 pos = mtod(m, uint8_t *) + off; 428 buflen = m->m_len - off; 429 for (;;) { 430 if (buflen > data_len) 431 buflen = data_len; 432 data_len -= buflen; 433 for (k = 0; k < buflen; k++) { 434 i = (i + 1) & 0xff; 435 j = (j + S[i]) & 0xff; 436 S_SWAP(i, j); 437 *pos ^= S[(S[i] + S[j]) & 0xff]; 438 crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8); 439 pos++; 440 } 441 m = m->m_next; 442 if (m == NULL) { 443 if (data_len != 0) { /* out of data */ 444 IEEE80211_DPRINTF(ctx->wc_ic, 445 IEEE80211_MSG_CRYPTO, 446 "[%s] out of data for WEP (data_len %zu)\n", 447 ether_sprintf(mtod(m0, 448 struct ieee80211_frame *)->i_addr2), 449 data_len); 450 return 0; 451 } 452 break; 453 } 454 pos = mtod(m, uint8_t *); 455 buflen = m->m_len; 456 } 457 crc = ~crc; 458 459 /* Encrypt little-endian CRC32 and verify that it matches with 460 * received ICV */ 461 icv[0] = crc; 462 icv[1] = crc >> 8; 463 icv[2] = crc >> 16; 464 icv[3] = crc >> 24; 465 for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) { 466 i = (i + 1) & 0xff; 467 j = (j + S[i]) & 0xff; 468 S_SWAP(i, j); 469 /* XXX assumes ICV is contiguous in mbuf */ 470 if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *pos++) { 471 /* ICV mismatch - drop frame */ 472 return 0; 473 } 474 } 475 return 1; 476 #undef S_SWAP 477 } 478 479 /* 480 * Module glue. 481 */ 482 static int 483 wep_modevent(module_t mod, int type, void *unused) 484 { 485 switch (type) { 486 case MOD_LOAD: 487 ieee80211_crypto_register(&wep); 488 return 0; 489 case MOD_UNLOAD: 490 case MOD_QUIESCE: 491 if (nrefs) { 492 printf("wlan_wep: still in use (%u dynamic refs)\n", 493 nrefs); 494 return EBUSY; 495 } 496 if (type == MOD_UNLOAD) 497 ieee80211_crypto_unregister(&wep); 498 return 0; 499 } 500 return EINVAL; 501 } 502 503 static moduledata_t wep_mod = { 504 "wlan_wep", 505 wep_modevent, 506 0 507 }; 508 DECLARE_MODULE(wlan_wep, wep_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST); 509 MODULE_VERSION(wlan_wep, 1); 510 MODULE_DEPEND(wlan_wep, wlan, 1, 1, 1); 511