1 /*- 2 * Copyright (c) 2002-2008 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 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include <sys/cdefs.h> 27 __FBSDID("$FreeBSD$"); 28 29 /* 30 * IEEE 802.11 WEP crypto support. 31 */ 32 #include "opt_wlan.h" 33 34 #include <sys/param.h> 35 #include <sys/systm.h> 36 #include <sys/mbuf.h> 37 #include <sys/malloc.h> 38 #include <sys/kernel.h> 39 #include <sys/module.h> 40 #include <sys/endian.h> 41 42 #include <sys/socket.h> 43 44 #include <net/if.h> 45 #include <net/if_media.h> 46 #include <net/ethernet.h> 47 48 #include <netproto/802_11/ieee80211_var.h> 49 50 static void *wep_attach(struct ieee80211vap *, struct ieee80211_key *); 51 static void wep_detach(struct ieee80211_key *); 52 static int wep_setkey(struct ieee80211_key *); 53 static int wep_encap(struct ieee80211_key *, struct mbuf *, uint8_t keyid); 54 static int wep_decap(struct ieee80211_key *, struct mbuf *, int hdrlen); 55 static int wep_enmic(struct ieee80211_key *, struct mbuf *, int); 56 static int wep_demic(struct ieee80211_key *, struct mbuf *, int); 57 58 static const struct ieee80211_cipher wep = { 59 .ic_name = "WEP", 60 .ic_cipher = IEEE80211_CIPHER_WEP, 61 .ic_header = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN, 62 .ic_trailer = IEEE80211_WEP_CRCLEN, 63 .ic_miclen = 0, 64 .ic_attach = wep_attach, 65 .ic_detach = wep_detach, 66 .ic_setkey = wep_setkey, 67 .ic_encap = wep_encap, 68 .ic_decap = wep_decap, 69 .ic_enmic = wep_enmic, 70 .ic_demic = wep_demic, 71 }; 72 73 static int wep_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen); 74 static int wep_decrypt(struct ieee80211_key *, struct mbuf *, int hdrlen); 75 76 struct wep_ctx { 77 struct ieee80211vap *wc_vap; /* for diagnostics+statistics */ 78 struct ieee80211com *wc_ic; 79 uint32_t wc_iv; /* initial vector for crypto */ 80 }; 81 82 /* number of references from net80211 layer */ 83 static int nrefs = 0; 84 85 static void * 86 wep_attach(struct ieee80211vap *vap, struct ieee80211_key *k) 87 { 88 struct wep_ctx *ctx; 89 90 ctx = (struct wep_ctx *) kmalloc(sizeof(struct wep_ctx), 91 M_80211_CRYPTO, M_INTWAIT | M_ZERO); 92 if (ctx == NULL) { 93 vap->iv_stats.is_crypto_nomem++; 94 return NULL; 95 } 96 97 ctx->wc_vap = vap; 98 ctx->wc_ic = vap->iv_ic; 99 get_random_bytes(&ctx->wc_iv, sizeof(ctx->wc_iv)); 100 nrefs++; /* NB: we assume caller locking */ 101 return ctx; 102 } 103 104 static void 105 wep_detach(struct ieee80211_key *k) 106 { 107 struct wep_ctx *ctx = k->wk_private; 108 109 kfree(ctx, M_80211_CRYPTO); 110 KASSERT(nrefs > 0, ("imbalanced attach/detach")); 111 nrefs--; /* NB: we assume caller locking */ 112 } 113 114 static int 115 wep_setkey(struct ieee80211_key *k) 116 { 117 return k->wk_keylen >= 40/NBBY; 118 } 119 120 /* 121 * Add privacy headers appropriate for the specified key. 122 */ 123 static int 124 wep_encap(struct ieee80211_key *k, struct mbuf *m, uint8_t keyid) 125 { 126 struct wep_ctx *ctx = k->wk_private; 127 struct ieee80211com *ic = ctx->wc_ic; 128 uint32_t iv; 129 uint8_t *ivp; 130 int hdrlen; 131 132 hdrlen = ieee80211_hdrspace(ic, mtod(m, void *)); 133 134 /* 135 * Copy down 802.11 header and add the IV + KeyID. 136 */ 137 M_PREPEND(m, wep.ic_header, M_NOWAIT); 138 if (m == NULL) 139 return 0; 140 ivp = mtod(m, uint8_t *); 141 ovbcopy(ivp + wep.ic_header, ivp, hdrlen); 142 ivp += hdrlen; 143 144 /* 145 * XXX 146 * IV must not duplicate during the lifetime of the key. 147 * But no mechanism to renew keys is defined in IEEE 802.11 148 * for WEP. And the IV may be duplicated at other stations 149 * because the session key itself is shared. So we use a 150 * pseudo random IV for now, though it is not the right way. 151 * 152 * NB: Rather than use a strictly random IV we select a 153 * random one to start and then increment the value for 154 * each frame. This is an explicit tradeoff between 155 * overhead and security. Given the basic insecurity of 156 * WEP this seems worthwhile. 157 */ 158 159 /* 160 * Skip 'bad' IVs from Fluhrer/Mantin/Shamir: 161 * (B, 255, N) with 3 <= B < 16 and 0 <= N <= 255 162 */ 163 iv = ctx->wc_iv; 164 if ((iv & 0xff00) == 0xff00) { 165 int B = (iv & 0xff0000) >> 16; 166 if (3 <= B && B < 16) 167 iv += 0x0100; 168 } 169 ctx->wc_iv = iv + 1; 170 171 /* 172 * NB: Preserve byte order of IV for packet 173 * sniffers; it doesn't matter otherwise. 174 */ 175 #if _BYTE_ORDER == _BIG_ENDIAN 176 ivp[0] = iv >> 0; 177 ivp[1] = iv >> 8; 178 ivp[2] = iv >> 16; 179 #else 180 ivp[2] = iv >> 0; 181 ivp[1] = iv >> 8; 182 ivp[0] = iv >> 16; 183 #endif 184 ivp[3] = keyid; 185 186 /* 187 * Finally, do software encrypt if neeed. 188 */ 189 if ((k->wk_flags & IEEE80211_KEY_SWENCRYPT) && 190 !wep_encrypt(k, m, hdrlen)) 191 return 0; 192 193 return 1; 194 } 195 196 /* 197 * Add MIC to the frame as needed. 198 */ 199 static int 200 wep_enmic(struct ieee80211_key *k, struct mbuf *m, int force) 201 { 202 203 return 1; 204 } 205 206 /* 207 * Validate and strip privacy headers (and trailer) for a 208 * received frame. If necessary, decrypt the frame using 209 * the specified key. 210 */ 211 static int 212 wep_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen) 213 { 214 struct wep_ctx *ctx = k->wk_private; 215 struct ieee80211vap *vap = ctx->wc_vap; 216 struct ieee80211_frame *wh; 217 218 wh = mtod(m, struct ieee80211_frame *); 219 220 /* 221 * Check if the device handled the decrypt in hardware. 222 * If so we just strip the header; otherwise we need to 223 * handle the decrypt in software. 224 */ 225 if ((k->wk_flags & IEEE80211_KEY_SWDECRYPT) && 226 !wep_decrypt(k, m, hdrlen)) { 227 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2, 228 "%s", "WEP ICV mismatch on decrypt"); 229 vap->iv_stats.is_rx_wepfail++; 230 return 0; 231 } 232 233 /* 234 * Copy up 802.11 header and strip crypto bits. 235 */ 236 ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + wep.ic_header, hdrlen); 237 m_adj(m, wep.ic_header); 238 m_adj(m, -wep.ic_trailer); 239 240 return 1; 241 } 242 243 /* 244 * Verify and strip MIC from the frame. 245 */ 246 static int 247 wep_demic(struct ieee80211_key *k, struct mbuf *skb, int force) 248 { 249 return 1; 250 } 251 252 static const uint32_t crc32_table[256] = { 253 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 254 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L, 255 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 256 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 257 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L, 258 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 259 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 260 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL, 261 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L, 262 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL, 263 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 264 0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 265 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L, 266 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL, 267 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 268 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L, 269 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 270 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L, 271 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 272 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L, 273 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL, 274 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 275 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 276 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL, 277 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L, 278 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L, 279 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L, 280 0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L, 281 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L, 282 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL, 283 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 284 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L, 285 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L, 286 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL, 287 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 288 0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 289 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL, 290 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L, 291 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 292 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L, 293 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL, 294 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L, 295 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 296 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL, 297 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L, 298 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 299 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 300 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L, 301 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L, 302 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L, 303 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 304 0x2d02ef8dL 305 }; 306 307 static int 308 wep_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen) 309 { 310 #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 311 struct wep_ctx *ctx = key->wk_private; 312 struct ieee80211vap *vap = ctx->wc_vap; 313 struct mbuf *m = m0; 314 uint8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE]; 315 uint8_t icv[IEEE80211_WEP_CRCLEN]; 316 uint32_t i, j, k, crc; 317 size_t buflen, data_len; 318 uint8_t S[256]; 319 uint8_t *pos; 320 u_int off, keylen; 321 322 vap->iv_stats.is_crypto_wep++; 323 324 /* NB: this assumes the header was pulled up */ 325 memcpy(rc4key, mtod(m, uint8_t *) + hdrlen, IEEE80211_WEP_IVLEN); 326 memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen); 327 328 /* Setup RC4 state */ 329 for (i = 0; i < 256; i++) 330 S[i] = i; 331 j = 0; 332 keylen = key->wk_keylen + IEEE80211_WEP_IVLEN; 333 for (i = 0; i < 256; i++) { 334 j = (j + S[i] + rc4key[i % keylen]) & 0xff; 335 S_SWAP(i, j); 336 } 337 338 off = hdrlen + wep.ic_header; 339 data_len = m->m_pkthdr.len - off; 340 341 /* Compute CRC32 over unencrypted data and apply RC4 to data */ 342 crc = ~0; 343 i = j = 0; 344 pos = mtod(m, uint8_t *) + off; 345 buflen = m->m_len - off; 346 for (;;) { 347 if (buflen > data_len) 348 buflen = data_len; 349 data_len -= buflen; 350 for (k = 0; k < buflen; k++) { 351 crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8); 352 i = (i + 1) & 0xff; 353 j = (j + S[i]) & 0xff; 354 S_SWAP(i, j); 355 *pos++ ^= S[(S[i] + S[j]) & 0xff]; 356 } 357 if (m->m_next == NULL) { 358 if (data_len != 0) { /* out of data */ 359 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, 360 ether_sprintf(mtod(m0, 361 struct ieee80211_frame *)->i_addr2), 362 "out of data for WEP (data_len %zu)", 363 data_len); 364 /* XXX stat */ 365 return 0; 366 } 367 break; 368 } 369 m = m->m_next; 370 pos = mtod(m, uint8_t *); 371 buflen = m->m_len; 372 } 373 crc = ~crc; 374 375 /* Append little-endian CRC32 and encrypt it to produce ICV */ 376 icv[0] = crc; 377 icv[1] = crc >> 8; 378 icv[2] = crc >> 16; 379 icv[3] = crc >> 24; 380 for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) { 381 i = (i + 1) & 0xff; 382 j = (j + S[i]) & 0xff; 383 S_SWAP(i, j); 384 icv[k] ^= S[(S[i] + S[j]) & 0xff]; 385 } 386 return m_append(m0, IEEE80211_WEP_CRCLEN, icv); 387 #undef S_SWAP 388 } 389 390 static int 391 wep_decrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen) 392 { 393 #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 394 struct wep_ctx *ctx = key->wk_private; 395 struct ieee80211vap *vap = ctx->wc_vap; 396 struct mbuf *m = m0; 397 uint8_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 vap->iv_stats.is_crypto_wep++; 406 407 /* NB: this assumes the header was pulled up */ 408 memcpy(rc4key, mtod(m, uint8_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_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, 445 mtod(m0, struct ieee80211_frame *)->i_addr2, 446 "out of data for WEP (data_len %zu)", 447 data_len); 448 return 0; 449 } 450 break; 451 } 452 pos = mtod(m, uint8_t *); 453 buflen = m->m_len; 454 } 455 crc = ~crc; 456 457 /* Encrypt little-endian CRC32 and verify that it matches with 458 * received ICV */ 459 icv[0] = crc; 460 icv[1] = crc >> 8; 461 icv[2] = crc >> 16; 462 icv[3] = crc >> 24; 463 for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) { 464 i = (i + 1) & 0xff; 465 j = (j + S[i]) & 0xff; 466 S_SWAP(i, j); 467 /* XXX assumes ICV is contiguous in mbuf */ 468 if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *pos++) { 469 /* ICV mismatch - drop frame */ 470 return 0; 471 } 472 } 473 return 1; 474 #undef S_SWAP 475 } 476 477 /* 478 * Module glue. 479 */ 480 IEEE80211_CRYPTO_MODULE(wep, 1); 481