Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/net80211/ieee80211_crypto_wep.c
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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: releng/11.1/sys/net80211/ieee80211_crypto_wep.c 305614 2016-09-08 15:05:25Z pfg $"); 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 <net80211/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 void wep_setiv(struct ieee80211_key *, uint8_t *); 54 static int wep_encap(struct ieee80211_key *, struct mbuf *); 55 static int wep_decap(struct ieee80211_key *, struct mbuf *, int); 56 static int wep_enmic(struct ieee80211_key *, struct mbuf *, int); 57 static int wep_demic(struct ieee80211_key *, struct mbuf *, int); 58 59 static const struct ieee80211_cipher wep = { 60 .ic_name = "WEP", 61 .ic_cipher = IEEE80211_CIPHER_WEP, 62 .ic_header = IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN, 63 .ic_trailer = IEEE80211_WEP_CRCLEN, 64 .ic_miclen = 0, 65 .ic_attach = wep_attach, 66 .ic_detach = wep_detach, 67 .ic_setkey = wep_setkey, 68 .ic_setiv = wep_setiv, 69 .ic_encap = wep_encap, 70 .ic_decap = wep_decap, 71 .ic_enmic = wep_enmic, 72 .ic_demic = wep_demic, 73 }; 74 75 static int wep_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen); 76 static int wep_decrypt(struct ieee80211_key *, struct mbuf *, int hdrlen); 77 78 struct wep_ctx { 79 struct ieee80211vap *wc_vap; /* for diagnostics+statistics */ 80 struct ieee80211com *wc_ic; 81 uint32_t wc_iv; /* initial vector for crypto */ 82 }; 83 84 /* number of references from net80211 layer */ 85 static int nrefs = 0; 86 87 static void * 88 wep_attach(struct ieee80211vap *vap, struct ieee80211_key *k) 89 { 90 struct wep_ctx *ctx; 91 92 ctx = (struct wep_ctx *) IEEE80211_MALLOC(sizeof(struct wep_ctx), 93 M_80211_CRYPTO, IEEE80211_M_NOWAIT | IEEE80211_M_ZERO); 94 if (ctx == NULL) { 95 vap->iv_stats.is_crypto_nomem++; 96 return NULL; 97 } 98 99 ctx->wc_vap = vap; 100 ctx->wc_ic = vap->iv_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 IEEE80211_FREE(ctx, M_80211_CRYPTO); 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 static void 123 wep_setiv(struct ieee80211_key *k, uint8_t *ivp) 124 { 125 struct wep_ctx *ctx = k->wk_private; 126 struct ieee80211vap *vap = ctx->wc_vap; 127 uint32_t iv; 128 uint8_t keyid; 129 130 keyid = ieee80211_crypto_get_keyid(vap, k) << 6; 131 132 /* 133 * XXX 134 * IV must not duplicate during the lifetime of the key. 135 * But no mechanism to renew keys is defined in IEEE 802.11 136 * for WEP. And the IV may be duplicated at other stations 137 * because the session key itself is shared. So we use a 138 * pseudo random IV for now, though it is not the right way. 139 * 140 * NB: Rather than use a strictly random IV we select a 141 * random one to start and then increment the value for 142 * each frame. This is an explicit tradeoff between 143 * overhead and security. Given the basic insecurity of 144 * WEP this seems worthwhile. 145 */ 146 147 /* 148 * Skip 'bad' IVs from Fluhrer/Mantin/Shamir: 149 * (B, 255, N) with 3 <= B < 16 and 0 <= N <= 255 150 */ 151 iv = ctx->wc_iv; 152 if ((iv & 0xff00) == 0xff00) { 153 int B = (iv & 0xff0000) >> 16; 154 if (3 <= B && B < 16) 155 iv += 0x0100; 156 } 157 ctx->wc_iv = iv + 1; 158 159 /* 160 * NB: Preserve byte order of IV for packet 161 * sniffers; it doesn't matter otherwise. 162 */ 163 #if _BYTE_ORDER == _BIG_ENDIAN 164 ivp[0] = iv >> 0; 165 ivp[1] = iv >> 8; 166 ivp[2] = iv >> 16; 167 #else 168 ivp[2] = iv >> 0; 169 ivp[1] = iv >> 8; 170 ivp[0] = iv >> 16; 171 #endif 172 ivp[3] = keyid; 173 } 174 175 /* 176 * Add privacy headers appropriate for the specified key. 177 */ 178 static int 179 wep_encap(struct ieee80211_key *k, struct mbuf *m) 180 { 181 struct wep_ctx *ctx = k->wk_private; 182 struct ieee80211com *ic = ctx->wc_ic; 183 uint8_t *ivp; 184 int hdrlen; 185 186 hdrlen = ieee80211_hdrspace(ic, mtod(m, void *)); 187 188 /* 189 * Copy down 802.11 header and add the IV + KeyID. 190 */ 191 M_PREPEND(m, wep.ic_header, M_NOWAIT); 192 if (m == NULL) 193 return 0; 194 ivp = mtod(m, uint8_t *); 195 ovbcopy(ivp + wep.ic_header, ivp, hdrlen); 196 ivp += hdrlen; 197 198 wep_setiv(k, ivp); 199 200 /* 201 * Finally, do software encrypt if needed. 202 */ 203 if ((k->wk_flags & IEEE80211_KEY_SWENCRYPT) && 204 !wep_encrypt(k, m, hdrlen)) 205 return 0; 206 207 return 1; 208 } 209 210 /* 211 * Add MIC to the frame as needed. 212 */ 213 static int 214 wep_enmic(struct ieee80211_key *k, struct mbuf *m, int force) 215 { 216 217 return 1; 218 } 219 220 /* 221 * Validate and strip privacy headers (and trailer) for a 222 * received frame. If necessary, decrypt the frame using 223 * the specified key. 224 */ 225 static int 226 wep_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen) 227 { 228 struct wep_ctx *ctx = k->wk_private; 229 struct ieee80211vap *vap = ctx->wc_vap; 230 struct ieee80211_frame *wh; 231 232 wh = mtod(m, struct ieee80211_frame *); 233 234 /* 235 * Check if the device handled the decrypt in hardware. 236 * If so we just strip the header; otherwise we need to 237 * handle the decrypt in software. 238 */ 239 if ((k->wk_flags & IEEE80211_KEY_SWDECRYPT) && 240 !wep_decrypt(k, m, hdrlen)) { 241 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2, 242 "%s", "WEP ICV mismatch on decrypt"); 243 vap->iv_stats.is_rx_wepfail++; 244 return 0; 245 } 246 247 /* 248 * Copy up 802.11 header and strip crypto bits. 249 */ 250 ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + wep.ic_header, hdrlen); 251 m_adj(m, wep.ic_header); 252 m_adj(m, -wep.ic_trailer); 253 254 return 1; 255 } 256 257 /* 258 * Verify and strip MIC from the frame. 259 */ 260 static int 261 wep_demic(struct ieee80211_key *k, struct mbuf *skb, int force) 262 { 263 return 1; 264 } 265 266 static const uint32_t crc32_table[256] = { 267 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 268 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L, 269 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 270 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 271 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L, 272 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 273 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 274 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL, 275 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L, 276 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL, 277 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 278 0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 279 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L, 280 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL, 281 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 282 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L, 283 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 284 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L, 285 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 286 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L, 287 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL, 288 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 289 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 290 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL, 291 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L, 292 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L, 293 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L, 294 0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L, 295 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L, 296 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL, 297 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 298 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L, 299 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L, 300 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL, 301 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 302 0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 303 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL, 304 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L, 305 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 306 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L, 307 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL, 308 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L, 309 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 310 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL, 311 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L, 312 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 313 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 314 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L, 315 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L, 316 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L, 317 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 318 0x2d02ef8dL 319 }; 320 321 static int 322 wep_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen) 323 { 324 #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 325 struct wep_ctx *ctx = key->wk_private; 326 struct ieee80211vap *vap = ctx->wc_vap; 327 struct mbuf *m = m0; 328 uint8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE]; 329 uint8_t icv[IEEE80211_WEP_CRCLEN]; 330 uint32_t i, j, k, crc; 331 size_t buflen, data_len; 332 uint8_t S[256]; 333 uint8_t *pos; 334 u_int off, keylen; 335 336 vap->iv_stats.is_crypto_wep++; 337 338 /* NB: this assumes the header was pulled up */ 339 memcpy(rc4key, mtod(m, uint8_t *) + hdrlen, IEEE80211_WEP_IVLEN); 340 memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen); 341 342 /* Setup RC4 state */ 343 for (i = 0; i < 256; i++) 344 S[i] = i; 345 j = 0; 346 keylen = key->wk_keylen + IEEE80211_WEP_IVLEN; 347 for (i = 0; i < 256; i++) { 348 j = (j + S[i] + rc4key[i % keylen]) & 0xff; 349 S_SWAP(i, j); 350 } 351 352 off = hdrlen + wep.ic_header; 353 data_len = m->m_pkthdr.len - off; 354 355 /* Compute CRC32 over unencrypted data and apply RC4 to data */ 356 crc = ~0; 357 i = j = 0; 358 pos = mtod(m, uint8_t *) + off; 359 buflen = m->m_len - off; 360 for (;;) { 361 if (buflen > data_len) 362 buflen = data_len; 363 data_len -= buflen; 364 for (k = 0; k < buflen; k++) { 365 crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8); 366 i = (i + 1) & 0xff; 367 j = (j + S[i]) & 0xff; 368 S_SWAP(i, j); 369 *pos++ ^= S[(S[i] + S[j]) & 0xff]; 370 } 371 if (m->m_next == NULL) { 372 if (data_len != 0) { /* out of data */ 373 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, 374 ether_sprintf(mtod(m0, 375 struct ieee80211_frame *)->i_addr2), 376 "out of data for WEP (data_len %zu)", 377 data_len); 378 /* XXX stat */ 379 return 0; 380 } 381 break; 382 } 383 m = m->m_next; 384 pos = mtod(m, uint8_t *); 385 buflen = m->m_len; 386 } 387 crc = ~crc; 388 389 /* Append little-endian CRC32 and encrypt it to produce ICV */ 390 icv[0] = crc; 391 icv[1] = crc >> 8; 392 icv[2] = crc >> 16; 393 icv[3] = crc >> 24; 394 for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) { 395 i = (i + 1) & 0xff; 396 j = (j + S[i]) & 0xff; 397 S_SWAP(i, j); 398 icv[k] ^= S[(S[i] + S[j]) & 0xff]; 399 } 400 return m_append(m0, IEEE80211_WEP_CRCLEN, icv); 401 #undef S_SWAP 402 } 403 404 static int 405 wep_decrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen) 406 { 407 #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 408 struct wep_ctx *ctx = key->wk_private; 409 struct ieee80211vap *vap = ctx->wc_vap; 410 struct mbuf *m = m0; 411 uint8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE]; 412 uint8_t icv[IEEE80211_WEP_CRCLEN]; 413 uint32_t i, j, k, crc; 414 size_t buflen, data_len; 415 uint8_t S[256]; 416 uint8_t *pos; 417 u_int off, keylen; 418 419 vap->iv_stats.is_crypto_wep++; 420 421 /* NB: this assumes the header was pulled up */ 422 memcpy(rc4key, mtod(m, uint8_t *) + hdrlen, IEEE80211_WEP_IVLEN); 423 memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen); 424 425 /* Setup RC4 state */ 426 for (i = 0; i < 256; i++) 427 S[i] = i; 428 j = 0; 429 keylen = key->wk_keylen + IEEE80211_WEP_IVLEN; 430 for (i = 0; i < 256; i++) { 431 j = (j + S[i] + rc4key[i % keylen]) & 0xff; 432 S_SWAP(i, j); 433 } 434 435 off = hdrlen + wep.ic_header; 436 data_len = m->m_pkthdr.len - (off + wep.ic_trailer); 437 438 /* Compute CRC32 over unencrypted data and apply RC4 to data */ 439 crc = ~0; 440 i = j = 0; 441 pos = mtod(m, uint8_t *) + off; 442 buflen = m->m_len - off; 443 for (;;) { 444 if (buflen > data_len) 445 buflen = data_len; 446 data_len -= buflen; 447 for (k = 0; k < buflen; k++) { 448 i = (i + 1) & 0xff; 449 j = (j + S[i]) & 0xff; 450 S_SWAP(i, j); 451 *pos ^= S[(S[i] + S[j]) & 0xff]; 452 crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8); 453 pos++; 454 } 455 m = m->m_next; 456 if (m == NULL) { 457 if (data_len != 0) { /* out of data */ 458 IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, 459 mtod(m0, struct ieee80211_frame *)->i_addr2, 460 "out of data for WEP (data_len %zu)", 461 data_len); 462 return 0; 463 } 464 break; 465 } 466 pos = mtod(m, uint8_t *); 467 buflen = m->m_len; 468 } 469 crc = ~crc; 470 471 /* Encrypt little-endian CRC32 and verify that it matches with 472 * received ICV */ 473 icv[0] = crc; 474 icv[1] = crc >> 8; 475 icv[2] = crc >> 16; 476 icv[3] = crc >> 24; 477 for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) { 478 i = (i + 1) & 0xff; 479 j = (j + S[i]) & 0xff; 480 S_SWAP(i, j); 481 /* XXX assumes ICV is contiguous in mbuf */ 482 if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *pos++) { 483 /* ICV mismatch - drop frame */ 484 return 0; 485 } 486 } 487 return 1; 488 #undef S_SWAP 489 } 490 491 /* 492 * Module glue. 493 */ 494 IEEE80211_CRYPTO_MODULE(wep, 1);
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