1 /* 2 * lib80211 crypt: host-based CCMP encryption implementation for lib80211 3 * 4 * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi> 5 * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. See README and COPYING for 10 * more details. 11 */ 12 13 #include <linux/kernel.h> 14 #include <linux/err.h> 15 #include <linux/module.h> 16 #include <linux/init.h> 17 #include <linux/slab.h> 18 #include <linux/random.h> 19 #include <linux/skbuff.h> 20 #include <linux/netdevice.h> 21 #include <linux/if_ether.h> 22 #include <linux/if_arp.h> 23 #include <asm/string.h> 24 #include <linux/wireless.h> 25 26 #include <linux/ieee80211.h> 27 28 #include <linux/crypto.h> 29 30 #include <net/lib80211.h> 31 32 MODULE_AUTHOR("Jouni Malinen"); 33 MODULE_DESCRIPTION("Host AP crypt: CCMP"); 34 MODULE_LICENSE("GPL"); 35 36 #define AES_BLOCK_LEN 16 37 #define CCMP_HDR_LEN 8 38 #define CCMP_MIC_LEN 8 39 #define CCMP_TK_LEN 16 40 #define CCMP_PN_LEN 6 41 42 struct lib80211_ccmp_data { 43 u8 key[CCMP_TK_LEN]; 44 int key_set; 45 46 u8 tx_pn[CCMP_PN_LEN]; 47 u8 rx_pn[CCMP_PN_LEN]; 48 49 u32 dot11RSNAStatsCCMPFormatErrors; 50 u32 dot11RSNAStatsCCMPReplays; 51 u32 dot11RSNAStatsCCMPDecryptErrors; 52 53 int key_idx; 54 55 struct crypto_cipher *tfm; 56 57 /* scratch buffers for virt_to_page() (crypto API) */ 58 u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN], 59 tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN]; 60 u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN]; 61 }; 62 63 static inline void lib80211_ccmp_aes_encrypt(struct crypto_cipher *tfm, 64 const u8 pt[16], u8 ct[16]) 65 { 66 crypto_cipher_encrypt_one(tfm, ct, pt); 67 } 68 69 static void *lib80211_ccmp_init(int key_idx) 70 { 71 struct lib80211_ccmp_data *priv; 72 73 priv = kzalloc(sizeof(*priv), GFP_ATOMIC); 74 if (priv == NULL) 75 goto fail; 76 priv->key_idx = key_idx; 77 78 priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC); 79 if (IS_ERR(priv->tfm)) { 80 priv->tfm = NULL; 81 goto fail; 82 } 83 84 return priv; 85 86 fail: 87 if (priv) { 88 if (priv->tfm) 89 crypto_free_cipher(priv->tfm); 90 kfree(priv); 91 } 92 93 return NULL; 94 } 95 96 static void lib80211_ccmp_deinit(void *priv) 97 { 98 struct lib80211_ccmp_data *_priv = priv; 99 if (_priv && _priv->tfm) 100 crypto_free_cipher(_priv->tfm); 101 kfree(priv); 102 } 103 104 static inline void xor_block(u8 * b, u8 * a, size_t len) 105 { 106 int i; 107 for (i = 0; i < len; i++) 108 b[i] ^= a[i]; 109 } 110 111 static void ccmp_init_blocks(struct crypto_cipher *tfm, 112 struct ieee80211_hdr *hdr, 113 u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0) 114 { 115 u8 *pos, qc = 0; 116 size_t aad_len; 117 int a4_included, qc_included; 118 u8 aad[2 * AES_BLOCK_LEN]; 119 120 a4_included = ieee80211_has_a4(hdr->frame_control); 121 qc_included = ieee80211_is_data_qos(hdr->frame_control); 122 123 aad_len = 22; 124 if (a4_included) 125 aad_len += 6; 126 if (qc_included) { 127 pos = (u8 *) & hdr->addr4; 128 if (a4_included) 129 pos += 6; 130 qc = *pos & 0x0f; 131 aad_len += 2; 132 } 133 134 /* CCM Initial Block: 135 * Flag (Include authentication header, M=3 (8-octet MIC), 136 * L=1 (2-octet Dlen)) 137 * Nonce: 0x00 | A2 | PN 138 * Dlen */ 139 b0[0] = 0x59; 140 b0[1] = qc; 141 memcpy(b0 + 2, hdr->addr2, ETH_ALEN); 142 memcpy(b0 + 8, pn, CCMP_PN_LEN); 143 b0[14] = (dlen >> 8) & 0xff; 144 b0[15] = dlen & 0xff; 145 146 /* AAD: 147 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one 148 * A1 | A2 | A3 149 * SC with bits 4..15 (seq#) masked to zero 150 * A4 (if present) 151 * QC (if present) 152 */ 153 pos = (u8 *) hdr; 154 aad[0] = 0; /* aad_len >> 8 */ 155 aad[1] = aad_len & 0xff; 156 aad[2] = pos[0] & 0x8f; 157 aad[3] = pos[1] & 0xc7; 158 memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN); 159 pos = (u8 *) & hdr->seq_ctrl; 160 aad[22] = pos[0] & 0x0f; 161 aad[23] = 0; /* all bits masked */ 162 memset(aad + 24, 0, 8); 163 if (a4_included) 164 memcpy(aad + 24, hdr->addr4, ETH_ALEN); 165 if (qc_included) { 166 aad[a4_included ? 30 : 24] = qc; 167 /* rest of QC masked */ 168 } 169 170 /* Start with the first block and AAD */ 171 lib80211_ccmp_aes_encrypt(tfm, b0, auth); 172 xor_block(auth, aad, AES_BLOCK_LEN); 173 lib80211_ccmp_aes_encrypt(tfm, auth, auth); 174 xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN); 175 lib80211_ccmp_aes_encrypt(tfm, auth, auth); 176 b0[0] &= 0x07; 177 b0[14] = b0[15] = 0; 178 lib80211_ccmp_aes_encrypt(tfm, b0, s0); 179 } 180 181 static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len, 182 u8 *aeskey, int keylen, void *priv) 183 { 184 struct lib80211_ccmp_data *key = priv; 185 int i; 186 u8 *pos; 187 188 if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len) 189 return -1; 190 191 if (aeskey != NULL && keylen >= CCMP_TK_LEN) 192 memcpy(aeskey, key->key, CCMP_TK_LEN); 193 194 pos = skb_push(skb, CCMP_HDR_LEN); 195 memmove(pos, pos + CCMP_HDR_LEN, hdr_len); 196 pos += hdr_len; 197 198 i = CCMP_PN_LEN - 1; 199 while (i >= 0) { 200 key->tx_pn[i]++; 201 if (key->tx_pn[i] != 0) 202 break; 203 i--; 204 } 205 206 *pos++ = key->tx_pn[5]; 207 *pos++ = key->tx_pn[4]; 208 *pos++ = 0; 209 *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ; 210 *pos++ = key->tx_pn[3]; 211 *pos++ = key->tx_pn[2]; 212 *pos++ = key->tx_pn[1]; 213 *pos++ = key->tx_pn[0]; 214 215 return CCMP_HDR_LEN; 216 } 217 218 static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv) 219 { 220 struct lib80211_ccmp_data *key = priv; 221 int data_len, i, blocks, last, len; 222 u8 *pos, *mic; 223 struct ieee80211_hdr *hdr; 224 u8 *b0 = key->tx_b0; 225 u8 *b = key->tx_b; 226 u8 *e = key->tx_e; 227 u8 *s0 = key->tx_s0; 228 229 if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len) 230 return -1; 231 232 data_len = skb->len - hdr_len; 233 len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv); 234 if (len < 0) 235 return -1; 236 237 pos = skb->data + hdr_len + CCMP_HDR_LEN; 238 hdr = (struct ieee80211_hdr *)skb->data; 239 ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0); 240 241 blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN); 242 last = data_len % AES_BLOCK_LEN; 243 244 for (i = 1; i <= blocks; i++) { 245 len = (i == blocks && last) ? last : AES_BLOCK_LEN; 246 /* Authentication */ 247 xor_block(b, pos, len); 248 lib80211_ccmp_aes_encrypt(key->tfm, b, b); 249 /* Encryption, with counter */ 250 b0[14] = (i >> 8) & 0xff; 251 b0[15] = i & 0xff; 252 lib80211_ccmp_aes_encrypt(key->tfm, b0, e); 253 xor_block(pos, e, len); 254 pos += len; 255 } 256 257 mic = skb_put(skb, CCMP_MIC_LEN); 258 for (i = 0; i < CCMP_MIC_LEN; i++) 259 mic[i] = b[i] ^ s0[i]; 260 261 return 0; 262 } 263 264 /* 265 * deal with seq counter wrapping correctly. 266 * refer to timer_after() for jiffies wrapping handling 267 */ 268 static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o) 269 { 270 u32 iv32_n, iv16_n; 271 u32 iv32_o, iv16_o; 272 273 iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3]; 274 iv16_n = (pn_n[4] << 8) | pn_n[5]; 275 276 iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3]; 277 iv16_o = (pn_o[4] << 8) | pn_o[5]; 278 279 if ((s32)iv32_n - (s32)iv32_o < 0 || 280 (iv32_n == iv32_o && iv16_n <= iv16_o)) 281 return 1; 282 return 0; 283 } 284 285 static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv) 286 { 287 struct lib80211_ccmp_data *key = priv; 288 u8 keyidx, *pos; 289 struct ieee80211_hdr *hdr; 290 u8 *b0 = key->rx_b0; 291 u8 *b = key->rx_b; 292 u8 *a = key->rx_a; 293 u8 pn[6]; 294 int i, blocks, last, len; 295 size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN; 296 u8 *mic = skb->data + skb->len - CCMP_MIC_LEN; 297 298 if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) { 299 key->dot11RSNAStatsCCMPFormatErrors++; 300 return -1; 301 } 302 303 hdr = (struct ieee80211_hdr *)skb->data; 304 pos = skb->data + hdr_len; 305 keyidx = pos[3]; 306 if (!(keyidx & (1 << 5))) { 307 net_dbg_ratelimited("CCMP: received packet without ExtIV flag from %pM\n", 308 hdr->addr2); 309 key->dot11RSNAStatsCCMPFormatErrors++; 310 return -2; 311 } 312 keyidx >>= 6; 313 if (key->key_idx != keyidx) { 314 net_dbg_ratelimited("CCMP: RX tkey->key_idx=%d frame keyidx=%d\n", 315 key->key_idx, keyidx); 316 return -6; 317 } 318 if (!key->key_set) { 319 net_dbg_ratelimited("CCMP: received packet from %pM with keyid=%d that does not have a configured key\n", 320 hdr->addr2, keyidx); 321 return -3; 322 } 323 324 pn[0] = pos[7]; 325 pn[1] = pos[6]; 326 pn[2] = pos[5]; 327 pn[3] = pos[4]; 328 pn[4] = pos[1]; 329 pn[5] = pos[0]; 330 pos += 8; 331 332 if (ccmp_replay_check(pn, key->rx_pn)) { 333 #ifdef CONFIG_LIB80211_DEBUG 334 net_dbg_ratelimited("CCMP: replay detected: STA=%pM previous PN %02x%02x%02x%02x%02x%02x received PN %02x%02x%02x%02x%02x%02x\n", 335 hdr->addr2, 336 key->rx_pn[0], key->rx_pn[1], key->rx_pn[2], 337 key->rx_pn[3], key->rx_pn[4], key->rx_pn[5], 338 pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]); 339 #endif 340 key->dot11RSNAStatsCCMPReplays++; 341 return -4; 342 } 343 344 ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b); 345 xor_block(mic, b, CCMP_MIC_LEN); 346 347 blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN); 348 last = data_len % AES_BLOCK_LEN; 349 350 for (i = 1; i <= blocks; i++) { 351 len = (i == blocks && last) ? last : AES_BLOCK_LEN; 352 /* Decrypt, with counter */ 353 b0[14] = (i >> 8) & 0xff; 354 b0[15] = i & 0xff; 355 lib80211_ccmp_aes_encrypt(key->tfm, b0, b); 356 xor_block(pos, b, len); 357 /* Authentication */ 358 xor_block(a, pos, len); 359 lib80211_ccmp_aes_encrypt(key->tfm, a, a); 360 pos += len; 361 } 362 363 if (memcmp(mic, a, CCMP_MIC_LEN) != 0) { 364 net_dbg_ratelimited("CCMP: decrypt failed: STA=%pM\n", 365 hdr->addr2); 366 key->dot11RSNAStatsCCMPDecryptErrors++; 367 return -5; 368 } 369 370 memcpy(key->rx_pn, pn, CCMP_PN_LEN); 371 372 /* Remove hdr and MIC */ 373 memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len); 374 skb_pull(skb, CCMP_HDR_LEN); 375 skb_trim(skb, skb->len - CCMP_MIC_LEN); 376 377 return keyidx; 378 } 379 380 static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv) 381 { 382 struct lib80211_ccmp_data *data = priv; 383 int keyidx; 384 struct crypto_cipher *tfm = data->tfm; 385 386 keyidx = data->key_idx; 387 memset(data, 0, sizeof(*data)); 388 data->key_idx = keyidx; 389 data->tfm = tfm; 390 if (len == CCMP_TK_LEN) { 391 memcpy(data->key, key, CCMP_TK_LEN); 392 data->key_set = 1; 393 if (seq) { 394 data->rx_pn[0] = seq[5]; 395 data->rx_pn[1] = seq[4]; 396 data->rx_pn[2] = seq[3]; 397 data->rx_pn[3] = seq[2]; 398 data->rx_pn[4] = seq[1]; 399 data->rx_pn[5] = seq[0]; 400 } 401 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN); 402 } else if (len == 0) 403 data->key_set = 0; 404 else 405 return -1; 406 407 return 0; 408 } 409 410 static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv) 411 { 412 struct lib80211_ccmp_data *data = priv; 413 414 if (len < CCMP_TK_LEN) 415 return -1; 416 417 if (!data->key_set) 418 return 0; 419 memcpy(key, data->key, CCMP_TK_LEN); 420 421 if (seq) { 422 seq[0] = data->tx_pn[5]; 423 seq[1] = data->tx_pn[4]; 424 seq[2] = data->tx_pn[3]; 425 seq[3] = data->tx_pn[2]; 426 seq[4] = data->tx_pn[1]; 427 seq[5] = data->tx_pn[0]; 428 } 429 430 return CCMP_TK_LEN; 431 } 432 433 static void lib80211_ccmp_print_stats(struct seq_file *m, void *priv) 434 { 435 struct lib80211_ccmp_data *ccmp = priv; 436 437 seq_printf(m, 438 "key[%d] alg=CCMP key_set=%d " 439 "tx_pn=%02x%02x%02x%02x%02x%02x " 440 "rx_pn=%02x%02x%02x%02x%02x%02x " 441 "format_errors=%d replays=%d decrypt_errors=%d\n", 442 ccmp->key_idx, ccmp->key_set, 443 ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2], 444 ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5], 445 ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2], 446 ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5], 447 ccmp->dot11RSNAStatsCCMPFormatErrors, 448 ccmp->dot11RSNAStatsCCMPReplays, 449 ccmp->dot11RSNAStatsCCMPDecryptErrors); 450 } 451 452 static struct lib80211_crypto_ops lib80211_crypt_ccmp = { 453 .name = "CCMP", 454 .init = lib80211_ccmp_init, 455 .deinit = lib80211_ccmp_deinit, 456 .encrypt_mpdu = lib80211_ccmp_encrypt, 457 .decrypt_mpdu = lib80211_ccmp_decrypt, 458 .encrypt_msdu = NULL, 459 .decrypt_msdu = NULL, 460 .set_key = lib80211_ccmp_set_key, 461 .get_key = lib80211_ccmp_get_key, 462 .print_stats = lib80211_ccmp_print_stats, 463 .extra_mpdu_prefix_len = CCMP_HDR_LEN, 464 .extra_mpdu_postfix_len = CCMP_MIC_LEN, 465 .owner = THIS_MODULE, 466 }; 467 468 static int __init lib80211_crypto_ccmp_init(void) 469 { 470 return lib80211_register_crypto_ops(&lib80211_crypt_ccmp); 471 } 472 473 static void __exit lib80211_crypto_ccmp_exit(void) 474 { 475 lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp); 476 } 477 478 module_init(lib80211_crypto_ccmp_init); 479 module_exit(lib80211_crypto_ccmp_exit); 480