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 printk(KERN_DEBUG "lib80211_crypt_ccmp: could not allocate " 81 "crypto API aes\n"); 82 priv->tfm = NULL; 83 goto fail; 84 } 85 86 return priv; 87 88 fail: 89 if (priv) { 90 if (priv->tfm) 91 crypto_free_cipher(priv->tfm); 92 kfree(priv); 93 } 94 95 return NULL; 96 } 97 98 static void lib80211_ccmp_deinit(void *priv) 99 { 100 struct lib80211_ccmp_data *_priv = priv; 101 if (_priv && _priv->tfm) 102 crypto_free_cipher(_priv->tfm); 103 kfree(priv); 104 } 105 106 static inline void xor_block(u8 * b, u8 * a, size_t len) 107 { 108 int i; 109 for (i = 0; i < len; i++) 110 b[i] ^= a[i]; 111 } 112 113 static void ccmp_init_blocks(struct crypto_cipher *tfm, 114 struct ieee80211_hdr *hdr, 115 u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0) 116 { 117 u8 *pos, qc = 0; 118 size_t aad_len; 119 int a4_included, qc_included; 120 u8 aad[2 * AES_BLOCK_LEN]; 121 122 a4_included = ieee80211_has_a4(hdr->frame_control); 123 qc_included = ieee80211_is_data_qos(hdr->frame_control); 124 125 aad_len = 22; 126 if (a4_included) 127 aad_len += 6; 128 if (qc_included) { 129 pos = (u8 *) & hdr->addr4; 130 if (a4_included) 131 pos += 6; 132 qc = *pos & 0x0f; 133 aad_len += 2; 134 } 135 136 /* CCM Initial Block: 137 * Flag (Include authentication header, M=3 (8-octet MIC), 138 * L=1 (2-octet Dlen)) 139 * Nonce: 0x00 | A2 | PN 140 * Dlen */ 141 b0[0] = 0x59; 142 b0[1] = qc; 143 memcpy(b0 + 2, hdr->addr2, ETH_ALEN); 144 memcpy(b0 + 8, pn, CCMP_PN_LEN); 145 b0[14] = (dlen >> 8) & 0xff; 146 b0[15] = dlen & 0xff; 147 148 /* AAD: 149 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one 150 * A1 | A2 | A3 151 * SC with bits 4..15 (seq#) masked to zero 152 * A4 (if present) 153 * QC (if present) 154 */ 155 pos = (u8 *) hdr; 156 aad[0] = 0; /* aad_len >> 8 */ 157 aad[1] = aad_len & 0xff; 158 aad[2] = pos[0] & 0x8f; 159 aad[3] = pos[1] & 0xc7; 160 memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN); 161 pos = (u8 *) & hdr->seq_ctrl; 162 aad[22] = pos[0] & 0x0f; 163 aad[23] = 0; /* all bits masked */ 164 memset(aad + 24, 0, 8); 165 if (a4_included) 166 memcpy(aad + 24, hdr->addr4, ETH_ALEN); 167 if (qc_included) { 168 aad[a4_included ? 30 : 24] = qc; 169 /* rest of QC masked */ 170 } 171 172 /* Start with the first block and AAD */ 173 lib80211_ccmp_aes_encrypt(tfm, b0, auth); 174 xor_block(auth, aad, AES_BLOCK_LEN); 175 lib80211_ccmp_aes_encrypt(tfm, auth, auth); 176 xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN); 177 lib80211_ccmp_aes_encrypt(tfm, auth, auth); 178 b0[0] &= 0x07; 179 b0[14] = b0[15] = 0; 180 lib80211_ccmp_aes_encrypt(tfm, b0, s0); 181 } 182 183 static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len, 184 u8 *aeskey, int keylen, void *priv) 185 { 186 struct lib80211_ccmp_data *key = priv; 187 int i; 188 u8 *pos; 189 190 if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len) 191 return -1; 192 193 if (aeskey != NULL && keylen >= CCMP_TK_LEN) 194 memcpy(aeskey, key->key, CCMP_TK_LEN); 195 196 pos = skb_push(skb, CCMP_HDR_LEN); 197 memmove(pos, pos + CCMP_HDR_LEN, hdr_len); 198 pos += hdr_len; 199 200 i = CCMP_PN_LEN - 1; 201 while (i >= 0) { 202 key->tx_pn[i]++; 203 if (key->tx_pn[i] != 0) 204 break; 205 i--; 206 } 207 208 *pos++ = key->tx_pn[5]; 209 *pos++ = key->tx_pn[4]; 210 *pos++ = 0; 211 *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ; 212 *pos++ = key->tx_pn[3]; 213 *pos++ = key->tx_pn[2]; 214 *pos++ = key->tx_pn[1]; 215 *pos++ = key->tx_pn[0]; 216 217 return CCMP_HDR_LEN; 218 } 219 220 static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv) 221 { 222 struct lib80211_ccmp_data *key = priv; 223 int data_len, i, blocks, last, len; 224 u8 *pos, *mic; 225 struct ieee80211_hdr *hdr; 226 u8 *b0 = key->tx_b0; 227 u8 *b = key->tx_b; 228 u8 *e = key->tx_e; 229 u8 *s0 = key->tx_s0; 230 231 if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len) 232 return -1; 233 234 data_len = skb->len - hdr_len; 235 len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv); 236 if (len < 0) 237 return -1; 238 239 pos = skb->data + hdr_len + CCMP_HDR_LEN; 240 hdr = (struct ieee80211_hdr *)skb->data; 241 ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0); 242 243 blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN); 244 last = data_len % AES_BLOCK_LEN; 245 246 for (i = 1; i <= blocks; i++) { 247 len = (i == blocks && last) ? last : AES_BLOCK_LEN; 248 /* Authentication */ 249 xor_block(b, pos, len); 250 lib80211_ccmp_aes_encrypt(key->tfm, b, b); 251 /* Encryption, with counter */ 252 b0[14] = (i >> 8) & 0xff; 253 b0[15] = i & 0xff; 254 lib80211_ccmp_aes_encrypt(key->tfm, b0, e); 255 xor_block(pos, e, len); 256 pos += len; 257 } 258 259 mic = skb_put(skb, CCMP_MIC_LEN); 260 for (i = 0; i < CCMP_MIC_LEN; i++) 261 mic[i] = b[i] ^ s0[i]; 262 263 return 0; 264 } 265 266 /* 267 * deal with seq counter wrapping correctly. 268 * refer to timer_after() for jiffies wrapping handling 269 */ 270 static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o) 271 { 272 u32 iv32_n, iv16_n; 273 u32 iv32_o, iv16_o; 274 275 iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3]; 276 iv16_n = (pn_n[4] << 8) | pn_n[5]; 277 278 iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3]; 279 iv16_o = (pn_o[4] << 8) | pn_o[5]; 280 281 if ((s32)iv32_n - (s32)iv32_o < 0 || 282 (iv32_n == iv32_o && iv16_n <= iv16_o)) 283 return 1; 284 return 0; 285 } 286 287 static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv) 288 { 289 struct lib80211_ccmp_data *key = priv; 290 u8 keyidx, *pos; 291 struct ieee80211_hdr *hdr; 292 u8 *b0 = key->rx_b0; 293 u8 *b = key->rx_b; 294 u8 *a = key->rx_a; 295 u8 pn[6]; 296 int i, blocks, last, len; 297 size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN; 298 u8 *mic = skb->data + skb->len - CCMP_MIC_LEN; 299 300 if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) { 301 key->dot11RSNAStatsCCMPFormatErrors++; 302 return -1; 303 } 304 305 hdr = (struct ieee80211_hdr *)skb->data; 306 pos = skb->data + hdr_len; 307 keyidx = pos[3]; 308 if (!(keyidx & (1 << 5))) { 309 if (net_ratelimit()) { 310 printk(KERN_DEBUG "CCMP: received packet without ExtIV" 311 " flag from %pM\n", hdr->addr2); 312 } 313 key->dot11RSNAStatsCCMPFormatErrors++; 314 return -2; 315 } 316 keyidx >>= 6; 317 if (key->key_idx != keyidx) { 318 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame " 319 "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv); 320 return -6; 321 } 322 if (!key->key_set) { 323 if (net_ratelimit()) { 324 printk(KERN_DEBUG "CCMP: received packet from %pM" 325 " with keyid=%d that does not have a configured" 326 " key\n", hdr->addr2, keyidx); 327 } 328 return -3; 329 } 330 331 pn[0] = pos[7]; 332 pn[1] = pos[6]; 333 pn[2] = pos[5]; 334 pn[3] = pos[4]; 335 pn[4] = pos[1]; 336 pn[5] = pos[0]; 337 pos += 8; 338 339 if (ccmp_replay_check(pn, key->rx_pn)) { 340 #ifdef CONFIG_LIB80211_DEBUG 341 if (net_ratelimit()) { 342 printk(KERN_DEBUG "CCMP: replay detected: STA=%pM " 343 "previous PN %02x%02x%02x%02x%02x%02x " 344 "received PN %02x%02x%02x%02x%02x%02x\n", 345 hdr->addr2, 346 key->rx_pn[0], key->rx_pn[1], key->rx_pn[2], 347 key->rx_pn[3], key->rx_pn[4], key->rx_pn[5], 348 pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]); 349 } 350 #endif 351 key->dot11RSNAStatsCCMPReplays++; 352 return -4; 353 } 354 355 ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b); 356 xor_block(mic, b, CCMP_MIC_LEN); 357 358 blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN); 359 last = data_len % AES_BLOCK_LEN; 360 361 for (i = 1; i <= blocks; i++) { 362 len = (i == blocks && last) ? last : AES_BLOCK_LEN; 363 /* Decrypt, with counter */ 364 b0[14] = (i >> 8) & 0xff; 365 b0[15] = i & 0xff; 366 lib80211_ccmp_aes_encrypt(key->tfm, b0, b); 367 xor_block(pos, b, len); 368 /* Authentication */ 369 xor_block(a, pos, len); 370 lib80211_ccmp_aes_encrypt(key->tfm, a, a); 371 pos += len; 372 } 373 374 if (memcmp(mic, a, CCMP_MIC_LEN) != 0) { 375 if (net_ratelimit()) { 376 printk(KERN_DEBUG "CCMP: decrypt failed: STA=" 377 "%pM\n", hdr->addr2); 378 } 379 key->dot11RSNAStatsCCMPDecryptErrors++; 380 return -5; 381 } 382 383 memcpy(key->rx_pn, pn, CCMP_PN_LEN); 384 385 /* Remove hdr and MIC */ 386 memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len); 387 skb_pull(skb, CCMP_HDR_LEN); 388 skb_trim(skb, skb->len - CCMP_MIC_LEN); 389 390 return keyidx; 391 } 392 393 static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv) 394 { 395 struct lib80211_ccmp_data *data = priv; 396 int keyidx; 397 struct crypto_cipher *tfm = data->tfm; 398 399 keyidx = data->key_idx; 400 memset(data, 0, sizeof(*data)); 401 data->key_idx = keyidx; 402 data->tfm = tfm; 403 if (len == CCMP_TK_LEN) { 404 memcpy(data->key, key, CCMP_TK_LEN); 405 data->key_set = 1; 406 if (seq) { 407 data->rx_pn[0] = seq[5]; 408 data->rx_pn[1] = seq[4]; 409 data->rx_pn[2] = seq[3]; 410 data->rx_pn[3] = seq[2]; 411 data->rx_pn[4] = seq[1]; 412 data->rx_pn[5] = seq[0]; 413 } 414 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN); 415 } else if (len == 0) 416 data->key_set = 0; 417 else 418 return -1; 419 420 return 0; 421 } 422 423 static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv) 424 { 425 struct lib80211_ccmp_data *data = priv; 426 427 if (len < CCMP_TK_LEN) 428 return -1; 429 430 if (!data->key_set) 431 return 0; 432 memcpy(key, data->key, CCMP_TK_LEN); 433 434 if (seq) { 435 seq[0] = data->tx_pn[5]; 436 seq[1] = data->tx_pn[4]; 437 seq[2] = data->tx_pn[3]; 438 seq[3] = data->tx_pn[2]; 439 seq[4] = data->tx_pn[1]; 440 seq[5] = data->tx_pn[0]; 441 } 442 443 return CCMP_TK_LEN; 444 } 445 446 static char *lib80211_ccmp_print_stats(char *p, void *priv) 447 { 448 struct lib80211_ccmp_data *ccmp = priv; 449 450 p += sprintf(p, "key[%d] alg=CCMP key_set=%d " 451 "tx_pn=%02x%02x%02x%02x%02x%02x " 452 "rx_pn=%02x%02x%02x%02x%02x%02x " 453 "format_errors=%d replays=%d decrypt_errors=%d\n", 454 ccmp->key_idx, ccmp->key_set, 455 ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2], 456 ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5], 457 ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2], 458 ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5], 459 ccmp->dot11RSNAStatsCCMPFormatErrors, 460 ccmp->dot11RSNAStatsCCMPReplays, 461 ccmp->dot11RSNAStatsCCMPDecryptErrors); 462 463 return p; 464 } 465 466 static struct lib80211_crypto_ops lib80211_crypt_ccmp = { 467 .name = "CCMP", 468 .init = lib80211_ccmp_init, 469 .deinit = lib80211_ccmp_deinit, 470 .build_iv = lib80211_ccmp_hdr, 471 .encrypt_mpdu = lib80211_ccmp_encrypt, 472 .decrypt_mpdu = lib80211_ccmp_decrypt, 473 .encrypt_msdu = NULL, 474 .decrypt_msdu = NULL, 475 .set_key = lib80211_ccmp_set_key, 476 .get_key = lib80211_ccmp_get_key, 477 .print_stats = lib80211_ccmp_print_stats, 478 .extra_mpdu_prefix_len = CCMP_HDR_LEN, 479 .extra_mpdu_postfix_len = CCMP_MIC_LEN, 480 .owner = THIS_MODULE, 481 }; 482 483 static int __init lib80211_crypto_ccmp_init(void) 484 { 485 return lib80211_register_crypto_ops(&lib80211_crypt_ccmp); 486 } 487 488 static void __exit lib80211_crypto_ccmp_exit(void) 489 { 490 lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp); 491 } 492 493 module_init(lib80211_crypto_ccmp_init); 494 module_exit(lib80211_crypto_ccmp_exit); 495