net/wireless/lib80211_crypt_ccmp.c

   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);