drivers/net/wireless/hostap/hostap_crypt_ccmp.c

   1 /*
   2  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
   3  *
   4  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation. See README and COPYING for
   9  * more details.
  10  */
  11
  12 #include <linux/config.h>
  13 #include <linux/version.h>
  14 #include <linux/module.h>
  15 #include <linux/init.h>
  16 #include <linux/slab.h>
  17 #include <linux/random.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/if_ether.h>
  21 #include <linux/if_arp.h>
  22 #include <linux/wireless.h>
  23 #include <net/iw_handler.h>
  24 #include <asm/string.h>
  25
  26 #include "hostap_crypt.h"
  27 #include "hostap_wlan.h"
  28 #include "hostap_80211.h"
  29
  30 #ifndef CONFIG_CRYPTO
  31 #error CONFIG_CRYPTO is required to build this module.
  32 #endif
  33 #include <linux/crypto.h>
  34 #include <asm/scatterlist.h>
  35
  36 MODULE_AUTHOR("Jouni Malinen");
  37 MODULE_DESCRIPTION("Host AP crypt: CCMP");
  38 MODULE_LICENSE("GPL");
  39
  40
  41 #define AES_BLOCK_LEN 16
  42 #define CCMP_HDR_LEN 8
  43 #define CCMP_MIC_LEN 8
  44 #define CCMP_TK_LEN 16
  45 #define CCMP_PN_LEN 6
  46
  47
  48 struct hostap_ccmp_data {
  49         u8 key[CCMP_TK_LEN];
  50         int key_set;
  51
  52         u8 tx_pn[CCMP_PN_LEN];
  53         u8 rx_pn[CCMP_PN_LEN];
  54
  55         u32 dot11RSNAStatsCCMPFormatErrors;
  56         u32 dot11RSNAStatsCCMPReplays;
  57         u32 dot11RSNAStatsCCMPDecryptErrors;
  58
  59         int key_idx;
  60
  61         struct crypto_tfm *tfm;
  62
  63         /* scratch buffers for virt_to_page() (crypto API) */
  64         u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
  65                 tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
  66         u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  67 };
  68
  69
  70 void hostap_ccmp_aes_encrypt(struct crypto_tfm *tfm,
  71                              const u8 pt[16], u8 ct[16])
  72 {
  73         struct scatterlist src, dst;
  74
  75         src.page = virt_to_page(pt);
  76         src.offset = offset_in_page(pt);
  77         src.length = AES_BLOCK_LEN;
  78
  79         dst.page = virt_to_page(ct);
  80         dst.offset = offset_in_page(ct);
  81         dst.length = AES_BLOCK_LEN;
  82
  83         crypto_cipher_encrypt(tfm, &dst, &src, AES_BLOCK_LEN);
  84 }
  85
  86
  87 static void * hostap_ccmp_init(int key_idx)
  88 {
  89         struct hostap_ccmp_data *priv;
  90
  91         if (!try_module_get(THIS_MODULE))
  92                 return NULL;
  93
  94         priv = (struct hostap_ccmp_data *) kmalloc(sizeof(*priv), GFP_ATOMIC);
  95         if (priv == NULL) {
  96                 goto fail;
  97         }
  98         memset(priv, 0, sizeof(*priv));
  99         priv->key_idx = key_idx;
 100
 101         priv->tfm = crypto_alloc_tfm("aes", 0);
 102         if (priv->tfm == NULL) {
 103                 printk(KERN_DEBUG "hostap_crypt_ccmp: could not allocate "
 104                        "crypto API aes\n");
 105                 goto fail;
 106         }
 107
 108         return priv;
 109
 110 fail:
 111         if (priv) {
 112                 if (priv->tfm)
 113                         crypto_free_tfm(priv->tfm);
 114                 kfree(priv);
 115         }
 116         module_put(THIS_MODULE);
 117         return NULL;
 118 }
 119
 120
 121 static void hostap_ccmp_deinit(void *priv)
 122 {
 123         struct hostap_ccmp_data *_priv = priv;
 124         if (_priv && _priv->tfm)
 125                 crypto_free_tfm(_priv->tfm);
 126         kfree(priv);
 127         module_put(THIS_MODULE);
 128 }
 129
 130
 131 static inline void xor_block(u8 *b, u8 *a, size_t len)
 132 {
 133         int i;
 134         for (i = 0; i < len; i++)
 135                 b[i] ^= a[i];
 136 }
 137
 138
 139 static void ccmp_init_blocks(struct crypto_tfm *tfm,
 140                              struct hostap_ieee80211_hdr *hdr,
 141                              u8 *pn, size_t dlen, u8 *b0, u8 *auth,
 142                              u8 *s0)
 143 {
 144         u8 *pos, qc = 0;
 145         size_t aad_len;
 146         u16 fc;
 147         int a4_included, qc_included;
 148         u8 aad[2 * AES_BLOCK_LEN];
 149
 150         fc = le16_to_cpu(hdr->frame_control);
 151         a4_included = ((fc & (WLAN_FC_TODS | WLAN_FC_FROMDS)) ==
 152                        (WLAN_FC_TODS | WLAN_FC_FROMDS));
 153         qc_included = ((WLAN_FC_GET_TYPE(fc) == WLAN_FC_TYPE_DATA) &&
 154                        (WLAN_FC_GET_STYPE(fc) & 0x08));
 155         aad_len = 22;
 156         if (a4_included)
 157                 aad_len += 6;
 158         if (qc_included) {
 159                 pos = (u8 *) &hdr->addr4;
 160                 if (a4_included)
 161                         pos += 6;
 162                 qc = *pos & 0x0f;
 163                 aad_len += 2;
 164         }
 165
 166         /* CCM Initial Block:
 167          * Flag (Include authentication header, M=3 (8-octet MIC),
 168          *       L=1 (2-octet Dlen))
 169          * Nonce: 0x00 | A2 | PN
 170          * Dlen */
 171         b0[0] = 0x59;
 172         b0[1] = qc;
 173         memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 174         memcpy(b0 + 8, pn, CCMP_PN_LEN);
 175         b0[14] = (dlen >> 8) & 0xff;
 176         b0[15] = dlen & 0xff;
 177
 178         /* AAD:
 179          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 180          * A1 | A2 | A3
 181          * SC with bits 4..15 (seq#) masked to zero
 182          * A4 (if present)
 183          * QC (if present)
 184          */
 185         pos = (u8 *) hdr;
 186         aad[0] = 0; /* aad_len >> 8 */
 187         aad[1] = aad_len & 0xff;
 188         aad[2] = pos[0] & 0x8f;
 189         aad[3] = pos[1] & 0xc7;
 190         memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 191         pos = (u8 *) &hdr->seq_ctrl;
 192         aad[22] = pos[0] & 0x0f;
 193         aad[23] = 0; /* all bits masked */
 194         memset(aad + 24, 0, 8);
 195         if (a4_included)
 196                 memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 197         if (qc_included) {
 198                 aad[a4_included ? 30 : 24] = qc;
 199                 /* rest of QC masked */
 200         }
 201
 202         /* Start with the first block and AAD */
 203         hostap_ccmp_aes_encrypt(tfm, b0, auth);
 204         xor_block(auth, aad, AES_BLOCK_LEN);
 205         hostap_ccmp_aes_encrypt(tfm, auth, auth);
 206         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 207         hostap_ccmp_aes_encrypt(tfm, auth, auth);
 208         b0[0] &= 0x07;
 209         b0[14] = b0[15] = 0;
 210         hostap_ccmp_aes_encrypt(tfm, b0, s0);
 211 }
 212
 213
 214 static int hostap_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 215 {
 216         struct hostap_ccmp_data *key = priv;
 217         int data_len, i, blocks, last, len;
 218         u8 *pos, *mic;
 219         struct hostap_ieee80211_hdr *hdr;
 220         u8 *b0 = key->tx_b0;
 221         u8 *b = key->tx_b;
 222         u8 *e = key->tx_e;
 223         u8 *s0 = key->tx_s0;
 224
 225         if (skb_headroom(skb) < CCMP_HDR_LEN ||
 226             skb_tailroom(skb) < CCMP_MIC_LEN ||
 227             skb->len < hdr_len)
 228                 return -1;
 229
 230         data_len = skb->len - hdr_len;
 231         pos = skb_push(skb, CCMP_HDR_LEN);
 232         memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 233         pos += hdr_len;
 234         mic = skb_put(skb, CCMP_MIC_LEN);
 235
 236         i = CCMP_PN_LEN - 1;
 237         while (i >= 0) {
 238                 key->tx_pn[i]++;
 239                 if (key->tx_pn[i] != 0)
 240                         break;
 241                 i--;
 242         }
 243
 244         *pos++ = key->tx_pn[5];
 245         *pos++ = key->tx_pn[4];
 246         *pos++ = 0;
 247         *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */;
 248         *pos++ = key->tx_pn[3];
 249         *pos++ = key->tx_pn[2];
 250         *pos++ = key->tx_pn[1];
 251         *pos++ = key->tx_pn[0];
 252
 253         hdr = (struct hostap_ieee80211_hdr *) skb->data;
 254         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 255
 256         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 257         last = data_len % AES_BLOCK_LEN;
 258
 259         for (i = 1; i <= blocks; i++) {
 260                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 261                 /* Authentication */
 262                 xor_block(b, pos, len);
 263                 hostap_ccmp_aes_encrypt(key->tfm, b, b);
 264                 /* Encryption, with counter */
 265                 b0[14] = (i >> 8) & 0xff;
 266                 b0[15] = i & 0xff;
 267                 hostap_ccmp_aes_encrypt(key->tfm, b0, e);
 268                 xor_block(pos, e, len);
 269                 pos += len;
 270         }
 271
 272         for (i = 0; i < CCMP_MIC_LEN; i++)
 273                 mic[i] = b[i] ^ s0[i];
 274
 275         return 0;
 276 }
 277
 278
 279 static int hostap_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 280 {
 281         struct hostap_ccmp_data *key = priv;
 282         u8 keyidx, *pos;
 283         struct hostap_ieee80211_hdr *hdr;
 284         u8 *b0 = key->rx_b0;
 285         u8 *b = key->rx_b;
 286         u8 *a = key->rx_a;
 287         u8 pn[6];
 288         int i, blocks, last, len;
 289         size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 290         u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 291
 292         if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 293                 key->dot11RSNAStatsCCMPFormatErrors++;
 294                 return -1;
 295         }
 296
 297         hdr = (struct hostap_ieee80211_hdr *) skb->data;
 298         pos = skb->data + hdr_len;
 299         keyidx = pos[3];
 300         if (!(keyidx & (1 << 5))) {
 301                 if (net_ratelimit()) {
 302                         printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 303                                " flag from " MACSTR "\n", MAC2STR(hdr->addr2));
 304                 }
 305                 key->dot11RSNAStatsCCMPFormatErrors++;
 306                 return -2;
 307         }
 308         keyidx >>= 6;
 309         if (key->key_idx != keyidx) {
 310                 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 311                        "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 312                 return -6;
 313         }
 314         if (!key->key_set) {
 315                 if (net_ratelimit()) {
 316                         printk(KERN_DEBUG "CCMP: received packet from " MACSTR
 317                                " with keyid=%d that does not have a configured"
 318                                " key\n", MAC2STR(hdr->addr2), keyidx);
 319                 }
 320                 return -3;
 321         }
 322
 323         pn[0] = pos[7];
 324         pn[1] = pos[6];
 325         pn[2] = pos[5];
 326         pn[3] = pos[4];
 327         pn[4] = pos[1];
 328         pn[5] = pos[0];
 329         pos += 8;
 330
 331         if (memcmp(pn, key->rx_pn, CCMP_PN_LEN) <= 0) {
 332                 if (net_ratelimit()) {
 333                         printk(KERN_DEBUG "CCMP: replay detected: STA=" MACSTR
 334                                " previous PN %02x%02x%02x%02x%02x%02x "
 335                                "received PN %02x%02x%02x%02x%02x%02x\n",
 336                                MAC2STR(hdr->addr2), MAC2STR(key->rx_pn),
 337                                MAC2STR(pn));
 338                 }
 339                 key->dot11RSNAStatsCCMPReplays++;
 340                 return -4;
 341         }
 342
 343         ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 344         xor_block(mic, b, CCMP_MIC_LEN);
 345
 346         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 347         last = data_len % AES_BLOCK_LEN;
 348
 349         for (i = 1; i <= blocks; i++) {
 350                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 351                 /* Decrypt, with counter */
 352                 b0[14] = (i >> 8) & 0xff;
 353                 b0[15] = i & 0xff;
 354                 hostap_ccmp_aes_encrypt(key->tfm, b0, b);
 355                 xor_block(pos, b, len);
 356                 /* Authentication */
 357                 xor_block(a, pos, len);
 358                 hostap_ccmp_aes_encrypt(key->tfm, a, a);
 359                 pos += len;
 360         }
 361
 362         if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 363                 if (net_ratelimit()) {
 364                         printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 365                                MACSTR "\n", MAC2STR(hdr->addr2));
 366                 }
 367                 key->dot11RSNAStatsCCMPDecryptErrors++;
 368                 return -5;
 369         }
 370
 371         memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 372
 373         /* Remove hdr and MIC */
 374         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 375         skb_pull(skb, CCMP_HDR_LEN);
 376         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 377
 378         return keyidx;
 379 }
 380
 381
 382 static int hostap_ccmp_set_key(void *key, int len, u8 *seq, void *priv)
 383 {
 384         struct hostap_ccmp_data *data = priv;
 385         int keyidx;
 386         struct crypto_tfm *tfm = data->tfm;
 387
 388         keyidx = data->key_idx;
 389         memset(data, 0, sizeof(*data));
 390         data->key_idx = keyidx;
 391         data->tfm = tfm;
 392         if (len == CCMP_TK_LEN) {
 393                 memcpy(data->key, key, CCMP_TK_LEN);
 394                 data->key_set = 1;
 395                 if (seq) {
 396                         data->rx_pn[0] = seq[5];
 397                         data->rx_pn[1] = seq[4];
 398                         data->rx_pn[2] = seq[3];
 399                         data->rx_pn[3] = seq[2];
 400                         data->rx_pn[4] = seq[1];
 401                         data->rx_pn[5] = seq[0];
 402                 }
 403                 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 404         } else if (len == 0) {
 405                 data->key_set = 0;
 406         } else
 407                 return -1;
 408
 409         return 0;
 410 }
 411
 412
 413 static int hostap_ccmp_get_key(void *key, int len, u8 *seq, void *priv)
 414 {
 415         struct hostap_ccmp_data *data = priv;
 416
 417         if (len < CCMP_TK_LEN)
 418                 return -1;
 419
 420         if (!data->key_set)
 421                 return 0;
 422         memcpy(key, data->key, CCMP_TK_LEN);
 423
 424         if (seq) {
 425                 seq[0] = data->tx_pn[5];
 426                 seq[1] = data->tx_pn[4];
 427                 seq[2] = data->tx_pn[3];
 428                 seq[3] = data->tx_pn[2];
 429                 seq[4] = data->tx_pn[1];
 430                 seq[5] = data->tx_pn[0];
 431         }
 432
 433         return CCMP_TK_LEN;
 434 }
 435
 436
 437 static char * hostap_ccmp_print_stats(char *p, void *priv)
 438 {
 439         struct hostap_ccmp_data *ccmp = priv;
 440         p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 441                      "tx_pn=%02x%02x%02x%02x%02x%02x "
 442                      "rx_pn=%02x%02x%02x%02x%02x%02x "
 443                      "format_errors=%d replays=%d decrypt_errors=%d\n",
 444                      ccmp->key_idx, ccmp->key_set,
 445                      MAC2STR(ccmp->tx_pn), MAC2STR(ccmp->rx_pn),
 446                      ccmp->dot11RSNAStatsCCMPFormatErrors,
 447                      ccmp->dot11RSNAStatsCCMPReplays,
 448                      ccmp->dot11RSNAStatsCCMPDecryptErrors);
 449
 450         return p;
 451 }
 452
 453
 454 static struct hostap_crypto_ops hostap_crypt_ccmp = {
 455         .name                   = "CCMP",
 456         .init                   = hostap_ccmp_init,
 457         .deinit                 = hostap_ccmp_deinit,
 458         .encrypt_mpdu           = hostap_ccmp_encrypt,
 459         .decrypt_mpdu           = hostap_ccmp_decrypt,
 460         .encrypt_msdu           = NULL,
 461         .decrypt_msdu           = NULL,
 462         .set_key                = hostap_ccmp_set_key,
 463         .get_key                = hostap_ccmp_get_key,
 464         .print_stats            = hostap_ccmp_print_stats,
 465         .extra_prefix_len       = CCMP_HDR_LEN,
 466         .extra_postfix_len      = CCMP_MIC_LEN
 467 };
 468
 469
 470 static int __init hostap_crypto_ccmp_init(void)
 471 {
 472         if (hostap_register_crypto_ops(&hostap_crypt_ccmp) < 0)
 473                 return -1;
 474
 475         return 0;
 476 }
 477
 478
 479 static void __exit hostap_crypto_ccmp_exit(void)
 480 {
 481         hostap_unregister_crypto_ops(&hostap_crypt_ccmp);
 482 }
 483
 484
 485 module_init(hostap_crypto_ccmp_init);
 486 module_exit(hostap_crypto_ccmp_exit);