net/ieee80211/ieee80211_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/module.h>
  13 #include <linux/init.h>
  14 #include <linux/slab.h>
  15 #include <linux/random.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/if_ether.h>
  19 #include <linux/if_arp.h>
  20 #include <asm/string.h>
  21 #include <linux/wireless.h>
  22
  23 #include <net/ieee80211.h>
  24
  25 #include <linux/crypto.h>
  26 #include <asm/scatterlist.h>
  27
  28 MODULE_AUTHOR("Jouni Malinen");
  29 MODULE_DESCRIPTION("Host AP crypt: CCMP");
  30 MODULE_LICENSE("GPL");
  31
  32 #define AES_BLOCK_LEN 16
  33 #define CCMP_HDR_LEN 8
  34 #define CCMP_MIC_LEN 8
  35 #define CCMP_TK_LEN 16
  36 #define CCMP_PN_LEN 6
  37
  38 struct ieee80211_ccmp_data {
  39         u8 key[CCMP_TK_LEN];
  40         int key_set;
  41
  42         u8 tx_pn[CCMP_PN_LEN];
  43         u8 rx_pn[CCMP_PN_LEN];
  44
  45         u32 dot11RSNAStatsCCMPFormatErrors;
  46         u32 dot11RSNAStatsCCMPReplays;
  47         u32 dot11RSNAStatsCCMPDecryptErrors;
  48
  49         int key_idx;
  50
  51         struct crypto_tfm *tfm;
  52
  53         /* scratch buffers for virt_to_page() (crypto API) */
  54         u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
  55             tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
  56         u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  57 };
  58
  59 static void ieee80211_ccmp_aes_encrypt(struct crypto_tfm *tfm,
  60                                        const u8 pt[16], u8 ct[16])
  61 {
  62         struct scatterlist src, dst;
  63
  64         src.page = virt_to_page(pt);
  65         src.offset = offset_in_page(pt);
  66         src.length = AES_BLOCK_LEN;
  67
  68         dst.page = virt_to_page(ct);
  69         dst.offset = offset_in_page(ct);
  70         dst.length = AES_BLOCK_LEN;
  71
  72         crypto_cipher_encrypt(tfm, &dst, &src, AES_BLOCK_LEN);
  73 }
  74
  75 static void *ieee80211_ccmp_init(int key_idx)
  76 {
  77         struct ieee80211_ccmp_data *priv;
  78
  79         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  80         if (priv == NULL)
  81                 goto fail;
  82         priv->key_idx = key_idx;
  83
  84         priv->tfm = crypto_alloc_tfm("aes", 0);
  85         if (priv->tfm == NULL) {
  86                 printk(KERN_DEBUG "ieee80211_crypt_ccmp: could not allocate "
  87                        "crypto API aes\n");
  88                 goto fail;
  89         }
  90
  91         return priv;
  92
  93       fail:
  94         if (priv) {
  95                 if (priv->tfm)
  96                         crypto_free_tfm(priv->tfm);
  97                 kfree(priv);
  98         }
  99
 100         return NULL;
 101 }
 102
 103 static void ieee80211_ccmp_deinit(void *priv)
 104 {
 105         struct ieee80211_ccmp_data *_priv = priv;
 106         if (_priv && _priv->tfm)
 107                 crypto_free_tfm(_priv->tfm);
 108         kfree(priv);
 109 }
 110
 111 static inline void xor_block(u8 * b, u8 * a, size_t len)
 112 {
 113         int i;
 114         for (i = 0; i < len; i++)
 115                 b[i] ^= a[i];
 116 }
 117
 118 static void ccmp_init_blocks(struct crypto_tfm *tfm,
 119                              struct ieee80211_hdr_4addr *hdr,
 120                              u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0)
 121 {
 122         u8 *pos, qc = 0;
 123         size_t aad_len;
 124         u16 fc;
 125         int a4_included, qc_included;
 126         u8 aad[2 * AES_BLOCK_LEN];
 127
 128         fc = le16_to_cpu(hdr->frame_ctl);
 129         a4_included = ((fc & (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) ==
 130                        (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS));
 131         qc_included = ((WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
 132                        (WLAN_FC_GET_STYPE(fc) & IEEE80211_STYPE_QOS_DATA));
 133         aad_len = 22;
 134         if (a4_included)
 135                 aad_len += 6;
 136         if (qc_included) {
 137                 pos = (u8 *) & hdr->addr4;
 138                 if (a4_included)
 139                         pos += 6;
 140                 qc = *pos & 0x0f;
 141                 aad_len += 2;
 142         }
 143
 144         /* CCM Initial Block:
 145          * Flag (Include authentication header, M=3 (8-octet MIC),
 146          *       L=1 (2-octet Dlen))
 147          * Nonce: 0x00 | A2 | PN
 148          * Dlen */
 149         b0[0] = 0x59;
 150         b0[1] = qc;
 151         memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 152         memcpy(b0 + 8, pn, CCMP_PN_LEN);
 153         b0[14] = (dlen >> 8) & 0xff;
 154         b0[15] = dlen & 0xff;
 155
 156         /* AAD:
 157          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 158          * A1 | A2 | A3
 159          * SC with bits 4..15 (seq#) masked to zero
 160          * A4 (if present)
 161          * QC (if present)
 162          */
 163         pos = (u8 *) hdr;
 164         aad[0] = 0;             /* aad_len >> 8 */
 165         aad[1] = aad_len & 0xff;
 166         aad[2] = pos[0] & 0x8f;
 167         aad[3] = pos[1] & 0xc7;
 168         memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 169         pos = (u8 *) & hdr->seq_ctl;
 170         aad[22] = pos[0] & 0x0f;
 171         aad[23] = 0;            /* all bits masked */
 172         memset(aad + 24, 0, 8);
 173         if (a4_included)
 174                 memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 175         if (qc_included) {
 176                 aad[a4_included ? 30 : 24] = qc;
 177                 /* rest of QC masked */
 178         }
 179
 180         /* Start with the first block and AAD */
 181         ieee80211_ccmp_aes_encrypt(tfm, b0, auth);
 182         xor_block(auth, aad, AES_BLOCK_LEN);
 183         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 184         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 185         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 186         b0[0] &= 0x07;
 187         b0[14] = b0[15] = 0;
 188         ieee80211_ccmp_aes_encrypt(tfm, b0, s0);
 189 }
 190
 191 static int ieee80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
 192                               u8 *aeskey, int keylen, void *priv)
 193 {
 194         struct ieee80211_ccmp_data *key = priv;
 195         int i;
 196         u8 *pos;
 197
 198         if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
 199                 return -1;
 200
 201         if (aeskey != NULL && keylen >= CCMP_TK_LEN)
 202                 memcpy(aeskey, key->key, CCMP_TK_LEN);
 203
 204         pos = skb_push(skb, CCMP_HDR_LEN);
 205         memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 206         pos += hdr_len;
 207
 208         i = CCMP_PN_LEN - 1;
 209         while (i >= 0) {
 210                 key->tx_pn[i]++;
 211                 if (key->tx_pn[i] != 0)
 212                         break;
 213                 i--;
 214         }
 215
 216         *pos++ = key->tx_pn[5];
 217         *pos++ = key->tx_pn[4];
 218         *pos++ = 0;
 219         *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
 220         *pos++ = key->tx_pn[3];
 221         *pos++ = key->tx_pn[2];
 222         *pos++ = key->tx_pn[1];
 223         *pos++ = key->tx_pn[0];
 224
 225         return CCMP_HDR_LEN;
 226 }
 227
 228 static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 229 {
 230         struct ieee80211_ccmp_data *key = priv;
 231         int data_len, i, blocks, last, len;
 232         u8 *pos, *mic;
 233         struct ieee80211_hdr_4addr *hdr;
 234         u8 *b0 = key->tx_b0;
 235         u8 *b = key->tx_b;
 236         u8 *e = key->tx_e;
 237         u8 *s0 = key->tx_s0;
 238
 239         if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
 240                 return -1;
 241
 242         data_len = skb->len - hdr_len;
 243         len = ieee80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
 244         if (len < 0)
 245                 return -1;
 246
 247         pos = skb->data + hdr_len + CCMP_HDR_LEN;
 248         mic = skb_put(skb, CCMP_MIC_LEN);
 249         hdr = (struct ieee80211_hdr_4addr *)skb->data;
 250         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 251
 252         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 253         last = data_len % AES_BLOCK_LEN;
 254
 255         for (i = 1; i <= blocks; i++) {
 256                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 257                 /* Authentication */
 258                 xor_block(b, pos, len);
 259                 ieee80211_ccmp_aes_encrypt(key->tfm, b, b);
 260                 /* Encryption, with counter */
 261                 b0[14] = (i >> 8) & 0xff;
 262                 b0[15] = i & 0xff;
 263                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);
 264                 xor_block(pos, e, len);
 265                 pos += len;
 266         }
 267
 268         for (i = 0; i < CCMP_MIC_LEN; i++)
 269                 mic[i] = b[i] ^ s0[i];
 270
 271         return 0;
 272 }
 273
 274 /*
 275  * deal with seq counter wrapping correctly.
 276  * refer to timer_after() for jiffies wrapping handling
 277  */
 278 static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
 279 {
 280         u32 iv32_n, iv16_n;
 281         u32 iv32_o, iv16_o;
 282
 283         iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
 284         iv16_n = (pn_n[4] << 8) | pn_n[5];
 285
 286         iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
 287         iv16_o = (pn_o[4] << 8) | pn_o[5];
 288
 289         if ((s32)iv32_n - (s32)iv32_o < 0 ||
 290             (iv32_n == iv32_o && iv16_n <= iv16_o))
 291                 return 1;
 292         return 0;
 293 }
 294
 295 static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 296 {
 297         struct ieee80211_ccmp_data *key = priv;
 298         u8 keyidx, *pos;
 299         struct ieee80211_hdr_4addr *hdr;
 300         u8 *b0 = key->rx_b0;
 301         u8 *b = key->rx_b;
 302         u8 *a = key->rx_a;
 303         u8 pn[6];
 304         int i, blocks, last, len;
 305         size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 306         u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 307
 308         if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 309                 key->dot11RSNAStatsCCMPFormatErrors++;
 310                 return -1;
 311         }
 312
 313         hdr = (struct ieee80211_hdr_4addr *)skb->data;
 314         pos = skb->data + hdr_len;
 315         keyidx = pos[3];
 316         if (!(keyidx & (1 << 5))) {
 317                 if (net_ratelimit()) {
 318                         printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 319                                " flag from " MAC_FMT "\n", MAC_ARG(hdr->addr2));
 320                 }
 321                 key->dot11RSNAStatsCCMPFormatErrors++;
 322                 return -2;
 323         }
 324         keyidx >>= 6;
 325         if (key->key_idx != keyidx) {
 326                 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 327                        "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 328                 return -6;
 329         }
 330         if (!key->key_set) {
 331                 if (net_ratelimit()) {
 332                         printk(KERN_DEBUG "CCMP: received packet from " MAC_FMT
 333                                " with keyid=%d that does not have a configured"
 334                                " key\n", MAC_ARG(hdr->addr2), keyidx);
 335                 }
 336                 return -3;
 337         }
 338
 339         pn[0] = pos[7];
 340         pn[1] = pos[6];
 341         pn[2] = pos[5];
 342         pn[3] = pos[4];
 343         pn[4] = pos[1];
 344         pn[5] = pos[0];
 345         pos += 8;
 346
 347         if (ccmp_replay_check(pn, key->rx_pn)) {
 348                 if (net_ratelimit()) {
 349                         printk(KERN_DEBUG "CCMP: replay detected: STA=" MAC_FMT
 350                                " previous PN %02x%02x%02x%02x%02x%02x "
 351                                "received PN %02x%02x%02x%02x%02x%02x\n",
 352                                MAC_ARG(hdr->addr2), MAC_ARG(key->rx_pn),
 353                                MAC_ARG(pn));
 354                 }
 355                 key->dot11RSNAStatsCCMPReplays++;
 356                 return -4;
 357         }
 358
 359         ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 360         xor_block(mic, b, CCMP_MIC_LEN);
 361
 362         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 363         last = data_len % AES_BLOCK_LEN;
 364
 365         for (i = 1; i <= blocks; i++) {
 366                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 367                 /* Decrypt, with counter */
 368                 b0[14] = (i >> 8) & 0xff;
 369                 b0[15] = i & 0xff;
 370                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);
 371                 xor_block(pos, b, len);
 372                 /* Authentication */
 373                 xor_block(a, pos, len);
 374                 ieee80211_ccmp_aes_encrypt(key->tfm, a, a);
 375                 pos += len;
 376         }
 377
 378         if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 379                 if (net_ratelimit()) {
 380                         printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 381                                MAC_FMT "\n", MAC_ARG(hdr->addr2));
 382                 }
 383                 key->dot11RSNAStatsCCMPDecryptErrors++;
 384                 return -5;
 385         }
 386
 387         memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 388
 389         /* Remove hdr and MIC */
 390         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 391         skb_pull(skb, CCMP_HDR_LEN);
 392         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 393
 394         return keyidx;
 395 }
 396
 397 static int ieee80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 398 {
 399         struct ieee80211_ccmp_data *data = priv;
 400         int keyidx;
 401         struct crypto_tfm *tfm = data->tfm;
 402
 403         keyidx = data->key_idx;
 404         memset(data, 0, sizeof(*data));
 405         data->key_idx = keyidx;
 406         data->tfm = tfm;
 407         if (len == CCMP_TK_LEN) {
 408                 memcpy(data->key, key, CCMP_TK_LEN);
 409                 data->key_set = 1;
 410                 if (seq) {
 411                         data->rx_pn[0] = seq[5];
 412                         data->rx_pn[1] = seq[4];
 413                         data->rx_pn[2] = seq[3];
 414                         data->rx_pn[3] = seq[2];
 415                         data->rx_pn[4] = seq[1];
 416                         data->rx_pn[5] = seq[0];
 417                 }
 418                 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 419         } else if (len == 0)
 420                 data->key_set = 0;
 421         else
 422                 return -1;
 423
 424         return 0;
 425 }
 426
 427 static int ieee80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 428 {
 429         struct ieee80211_ccmp_data *data = priv;
 430
 431         if (len < CCMP_TK_LEN)
 432                 return -1;
 433
 434         if (!data->key_set)
 435                 return 0;
 436         memcpy(key, data->key, CCMP_TK_LEN);
 437
 438         if (seq) {
 439                 seq[0] = data->tx_pn[5];
 440                 seq[1] = data->tx_pn[4];
 441                 seq[2] = data->tx_pn[3];
 442                 seq[3] = data->tx_pn[2];
 443                 seq[4] = data->tx_pn[1];
 444                 seq[5] = data->tx_pn[0];
 445         }
 446
 447         return CCMP_TK_LEN;
 448 }
 449
 450 static char *ieee80211_ccmp_print_stats(char *p, void *priv)
 451 {
 452         struct ieee80211_ccmp_data *ccmp = priv;
 453         p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 454                      "tx_pn=%02x%02x%02x%02x%02x%02x "
 455                      "rx_pn=%02x%02x%02x%02x%02x%02x "
 456                      "format_errors=%d replays=%d decrypt_errors=%d\n",
 457                      ccmp->key_idx, ccmp->key_set,
 458                      MAC_ARG(ccmp->tx_pn), MAC_ARG(ccmp->rx_pn),
 459                      ccmp->dot11RSNAStatsCCMPFormatErrors,
 460                      ccmp->dot11RSNAStatsCCMPReplays,
 461                      ccmp->dot11RSNAStatsCCMPDecryptErrors);
 462
 463         return p;
 464 }
 465
 466 static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {
 467         .name = "CCMP",
 468         .init = ieee80211_ccmp_init,
 469         .deinit = ieee80211_ccmp_deinit,
 470         .build_iv = ieee80211_ccmp_hdr,
 471         .encrypt_mpdu = ieee80211_ccmp_encrypt,
 472         .decrypt_mpdu = ieee80211_ccmp_decrypt,
 473         .encrypt_msdu = NULL,
 474         .decrypt_msdu = NULL,
 475         .set_key = ieee80211_ccmp_set_key,
 476         .get_key = ieee80211_ccmp_get_key,
 477         .print_stats = ieee80211_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 ieee80211_crypto_ccmp_init(void)
 484 {
 485         return ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp);
 486 }
 487
 488 static void __exit ieee80211_crypto_ccmp_exit(void)
 489 {
 490         ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);
 491 }
 492
 493 module_init(ieee80211_crypto_ccmp_init);
 494 module_exit(ieee80211_crypto_ccmp_exit);