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 <j@w1.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/kernel.h>
  13 #include <linux/err.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 <asm/string.h>
  23 #include <linux/wireless.h>
  24
  25 #include <net/ieee80211.h>
  26
  27 #include <linux/crypto.h>
  28 #include <asm/scatterlist.h>
  29
  30 MODULE_AUTHOR("Jouni Malinen");
  31 MODULE_DESCRIPTION("Host AP crypt: CCMP");
  32 MODULE_LICENSE("GPL");
  33
  34 #define AES_BLOCK_LEN 16
  35 #define CCMP_HDR_LEN 8
  36 #define CCMP_MIC_LEN 8
  37 #define CCMP_TK_LEN 16
  38 #define CCMP_PN_LEN 6
  39
  40 struct ieee80211_ccmp_data {
  41         u8 key[CCMP_TK_LEN];
  42         int key_set;
  43
  44         u8 tx_pn[CCMP_PN_LEN];
  45         u8 rx_pn[CCMP_PN_LEN];
  46
  47         u32 dot11RSNAStatsCCMPFormatErrors;
  48         u32 dot11RSNAStatsCCMPReplays;
  49         u32 dot11RSNAStatsCCMPDecryptErrors;
  50
  51         int key_idx;
  52
  53         struct crypto_cipher *tfm;
  54
  55         /* scratch buffers for virt_to_page() (crypto API) */
  56         u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
  57             tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
  58         u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  59 };
  60
  61 static inline void ieee80211_ccmp_aes_encrypt(struct crypto_cipher *tfm,
  62                                               const u8 pt[16], u8 ct[16])
  63 {
  64         crypto_cipher_encrypt_one(tfm, ct, pt);
  65 }
  66
  67 static void *ieee80211_ccmp_init(int key_idx)
  68 {
  69         struct ieee80211_ccmp_data *priv;
  70
  71         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  72         if (priv == NULL)
  73                 goto fail;
  74         priv->key_idx = key_idx;
  75
  76         priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
  77         if (IS_ERR(priv->tfm)) {
  78                 printk(KERN_DEBUG "ieee80211_crypt_ccmp: could not allocate "
  79                        "crypto API aes\n");
  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 ieee80211_ccmp_deinit(void *priv)
  97 {
  98         struct ieee80211_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_4addr *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         u16 fc;
 118         int a4_included, qc_included;
 119         u8 aad[2 * AES_BLOCK_LEN];
 120
 121         fc = le16_to_cpu(hdr->frame_ctl);
 122         a4_included = ((fc & (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) ==
 123                        (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS));
 124         qc_included = ((WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
 125                        (WLAN_FC_GET_STYPE(fc) & IEEE80211_STYPE_QOS_DATA));
 126         aad_len = 22;
 127         if (a4_included)
 128                 aad_len += 6;
 129         if (qc_included) {
 130                 pos = (u8 *) & hdr->addr4;
 131                 if (a4_included)
 132                         pos += 6;
 133                 qc = *pos & 0x0f;
 134                 aad_len += 2;
 135         }
 136
 137         /* CCM Initial Block:
 138          * Flag (Include authentication header, M=3 (8-octet MIC),
 139          *       L=1 (2-octet Dlen))
 140          * Nonce: 0x00 | A2 | PN
 141          * Dlen */
 142         b0[0] = 0x59;
 143         b0[1] = qc;
 144         memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 145         memcpy(b0 + 8, pn, CCMP_PN_LEN);
 146         b0[14] = (dlen >> 8) & 0xff;
 147         b0[15] = dlen & 0xff;
 148
 149         /* AAD:
 150          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 151          * A1 | A2 | A3
 152          * SC with bits 4..15 (seq#) masked to zero
 153          * A4 (if present)
 154          * QC (if present)
 155          */
 156         pos = (u8 *) hdr;
 157         aad[0] = 0;             /* aad_len >> 8 */
 158         aad[1] = aad_len & 0xff;
 159         aad[2] = pos[0] & 0x8f;
 160         aad[3] = pos[1] & 0xc7;
 161         memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 162         pos = (u8 *) & hdr->seq_ctl;
 163         aad[22] = pos[0] & 0x0f;
 164         aad[23] = 0;            /* all bits masked */
 165         memset(aad + 24, 0, 8);
 166         if (a4_included)
 167                 memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 168         if (qc_included) {
 169                 aad[a4_included ? 30 : 24] = qc;
 170                 /* rest of QC masked */
 171         }
 172
 173         /* Start with the first block and AAD */
 174         ieee80211_ccmp_aes_encrypt(tfm, b0, auth);
 175         xor_block(auth, aad, AES_BLOCK_LEN);
 176         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 177         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 178         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 179         b0[0] &= 0x07;
 180         b0[14] = b0[15] = 0;
 181         ieee80211_ccmp_aes_encrypt(tfm, b0, s0);
 182 }
 183
 184 static int ieee80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
 185                               u8 *aeskey, int keylen, void *priv)
 186 {
 187         struct ieee80211_ccmp_data *key = priv;
 188         int i;
 189         u8 *pos;
 190
 191         if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
 192                 return -1;
 193
 194         if (aeskey != NULL && keylen >= CCMP_TK_LEN)
 195                 memcpy(aeskey, key->key, CCMP_TK_LEN);
 196
 197         pos = skb_push(skb, CCMP_HDR_LEN);
 198         memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 199         pos += hdr_len;
 200
 201         i = CCMP_PN_LEN - 1;
 202         while (i >= 0) {
 203                 key->tx_pn[i]++;
 204                 if (key->tx_pn[i] != 0)
 205                         break;
 206                 i--;
 207         }
 208
 209         *pos++ = key->tx_pn[5];
 210         *pos++ = key->tx_pn[4];
 211         *pos++ = 0;
 212         *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
 213         *pos++ = key->tx_pn[3];
 214         *pos++ = key->tx_pn[2];
 215         *pos++ = key->tx_pn[1];
 216         *pos++ = key->tx_pn[0];
 217
 218         return CCMP_HDR_LEN;
 219 }
 220
 221 static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 222 {
 223         struct ieee80211_ccmp_data *key = priv;
 224         int data_len, i, blocks, last, len;
 225         u8 *pos, *mic;
 226         struct ieee80211_hdr_4addr *hdr;
 227         u8 *b0 = key->tx_b0;
 228         u8 *b = key->tx_b;
 229         u8 *e = key->tx_e;
 230         u8 *s0 = key->tx_s0;
 231
 232         if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
 233                 return -1;
 234
 235         data_len = skb->len - hdr_len;
 236         len = ieee80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
 237         if (len < 0)
 238                 return -1;
 239
 240         pos = skb->data + hdr_len + CCMP_HDR_LEN;
 241         mic = skb_put(skb, CCMP_MIC_LEN);
 242         hdr = (struct ieee80211_hdr_4addr *)skb->data;
 243         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 244
 245         blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 246         last = data_len % AES_BLOCK_LEN;
 247
 248         for (i = 1; i <= blocks; i++) {
 249                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 250                 /* Authentication */
 251                 xor_block(b, pos, len);
 252                 ieee80211_ccmp_aes_encrypt(key->tfm, b, b);
 253                 /* Encryption, with counter */
 254                 b0[14] = (i >> 8) & 0xff;
 255                 b0[15] = i & 0xff;
 256                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);
 257                 xor_block(pos, e, len);
 258                 pos += len;
 259         }
 260
 261         for (i = 0; i < CCMP_MIC_LEN; i++)
 262                 mic[i] = b[i] ^ s0[i];
 263
 264         return 0;
 265 }
 266
 267 /*
 268  * deal with seq counter wrapping correctly.
 269  * refer to timer_after() for jiffies wrapping handling
 270  */
 271 static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
 272 {
 273         u32 iv32_n, iv16_n;
 274         u32 iv32_o, iv16_o;
 275
 276         iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
 277         iv16_n = (pn_n[4] << 8) | pn_n[5];
 278
 279         iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
 280         iv16_o = (pn_o[4] << 8) | pn_o[5];
 281
 282         if ((s32)iv32_n - (s32)iv32_o < 0 ||
 283             (iv32_n == iv32_o && iv16_n <= iv16_o))
 284                 return 1;
 285         return 0;
 286 }
 287
 288 static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 289 {
 290         struct ieee80211_ccmp_data *key = priv;
 291         u8 keyidx, *pos;
 292         struct ieee80211_hdr_4addr *hdr;
 293         u8 *b0 = key->rx_b0;
 294         u8 *b = key->rx_b;
 295         u8 *a = key->rx_a;
 296         u8 pn[6];
 297         int i, blocks, last, len;
 298         size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 299         u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 300         DECLARE_MAC_BUF(mac);
 301
 302         if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 303                 key->dot11RSNAStatsCCMPFormatErrors++;
 304                 return -1;
 305         }
 306
 307         hdr = (struct ieee80211_hdr_4addr *)skb->data;
 308         pos = skb->data + hdr_len;
 309         keyidx = pos[3];
 310         if (!(keyidx & (1 << 5))) {
 311                 if (net_ratelimit()) {
 312                         printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 313                                " flag from %s\n", print_mac(mac, hdr->addr2));
 314                 }
 315                 key->dot11RSNAStatsCCMPFormatErrors++;
 316                 return -2;
 317         }
 318         keyidx >>= 6;
 319         if (key->key_idx != keyidx) {
 320                 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 321                        "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 322                 return -6;
 323         }
 324         if (!key->key_set) {
 325                 if (net_ratelimit()) {
 326                         printk(KERN_DEBUG "CCMP: received packet from %s"
 327                                " with keyid=%d that does not have a configured"
 328                                " key\n", print_mac(mac, hdr->addr2), keyidx);
 329                 }
 330                 return -3;
 331         }
 332
 333         pn[0] = pos[7];
 334         pn[1] = pos[6];
 335         pn[2] = pos[5];
 336         pn[3] = pos[4];
 337         pn[4] = pos[1];
 338         pn[5] = pos[0];
 339         pos += 8;
 340
 341         if (ccmp_replay_check(pn, key->rx_pn)) {
 342                 if (net_ratelimit()) {
 343                         IEEE80211_DEBUG_DROP("CCMP: replay detected: STA=%s "
 344                                  "previous PN %02x%02x%02x%02x%02x%02x "
 345                                  "received PN %02x%02x%02x%02x%02x%02x\n",
 346                                  print_mac(mac, hdr->addr2),
 347                                  key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
 348                                  key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
 349                                  pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
 350                 }
 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                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);
 367                 xor_block(pos, b, len);
 368                 /* Authentication */
 369                 xor_block(a, pos, len);
 370                 ieee80211_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                                "%s\n", print_mac(mac, 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 ieee80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 394 {
 395         struct ieee80211_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 ieee80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 424 {
 425         struct ieee80211_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 *ieee80211_ccmp_print_stats(char *p, void *priv)
 447 {
 448         struct ieee80211_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 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);