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                 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         mic = skb_put(skb, CCMP_MIC_LEN);
 241         hdr = (struct ieee80211_hdr *)skb->data;
 242         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 243
 244         blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 245         last = data_len % AES_BLOCK_LEN;
 246
 247         for (i = 1; i <= blocks; i++) {
 248                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 249                 /* Authentication */
 250                 xor_block(b, pos, len);
 251                 lib80211_ccmp_aes_encrypt(key->tfm, b, b);
 252                 /* Encryption, with counter */
 253                 b0[14] = (i >> 8) & 0xff;
 254                 b0[15] = i & 0xff;
 255                 lib80211_ccmp_aes_encrypt(key->tfm, b0, e);
 256                 xor_block(pos, e, len);
 257                 pos += len;
 258         }
 259
 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                 if (net_ratelimit()) {
 341                         printk(KERN_DEBUG "CCMP: replay detected: STA=%pM "
 342                                  "previous PN %02x%02x%02x%02x%02x%02x "
 343                                  "received PN %02x%02x%02x%02x%02x%02x\n",
 344                                  hdr->addr2,
 345                                  key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
 346                                  key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
 347                                  pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
 348                 }
 349                 key->dot11RSNAStatsCCMPReplays++;
 350                 return -4;
 351         }
 352
 353         ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 354         xor_block(mic, b, CCMP_MIC_LEN);
 355
 356         blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 357         last = data_len % AES_BLOCK_LEN;
 358
 359         for (i = 1; i <= blocks; i++) {
 360                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 361                 /* Decrypt, with counter */
 362                 b0[14] = (i >> 8) & 0xff;
 363                 b0[15] = i & 0xff;
 364                 lib80211_ccmp_aes_encrypt(key->tfm, b0, b);
 365                 xor_block(pos, b, len);
 366                 /* Authentication */
 367                 xor_block(a, pos, len);
 368                 lib80211_ccmp_aes_encrypt(key->tfm, a, a);
 369                 pos += len;
 370         }
 371
 372         if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 373                 if (net_ratelimit()) {
 374                         printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 375                                "%pM\n", hdr->addr2);
 376                 }
 377                 key->dot11RSNAStatsCCMPDecryptErrors++;
 378                 return -5;
 379         }
 380
 381         memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 382
 383         /* Remove hdr and MIC */
 384         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 385         skb_pull(skb, CCMP_HDR_LEN);
 386         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 387
 388         return keyidx;
 389 }
 390
 391 static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 392 {
 393         struct lib80211_ccmp_data *data = priv;
 394         int keyidx;
 395         struct crypto_cipher *tfm = data->tfm;
 396
 397         keyidx = data->key_idx;
 398         memset(data, 0, sizeof(*data));
 399         data->key_idx = keyidx;
 400         data->tfm = tfm;
 401         if (len == CCMP_TK_LEN) {
 402                 memcpy(data->key, key, CCMP_TK_LEN);
 403                 data->key_set = 1;
 404                 if (seq) {
 405                         data->rx_pn[0] = seq[5];
 406                         data->rx_pn[1] = seq[4];
 407                         data->rx_pn[2] = seq[3];
 408                         data->rx_pn[3] = seq[2];
 409                         data->rx_pn[4] = seq[1];
 410                         data->rx_pn[5] = seq[0];
 411                 }
 412                 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 413         } else if (len == 0)
 414                 data->key_set = 0;
 415         else
 416                 return -1;
 417
 418         return 0;
 419 }
 420
 421 static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 422 {
 423         struct lib80211_ccmp_data *data = priv;
 424
 425         if (len < CCMP_TK_LEN)
 426                 return -1;
 427
 428         if (!data->key_set)
 429                 return 0;
 430         memcpy(key, data->key, CCMP_TK_LEN);
 431
 432         if (seq) {
 433                 seq[0] = data->tx_pn[5];
 434                 seq[1] = data->tx_pn[4];
 435                 seq[2] = data->tx_pn[3];
 436                 seq[3] = data->tx_pn[2];
 437                 seq[4] = data->tx_pn[1];
 438                 seq[5] = data->tx_pn[0];
 439         }
 440
 441         return CCMP_TK_LEN;
 442 }
 443
 444 static char *lib80211_ccmp_print_stats(char *p, void *priv)
 445 {
 446         struct lib80211_ccmp_data *ccmp = priv;
 447
 448         p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 449                      "tx_pn=%02x%02x%02x%02x%02x%02x "
 450                      "rx_pn=%02x%02x%02x%02x%02x%02x "
 451                      "format_errors=%d replays=%d decrypt_errors=%d\n",
 452                      ccmp->key_idx, ccmp->key_set,
 453                      ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
 454                      ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
 455                      ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
 456                      ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
 457                      ccmp->dot11RSNAStatsCCMPFormatErrors,
 458                      ccmp->dot11RSNAStatsCCMPReplays,
 459                      ccmp->dot11RSNAStatsCCMPDecryptErrors);
 460
 461         return p;
 462 }
 463
 464 static struct lib80211_crypto_ops lib80211_crypt_ccmp = {
 465         .name = "CCMP",
 466         .init = lib80211_ccmp_init,
 467         .deinit = lib80211_ccmp_deinit,
 468         .build_iv = lib80211_ccmp_hdr,
 469         .encrypt_mpdu = lib80211_ccmp_encrypt,
 470         .decrypt_mpdu = lib80211_ccmp_decrypt,
 471         .encrypt_msdu = NULL,
 472         .decrypt_msdu = NULL,
 473         .set_key = lib80211_ccmp_set_key,
 474         .get_key = lib80211_ccmp_get_key,
 475         .print_stats = lib80211_ccmp_print_stats,
 476         .extra_mpdu_prefix_len = CCMP_HDR_LEN,
 477         .extra_mpdu_postfix_len = CCMP_MIC_LEN,
 478         .owner = THIS_MODULE,
 479 };
 480
 481 static int __init lib80211_crypto_ccmp_init(void)
 482 {
 483         return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
 484 }
 485
 486 static void __exit lib80211_crypto_ccmp_exit(void)
 487 {
 488         lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
 489 }
 490
 491 module_init(lib80211_crypto_ccmp_init);
 492 module_exit(lib80211_crypto_ccmp_exit);