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/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 <asm/string.h>
  23 #include <linux/wireless.h>
  24
  25 #include <net/ieee80211.h>
  26
  27
  28 #include <linux/crypto.h>
  29 #include <asm/scatterlist.h>
  30
  31 MODULE_AUTHOR("Jouni Malinen");
  32 MODULE_DESCRIPTION("Host AP crypt: CCMP");
  33 MODULE_LICENSE("GPL");
  34
  35 #define AES_BLOCK_LEN 16
  36 #define CCMP_HDR_LEN 8
  37 #define CCMP_MIC_LEN 8
  38 #define CCMP_TK_LEN 16
  39 #define CCMP_PN_LEN 6
  40
  41 struct ieee80211_ccmp_data {
  42         u8 key[CCMP_TK_LEN];
  43         int key_set;
  44
  45         u8 tx_pn[CCMP_PN_LEN];
  46         u8 rx_pn[CCMP_PN_LEN];
  47
  48         u32 dot11RSNAStatsCCMPFormatErrors;
  49         u32 dot11RSNAStatsCCMPReplays;
  50         u32 dot11RSNAStatsCCMPDecryptErrors;
  51
  52         int key_idx;
  53
  54         struct crypto_tfm *tfm;
  55
  56         /* scratch buffers for virt_to_page() (crypto API) */
  57         u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
  58                 tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
  59         u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  60 };
  61
  62 static void ieee80211_ccmp_aes_encrypt(struct crypto_tfm *tfm,
  63                                        const u8 pt[16], u8 ct[16])
  64 {
  65         struct scatterlist src, dst;
  66
  67         src.page = virt_to_page(pt);
  68         src.offset = offset_in_page(pt);
  69         src.length = AES_BLOCK_LEN;
  70
  71         dst.page = virt_to_page(ct);
  72         dst.offset = offset_in_page(ct);
  73         dst.length = AES_BLOCK_LEN;
  74
  75         crypto_cipher_encrypt(tfm, &dst, &src, AES_BLOCK_LEN);
  76 }
  77
  78 static void * ieee80211_ccmp_init(int key_idx)
  79 {
  80         struct ieee80211_ccmp_data *priv;
  81
  82         priv = kmalloc(sizeof(*priv), GFP_ATOMIC);
  83         if (priv == NULL)
  84                 goto fail;
  85         memset(priv, 0, sizeof(*priv));
  86         priv->key_idx = key_idx;
  87
  88         priv->tfm = crypto_alloc_tfm("aes", 0);
  89         if (priv->tfm == NULL) {
  90                 printk(KERN_DEBUG "ieee80211_crypt_ccmp: could not allocate "
  91                        "crypto API aes\n");
  92                 goto fail;
  93         }
  94
  95         return priv;
  96
  97 fail:
  98         if (priv) {
  99                 if (priv->tfm)
 100                         crypto_free_tfm(priv->tfm);
 101                 kfree(priv);
 102         }
 103
 104         return NULL;
 105 }
 106
 107
 108 static void ieee80211_ccmp_deinit(void *priv)
 109 {
 110         struct ieee80211_ccmp_data *_priv = priv;
 111         if (_priv && _priv->tfm)
 112                 crypto_free_tfm(_priv->tfm);
 113         kfree(priv);
 114 }
 115
 116
 117 static inline void xor_block(u8 *b, u8 *a, size_t len)
 118 {
 119         int i;
 120         for (i = 0; i < len; i++)
 121                 b[i] ^= a[i];
 122 }
 123
 124
 125 static void ccmp_init_blocks(struct crypto_tfm *tfm,
 126                              struct ieee80211_hdr *hdr,
 127                              u8 *pn, size_t dlen, u8 *b0, u8 *auth,
 128                              u8 *s0)
 129 {
 130         u8 *pos, qc = 0;
 131         size_t aad_len;
 132         u16 fc;
 133         int a4_included, qc_included;
 134         u8 aad[2 * AES_BLOCK_LEN];
 135
 136         fc = le16_to_cpu(hdr->frame_ctl);
 137         a4_included = ((fc & (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) ==
 138                        (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS));
 139         qc_included = ((WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
 140                        (WLAN_FC_GET_STYPE(fc) & 0x08));
 141         aad_len = 22;
 142         if (a4_included)
 143                 aad_len += 6;
 144         if (qc_included) {
 145                 pos = (u8 *) &hdr->addr4;
 146                 if (a4_included)
 147                         pos += 6;
 148                 qc = *pos & 0x0f;
 149                 aad_len += 2;
 150         }
 151
 152         /* CCM Initial Block:
 153          * Flag (Include authentication header, M=3 (8-octet MIC),
 154          *       L=1 (2-octet Dlen))
 155          * Nonce: 0x00 | A2 | PN
 156          * Dlen */
 157         b0[0] = 0x59;
 158         b0[1] = qc;
 159         memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 160         memcpy(b0 + 8, pn, CCMP_PN_LEN);
 161         b0[14] = (dlen >> 8) & 0xff;
 162         b0[15] = dlen & 0xff;
 163
 164         /* AAD:
 165          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 166          * A1 | A2 | A3
 167          * SC with bits 4..15 (seq#) masked to zero
 168          * A4 (if present)
 169          * QC (if present)
 170          */
 171         pos = (u8 *) hdr;
 172         aad[0] = 0; /* aad_len >> 8 */
 173         aad[1] = aad_len & 0xff;
 174         aad[2] = pos[0] & 0x8f;
 175         aad[3] = pos[1] & 0xc7;
 176         memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 177         pos = (u8 *) &hdr->seq_ctl;
 178         aad[22] = pos[0] & 0x0f;
 179         aad[23] = 0; /* all bits masked */
 180         memset(aad + 24, 0, 8);
 181         if (a4_included)
 182                 memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 183         if (qc_included) {
 184                 aad[a4_included ? 30 : 24] = qc;
 185                 /* rest of QC masked */
 186         }
 187
 188         /* Start with the first block and AAD */
 189         ieee80211_ccmp_aes_encrypt(tfm, b0, auth);
 190         xor_block(auth, aad, AES_BLOCK_LEN);
 191         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 192         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 193         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 194         b0[0] &= 0x07;
 195         b0[14] = b0[15] = 0;
 196         ieee80211_ccmp_aes_encrypt(tfm, b0, s0);
 197 }
 198
 199
 200 static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 201 {
 202         struct ieee80211_ccmp_data *key = priv;
 203         int data_len, i, blocks, last, len;
 204         u8 *pos, *mic;
 205         struct ieee80211_hdr *hdr;
 206         u8 *b0 = key->tx_b0;
 207         u8 *b = key->tx_b;
 208         u8 *e = key->tx_e;
 209         u8 *s0 = key->tx_s0;
 210
 211         if (skb_headroom(skb) < CCMP_HDR_LEN ||
 212             skb_tailroom(skb) < CCMP_MIC_LEN ||
 213             skb->len < hdr_len)
 214                 return -1;
 215
 216         data_len = skb->len - hdr_len;
 217         pos = skb_push(skb, CCMP_HDR_LEN);
 218         memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 219         pos += hdr_len;
 220         mic = skb_put(skb, CCMP_MIC_LEN);
 221
 222         i = CCMP_PN_LEN - 1;
 223         while (i >= 0) {
 224                 key->tx_pn[i]++;
 225                 if (key->tx_pn[i] != 0)
 226                         break;
 227                 i--;
 228         }
 229
 230         *pos++ = key->tx_pn[5];
 231         *pos++ = key->tx_pn[4];
 232         *pos++ = 0;
 233         *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */;
 234         *pos++ = key->tx_pn[3];
 235         *pos++ = key->tx_pn[2];
 236         *pos++ = key->tx_pn[1];
 237         *pos++ = key->tx_pn[0];
 238
 239         hdr = (struct ieee80211_hdr *) skb->data;
 240         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 241
 242         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 243         last = data_len % AES_BLOCK_LEN;
 244
 245         for (i = 1; i <= blocks; i++) {
 246                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 247                 /* Authentication */
 248                 xor_block(b, pos, len);
 249                 ieee80211_ccmp_aes_encrypt(key->tfm, b, b);
 250                 /* Encryption, with counter */
 251                 b0[14] = (i >> 8) & 0xff;
 252                 b0[15] = i & 0xff;
 253                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);
 254                 xor_block(pos, e, len);
 255                 pos += len;
 256         }
 257
 258         for (i = 0; i < CCMP_MIC_LEN; i++)
 259                 mic[i] = b[i] ^ s0[i];
 260
 261         return 0;
 262 }
 263
 264
 265 static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 266 {
 267         struct ieee80211_ccmp_data *key = priv;
 268         u8 keyidx, *pos;
 269         struct ieee80211_hdr *hdr;
 270         u8 *b0 = key->rx_b0;
 271         u8 *b = key->rx_b;
 272         u8 *a = key->rx_a;
 273         u8 pn[6];
 274         int i, blocks, last, len;
 275         size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 276         u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 277
 278         if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 279                 key->dot11RSNAStatsCCMPFormatErrors++;
 280                 return -1;
 281         }
 282
 283         hdr = (struct ieee80211_hdr *) skb->data;
 284         pos = skb->data + hdr_len;
 285         keyidx = pos[3];
 286         if (!(keyidx & (1 << 5))) {
 287                 if (net_ratelimit()) {
 288                         printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 289                                " flag from " MAC_FMT "\n", MAC_ARG(hdr->addr2));
 290                 }
 291                 key->dot11RSNAStatsCCMPFormatErrors++;
 292                 return -2;
 293         }
 294         keyidx >>= 6;
 295         if (key->key_idx != keyidx) {
 296                 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 297                        "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 298                 return -6;
 299         }
 300         if (!key->key_set) {
 301                 if (net_ratelimit()) {
 302                         printk(KERN_DEBUG "CCMP: received packet from " MAC_FMT
 303                                " with keyid=%d that does not have a configured"
 304                                " key\n", MAC_ARG(hdr->addr2), keyidx);
 305                 }
 306                 return -3;
 307         }
 308
 309         pn[0] = pos[7];
 310         pn[1] = pos[6];
 311         pn[2] = pos[5];
 312         pn[3] = pos[4];
 313         pn[4] = pos[1];
 314         pn[5] = pos[0];
 315         pos += 8;
 316
 317         if (memcmp(pn, key->rx_pn, CCMP_PN_LEN) <= 0) {
 318                 if (net_ratelimit()) {
 319                         printk(KERN_DEBUG "CCMP: replay detected: STA=" MAC_FMT
 320                                " previous PN %02x%02x%02x%02x%02x%02x "
 321                                "received PN %02x%02x%02x%02x%02x%02x\n",
 322                                MAC_ARG(hdr->addr2), MAC_ARG(key->rx_pn),
 323                                MAC_ARG(pn));
 324                 }
 325                 key->dot11RSNAStatsCCMPReplays++;
 326                 return -4;
 327         }
 328
 329         ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 330         xor_block(mic, b, CCMP_MIC_LEN);
 331
 332         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 333         last = data_len % AES_BLOCK_LEN;
 334
 335         for (i = 1; i <= blocks; i++) {
 336                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 337                 /* Decrypt, with counter */
 338                 b0[14] = (i >> 8) & 0xff;
 339                 b0[15] = i & 0xff;
 340                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);
 341                 xor_block(pos, b, len);
 342                 /* Authentication */
 343                 xor_block(a, pos, len);
 344                 ieee80211_ccmp_aes_encrypt(key->tfm, a, a);
 345                 pos += len;
 346         }
 347
 348         if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 349                 if (net_ratelimit()) {
 350                         printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 351                                MAC_FMT "\n", MAC_ARG(hdr->addr2));
 352                 }
 353                 key->dot11RSNAStatsCCMPDecryptErrors++;
 354                 return -5;
 355         }
 356
 357         memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 358
 359         /* Remove hdr and MIC */
 360         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 361         skb_pull(skb, CCMP_HDR_LEN);
 362         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 363
 364         return keyidx;
 365 }
 366
 367
 368 static int ieee80211_ccmp_set_key(void *key, int len, u8 *seq, void *priv)
 369 {
 370         struct ieee80211_ccmp_data *data = priv;
 371         int keyidx;
 372         struct crypto_tfm *tfm = data->tfm;
 373
 374         keyidx = data->key_idx;
 375         memset(data, 0, sizeof(*data));
 376         data->key_idx = keyidx;
 377         data->tfm = tfm;
 378         if (len == CCMP_TK_LEN) {
 379                 memcpy(data->key, key, CCMP_TK_LEN);
 380                 data->key_set = 1;
 381                 if (seq) {
 382                         data->rx_pn[0] = seq[5];
 383                         data->rx_pn[1] = seq[4];
 384                         data->rx_pn[2] = seq[3];
 385                         data->rx_pn[3] = seq[2];
 386                         data->rx_pn[4] = seq[1];
 387                         data->rx_pn[5] = seq[0];
 388                 }
 389                 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 390         } else if (len == 0)
 391                 data->key_set = 0;
 392         else
 393                 return -1;
 394
 395         return 0;
 396 }
 397
 398
 399 static int ieee80211_ccmp_get_key(void *key, int len, u8 *seq, void *priv)
 400 {
 401         struct ieee80211_ccmp_data *data = priv;
 402
 403         if (len < CCMP_TK_LEN)
 404                 return -1;
 405
 406         if (!data->key_set)
 407                 return 0;
 408         memcpy(key, data->key, CCMP_TK_LEN);
 409
 410         if (seq) {
 411                 seq[0] = data->tx_pn[5];
 412                 seq[1] = data->tx_pn[4];
 413                 seq[2] = data->tx_pn[3];
 414                 seq[3] = data->tx_pn[2];
 415                 seq[4] = data->tx_pn[1];
 416                 seq[5] = data->tx_pn[0];
 417         }
 418
 419         return CCMP_TK_LEN;
 420 }
 421
 422
 423 static char * ieee80211_ccmp_print_stats(char *p, void *priv)
 424 {
 425         struct ieee80211_ccmp_data *ccmp = priv;
 426         p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 427                      "tx_pn=%02x%02x%02x%02x%02x%02x "
 428                      "rx_pn=%02x%02x%02x%02x%02x%02x "
 429                      "format_errors=%d replays=%d decrypt_errors=%d\n",
 430                      ccmp->key_idx, ccmp->key_set,
 431                      MAC_ARG(ccmp->tx_pn), MAC_ARG(ccmp->rx_pn),
 432                      ccmp->dot11RSNAStatsCCMPFormatErrors,
 433                      ccmp->dot11RSNAStatsCCMPReplays,
 434                      ccmp->dot11RSNAStatsCCMPDecryptErrors);
 435
 436         return p;
 437 }
 438
 439
 440 static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {
 441         .name                   = "CCMP",
 442         .init                   = ieee80211_ccmp_init,
 443         .deinit                 = ieee80211_ccmp_deinit,
 444         .encrypt_mpdu           = ieee80211_ccmp_encrypt,
 445         .decrypt_mpdu           = ieee80211_ccmp_decrypt,
 446         .encrypt_msdu           = NULL,
 447         .decrypt_msdu           = NULL,
 448         .set_key                = ieee80211_ccmp_set_key,
 449         .get_key                = ieee80211_ccmp_get_key,
 450         .print_stats            = ieee80211_ccmp_print_stats,
 451         .extra_prefix_len       = CCMP_HDR_LEN,
 452         .extra_postfix_len      = CCMP_MIC_LEN,
 453         .owner                  = THIS_MODULE,
 454 };
 455
 456
 457 static int __init ieee80211_crypto_ccmp_init(void)
 458 {
 459         return ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp);
 460 }
 461
 462
 463 static void __exit ieee80211_crypto_ccmp_exit(void)
 464 {
 465         ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);
 466 }
 467
 468
 469 module_init(ieee80211_crypto_ccmp_init);
 470 module_exit(ieee80211_crypto_ccmp_exit);