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