drivers/net/wireless/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 "ieee80211.h"
  26
  27 #ifndef CONFIG_CRYPTO
  28 #error CONFIG_CRYPTO is required to build this module.
  29 #endif
  30
  31 #include <linux/crypto.h>
  32 #include <asm/scatterlist.h>
  33
  34 MODULE_AUTHOR("Jouni Malinen");
  35 MODULE_DESCRIPTION("Host AP crypt: CCMP");
  36 MODULE_LICENSE("GPL");
  37
  38 #define AES_BLOCK_LEN 16
  39 #define CCMP_HDR_LEN 8
  40 #define CCMP_MIC_LEN 8
  41 #define CCMP_TK_LEN 16
  42 #define CCMP_PN_LEN 6
  43
  44 struct ieee80211_ccmp_data {
  45         u8 key[CCMP_TK_LEN];
  46         int key_set;
  47
  48         u8 tx_pn[CCMP_PN_LEN];
  49         u8 rx_pn[CCMP_PN_LEN];
  50
  51         u32 dot11RSNAStatsCCMPFormatErrors;
  52         u32 dot11RSNAStatsCCMPReplays;
  53         u32 dot11RSNAStatsCCMPDecryptErrors;
  54
  55         int key_idx;
  56
  57         struct crypto_tfm *tfm;
  58
  59         /* scratch buffers for virt_to_page() (crypto API) */
  60         u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
  61                 tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
  62         u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  63 };
  64
  65 void ieee80211_ccmp_aes_encrypt(struct crypto_tfm *tfm,
  66                              const u8 pt[16], u8 ct[16])
  67 {
  68         struct scatterlist src, dst;
  69
  70         src.page = virt_to_page(pt);
  71         src.offset = offset_in_page(pt);
  72         src.length = AES_BLOCK_LEN;
  73
  74         dst.page = virt_to_page(ct);
  75         dst.offset = offset_in_page(ct);
  76         dst.length = AES_BLOCK_LEN;
  77
  78         crypto_cipher_encrypt(tfm, &dst, &src, AES_BLOCK_LEN);
  79 }
  80
  81 static void * ieee80211_ccmp_init(int key_idx)
  82 {
  83         struct ieee80211_ccmp_data *priv;
  84
  85         priv = kmalloc(sizeof(*priv), GFP_ATOMIC);
  86         if (priv == NULL) {
  87                 goto fail;
  88         }
  89         memset(priv, 0, sizeof(*priv));
  90         priv->key_idx = key_idx;
  91
  92         priv->tfm = crypto_alloc_tfm("aes", 0);
  93         if (priv->tfm == NULL) {
  94                 printk(KERN_DEBUG "ieee80211_crypt_ccmp: could not allocate "
  95                        "crypto API aes\n");
  96                 goto fail;
  97         }
  98
  99         return priv;
 100
 101 fail:
 102         if (priv) {
 103                 if (priv->tfm)
 104                         crypto_free_tfm(priv->tfm);
 105                 kfree(priv);
 106         }
 107
 108         return NULL;
 109 }
 110
 111
 112 static void ieee80211_ccmp_deinit(void *priv)
 113 {
 114         struct ieee80211_ccmp_data *_priv = priv;
 115         if (_priv && _priv->tfm)
 116                 crypto_free_tfm(_priv->tfm);
 117         kfree(priv);
 118 }
 119
 120
 121 static inline void xor_block(u8 *b, u8 *a, size_t len)
 122 {
 123         int i;
 124         for (i = 0; i < len; i++)
 125                 b[i] ^= a[i];
 126 }
 127
 128
 129 static void ccmp_init_blocks(struct crypto_tfm *tfm,
 130                              struct ieee80211_hdr *hdr,
 131                              u8 *pn, size_t dlen, u8 *b0, u8 *auth,
 132                              u8 *s0)
 133 {
 134         u8 *pos, qc = 0;
 135         size_t aad_len;
 136         u16 fc;
 137         int a4_included, qc_included;
 138         u8 aad[2 * AES_BLOCK_LEN];
 139
 140         fc = le16_to_cpu(hdr->frame_ctl);
 141         a4_included = ((fc & (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) ==
 142                        (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS));
 143         qc_included = ((WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
 144                        (WLAN_FC_GET_STYPE(fc) & 0x08));
 145         aad_len = 22;
 146         if (a4_included)
 147                 aad_len += 6;
 148         if (qc_included) {
 149                 pos = (u8 *) &hdr->addr4;
 150                 if (a4_included)
 151                         pos += 6;
 152                 qc = *pos & 0x0f;
 153                 aad_len += 2;
 154         }
 155
 156         /* CCM Initial Block:
 157          * Flag (Include authentication header, M=3 (8-octet MIC),
 158          *       L=1 (2-octet Dlen))
 159          * Nonce: 0x00 | A2 | PN
 160          * Dlen */
 161         b0[0] = 0x59;
 162         b0[1] = qc;
 163         memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 164         memcpy(b0 + 8, pn, CCMP_PN_LEN);
 165         b0[14] = (dlen >> 8) & 0xff;
 166         b0[15] = dlen & 0xff;
 167
 168         /* AAD:
 169          * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 170          * A1 | A2 | A3
 171          * SC with bits 4..15 (seq#) masked to zero
 172          * A4 (if present)
 173          * QC (if present)
 174          */
 175         pos = (u8 *) hdr;
 176         aad[0] = 0; /* aad_len >> 8 */
 177         aad[1] = aad_len & 0xff;
 178         aad[2] = pos[0] & 0x8f;
 179         aad[3] = pos[1] & 0xc7;
 180         memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 181         pos = (u8 *) &hdr->seq_ctl;
 182         aad[22] = pos[0] & 0x0f;
 183         aad[23] = 0; /* all bits masked */
 184         memset(aad + 24, 0, 8);
 185         if (a4_included)
 186                 memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 187         if (qc_included) {
 188                 aad[a4_included ? 30 : 24] = qc;
 189                 /* rest of QC masked */
 190         }
 191
 192         /* Start with the first block and AAD */
 193         ieee80211_ccmp_aes_encrypt(tfm, b0, auth);
 194         xor_block(auth, aad, AES_BLOCK_LEN);
 195         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 196         xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 197         ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 198         b0[0] &= 0x07;
 199         b0[14] = b0[15] = 0;
 200         ieee80211_ccmp_aes_encrypt(tfm, b0, s0);
 201 }
 202
 203
 204 static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 205 {
 206         struct ieee80211_ccmp_data *key = priv;
 207         int data_len, i, blocks, last, len;
 208         u8 *pos, *mic;
 209         struct ieee80211_hdr *hdr;
 210         u8 *b0 = key->tx_b0;
 211         u8 *b = key->tx_b;
 212         u8 *e = key->tx_e;
 213         u8 *s0 = key->tx_s0;
 214
 215         if (skb_headroom(skb) < CCMP_HDR_LEN ||
 216             skb_tailroom(skb) < CCMP_MIC_LEN ||
 217             skb->len < hdr_len)
 218                 return -1;
 219
 220         data_len = skb->len - hdr_len;
 221         pos = skb_push(skb, CCMP_HDR_LEN);
 222         memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 223         pos += hdr_len;
 224         mic = skb_put(skb, CCMP_MIC_LEN);
 225
 226         i = CCMP_PN_LEN - 1;
 227         while (i >= 0) {
 228                 key->tx_pn[i]++;
 229                 if (key->tx_pn[i] != 0)
 230                         break;
 231                 i--;
 232         }
 233
 234         *pos++ = key->tx_pn[5];
 235         *pos++ = key->tx_pn[4];
 236         *pos++ = 0;
 237         *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */;
 238         *pos++ = key->tx_pn[3];
 239         *pos++ = key->tx_pn[2];
 240         *pos++ = key->tx_pn[1];
 241         *pos++ = key->tx_pn[0];
 242
 243         hdr = (struct ieee80211_hdr *) skb->data;
 244         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 245
 246         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 247         last = data_len % AES_BLOCK_LEN;
 248
 249         for (i = 1; i <= blocks; i++) {
 250                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 251                 /* Authentication */
 252                 xor_block(b, pos, len);
 253                 ieee80211_ccmp_aes_encrypt(key->tfm, b, b);
 254                 /* Encryption, with counter */
 255                 b0[14] = (i >> 8) & 0xff;
 256                 b0[15] = i & 0xff;
 257                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);
 258                 xor_block(pos, e, len);
 259                 pos += len;
 260         }
 261
 262         for (i = 0; i < CCMP_MIC_LEN; i++)
 263                 mic[i] = b[i] ^ s0[i];
 264
 265         return 0;
 266 }
 267
 268
 269 static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 270 {
 271         struct ieee80211_ccmp_data *key = priv;
 272         u8 keyidx, *pos;
 273         struct ieee80211_hdr *hdr;
 274         u8 *b0 = key->rx_b0;
 275         u8 *b = key->rx_b;
 276         u8 *a = key->rx_a;
 277         u8 pn[6];
 278         int i, blocks, last, len;
 279         size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 280         u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 281
 282         if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 283                 key->dot11RSNAStatsCCMPFormatErrors++;
 284                 return -1;
 285         }
 286
 287         hdr = (struct ieee80211_hdr *) skb->data;
 288         pos = skb->data + hdr_len;
 289         keyidx = pos[3];
 290         if (!(keyidx & (1 << 5))) {
 291                 if (net_ratelimit()) {
 292                         printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 293                                " flag from " MAC_FMT "\n", MAC_ARG(hdr->addr2));
 294                 }
 295                 key->dot11RSNAStatsCCMPFormatErrors++;
 296                 return -2;
 297         }
 298         keyidx >>= 6;
 299         if (key->key_idx != keyidx) {
 300                 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 301                        "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 302                 return -6;
 303         }
 304         if (!key->key_set) {
 305                 if (net_ratelimit()) {
 306                         printk(KERN_DEBUG "CCMP: received packet from " MAC_FMT
 307                                " with keyid=%d that does not have a configured"
 308                                " key\n", MAC_ARG(hdr->addr2), keyidx);
 309                 }
 310                 return -3;
 311         }
 312
 313         pn[0] = pos[7];
 314         pn[1] = pos[6];
 315         pn[2] = pos[5];
 316         pn[3] = pos[4];
 317         pn[4] = pos[1];
 318         pn[5] = pos[0];
 319         pos += 8;
 320
 321         if (memcmp(pn, key->rx_pn, CCMP_PN_LEN) <= 0) {
 322                 if (net_ratelimit()) {
 323                         printk(KERN_DEBUG "CCMP: replay detected: STA=" MAC_FMT
 324                                " previous PN %02x%02x%02x%02x%02x%02x "
 325                                "received PN %02x%02x%02x%02x%02x%02x\n",
 326                                MAC_ARG(hdr->addr2), MAC_ARG(key->rx_pn),
 327                                MAC_ARG(pn));
 328                 }
 329                 key->dot11RSNAStatsCCMPReplays++;
 330                 return -4;
 331         }
 332
 333         ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 334         xor_block(mic, b, CCMP_MIC_LEN);
 335
 336         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 337         last = data_len % AES_BLOCK_LEN;
 338
 339         for (i = 1; i <= blocks; i++) {
 340                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 341                 /* Decrypt, with counter */
 342                 b0[14] = (i >> 8) & 0xff;
 343                 b0[15] = i & 0xff;
 344                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);
 345                 xor_block(pos, b, len);
 346                 /* Authentication */
 347                 xor_block(a, pos, len);
 348                 ieee80211_ccmp_aes_encrypt(key->tfm, a, a);
 349                 pos += len;
 350         }
 351
 352         if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 353                 if (net_ratelimit()) {
 354                         printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 355                                MAC_FMT "\n", MAC_ARG(hdr->addr2));
 356                 }
 357                 key->dot11RSNAStatsCCMPDecryptErrors++;
 358                 return -5;
 359         }
 360
 361         memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 362
 363         /* Remove hdr and MIC */
 364         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 365         skb_pull(skb, CCMP_HDR_LEN);
 366         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 367
 368         return keyidx;
 369 }
 370
 371
 372 static int ieee80211_ccmp_set_key(void *key, int len, u8 *seq, void *priv)
 373 {
 374         struct ieee80211_ccmp_data *data = priv;
 375         int keyidx;
 376         struct crypto_tfm *tfm = data->tfm;
 377
 378         keyidx = data->key_idx;
 379         memset(data, 0, sizeof(*data));
 380         data->key_idx = keyidx;
 381         data->tfm = tfm;
 382         if (len == CCMP_TK_LEN) {
 383                 memcpy(data->key, key, CCMP_TK_LEN);
 384                 data->key_set = 1;
 385                 if (seq) {
 386                         data->rx_pn[0] = seq[5];
 387                         data->rx_pn[1] = seq[4];
 388                         data->rx_pn[2] = seq[3];
 389                         data->rx_pn[3] = seq[2];
 390                         data->rx_pn[4] = seq[1];
 391                         data->rx_pn[5] = seq[0];
 392                 }
 393                 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 394         } else if (len == 0) {
 395                 data->key_set = 0;
 396         } else
 397                 return -1;
 398
 399         return 0;
 400 }
 401
 402
 403 static int ieee80211_ccmp_get_key(void *key, int len, u8 *seq, void *priv)
 404 {
 405         struct ieee80211_ccmp_data *data = priv;
 406
 407         if (len < CCMP_TK_LEN)
 408                 return -1;
 409
 410         if (!data->key_set)
 411                 return 0;
 412         memcpy(key, data->key, CCMP_TK_LEN);
 413
 414         if (seq) {
 415                 seq[0] = data->tx_pn[5];
 416                 seq[1] = data->tx_pn[4];
 417                 seq[2] = data->tx_pn[3];
 418                 seq[3] = data->tx_pn[2];
 419                 seq[4] = data->tx_pn[1];
 420                 seq[5] = data->tx_pn[0];
 421         }
 422
 423         return CCMP_TK_LEN;
 424 }
 425
 426
 427 static char * ieee80211_ccmp_print_stats(char *p, void *priv)
 428 {
 429         struct ieee80211_ccmp_data *ccmp = priv;
 430         p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 431                      "tx_pn=%02x%02x%02x%02x%02x%02x "
 432                      "rx_pn=%02x%02x%02x%02x%02x%02x "
 433                      "format_errors=%d replays=%d decrypt_errors=%d\n",
 434                      ccmp->key_idx, ccmp->key_set,
 435                      MAC_ARG(ccmp->tx_pn), MAC_ARG(ccmp->rx_pn),
 436                      ccmp->dot11RSNAStatsCCMPFormatErrors,
 437                      ccmp->dot11RSNAStatsCCMPReplays,
 438                      ccmp->dot11RSNAStatsCCMPDecryptErrors);
 439
 440         return p;
 441 }
 442
 443
 444 static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {
 445         .name                   = "CCMP",
 446         .init                   = ieee80211_ccmp_init,
 447         .deinit                 = ieee80211_ccmp_deinit,
 448         .encrypt_mpdu           = ieee80211_ccmp_encrypt,
 449         .decrypt_mpdu           = ieee80211_ccmp_decrypt,
 450         .encrypt_msdu           = NULL,
 451         .decrypt_msdu           = NULL,
 452         .set_key                = ieee80211_ccmp_set_key,
 453         .get_key                = ieee80211_ccmp_get_key,
 454         .print_stats            = ieee80211_ccmp_print_stats,
 455         .extra_prefix_len       = CCMP_HDR_LEN,
 456         .extra_postfix_len      = CCMP_MIC_LEN,
 457         .owner                  = THIS_MODULE,
 458 };
 459
 460
 461 static int __init ieee80211_crypto_ccmp_init(void)
 462 {
 463         if (ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp) < 0)
 464                 return -1;
 465
 466         return 0;
 467 }
 468
 469
 470 static void __exit ieee80211_crypto_ccmp_exit(void)
 471 {
 472         ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);
 473 }
 474
 475
 476 module_init(ieee80211_crypto_ccmp_init);
 477 module_exit(ieee80211_crypto_ccmp_exit);