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, void *priv)
 194 {
 195         struct ieee80211_ccmp_data *key = priv;
 196         int i;
 197         u8 *pos;
 198
 199         if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
 200                 return -1;
 201
 202         pos = skb_push(skb, CCMP_HDR_LEN);
 203         memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 204         pos += hdr_len;
 205
 206         i = CCMP_PN_LEN - 1;
 207         while (i >= 0) {
 208                 key->tx_pn[i]++;
 209                 if (key->tx_pn[i] != 0)
 210                         break;
 211                 i--;
 212         }
 213
 214         *pos++ = key->tx_pn[5];
 215         *pos++ = key->tx_pn[4];
 216         *pos++ = 0;
 217         *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
 218         *pos++ = key->tx_pn[3];
 219         *pos++ = key->tx_pn[2];
 220         *pos++ = key->tx_pn[1];
 221         *pos++ = key->tx_pn[0];
 222
 223         return CCMP_HDR_LEN;
 224 }
 225
 226 static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 227 {
 228         struct ieee80211_ccmp_data *key = priv;
 229         int data_len, i, blocks, last, len;
 230         u8 *pos, *mic;
 231         struct ieee80211_hdr_4addr *hdr;
 232         u8 *b0 = key->tx_b0;
 233         u8 *b = key->tx_b;
 234         u8 *e = key->tx_e;
 235         u8 *s0 = key->tx_s0;
 236
 237         if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
 238                 return -1;
 239
 240         data_len = skb->len - hdr_len;
 241         len = ieee80211_ccmp_hdr(skb, hdr_len, priv);
 242         if (len < 0)
 243                 return -1;
 244
 245         pos = skb->data + hdr_len + CCMP_HDR_LEN;
 246         mic = skb_put(skb, CCMP_MIC_LEN);
 247         hdr = (struct ieee80211_hdr_4addr *)skb->data;
 248         ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 249
 250         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 251         last = data_len % AES_BLOCK_LEN;
 252
 253         for (i = 1; i <= blocks; i++) {
 254                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 255                 /* Authentication */
 256                 xor_block(b, pos, len);
 257                 ieee80211_ccmp_aes_encrypt(key->tfm, b, b);
 258                 /* Encryption, with counter */
 259                 b0[14] = (i >> 8) & 0xff;
 260                 b0[15] = i & 0xff;
 261                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);
 262                 xor_block(pos, e, len);
 263                 pos += len;
 264         }
 265
 266         for (i = 0; i < CCMP_MIC_LEN; i++)
 267                 mic[i] = b[i] ^ s0[i];
 268
 269         return 0;
 270 }
 271
 272 static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 273 {
 274         struct ieee80211_ccmp_data *key = priv;
 275         u8 keyidx, *pos;
 276         struct ieee80211_hdr_4addr *hdr;
 277         u8 *b0 = key->rx_b0;
 278         u8 *b = key->rx_b;
 279         u8 *a = key->rx_a;
 280         u8 pn[6];
 281         int i, blocks, last, len;
 282         size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 283         u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 284
 285         if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 286                 key->dot11RSNAStatsCCMPFormatErrors++;
 287                 return -1;
 288         }
 289
 290         hdr = (struct ieee80211_hdr_4addr *)skb->data;
 291         pos = skb->data + hdr_len;
 292         keyidx = pos[3];
 293         if (!(keyidx & (1 << 5))) {
 294                 if (net_ratelimit()) {
 295                         printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 296                                " flag from " MAC_FMT "\n", MAC_ARG(hdr->addr2));
 297                 }
 298                 key->dot11RSNAStatsCCMPFormatErrors++;
 299                 return -2;
 300         }
 301         keyidx >>= 6;
 302         if (key->key_idx != keyidx) {
 303                 printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 304                        "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 305                 return -6;
 306         }
 307         if (!key->key_set) {
 308                 if (net_ratelimit()) {
 309                         printk(KERN_DEBUG "CCMP: received packet from " MAC_FMT
 310                                " with keyid=%d that does not have a configured"
 311                                " key\n", MAC_ARG(hdr->addr2), keyidx);
 312                 }
 313                 return -3;
 314         }
 315
 316         pn[0] = pos[7];
 317         pn[1] = pos[6];
 318         pn[2] = pos[5];
 319         pn[3] = pos[4];
 320         pn[4] = pos[1];
 321         pn[5] = pos[0];
 322         pos += 8;
 323
 324         if (memcmp(pn, key->rx_pn, CCMP_PN_LEN) <= 0) {
 325                 if (net_ratelimit()) {
 326                         printk(KERN_DEBUG "CCMP: replay detected: STA=" MAC_FMT
 327                                " previous PN %02x%02x%02x%02x%02x%02x "
 328                                "received PN %02x%02x%02x%02x%02x%02x\n",
 329                                MAC_ARG(hdr->addr2), MAC_ARG(key->rx_pn),
 330                                MAC_ARG(pn));
 331                 }
 332                 key->dot11RSNAStatsCCMPReplays++;
 333                 return -4;
 334         }
 335
 336         ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 337         xor_block(mic, b, CCMP_MIC_LEN);
 338
 339         blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
 340         last = data_len % AES_BLOCK_LEN;
 341
 342         for (i = 1; i <= blocks; i++) {
 343                 len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 344                 /* Decrypt, with counter */
 345                 b0[14] = (i >> 8) & 0xff;
 346                 b0[15] = i & 0xff;
 347                 ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);
 348                 xor_block(pos, b, len);
 349                 /* Authentication */
 350                 xor_block(a, pos, len);
 351                 ieee80211_ccmp_aes_encrypt(key->tfm, a, a);
 352                 pos += len;
 353         }
 354
 355         if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 356                 if (net_ratelimit()) {
 357                         printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 358                                MAC_FMT "\n", MAC_ARG(hdr->addr2));
 359                 }
 360                 key->dot11RSNAStatsCCMPDecryptErrors++;
 361                 return -5;
 362         }
 363
 364         memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 365
 366         /* Remove hdr and MIC */
 367         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 368         skb_pull(skb, CCMP_HDR_LEN);
 369         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 370
 371         return keyidx;
 372 }
 373
 374 static int ieee80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 375 {
 376         struct ieee80211_ccmp_data *data = priv;
 377         int keyidx;
 378         struct crypto_tfm *tfm = data->tfm;
 379
 380         keyidx = data->key_idx;
 381         memset(data, 0, sizeof(*data));
 382         data->key_idx = keyidx;
 383         data->tfm = tfm;
 384         if (len == CCMP_TK_LEN) {
 385                 memcpy(data->key, key, CCMP_TK_LEN);
 386                 data->key_set = 1;
 387                 if (seq) {
 388                         data->rx_pn[0] = seq[5];
 389                         data->rx_pn[1] = seq[4];
 390                         data->rx_pn[2] = seq[3];
 391                         data->rx_pn[3] = seq[2];
 392                         data->rx_pn[4] = seq[1];
 393                         data->rx_pn[5] = seq[0];
 394                 }
 395                 crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 396         } else if (len == 0)
 397                 data->key_set = 0;
 398         else
 399                 return -1;
 400
 401         return 0;
 402 }
 403
 404 static int ieee80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 405 {
 406         struct ieee80211_ccmp_data *data = priv;
 407
 408         if (len < CCMP_TK_LEN)
 409                 return -1;
 410
 411         if (!data->key_set)
 412                 return 0;
 413         memcpy(key, data->key, CCMP_TK_LEN);
 414
 415         if (seq) {
 416                 seq[0] = data->tx_pn[5];
 417                 seq[1] = data->tx_pn[4];
 418                 seq[2] = data->tx_pn[3];
 419                 seq[3] = data->tx_pn[2];
 420                 seq[4] = data->tx_pn[1];
 421                 seq[5] = data->tx_pn[0];
 422         }
 423
 424         return CCMP_TK_LEN;
 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 static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {
 444         .name = "CCMP",
 445         .init = ieee80211_ccmp_init,
 446         .deinit = ieee80211_ccmp_deinit,
 447         .build_iv = ieee80211_ccmp_hdr,
 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_mpdu_prefix_len = CCMP_HDR_LEN,
 456         .extra_mpdu_postfix_len = CCMP_MIC_LEN,
 457         .owner = THIS_MODULE,
 458 };
 459
 460 static int __init ieee80211_crypto_ccmp_init(void)
 461 {
 462         return ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp);
 463 }
 464
 465 static void __exit ieee80211_crypto_ccmp_exit(void)
 466 {
 467         ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);
 468 }
 469
 470 module_init(ieee80211_crypto_ccmp_init);
 471 module_exit(ieee80211_crypto_ccmp_exit);