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