linux/net/ieee80211/ieee80211_crypt_ccmp.c
<<
>>
Prefs
   1/*
   2 * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
   3 *
   4 * Copyright (c) 2003-2004, Jouni Malinen <j@w1.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/kernel.h>
  13#include <linux/err.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
  29MODULE_AUTHOR("Jouni Malinen");
  30MODULE_DESCRIPTION("Host AP crypt: CCMP");
  31MODULE_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
  39struct 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_cipher *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
  60static inline void ieee80211_ccmp_aes_encrypt(struct crypto_cipher *tfm,
  61                                              const u8 pt[16], u8 ct[16])
  62{
  63        crypto_cipher_encrypt_one(tfm, ct, pt);
  64}
  65
  66static void *ieee80211_ccmp_init(int key_idx)
  67{
  68        struct ieee80211_ccmp_data *priv;
  69
  70        priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  71        if (priv == NULL)
  72                goto fail;
  73        priv->key_idx = key_idx;
  74
  75        priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
  76        if (IS_ERR(priv->tfm)) {
  77                printk(KERN_DEBUG "ieee80211_crypt_ccmp: could not allocate "
  78                       "crypto API aes\n");
  79                priv->tfm = NULL;
  80                goto fail;
  81        }
  82
  83        return priv;
  84
  85      fail:
  86        if (priv) {
  87                if (priv->tfm)
  88                        crypto_free_cipher(priv->tfm);
  89                kfree(priv);
  90        }
  91
  92        return NULL;
  93}
  94
  95static void ieee80211_ccmp_deinit(void *priv)
  96{
  97        struct ieee80211_ccmp_data *_priv = priv;
  98        if (_priv && _priv->tfm)
  99                crypto_free_cipher(_priv->tfm);
 100        kfree(priv);
 101}
 102
 103static inline void xor_block(u8 * b, u8 * a, size_t len)
 104{
 105        int i;
 106        for (i = 0; i < len; i++)
 107                b[i] ^= a[i];
 108}
 109
 110static void ccmp_init_blocks(struct crypto_cipher *tfm,
 111                             struct ieee80211_hdr_4addr *hdr,
 112                             u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0)
 113{
 114        u8 *pos, qc = 0;
 115        size_t aad_len;
 116        u16 fc;
 117        int a4_included, qc_included;
 118        u8 aad[2 * AES_BLOCK_LEN];
 119
 120        fc = le16_to_cpu(hdr->frame_ctl);
 121        a4_included = ((fc & (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) ==
 122                       (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS));
 123        qc_included = ((WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
 124                       (WLAN_FC_GET_STYPE(fc) & IEEE80211_STYPE_QOS_DATA));
 125        aad_len = 22;
 126        if (a4_included)
 127                aad_len += 6;
 128        if (qc_included) {
 129                pos = (u8 *) & hdr->addr4;
 130                if (a4_included)
 131                        pos += 6;
 132                qc = *pos & 0x0f;
 133                aad_len += 2;
 134        }
 135
 136        /* CCM Initial Block:
 137         * Flag (Include authentication header, M=3 (8-octet MIC),
 138         *       L=1 (2-octet Dlen))
 139         * Nonce: 0x00 | A2 | PN
 140         * Dlen */
 141        b0[0] = 0x59;
 142        b0[1] = qc;
 143        memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 144        memcpy(b0 + 8, pn, CCMP_PN_LEN);
 145        b0[14] = (dlen >> 8) & 0xff;
 146        b0[15] = dlen & 0xff;
 147
 148        /* AAD:
 149         * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 150         * A1 | A2 | A3
 151         * SC with bits 4..15 (seq#) masked to zero
 152         * A4 (if present)
 153         * QC (if present)
 154         */
 155        pos = (u8 *) hdr;
 156        aad[0] = 0;             /* aad_len >> 8 */
 157        aad[1] = aad_len & 0xff;
 158        aad[2] = pos[0] & 0x8f;
 159        aad[3] = pos[1] & 0xc7;
 160        memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 161        pos = (u8 *) & hdr->seq_ctl;
 162        aad[22] = pos[0] & 0x0f;
 163        aad[23] = 0;            /* all bits masked */
 164        memset(aad + 24, 0, 8);
 165        if (a4_included)
 166                memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 167        if (qc_included) {
 168                aad[a4_included ? 30 : 24] = qc;
 169                /* rest of QC masked */
 170        }
 171
 172        /* Start with the first block and AAD */
 173        ieee80211_ccmp_aes_encrypt(tfm, b0, auth);
 174        xor_block(auth, aad, AES_BLOCK_LEN);
 175        ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 176        xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 177        ieee80211_ccmp_aes_encrypt(tfm, auth, auth);
 178        b0[0] &= 0x07;
 179        b0[14] = b0[15] = 0;
 180        ieee80211_ccmp_aes_encrypt(tfm, b0, s0);
 181}
 182
 183static int ieee80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
 184                              u8 *aeskey, int keylen, void *priv)
 185{
 186        struct ieee80211_ccmp_data *key = priv;
 187        int i;
 188        u8 *pos;
 189
 190        if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
 191                return -1;
 192
 193        if (aeskey != NULL && keylen >= CCMP_TK_LEN)
 194                memcpy(aeskey, key->key, CCMP_TK_LEN);
 195
 196        pos = skb_push(skb, CCMP_HDR_LEN);
 197        memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 198        pos += hdr_len;
 199
 200        i = CCMP_PN_LEN - 1;
 201        while (i >= 0) {
 202                key->tx_pn[i]++;
 203                if (key->tx_pn[i] != 0)
 204                        break;
 205                i--;
 206        }
 207
 208        *pos++ = key->tx_pn[5];
 209        *pos++ = key->tx_pn[4];
 210        *pos++ = 0;
 211        *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
 212        *pos++ = key->tx_pn[3];
 213        *pos++ = key->tx_pn[2];
 214        *pos++ = key->tx_pn[1];
 215        *pos++ = key->tx_pn[0];
 216
 217        return CCMP_HDR_LEN;
 218}
 219
 220static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 221{
 222        struct ieee80211_ccmp_data *key = priv;
 223        int data_len, i, blocks, last, len;
 224        u8 *pos, *mic;
 225        struct ieee80211_hdr_4addr *hdr;
 226        u8 *b0 = key->tx_b0;
 227        u8 *b = key->tx_b;
 228        u8 *e = key->tx_e;
 229        u8 *s0 = key->tx_s0;
 230
 231        if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
 232                return -1;
 233
 234        data_len = skb->len - hdr_len;
 235        len = ieee80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
 236        if (len < 0)
 237                return -1;
 238
 239        pos = skb->data + hdr_len + CCMP_HDR_LEN;
 240        mic = skb_put(skb, CCMP_MIC_LEN);
 241        hdr = (struct ieee80211_hdr_4addr *)skb->data;
 242        ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 243
 244        blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 245        last = data_len % AES_BLOCK_LEN;
 246
 247        for (i = 1; i <= blocks; i++) {
 248                len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 249                /* Authentication */
 250                xor_block(b, pos, len);
 251                ieee80211_ccmp_aes_encrypt(key->tfm, b, b);
 252                /* Encryption, with counter */
 253                b0[14] = (i >> 8) & 0xff;
 254                b0[15] = i & 0xff;
 255                ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);
 256                xor_block(pos, e, len);
 257                pos += len;
 258        }
 259
 260        for (i = 0; i < CCMP_MIC_LEN; i++)
 261                mic[i] = b[i] ^ s0[i];
 262
 263        return 0;
 264}
 265
 266/*
 267 * deal with seq counter wrapping correctly.
 268 * refer to timer_after() for jiffies wrapping handling
 269 */
 270static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
 271{
 272        u32 iv32_n, iv16_n;
 273        u32 iv32_o, iv16_o;
 274
 275        iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
 276        iv16_n = (pn_n[4] << 8) | pn_n[5];
 277
 278        iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
 279        iv16_o = (pn_o[4] << 8) | pn_o[5];
 280
 281        if ((s32)iv32_n - (s32)iv32_o < 0 ||
 282            (iv32_n == iv32_o && iv16_n <= iv16_o))
 283                return 1;
 284        return 0;
 285}
 286
 287static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 288{
 289        struct ieee80211_ccmp_data *key = priv;
 290        u8 keyidx, *pos;
 291        struct ieee80211_hdr_4addr *hdr;
 292        u8 *b0 = key->rx_b0;
 293        u8 *b = key->rx_b;
 294        u8 *a = key->rx_a;
 295        u8 pn[6];
 296        int i, blocks, last, len;
 297        size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 298        u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 299        DECLARE_MAC_BUF(mac);
 300
 301        if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 302                key->dot11RSNAStatsCCMPFormatErrors++;
 303                return -1;
 304        }
 305
 306        hdr = (struct ieee80211_hdr_4addr *)skb->data;
 307        pos = skb->data + hdr_len;
 308        keyidx = pos[3];
 309        if (!(keyidx & (1 << 5))) {
 310                if (net_ratelimit()) {
 311                        printk(KERN_DEBUG "CCMP: received packet without ExtIV"
 312                               " flag from %s\n", print_mac(mac, hdr->addr2));
 313                }
 314                key->dot11RSNAStatsCCMPFormatErrors++;
 315                return -2;
 316        }
 317        keyidx >>= 6;
 318        if (key->key_idx != keyidx) {
 319                printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 320                       "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 321                return -6;
 322        }
 323        if (!key->key_set) {
 324                if (net_ratelimit()) {
 325                        printk(KERN_DEBUG "CCMP: received packet from %s"
 326                               " with keyid=%d that does not have a configured"
 327                               " key\n", print_mac(mac, hdr->addr2), keyidx);
 328                }
 329                return -3;
 330        }
 331
 332        pn[0] = pos[7];
 333        pn[1] = pos[6];
 334        pn[2] = pos[5];
 335        pn[3] = pos[4];
 336        pn[4] = pos[1];
 337        pn[5] = pos[0];
 338        pos += 8;
 339
 340        if (ccmp_replay_check(pn, key->rx_pn)) {
 341                if (ieee80211_ratelimit_debug(IEEE80211_DL_DROP)) {
 342                        IEEE80211_DEBUG_DROP("CCMP: replay detected: STA=%s "
 343                                 "previous PN %02x%02x%02x%02x%02x%02x "
 344                                 "received PN %02x%02x%02x%02x%02x%02x\n",
 345                                 print_mac(mac, hdr->addr2),
 346                                 key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
 347                                 key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
 348                                 pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
 349                }
 350                key->dot11RSNAStatsCCMPReplays++;
 351                return -4;
 352        }
 353
 354        ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 355        xor_block(mic, b, CCMP_MIC_LEN);
 356
 357        blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 358        last = data_len % AES_BLOCK_LEN;
 359
 360        for (i = 1; i <= blocks; i++) {
 361                len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 362                /* Decrypt, with counter */
 363                b0[14] = (i >> 8) & 0xff;
 364                b0[15] = i & 0xff;
 365                ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);
 366                xor_block(pos, b, len);
 367                /* Authentication */
 368                xor_block(a, pos, len);
 369                ieee80211_ccmp_aes_encrypt(key->tfm, a, a);
 370                pos += len;
 371        }
 372
 373        if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 374                if (net_ratelimit()) {
 375                        printk(KERN_DEBUG "CCMP: decrypt failed: STA="
 376                               "%s\n", print_mac(mac, hdr->addr2));
 377                }
 378                key->dot11RSNAStatsCCMPDecryptErrors++;
 379                return -5;
 380        }
 381
 382        memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 383
 384        /* Remove hdr and MIC */
 385        memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 386        skb_pull(skb, CCMP_HDR_LEN);
 387        skb_trim(skb, skb->len - CCMP_MIC_LEN);
 388
 389        return keyidx;
 390}
 391
 392static int ieee80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 393{
 394        struct ieee80211_ccmp_data *data = priv;
 395        int keyidx;
 396        struct crypto_cipher *tfm = data->tfm;
 397
 398        keyidx = data->key_idx;
 399        memset(data, 0, sizeof(*data));
 400        data->key_idx = keyidx;
 401        data->tfm = tfm;
 402        if (len == CCMP_TK_LEN) {
 403                memcpy(data->key, key, CCMP_TK_LEN);
 404                data->key_set = 1;
 405                if (seq) {
 406                        data->rx_pn[0] = seq[5];
 407                        data->rx_pn[1] = seq[4];
 408                        data->rx_pn[2] = seq[3];
 409                        data->rx_pn[3] = seq[2];
 410                        data->rx_pn[4] = seq[1];
 411                        data->rx_pn[5] = seq[0];
 412                }
 413                crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 414        } else if (len == 0)
 415                data->key_set = 0;
 416        else
 417                return -1;
 418
 419        return 0;
 420}
 421
 422static int ieee80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 423{
 424        struct ieee80211_ccmp_data *data = priv;
 425
 426        if (len < CCMP_TK_LEN)
 427                return -1;
 428
 429        if (!data->key_set)
 430                return 0;
 431        memcpy(key, data->key, CCMP_TK_LEN);
 432
 433        if (seq) {
 434                seq[0] = data->tx_pn[5];
 435                seq[1] = data->tx_pn[4];
 436                seq[2] = data->tx_pn[3];
 437                seq[3] = data->tx_pn[2];
 438                seq[4] = data->tx_pn[1];
 439                seq[5] = data->tx_pn[0];
 440        }
 441
 442        return CCMP_TK_LEN;
 443}
 444
 445static char *ieee80211_ccmp_print_stats(char *p, void *priv)
 446{
 447        struct ieee80211_ccmp_data *ccmp = priv;
 448
 449        p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 450                     "tx_pn=%02x%02x%02x%02x%02x%02x "
 451                     "rx_pn=%02x%02x%02x%02x%02x%02x "
 452                     "format_errors=%d replays=%d decrypt_errors=%d\n",
 453                     ccmp->key_idx, ccmp->key_set,
 454                     ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
 455                     ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
 456                     ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
 457                     ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
 458                     ccmp->dot11RSNAStatsCCMPFormatErrors,
 459                     ccmp->dot11RSNAStatsCCMPReplays,
 460                     ccmp->dot11RSNAStatsCCMPDecryptErrors);
 461
 462        return p;
 463}
 464
 465static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {
 466        .name = "CCMP",
 467        .init = ieee80211_ccmp_init,
 468        .deinit = ieee80211_ccmp_deinit,
 469        .build_iv = ieee80211_ccmp_hdr,
 470        .encrypt_mpdu = ieee80211_ccmp_encrypt,
 471        .decrypt_mpdu = ieee80211_ccmp_decrypt,
 472        .encrypt_msdu = NULL,
 473        .decrypt_msdu = NULL,
 474        .set_key = ieee80211_ccmp_set_key,
 475        .get_key = ieee80211_ccmp_get_key,
 476        .print_stats = ieee80211_ccmp_print_stats,
 477        .extra_mpdu_prefix_len = CCMP_HDR_LEN,
 478        .extra_mpdu_postfix_len = CCMP_MIC_LEN,
 479        .owner = THIS_MODULE,
 480};
 481
 482static int __init ieee80211_crypto_ccmp_init(void)
 483{
 484        return ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp);
 485}
 486
 487static void __exit ieee80211_crypto_ccmp_exit(void)
 488{
 489        ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);
 490}
 491
 492module_init(ieee80211_crypto_ccmp_init);
 493module_exit(ieee80211_crypto_ccmp_exit);
 494
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.