linux/net/wireless/lib80211_crypt_ccmp.c
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   1/*
   2 * lib80211 crypt: host-based CCMP encryption implementation for lib80211
   3 *
   4 * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi>
   5 * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation. See README and COPYING for
  10 * more details.
  11 */
  12
  13#include <linux/kernel.h>
  14#include <linux/err.h>
  15#include <linux/module.h>
  16#include <linux/init.h>
  17#include <linux/slab.h>
  18#include <linux/random.h>
  19#include <linux/skbuff.h>
  20#include <linux/netdevice.h>
  21#include <linux/if_ether.h>
  22#include <linux/if_arp.h>
  23#include <asm/string.h>
  24#include <linux/wireless.h>
  25
  26#include <linux/ieee80211.h>
  27
  28#include <linux/crypto.h>
  29
  30#include <net/lib80211.h>
  31
  32MODULE_AUTHOR("Jouni Malinen");
  33MODULE_DESCRIPTION("Host AP crypt: CCMP");
  34MODULE_LICENSE("GPL");
  35
  36#define AES_BLOCK_LEN 16
  37#define CCMP_HDR_LEN 8
  38#define CCMP_MIC_LEN 8
  39#define CCMP_TK_LEN 16
  40#define CCMP_PN_LEN 6
  41
  42struct lib80211_ccmp_data {
  43        u8 key[CCMP_TK_LEN];
  44        int key_set;
  45
  46        u8 tx_pn[CCMP_PN_LEN];
  47        u8 rx_pn[CCMP_PN_LEN];
  48
  49        u32 dot11RSNAStatsCCMPFormatErrors;
  50        u32 dot11RSNAStatsCCMPReplays;
  51        u32 dot11RSNAStatsCCMPDecryptErrors;
  52
  53        int key_idx;
  54
  55        struct crypto_cipher *tfm;
  56
  57        /* scratch buffers for virt_to_page() (crypto API) */
  58        u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
  59            tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
  60        u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  61};
  62
  63static inline void lib80211_ccmp_aes_encrypt(struct crypto_cipher *tfm,
  64                                              const u8 pt[16], u8 ct[16])
  65{
  66        crypto_cipher_encrypt_one(tfm, ct, pt);
  67}
  68
  69static void *lib80211_ccmp_init(int key_idx)
  70{
  71        struct lib80211_ccmp_data *priv;
  72
  73        priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  74        if (priv == NULL)
  75                goto fail;
  76        priv->key_idx = key_idx;
  77
  78        priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
  79        if (IS_ERR(priv->tfm)) {
  80                priv->tfm = NULL;
  81                goto fail;
  82        }
  83
  84        return priv;
  85
  86      fail:
  87        if (priv) {
  88                if (priv->tfm)
  89                        crypto_free_cipher(priv->tfm);
  90                kfree(priv);
  91        }
  92
  93        return NULL;
  94}
  95
  96static void lib80211_ccmp_deinit(void *priv)
  97{
  98        struct lib80211_ccmp_data *_priv = priv;
  99        if (_priv && _priv->tfm)
 100                crypto_free_cipher(_priv->tfm);
 101        kfree(priv);
 102}
 103
 104static inline void xor_block(u8 * b, u8 * a, size_t len)
 105{
 106        int i;
 107        for (i = 0; i < len; i++)
 108                b[i] ^= a[i];
 109}
 110
 111static void ccmp_init_blocks(struct crypto_cipher *tfm,
 112                             struct ieee80211_hdr *hdr,
 113                             u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0)
 114{
 115        u8 *pos, qc = 0;
 116        size_t aad_len;
 117        int a4_included, qc_included;
 118        u8 aad[2 * AES_BLOCK_LEN];
 119
 120        a4_included = ieee80211_has_a4(hdr->frame_control);
 121        qc_included = ieee80211_is_data_qos(hdr->frame_control);
 122
 123        aad_len = 22;
 124        if (a4_included)
 125                aad_len += 6;
 126        if (qc_included) {
 127                pos = (u8 *) & hdr->addr4;
 128                if (a4_included)
 129                        pos += 6;
 130                qc = *pos & 0x0f;
 131                aad_len += 2;
 132        }
 133
 134        /* CCM Initial Block:
 135         * Flag (Include authentication header, M=3 (8-octet MIC),
 136         *       L=1 (2-octet Dlen))
 137         * Nonce: 0x00 | A2 | PN
 138         * Dlen */
 139        b0[0] = 0x59;
 140        b0[1] = qc;
 141        memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
 142        memcpy(b0 + 8, pn, CCMP_PN_LEN);
 143        b0[14] = (dlen >> 8) & 0xff;
 144        b0[15] = dlen & 0xff;
 145
 146        /* AAD:
 147         * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 148         * A1 | A2 | A3
 149         * SC with bits 4..15 (seq#) masked to zero
 150         * A4 (if present)
 151         * QC (if present)
 152         */
 153        pos = (u8 *) hdr;
 154        aad[0] = 0;             /* aad_len >> 8 */
 155        aad[1] = aad_len & 0xff;
 156        aad[2] = pos[0] & 0x8f;
 157        aad[3] = pos[1] & 0xc7;
 158        memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
 159        pos = (u8 *) & hdr->seq_ctrl;
 160        aad[22] = pos[0] & 0x0f;
 161        aad[23] = 0;            /* all bits masked */
 162        memset(aad + 24, 0, 8);
 163        if (a4_included)
 164                memcpy(aad + 24, hdr->addr4, ETH_ALEN);
 165        if (qc_included) {
 166                aad[a4_included ? 30 : 24] = qc;
 167                /* rest of QC masked */
 168        }
 169
 170        /* Start with the first block and AAD */
 171        lib80211_ccmp_aes_encrypt(tfm, b0, auth);
 172        xor_block(auth, aad, AES_BLOCK_LEN);
 173        lib80211_ccmp_aes_encrypt(tfm, auth, auth);
 174        xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
 175        lib80211_ccmp_aes_encrypt(tfm, auth, auth);
 176        b0[0] &= 0x07;
 177        b0[14] = b0[15] = 0;
 178        lib80211_ccmp_aes_encrypt(tfm, b0, s0);
 179}
 180
 181static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
 182                              u8 *aeskey, int keylen, void *priv)
 183{
 184        struct lib80211_ccmp_data *key = priv;
 185        int i;
 186        u8 *pos;
 187
 188        if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
 189                return -1;
 190
 191        if (aeskey != NULL && keylen >= CCMP_TK_LEN)
 192                memcpy(aeskey, key->key, CCMP_TK_LEN);
 193
 194        pos = skb_push(skb, CCMP_HDR_LEN);
 195        memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 196        pos += hdr_len;
 197
 198        i = CCMP_PN_LEN - 1;
 199        while (i >= 0) {
 200                key->tx_pn[i]++;
 201                if (key->tx_pn[i] != 0)
 202                        break;
 203                i--;
 204        }
 205
 206        *pos++ = key->tx_pn[5];
 207        *pos++ = key->tx_pn[4];
 208        *pos++ = 0;
 209        *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
 210        *pos++ = key->tx_pn[3];
 211        *pos++ = key->tx_pn[2];
 212        *pos++ = key->tx_pn[1];
 213        *pos++ = key->tx_pn[0];
 214
 215        return CCMP_HDR_LEN;
 216}
 217
 218static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 219{
 220        struct lib80211_ccmp_data *key = priv;
 221        int data_len, i, blocks, last, len;
 222        u8 *pos, *mic;
 223        struct ieee80211_hdr *hdr;
 224        u8 *b0 = key->tx_b0;
 225        u8 *b = key->tx_b;
 226        u8 *e = key->tx_e;
 227        u8 *s0 = key->tx_s0;
 228
 229        if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
 230                return -1;
 231
 232        data_len = skb->len - hdr_len;
 233        len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
 234        if (len < 0)
 235                return -1;
 236
 237        pos = skb->data + hdr_len + CCMP_HDR_LEN;
 238        hdr = (struct ieee80211_hdr *)skb->data;
 239        ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
 240
 241        blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 242        last = data_len % AES_BLOCK_LEN;
 243
 244        for (i = 1; i <= blocks; i++) {
 245                len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 246                /* Authentication */
 247                xor_block(b, pos, len);
 248                lib80211_ccmp_aes_encrypt(key->tfm, b, b);
 249                /* Encryption, with counter */
 250                b0[14] = (i >> 8) & 0xff;
 251                b0[15] = i & 0xff;
 252                lib80211_ccmp_aes_encrypt(key->tfm, b0, e);
 253                xor_block(pos, e, len);
 254                pos += len;
 255        }
 256
 257        mic = skb_put(skb, CCMP_MIC_LEN);
 258        for (i = 0; i < CCMP_MIC_LEN; i++)
 259                mic[i] = b[i] ^ s0[i];
 260
 261        return 0;
 262}
 263
 264/*
 265 * deal with seq counter wrapping correctly.
 266 * refer to timer_after() for jiffies wrapping handling
 267 */
 268static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
 269{
 270        u32 iv32_n, iv16_n;
 271        u32 iv32_o, iv16_o;
 272
 273        iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
 274        iv16_n = (pn_n[4] << 8) | pn_n[5];
 275
 276        iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
 277        iv16_o = (pn_o[4] << 8) | pn_o[5];
 278
 279        if ((s32)iv32_n - (s32)iv32_o < 0 ||
 280            (iv32_n == iv32_o && iv16_n <= iv16_o))
 281                return 1;
 282        return 0;
 283}
 284
 285static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 286{
 287        struct lib80211_ccmp_data *key = priv;
 288        u8 keyidx, *pos;
 289        struct ieee80211_hdr *hdr;
 290        u8 *b0 = key->rx_b0;
 291        u8 *b = key->rx_b;
 292        u8 *a = key->rx_a;
 293        u8 pn[6];
 294        int i, blocks, last, len;
 295        size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
 296        u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
 297
 298        if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 299                key->dot11RSNAStatsCCMPFormatErrors++;
 300                return -1;
 301        }
 302
 303        hdr = (struct ieee80211_hdr *)skb->data;
 304        pos = skb->data + hdr_len;
 305        keyidx = pos[3];
 306        if (!(keyidx & (1 << 5))) {
 307                net_dbg_ratelimited("CCMP: received packet without ExtIV flag from %pM\n",
 308                                    hdr->addr2);
 309                key->dot11RSNAStatsCCMPFormatErrors++;
 310                return -2;
 311        }
 312        keyidx >>= 6;
 313        if (key->key_idx != keyidx) {
 314                printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
 315                       "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
 316                return -6;
 317        }
 318        if (!key->key_set) {
 319                net_dbg_ratelimited("CCMP: received packet from %pM with keyid=%d that does not have a configured key\n",
 320                                    hdr->addr2, keyidx);
 321                return -3;
 322        }
 323
 324        pn[0] = pos[7];
 325        pn[1] = pos[6];
 326        pn[2] = pos[5];
 327        pn[3] = pos[4];
 328        pn[4] = pos[1];
 329        pn[5] = pos[0];
 330        pos += 8;
 331
 332        if (ccmp_replay_check(pn, key->rx_pn)) {
 333#ifdef CONFIG_LIB80211_DEBUG
 334                net_dbg_ratelimited("CCMP: replay detected: STA=%pM previous PN %02x%02x%02x%02x%02x%02x received PN %02x%02x%02x%02x%02x%02x\n",
 335                                    hdr->addr2,
 336                                    key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
 337                                    key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
 338                                    pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
 339#endif
 340                key->dot11RSNAStatsCCMPReplays++;
 341                return -4;
 342        }
 343
 344        ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
 345        xor_block(mic, b, CCMP_MIC_LEN);
 346
 347        blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 348        last = data_len % AES_BLOCK_LEN;
 349
 350        for (i = 1; i <= blocks; i++) {
 351                len = (i == blocks && last) ? last : AES_BLOCK_LEN;
 352                /* Decrypt, with counter */
 353                b0[14] = (i >> 8) & 0xff;
 354                b0[15] = i & 0xff;
 355                lib80211_ccmp_aes_encrypt(key->tfm, b0, b);
 356                xor_block(pos, b, len);
 357                /* Authentication */
 358                xor_block(a, pos, len);
 359                lib80211_ccmp_aes_encrypt(key->tfm, a, a);
 360                pos += len;
 361        }
 362
 363        if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
 364                net_dbg_ratelimited("CCMP: decrypt failed: STA=%pM\n",
 365                                    hdr->addr2);
 366                key->dot11RSNAStatsCCMPDecryptErrors++;
 367                return -5;
 368        }
 369
 370        memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 371
 372        /* Remove hdr and MIC */
 373        memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 374        skb_pull(skb, CCMP_HDR_LEN);
 375        skb_trim(skb, skb->len - CCMP_MIC_LEN);
 376
 377        return keyidx;
 378}
 379
 380static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 381{
 382        struct lib80211_ccmp_data *data = priv;
 383        int keyidx;
 384        struct crypto_cipher *tfm = data->tfm;
 385
 386        keyidx = data->key_idx;
 387        memset(data, 0, sizeof(*data));
 388        data->key_idx = keyidx;
 389        data->tfm = tfm;
 390        if (len == CCMP_TK_LEN) {
 391                memcpy(data->key, key, CCMP_TK_LEN);
 392                data->key_set = 1;
 393                if (seq) {
 394                        data->rx_pn[0] = seq[5];
 395                        data->rx_pn[1] = seq[4];
 396                        data->rx_pn[2] = seq[3];
 397                        data->rx_pn[3] = seq[2];
 398                        data->rx_pn[4] = seq[1];
 399                        data->rx_pn[5] = seq[0];
 400                }
 401                crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
 402        } else if (len == 0)
 403                data->key_set = 0;
 404        else
 405                return -1;
 406
 407        return 0;
 408}
 409
 410static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 411{
 412        struct lib80211_ccmp_data *data = priv;
 413
 414        if (len < CCMP_TK_LEN)
 415                return -1;
 416
 417        if (!data->key_set)
 418                return 0;
 419        memcpy(key, data->key, CCMP_TK_LEN);
 420
 421        if (seq) {
 422                seq[0] = data->tx_pn[5];
 423                seq[1] = data->tx_pn[4];
 424                seq[2] = data->tx_pn[3];
 425                seq[3] = data->tx_pn[2];
 426                seq[4] = data->tx_pn[1];
 427                seq[5] = data->tx_pn[0];
 428        }
 429
 430        return CCMP_TK_LEN;
 431}
 432
 433static char *lib80211_ccmp_print_stats(char *p, void *priv)
 434{
 435        struct lib80211_ccmp_data *ccmp = priv;
 436
 437        p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
 438                     "tx_pn=%02x%02x%02x%02x%02x%02x "
 439                     "rx_pn=%02x%02x%02x%02x%02x%02x "
 440                     "format_errors=%d replays=%d decrypt_errors=%d\n",
 441                     ccmp->key_idx, ccmp->key_set,
 442                     ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
 443                     ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
 444                     ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
 445                     ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
 446                     ccmp->dot11RSNAStatsCCMPFormatErrors,
 447                     ccmp->dot11RSNAStatsCCMPReplays,
 448                     ccmp->dot11RSNAStatsCCMPDecryptErrors);
 449
 450        return p;
 451}
 452
 453static struct lib80211_crypto_ops lib80211_crypt_ccmp = {
 454        .name = "CCMP",
 455        .init = lib80211_ccmp_init,
 456        .deinit = lib80211_ccmp_deinit,
 457        .encrypt_mpdu = lib80211_ccmp_encrypt,
 458        .decrypt_mpdu = lib80211_ccmp_decrypt,
 459        .encrypt_msdu = NULL,
 460        .decrypt_msdu = NULL,
 461        .set_key = lib80211_ccmp_set_key,
 462        .get_key = lib80211_ccmp_get_key,
 463        .print_stats = lib80211_ccmp_print_stats,
 464        .extra_mpdu_prefix_len = CCMP_HDR_LEN,
 465        .extra_mpdu_postfix_len = CCMP_MIC_LEN,
 466        .owner = THIS_MODULE,
 467};
 468
 469static int __init lib80211_crypto_ccmp_init(void)
 470{
 471        return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
 472}
 473
 474static void __exit lib80211_crypto_ccmp_exit(void)
 475{
 476        lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
 477}
 478
 479module_init(lib80211_crypto_ccmp_init);
 480module_exit(lib80211_crypto_ccmp_exit);
 481
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