linux/net/wireless/lib80211_crypt_ccmp.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * lib80211 crypt: host-based CCMP encryption implementation for lib80211
   4 *
   5 * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi>
   6 * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
   7 */
   8
   9#include <linux/kernel.h>
  10#include <linux/err.h>
  11#include <linux/module.h>
  12#include <linux/init.h>
  13#include <linux/slab.h>
  14#include <linux/random.h>
  15#include <linux/skbuff.h>
  16#include <linux/netdevice.h>
  17#include <linux/if_ether.h>
  18#include <linux/if_arp.h>
  19#include <asm/string.h>
  20#include <linux/wireless.h>
  21
  22#include <linux/ieee80211.h>
  23
  24#include <linux/crypto.h>
  25#include <crypto/aead.h>
  26
  27#include <net/lib80211.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 lib80211_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_aead *tfm;
  53
  54        /* scratch buffers for virt_to_page() (crypto API) */
  55        u8 tx_aad[2 * AES_BLOCK_LEN];
  56        u8 rx_aad[2 * AES_BLOCK_LEN];
  57};
  58
  59static void *lib80211_ccmp_init(int key_idx)
  60{
  61        struct lib80211_ccmp_data *priv;
  62
  63        priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  64        if (priv == NULL)
  65                goto fail;
  66        priv->key_idx = key_idx;
  67
  68        priv->tfm = crypto_alloc_aead("ccm(aes)", 0, CRYPTO_ALG_ASYNC);
  69        if (IS_ERR(priv->tfm)) {
  70                priv->tfm = NULL;
  71                goto fail;
  72        }
  73
  74        return priv;
  75
  76      fail:
  77        if (priv) {
  78                if (priv->tfm)
  79                        crypto_free_aead(priv->tfm);
  80                kfree(priv);
  81        }
  82
  83        return NULL;
  84}
  85
  86static void lib80211_ccmp_deinit(void *priv)
  87{
  88        struct lib80211_ccmp_data *_priv = priv;
  89        if (_priv && _priv->tfm)
  90                crypto_free_aead(_priv->tfm);
  91        kfree(priv);
  92}
  93
  94static int ccmp_init_iv_and_aad(const struct ieee80211_hdr *hdr,
  95                                const u8 *pn, u8 *iv, u8 *aad)
  96{
  97        u8 *pos, qc = 0;
  98        size_t aad_len;
  99        int a4_included, qc_included;
 100
 101        a4_included = ieee80211_has_a4(hdr->frame_control);
 102        qc_included = ieee80211_is_data_qos(hdr->frame_control);
 103
 104        aad_len = 22;
 105        if (a4_included)
 106                aad_len += 6;
 107        if (qc_included) {
 108                pos = (u8 *) & hdr->addr4;
 109                if (a4_included)
 110                        pos += 6;
 111                qc = *pos & 0x0f;
 112                aad_len += 2;
 113        }
 114
 115        /* In CCM, the initial vectors (IV) used for CTR mode encryption and CBC
 116         * mode authentication are not allowed to collide, yet both are derived
 117         * from the same vector. We only set L := 1 here to indicate that the
 118         * data size can be represented in (L+1) bytes. The CCM layer will take
 119         * care of storing the data length in the top (L+1) bytes and setting
 120         * and clearing the other bits as is required to derive the two IVs.
 121         */
 122        iv[0] = 0x1;
 123
 124        /* Nonce: QC | A2 | PN */
 125        iv[1] = qc;
 126        memcpy(iv + 2, hdr->addr2, ETH_ALEN);
 127        memcpy(iv + 8, pn, CCMP_PN_LEN);
 128
 129        /* AAD:
 130         * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
 131         * A1 | A2 | A3
 132         * SC with bits 4..15 (seq#) masked to zero
 133         * A4 (if present)
 134         * QC (if present)
 135         */
 136        pos = (u8 *) hdr;
 137        aad[0] = pos[0] & 0x8f;
 138        aad[1] = pos[1] & 0xc7;
 139        memcpy(aad + 2, hdr->addr1, 3 * ETH_ALEN);
 140        pos = (u8 *) & hdr->seq_ctrl;
 141        aad[20] = pos[0] & 0x0f;
 142        aad[21] = 0;            /* all bits masked */
 143        memset(aad + 22, 0, 8);
 144        if (a4_included)
 145                memcpy(aad + 22, hdr->addr4, ETH_ALEN);
 146        if (qc_included) {
 147                aad[a4_included ? 28 : 22] = qc;
 148                /* rest of QC masked */
 149        }
 150        return aad_len;
 151}
 152
 153static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
 154                              u8 *aeskey, int keylen, void *priv)
 155{
 156        struct lib80211_ccmp_data *key = priv;
 157        int i;
 158        u8 *pos;
 159
 160        if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
 161                return -1;
 162
 163        if (aeskey != NULL && keylen >= CCMP_TK_LEN)
 164                memcpy(aeskey, key->key, CCMP_TK_LEN);
 165
 166        pos = skb_push(skb, CCMP_HDR_LEN);
 167        memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
 168        pos += hdr_len;
 169
 170        i = CCMP_PN_LEN - 1;
 171        while (i >= 0) {
 172                key->tx_pn[i]++;
 173                if (key->tx_pn[i] != 0)
 174                        break;
 175                i--;
 176        }
 177
 178        *pos++ = key->tx_pn[5];
 179        *pos++ = key->tx_pn[4];
 180        *pos++ = 0;
 181        *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
 182        *pos++ = key->tx_pn[3];
 183        *pos++ = key->tx_pn[2];
 184        *pos++ = key->tx_pn[1];
 185        *pos++ = key->tx_pn[0];
 186
 187        return CCMP_HDR_LEN;
 188}
 189
 190static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 191{
 192        struct lib80211_ccmp_data *key = priv;
 193        struct ieee80211_hdr *hdr;
 194        struct aead_request *req;
 195        struct scatterlist sg[2];
 196        u8 *aad = key->tx_aad;
 197        u8 iv[AES_BLOCK_LEN];
 198        int len, data_len, aad_len;
 199        int ret;
 200
 201        if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
 202                return -1;
 203
 204        data_len = skb->len - hdr_len;
 205        len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
 206        if (len < 0)
 207                return -1;
 208
 209        req = aead_request_alloc(key->tfm, GFP_ATOMIC);
 210        if (!req)
 211                return -ENOMEM;
 212
 213        hdr = (struct ieee80211_hdr *)skb->data;
 214        aad_len = ccmp_init_iv_and_aad(hdr, key->tx_pn, iv, aad);
 215
 216        skb_put(skb, CCMP_MIC_LEN);
 217
 218        sg_init_table(sg, 2);
 219        sg_set_buf(&sg[0], aad, aad_len);
 220        sg_set_buf(&sg[1], skb->data + hdr_len + CCMP_HDR_LEN,
 221                   data_len + CCMP_MIC_LEN);
 222
 223        aead_request_set_callback(req, 0, NULL, NULL);
 224        aead_request_set_ad(req, aad_len);
 225        aead_request_set_crypt(req, sg, sg, data_len, iv);
 226
 227        ret = crypto_aead_encrypt(req);
 228        aead_request_free(req);
 229
 230        return ret;
 231}
 232
 233/*
 234 * deal with seq counter wrapping correctly.
 235 * refer to timer_after() for jiffies wrapping handling
 236 */
 237static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
 238{
 239        u32 iv32_n, iv16_n;
 240        u32 iv32_o, iv16_o;
 241
 242        iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
 243        iv16_n = (pn_n[4] << 8) | pn_n[5];
 244
 245        iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
 246        iv16_o = (pn_o[4] << 8) | pn_o[5];
 247
 248        if ((s32)iv32_n - (s32)iv32_o < 0 ||
 249            (iv32_n == iv32_o && iv16_n <= iv16_o))
 250                return 1;
 251        return 0;
 252}
 253
 254static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 255{
 256        struct lib80211_ccmp_data *key = priv;
 257        u8 keyidx, *pos;
 258        struct ieee80211_hdr *hdr;
 259        struct aead_request *req;
 260        struct scatterlist sg[2];
 261        u8 *aad = key->rx_aad;
 262        u8 iv[AES_BLOCK_LEN];
 263        u8 pn[6];
 264        int aad_len, ret;
 265        size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN;
 266
 267        if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
 268                key->dot11RSNAStatsCCMPFormatErrors++;
 269                return -1;
 270        }
 271
 272        hdr = (struct ieee80211_hdr *)skb->data;
 273        pos = skb->data + hdr_len;
 274        keyidx = pos[3];
 275        if (!(keyidx & (1 << 5))) {
 276                net_dbg_ratelimited("CCMP: received packet without ExtIV flag from %pM\n",
 277                                    hdr->addr2);
 278                key->dot11RSNAStatsCCMPFormatErrors++;
 279                return -2;
 280        }
 281        keyidx >>= 6;
 282        if (key->key_idx != keyidx) {
 283                net_dbg_ratelimited("CCMP: RX tkey->key_idx=%d frame keyidx=%d\n",
 284                                    key->key_idx, keyidx);
 285                return -6;
 286        }
 287        if (!key->key_set) {
 288                net_dbg_ratelimited("CCMP: received packet from %pM with keyid=%d that does not have a configured key\n",
 289                                    hdr->addr2, keyidx);
 290                return -3;
 291        }
 292
 293        pn[0] = pos[7];
 294        pn[1] = pos[6];
 295        pn[2] = pos[5];
 296        pn[3] = pos[4];
 297        pn[4] = pos[1];
 298        pn[5] = pos[0];
 299        pos += 8;
 300
 301        if (ccmp_replay_check(pn, key->rx_pn)) {
 302#ifdef CONFIG_LIB80211_DEBUG
 303                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",
 304                                    hdr->addr2,
 305                                    key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
 306                                    key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
 307                                    pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
 308#endif
 309                key->dot11RSNAStatsCCMPReplays++;
 310                return -4;
 311        }
 312
 313        req = aead_request_alloc(key->tfm, GFP_ATOMIC);
 314        if (!req)
 315                return -ENOMEM;
 316
 317        aad_len = ccmp_init_iv_and_aad(hdr, pn, iv, aad);
 318
 319        sg_init_table(sg, 2);
 320        sg_set_buf(&sg[0], aad, aad_len);
 321        sg_set_buf(&sg[1], pos, data_len);
 322
 323        aead_request_set_callback(req, 0, NULL, NULL);
 324        aead_request_set_ad(req, aad_len);
 325        aead_request_set_crypt(req, sg, sg, data_len, iv);
 326
 327        ret = crypto_aead_decrypt(req);
 328        aead_request_free(req);
 329
 330        if (ret) {
 331                net_dbg_ratelimited("CCMP: decrypt failed: STA=%pM (%d)\n",
 332                                    hdr->addr2, ret);
 333                key->dot11RSNAStatsCCMPDecryptErrors++;
 334                return -5;
 335        }
 336
 337        memcpy(key->rx_pn, pn, CCMP_PN_LEN);
 338
 339        /* Remove hdr and MIC */
 340        memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
 341        skb_pull(skb, CCMP_HDR_LEN);
 342        skb_trim(skb, skb->len - CCMP_MIC_LEN);
 343
 344        return keyidx;
 345}
 346
 347static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
 348{
 349        struct lib80211_ccmp_data *data = priv;
 350        int keyidx;
 351        struct crypto_aead *tfm = data->tfm;
 352
 353        keyidx = data->key_idx;
 354        memset(data, 0, sizeof(*data));
 355        data->key_idx = keyidx;
 356        data->tfm = tfm;
 357        if (len == CCMP_TK_LEN) {
 358                memcpy(data->key, key, CCMP_TK_LEN);
 359                data->key_set = 1;
 360                if (seq) {
 361                        data->rx_pn[0] = seq[5];
 362                        data->rx_pn[1] = seq[4];
 363                        data->rx_pn[2] = seq[3];
 364                        data->rx_pn[3] = seq[2];
 365                        data->rx_pn[4] = seq[1];
 366                        data->rx_pn[5] = seq[0];
 367                }
 368                if (crypto_aead_setauthsize(data->tfm, CCMP_MIC_LEN) ||
 369                    crypto_aead_setkey(data->tfm, data->key, CCMP_TK_LEN))
 370                        return -1;
 371        } else if (len == 0)
 372                data->key_set = 0;
 373        else
 374                return -1;
 375
 376        return 0;
 377}
 378
 379static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
 380{
 381        struct lib80211_ccmp_data *data = priv;
 382
 383        if (len < CCMP_TK_LEN)
 384                return -1;
 385
 386        if (!data->key_set)
 387                return 0;
 388        memcpy(key, data->key, CCMP_TK_LEN);
 389
 390        if (seq) {
 391                seq[0] = data->tx_pn[5];
 392                seq[1] = data->tx_pn[4];
 393                seq[2] = data->tx_pn[3];
 394                seq[3] = data->tx_pn[2];
 395                seq[4] = data->tx_pn[1];
 396                seq[5] = data->tx_pn[0];
 397        }
 398
 399        return CCMP_TK_LEN;
 400}
 401
 402static void lib80211_ccmp_print_stats(struct seq_file *m, void *priv)
 403{
 404        struct lib80211_ccmp_data *ccmp = priv;
 405
 406        seq_printf(m,
 407                   "key[%d] alg=CCMP key_set=%d "
 408                   "tx_pn=%02x%02x%02x%02x%02x%02x "
 409                   "rx_pn=%02x%02x%02x%02x%02x%02x "
 410                   "format_errors=%d replays=%d decrypt_errors=%d\n",
 411                   ccmp->key_idx, ccmp->key_set,
 412                   ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
 413                   ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
 414                   ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
 415                   ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
 416                   ccmp->dot11RSNAStatsCCMPFormatErrors,
 417                   ccmp->dot11RSNAStatsCCMPReplays,
 418                   ccmp->dot11RSNAStatsCCMPDecryptErrors);
 419}
 420
 421static struct lib80211_crypto_ops lib80211_crypt_ccmp = {
 422        .name = "CCMP",
 423        .init = lib80211_ccmp_init,
 424        .deinit = lib80211_ccmp_deinit,
 425        .encrypt_mpdu = lib80211_ccmp_encrypt,
 426        .decrypt_mpdu = lib80211_ccmp_decrypt,
 427        .encrypt_msdu = NULL,
 428        .decrypt_msdu = NULL,
 429        .set_key = lib80211_ccmp_set_key,
 430        .get_key = lib80211_ccmp_get_key,
 431        .print_stats = lib80211_ccmp_print_stats,
 432        .extra_mpdu_prefix_len = CCMP_HDR_LEN,
 433        .extra_mpdu_postfix_len = CCMP_MIC_LEN,
 434        .owner = THIS_MODULE,
 435};
 436
 437static int __init lib80211_crypto_ccmp_init(void)
 438{
 439        return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
 440}
 441
 442static void __exit lib80211_crypto_ccmp_exit(void)
 443{
 444        lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
 445}
 446
 447module_init(lib80211_crypto_ccmp_init);
 448module_exit(lib80211_crypto_ccmp_exit);
 449