net/wireless/lib80211_crypt_ccmp.c

   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
  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 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
  59 static 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
  86 static 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
  94 static 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
 153 static 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
 190 static 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  */
 237 static 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
 254 static 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
 347 static 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
 379 static 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
 402 static 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
 421 static 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
 437 static int __init lib80211_crypto_ccmp_init(void)
 438 {
 439         return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
 440 }
 441
 442 static void __exit lib80211_crypto_ccmp_exit(void)
 443 {
 444         lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
 445 }
 446
 447 module_init(lib80211_crypto_ccmp_init);
 448 module_exit(lib80211_crypto_ccmp_exit);