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