wpa_supplicant/mesh_rsn.c

   1 /*
   2  * WPA Supplicant - Mesh RSN routines
   3  * Copyright (c) 2013-2014, cozybit, Inc.  All rights reserved.
   4  *
   5  * This software may be distributed under the terms of the BSD license.
   6  * See README for more details.
   7  */
   8
   9 #include "utils/includes.h"
  10
  11 #include "utils/common.h"
  12 #include "utils/eloop.h"
  13 #include "crypto/sha256.h"
  14 #include "crypto/random.h"
  15 #include "crypto/aes.h"
  16 #include "crypto/aes_siv.h"
  17 #include "rsn_supp/wpa.h"
  18 #include "ap/hostapd.h"
  19 #include "ap/wpa_auth.h"
  20 #include "ap/sta_info.h"
  21 #include "ap/ieee802_11.h"
  22 #include "wpa_supplicant_i.h"
  23 #include "driver_i.h"
  24 #include "wpas_glue.h"
  25 #include "mesh_mpm.h"
  26 #include "mesh_rsn.h"
  27
  28 #define MESH_AUTH_TIMEOUT 10
  29 #define MESH_AUTH_RETRY 3
  30
  31 void mesh_auth_timer(void *eloop_ctx, void *user_data)
  32 {
  33         struct wpa_supplicant *wpa_s = eloop_ctx;
  34         struct sta_info *sta = user_data;
  35
  36         if (sta->sae->state != SAE_ACCEPTED) {
  37                 wpa_printf(MSG_DEBUG, "AUTH: Re-authenticate with " MACSTR
  38                            " (attempt %d) ",
  39                            MAC2STR(sta->addr), sta->sae_auth_retry);
  40                 if (sta->sae_auth_retry < MESH_AUTH_RETRY) {
  41                         mesh_rsn_auth_sae_sta(wpa_s, sta);
  42                 } else {
  43                         /* block the STA if exceeded the number of attempts */
  44                         sta->plink_state = PLINK_BLOCKED;
  45                         sta->sae->state = SAE_NOTHING;
  46                 }
  47                 sta->sae_auth_retry++;
  48         }
  49 }
  50
  51
  52 static void auth_logger(void *ctx, const u8 *addr, logger_level level,
  53                         const char *txt)
  54 {
  55         if (addr)
  56                 wpa_printf(MSG_DEBUG, "AUTH: " MACSTR " - %s",
  57                            MAC2STR(addr), txt);
  58         else
  59                 wpa_printf(MSG_DEBUG, "AUTH: %s", txt);
  60 }
  61
  62
  63 static const u8 *auth_get_psk(void *ctx, const u8 *addr,
  64                               const u8 *p2p_dev_addr, const u8 *prev_psk)
  65 {
  66         struct mesh_rsn *mesh_rsn = ctx;
  67         struct hostapd_data *hapd = mesh_rsn->wpa_s->ifmsh->bss[0];
  68         struct sta_info *sta = ap_get_sta(hapd, addr);
  69
  70         wpa_printf(MSG_DEBUG, "AUTH: %s (addr=" MACSTR " prev_psk=%p)",
  71                    __func__, MAC2STR(addr), prev_psk);
  72
  73         if (sta && sta->auth_alg == WLAN_AUTH_SAE) {
  74                 if (!sta->sae || prev_psk)
  75                         return NULL;
  76                 return sta->sae->pmk;
  77         }
  78
  79         return NULL;
  80 }
  81
  82
  83 static int auth_set_key(void *ctx, int vlan_id, enum wpa_alg alg,
  84                         const u8 *addr, int idx, u8 *key, size_t key_len)
  85 {
  86         struct mesh_rsn *mesh_rsn = ctx;
  87         u8 seq[6];
  88
  89         os_memset(seq, 0, sizeof(seq));
  90
  91         if (addr) {
  92                 wpa_printf(MSG_DEBUG, "AUTH: %s(alg=%d addr=" MACSTR
  93                            " key_idx=%d)",
  94                            __func__, alg, MAC2STR(addr), idx);
  95         } else {
  96                 wpa_printf(MSG_DEBUG, "AUTH: %s(alg=%d key_idx=%d)",
  97                            __func__, alg, idx);
  98         }
  99         wpa_hexdump_key(MSG_DEBUG, "AUTH: set_key - key", key, key_len);
 100
 101         return wpa_drv_set_key(mesh_rsn->wpa_s, alg, addr, idx,
 102                                1, seq, 6, key, key_len);
 103 }
 104
 105
 106 static int auth_start_ampe(void *ctx, const u8 *addr)
 107 {
 108         struct mesh_rsn *mesh_rsn = ctx;
 109         struct hostapd_data *hapd;
 110         struct sta_info *sta;
 111
 112         if (mesh_rsn->wpa_s->current_ssid->mode != WPAS_MODE_MESH)
 113                 return -1;
 114
 115         hapd = mesh_rsn->wpa_s->ifmsh->bss[0];
 116         sta = ap_get_sta(hapd, addr);
 117         if (sta)
 118                 eloop_cancel_timeout(mesh_auth_timer, mesh_rsn->wpa_s, sta);
 119
 120         mesh_mpm_auth_peer(mesh_rsn->wpa_s, addr);
 121         return 0;
 122 }
 123
 124
 125 static int __mesh_rsn_auth_init(struct mesh_rsn *rsn, const u8 *addr)
 126 {
 127         struct wpa_auth_config conf;
 128         struct wpa_auth_callbacks cb;
 129         u8 seq[6] = {};
 130
 131         wpa_printf(MSG_DEBUG, "AUTH: Initializing group state machine");
 132
 133         os_memset(&conf, 0, sizeof(conf));
 134         conf.wpa = 2;
 135         conf.wpa_key_mgmt = WPA_KEY_MGMT_SAE;
 136         conf.wpa_pairwise = WPA_CIPHER_CCMP;
 137         conf.rsn_pairwise = WPA_CIPHER_CCMP;
 138         conf.wpa_group = WPA_CIPHER_CCMP;
 139         conf.eapol_version = 0;
 140         conf.wpa_group_rekey = -1;
 141
 142         os_memset(&cb, 0, sizeof(cb));
 143         cb.ctx = rsn;
 144         cb.logger = auth_logger;
 145         cb.get_psk = auth_get_psk;
 146         cb.set_key = auth_set_key;
 147         cb.start_ampe = auth_start_ampe;
 148
 149         rsn->auth = wpa_init(addr, &conf, &cb);
 150         if (rsn->auth == NULL) {
 151                 wpa_printf(MSG_DEBUG, "AUTH: wpa_init() failed");
 152                 return -1;
 153         }
 154
 155         /* TODO: support rekeying */
 156         if (random_get_bytes(rsn->mgtk, 16) < 0) {
 157                 wpa_deinit(rsn->auth);
 158                 return -1;
 159         }
 160
 161         /* group mgmt */
 162         wpa_drv_set_key(rsn->wpa_s, WPA_ALG_IGTK, NULL, 4, 1,
 163                         seq, sizeof(seq), rsn->mgtk, sizeof(rsn->mgtk));
 164
 165         /* group privacy / data frames */
 166         wpa_drv_set_key(rsn->wpa_s, WPA_ALG_CCMP, NULL, 1, 1,
 167                         seq, sizeof(seq), rsn->mgtk, sizeof(rsn->mgtk));
 168
 169         return 0;
 170 }
 171
 172
 173 static void mesh_rsn_deinit(struct mesh_rsn *rsn)
 174 {
 175         os_memset(rsn->mgtk, 0, sizeof(rsn->mgtk));
 176         wpa_deinit(rsn->auth);
 177 }
 178
 179
 180 struct mesh_rsn *mesh_rsn_auth_init(struct wpa_supplicant *wpa_s,
 181                                     struct mesh_conf *conf)
 182 {
 183         struct mesh_rsn *mesh_rsn;
 184         struct hostapd_data *bss = wpa_s->ifmsh->bss[0];
 185         const u8 *ie;
 186         size_t ie_len;
 187
 188         mesh_rsn = os_zalloc(sizeof(*mesh_rsn));
 189         if (mesh_rsn == NULL)
 190                 return NULL;
 191         mesh_rsn->wpa_s = wpa_s;
 192
 193         if (__mesh_rsn_auth_init(mesh_rsn, wpa_s->own_addr) < 0) {
 194                 mesh_rsn_deinit(mesh_rsn);
 195                 return NULL;
 196         }
 197
 198         bss->wpa_auth = mesh_rsn->auth;
 199
 200         ie = wpa_auth_get_wpa_ie(mesh_rsn->auth, &ie_len);
 201         conf->ies = (u8 *) ie;
 202         conf->ie_len = ie_len;
 203
 204         wpa_supplicant_rsn_supp_set_config(wpa_s, wpa_s->current_ssid);
 205
 206         return mesh_rsn;
 207 }
 208
 209
 210 static int index_within_array(const int *array, int idx)
 211 {
 212         int i;
 213
 214         for (i = 0; i < idx; i++) {
 215                 if (array[i] == -1)
 216                         return 0;
 217         }
 218
 219         return 1;
 220 }
 221
 222
 223 static int mesh_rsn_sae_group(struct wpa_supplicant *wpa_s,
 224                               struct sae_data *sae)
 225 {
 226         int *groups = wpa_s->ifmsh->bss[0]->conf->sae_groups;
 227
 228         /* Configuration may have changed, so validate current index */
 229         if (!index_within_array(groups, wpa_s->mesh_rsn->sae_group_index))
 230                 return -1;
 231
 232         for (;;) {
 233                 int group = groups[wpa_s->mesh_rsn->sae_group_index];
 234
 235                 if (group <= 0)
 236                         break;
 237                 if (sae_set_group(sae, group) == 0) {
 238                         wpa_dbg(wpa_s, MSG_DEBUG, "SME: Selected SAE group %d",
 239                                 sae->group);
 240                         return 0;
 241                 }
 242                 wpa_s->mesh_rsn->sae_group_index++;
 243         }
 244
 245         return -1;
 246 }
 247
 248
 249 static int mesh_rsn_build_sae_commit(struct wpa_supplicant *wpa_s,
 250                                      struct wpa_ssid *ssid,
 251                                      struct sta_info *sta)
 252 {
 253         if (ssid->passphrase == NULL) {
 254                 wpa_msg(wpa_s, MSG_DEBUG, "SAE: No password available");
 255                 return -1;
 256         }
 257
 258         if (mesh_rsn_sae_group(wpa_s, sta->sae) < 0) {
 259                 wpa_msg(wpa_s, MSG_DEBUG, "SAE: Failed to select group");
 260                 return -1;
 261         }
 262
 263         return sae_prepare_commit(wpa_s->own_addr, sta->addr,
 264                                   (u8 *) ssid->passphrase,
 265                                   os_strlen(ssid->passphrase), sta->sae);
 266 }
 267
 268
 269 /* initiate new SAE authentication with sta */
 270 int mesh_rsn_auth_sae_sta(struct wpa_supplicant *wpa_s,
 271                           struct sta_info *sta)
 272 {
 273         struct hostapd_data *hapd = wpa_s->ifmsh->bss[0];
 274         struct wpa_ssid *ssid = wpa_s->current_ssid;
 275         unsigned int rnd;
 276         int ret;
 277
 278         if (!ssid) {
 279                 wpa_msg(wpa_s, MSG_DEBUG,
 280                         "AUTH: No current_ssid known to initiate new SAE");
 281                 return -1;
 282         }
 283
 284         if (!sta->sae) {
 285                 sta->sae = os_zalloc(sizeof(*sta->sae));
 286                 if (sta->sae == NULL)
 287                         return -1;
 288         }
 289
 290         if (mesh_rsn_build_sae_commit(wpa_s, ssid, sta))
 291                 return -1;
 292
 293         wpa_msg(wpa_s, MSG_DEBUG,
 294                 "AUTH: started authentication with SAE peer: " MACSTR,
 295                 MAC2STR(sta->addr));
 296
 297         wpa_supplicant_set_state(wpa_s, WPA_AUTHENTICATING);
 298         ret = auth_sae_init_committed(hapd, sta);
 299         if (ret)
 300                 return ret;
 301
 302         rnd = rand() % MESH_AUTH_TIMEOUT;
 303         eloop_register_timeout(MESH_AUTH_TIMEOUT + rnd, 0, mesh_auth_timer,
 304                                wpa_s, sta);
 305         return 0;
 306 }
 307
 308
 309 void mesh_rsn_get_pmkid(struct mesh_rsn *rsn, struct sta_info *sta, u8 *pmkid)
 310 {
 311         /* don't expect wpa auth to cache the pmkid for now */
 312         rsn_pmkid(sta->sae->pmk, PMK_LEN, rsn->wpa_s->own_addr,
 313                   sta->addr, pmkid,
 314                   wpa_key_mgmt_sha256(wpa_auth_sta_key_mgmt(sta->wpa_sm)));
 315 }
 316
 317
 318 static void
 319 mesh_rsn_derive_aek(struct mesh_rsn *rsn, struct sta_info *sta)
 320 {
 321         u8 *myaddr = rsn->wpa_s->own_addr;
 322         u8 *peer = sta->addr;
 323         u8 *addr1 = peer, *addr2 = myaddr;
 324         u8 context[AES_BLOCK_SIZE];
 325
 326         /* SAE */
 327         RSN_SELECTOR_PUT(context, wpa_cipher_to_suite(0, WPA_CIPHER_GCMP));
 328
 329         if (os_memcmp(myaddr, peer, ETH_ALEN) < 0) {
 330                 addr1 = myaddr;
 331                 addr2 = peer;
 332         }
 333         os_memcpy(context + 4, addr1, ETH_ALEN);
 334         os_memcpy(context + 10, addr2, ETH_ALEN);
 335
 336         sha256_prf(sta->sae->pmk, sizeof(sta->sae->pmk), "AEK Derivation",
 337                    context, sizeof(context), sta->aek, sizeof(sta->aek));
 338 }
 339
 340
 341 /* derive mesh temporal key from pmk */
 342 int mesh_rsn_derive_mtk(struct wpa_supplicant *wpa_s, struct sta_info *sta)
 343 {
 344         u8 *ptr;
 345         u8 *min, *max;
 346         u16 min_lid, max_lid;
 347         size_t nonce_len = sizeof(sta->my_nonce);
 348         size_t lid_len = sizeof(sta->my_lid);
 349         u8 *myaddr = wpa_s->own_addr;
 350         u8 *peer = sta->addr;
 351         /* 2 nonces, 2 linkids, akm suite, 2 mac addrs */
 352         u8 context[64 + 4 + 4 + 12];
 353
 354         ptr = context;
 355         if (os_memcmp(sta->my_nonce, sta->peer_nonce, nonce_len) < 0) {
 356                 min = sta->my_nonce;
 357                 max = sta->peer_nonce;
 358         } else {
 359                 min = sta->peer_nonce;
 360                 max = sta->my_nonce;
 361         }
 362         os_memcpy(ptr, min, nonce_len);
 363         os_memcpy(ptr + nonce_len, max, nonce_len);
 364         ptr += 2 * nonce_len;
 365
 366         if (sta->my_lid < sta->peer_lid) {
 367                 min_lid = host_to_le16(sta->my_lid);
 368                 max_lid = host_to_le16(sta->peer_lid);
 369         } else {
 370                 min_lid = host_to_le16(sta->peer_lid);
 371                 max_lid = host_to_le16(sta->my_lid);
 372         }
 373         os_memcpy(ptr, &min_lid, lid_len);
 374         os_memcpy(ptr + lid_len, &max_lid, lid_len);
 375         ptr += 2 * lid_len;
 376
 377         /* SAE */
 378         RSN_SELECTOR_PUT(ptr, wpa_cipher_to_suite(0, WPA_CIPHER_GCMP));
 379         ptr += 4;
 380
 381         if (os_memcmp(myaddr, peer, ETH_ALEN) < 0) {
 382                 min = myaddr;
 383                 max = peer;
 384         } else {
 385                 min = peer;
 386                 max = myaddr;
 387         }
 388         os_memcpy(ptr, min, ETH_ALEN);
 389         os_memcpy(ptr + ETH_ALEN, max, ETH_ALEN);
 390
 391         sha256_prf(sta->sae->pmk, sizeof(sta->sae->pmk),
 392                    "Temporal Key Derivation", context, sizeof(context),
 393                    sta->mtk, sizeof(sta->mtk));
 394         return 0;
 395 }
 396
 397
 398 void mesh_rsn_init_ampe_sta(struct wpa_supplicant *wpa_s, struct sta_info *sta)
 399 {
 400         if (random_get_bytes(sta->my_nonce, 32) < 0) {
 401                 wpa_printf(MSG_INFO, "mesh: Failed to derive random nonce");
 402                 /* TODO: How to handle this more cleanly? */
 403         }
 404         os_memset(sta->peer_nonce, 0, 32);
 405         mesh_rsn_derive_aek(wpa_s->mesh_rsn, sta);
 406 }
 407
 408
 409 /* insert AMPE and encrypted MIC at @ie.
 410  * @mesh_rsn: mesh RSN context
 411  * @sta: STA we're sending to
 412  * @cat: pointer to category code in frame header.
 413  * @buf: wpabuf to add encrypted AMPE and MIC to.
 414  * */
 415 int mesh_rsn_protect_frame(struct mesh_rsn *rsn, struct sta_info *sta,
 416                            const u8 *cat, struct wpabuf *buf)
 417 {
 418         struct ieee80211_ampe_ie *ampe;
 419         u8 const *ie = wpabuf_head_u8(buf) + wpabuf_len(buf);
 420         u8 *ampe_ie = NULL, *mic_ie = NULL, *mic_payload;
 421         const u8 *aad[] = { rsn->wpa_s->own_addr, sta->addr, cat };
 422         const size_t aad_len[] = { ETH_ALEN, ETH_ALEN, ie - cat };
 423         int ret = 0;
 424
 425         if (AES_BLOCK_SIZE + 2 + sizeof(*ampe) + 2 > wpabuf_tailroom(buf)) {
 426                 wpa_printf(MSG_ERROR, "protect frame: buffer too small");
 427                 return -EINVAL;
 428         }
 429
 430         ampe_ie = os_zalloc(2 + sizeof(*ampe));
 431         if (!ampe_ie) {
 432                 wpa_printf(MSG_ERROR, "protect frame: out of memory");
 433                 return -ENOMEM;
 434         }
 435
 436         mic_ie = os_zalloc(2 + AES_BLOCK_SIZE);
 437         if (!mic_ie) {
 438                 wpa_printf(MSG_ERROR, "protect frame: out of memory");
 439                 ret = -ENOMEM;
 440                 goto free;
 441         }
 442
 443         /*  IE: AMPE */
 444         ampe_ie[0] = WLAN_EID_AMPE;
 445         ampe_ie[1] = sizeof(*ampe);
 446         ampe = (struct ieee80211_ampe_ie *) (ampe_ie + 2);
 447
 448         RSN_SELECTOR_PUT(ampe->selected_pairwise_suite,
 449                      wpa_cipher_to_suite(WPA_PROTO_RSN, WPA_CIPHER_CCMP));
 450         os_memcpy(ampe->local_nonce, sta->my_nonce, 32);
 451         os_memcpy(ampe->peer_nonce, sta->peer_nonce, 32);
 452         /* incomplete: see 13.5.4 */
 453         /* TODO: static mgtk for now since we don't support rekeying! */
 454         os_memcpy(ampe->mgtk, rsn->mgtk, 16);
 455         /*  TODO: Populate Key RSC */
 456         /*  expire in 13 decades or so */
 457         os_memset(ampe->key_expiration, 0xff, 4);
 458
 459         /* IE: MIC */
 460         mic_ie[0] = WLAN_EID_MIC;
 461         mic_ie[1] = AES_BLOCK_SIZE;
 462         wpabuf_put_data(buf, mic_ie, 2);
 463         /* MIC field is output ciphertext */
 464
 465         /* encrypt after MIC */
 466         mic_payload = (u8 *) wpabuf_put(buf, 2 + sizeof(*ampe) +
 467                                         AES_BLOCK_SIZE);
 468
 469         if (aes_siv_encrypt(sta->aek, ampe_ie, 2 + sizeof(*ampe), 3,
 470                             aad, aad_len, mic_payload)) {
 471                 wpa_printf(MSG_ERROR, "protect frame: failed to encrypt");
 472                 ret = -ENOMEM;
 473                 goto free;
 474         }
 475
 476 free:
 477         os_free(ampe_ie);
 478         os_free(mic_ie);
 479
 480         return ret;
 481 }
 482
 483
 484 int mesh_rsn_process_ampe(struct wpa_supplicant *wpa_s, struct sta_info *sta,
 485                           struct ieee802_11_elems *elems, const u8 *cat,
 486                           const u8 *start, size_t elems_len)
 487 {
 488         int ret = 0;
 489         struct ieee80211_ampe_ie *ampe;
 490         u8 null_nonce[32] = {};
 491         u8 ampe_eid;
 492         u8 ampe_ie_len;
 493         u8 *ampe_buf, *crypt = NULL;
 494         size_t crypt_len;
 495         const u8 *aad[] = { sta->addr, wpa_s->own_addr, cat };
 496         const size_t aad_len[] = { ETH_ALEN, ETH_ALEN,
 497                                    (elems->mic - 2) - cat };
 498
 499         if (!elems->mic || elems->mic_len < AES_BLOCK_SIZE) {
 500                 wpa_msg(wpa_s, MSG_DEBUG, "Mesh RSN: missing mic ie");
 501                 return -1;
 502         }
 503
 504         ampe_buf = (u8 *) elems->mic + elems->mic_len;
 505         if ((int) elems_len < ampe_buf - start)
 506                 return -1;
 507
 508         crypt_len = elems_len - (elems->mic - start);
 509         if (crypt_len < 2) {
 510                 wpa_msg(wpa_s, MSG_DEBUG, "Mesh RSN: missing ampe ie");
 511                 return -1;
 512         }
 513
 514         /* crypt is modified by siv_decrypt */
 515         crypt = os_zalloc(crypt_len);
 516         if (!crypt) {
 517                 wpa_printf(MSG_ERROR, "Mesh RSN: out of memory");
 518                 ret = -ENOMEM;
 519                 goto free;
 520         }
 521
 522         os_memcpy(crypt, elems->mic, crypt_len);
 523
 524         if (aes_siv_decrypt(sta->aek, crypt, crypt_len, 3,
 525                             aad, aad_len, ampe_buf)) {
 526                 wpa_printf(MSG_ERROR, "Mesh RSN: frame verification failed!");
 527                 ret = -1;
 528                 goto free;
 529         }
 530
 531         ampe_eid = *ampe_buf++;
 532         ampe_ie_len = *ampe_buf++;
 533
 534         if (ampe_eid != WLAN_EID_AMPE ||
 535             ampe_ie_len < sizeof(struct ieee80211_ampe_ie)) {
 536                 wpa_msg(wpa_s, MSG_DEBUG, "Mesh RSN: invalid ampe ie");
 537                 ret = -1;
 538                 goto free;
 539         }
 540
 541         ampe = (struct ieee80211_ampe_ie *) ampe_buf;
 542         if (os_memcmp(ampe->peer_nonce, null_nonce, 32) != 0 &&
 543             os_memcmp(ampe->peer_nonce, sta->my_nonce, 32) != 0) {
 544                 wpa_msg(wpa_s, MSG_DEBUG, "Mesh RSN: invalid peer nonce");
 545                 ret = -1;
 546                 goto free;
 547         }
 548         os_memcpy(sta->peer_nonce, ampe->local_nonce,
 549                   sizeof(ampe->local_nonce));
 550         os_memcpy(sta->mgtk, ampe->mgtk, sizeof(ampe->mgtk));
 551
 552         /* todo parse mgtk expiration */
 553 free:
 554         os_free(crypt);
 555         return ret;
 556 }