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      1 /*
      2  * WPA Supplicant - RSN PMKSA cache
      3  * Copyright (c) 2004-2009, 2011-2012, Jouni Malinen <j (at) w1.fi>
      4  *
      5  * This software may be distributed under the terms of the BSD license.
      6  * See README for more details.
      7  */
      8 
      9 #include "includes.h"
     10 
     11 #include "common.h"
     12 #include "eloop.h"
     13 #include "eapol_supp/eapol_supp_sm.h"
     14 #include "wpa.h"
     15 #include "wpa_i.h"
     16 #include "pmksa_cache.h"
     17 
     18 #if defined(IEEE8021X_EAPOL) && !defined(CONFIG_NO_WPA2)
     19 
     20 static const int pmksa_cache_max_entries = 32;
     21 
     22 struct rsn_pmksa_cache {
     23 	struct rsn_pmksa_cache_entry *pmksa; /* PMKSA cache */
     24 	int pmksa_count; /* number of entries in PMKSA cache */
     25 	struct wpa_sm *sm; /* TODO: get rid of this reference(?) */
     26 
     27 	void (*free_cb)(struct rsn_pmksa_cache_entry *entry, void *ctx,
     28 			int replace);
     29 	void *ctx;
     30 };
     31 
     32 
     33 static void pmksa_cache_set_expiration(struct rsn_pmksa_cache *pmksa);
     34 
     35 
     36 static void _pmksa_cache_free_entry(struct rsn_pmksa_cache_entry *entry)
     37 {
     38 	os_free(entry);
     39 }
     40 
     41 
     42 static void pmksa_cache_free_entry(struct rsn_pmksa_cache *pmksa,
     43 				   struct rsn_pmksa_cache_entry *entry,
     44 				   int replace)
     45 {
     46 	wpa_sm_remove_pmkid(pmksa->sm, entry->aa, entry->pmkid);
     47 	pmksa->pmksa_count--;
     48 	pmksa->free_cb(entry, pmksa->ctx, replace);
     49 	_pmksa_cache_free_entry(entry);
     50 }
     51 
     52 
     53 static void pmksa_cache_expire(void *eloop_ctx, void *timeout_ctx)
     54 {
     55 	struct rsn_pmksa_cache *pmksa = eloop_ctx;
     56 	struct os_time now;
     57 
     58 	os_get_time(&now);
     59 	while (pmksa->pmksa && pmksa->pmksa->expiration <= now.sec) {
     60 		struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;
     61 		pmksa->pmksa = entry->next;
     62 		wpa_printf(MSG_DEBUG, "RSN: expired PMKSA cache entry for "
     63 			   MACSTR, MAC2STR(entry->aa));
     64 		pmksa_cache_free_entry(pmksa, entry, 0);
     65 	}
     66 
     67 	pmksa_cache_set_expiration(pmksa);
     68 }
     69 
     70 
     71 static void pmksa_cache_reauth(void *eloop_ctx, void *timeout_ctx)
     72 {
     73 	struct rsn_pmksa_cache *pmksa = eloop_ctx;
     74 	pmksa->sm->cur_pmksa = NULL;
     75 	eapol_sm_request_reauth(pmksa->sm->eapol);
     76 }
     77 
     78 
     79 static void pmksa_cache_set_expiration(struct rsn_pmksa_cache *pmksa)
     80 {
     81 	int sec;
     82 	struct rsn_pmksa_cache_entry *entry;
     83 	struct os_time now;
     84 
     85 	eloop_cancel_timeout(pmksa_cache_expire, pmksa, NULL);
     86 	eloop_cancel_timeout(pmksa_cache_reauth, pmksa, NULL);
     87 	if (pmksa->pmksa == NULL)
     88 		return;
     89 	os_get_time(&now);
     90 	sec = pmksa->pmksa->expiration - now.sec;
     91 	if (sec < 0)
     92 		sec = 0;
     93 	eloop_register_timeout(sec + 1, 0, pmksa_cache_expire, pmksa, NULL);
     94 
     95 	entry = pmksa->sm->cur_pmksa ? pmksa->sm->cur_pmksa :
     96 		pmksa_cache_get(pmksa, pmksa->sm->bssid, NULL, NULL);
     97 	if (entry) {
     98 		sec = pmksa->pmksa->reauth_time - now.sec;
     99 		if (sec < 0)
    100 			sec = 0;
    101 		eloop_register_timeout(sec, 0, pmksa_cache_reauth, pmksa,
    102 				       NULL);
    103 	}
    104 }
    105 
    106 
    107 /**
    108  * pmksa_cache_add - Add a PMKSA cache entry
    109  * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
    110  * @pmk: The new pairwise master key
    111  * @pmk_len: PMK length in bytes, usually PMK_LEN (32)
    112  * @aa: Authenticator address
    113  * @spa: Supplicant address
    114  * @network_ctx: Network configuration context for this PMK
    115  * @akmp: WPA_KEY_MGMT_* used in key derivation
    116  * Returns: Pointer to the added PMKSA cache entry or %NULL on error
    117  *
    118  * This function create a PMKSA entry for a new PMK and adds it to the PMKSA
    119  * cache. If an old entry is already in the cache for the same Authenticator,
    120  * this entry will be replaced with the new entry. PMKID will be calculated
    121  * based on the PMK and the driver interface is notified of the new PMKID.
    122  */
    123 struct rsn_pmksa_cache_entry *
    124 pmksa_cache_add(struct rsn_pmksa_cache *pmksa, const u8 *pmk, size_t pmk_len,
    125 		const u8 *aa, const u8 *spa, void *network_ctx, int akmp)
    126 {
    127 	struct rsn_pmksa_cache_entry *entry, *pos, *prev;
    128 	struct os_time now;
    129 
    130 	if (pmk_len > PMK_LEN)
    131 		return NULL;
    132 
    133 	entry = os_zalloc(sizeof(*entry));
    134 	if (entry == NULL)
    135 		return NULL;
    136 	os_memcpy(entry->pmk, pmk, pmk_len);
    137 	entry->pmk_len = pmk_len;
    138 	rsn_pmkid(pmk, pmk_len, aa, spa, entry->pmkid,
    139 		  wpa_key_mgmt_sha256(akmp));
    140 	os_get_time(&now);
    141 	entry->expiration = now.sec + pmksa->sm->dot11RSNAConfigPMKLifetime;
    142 	entry->reauth_time = now.sec + pmksa->sm->dot11RSNAConfigPMKLifetime *
    143 		pmksa->sm->dot11RSNAConfigPMKReauthThreshold / 100;
    144 	entry->akmp = akmp;
    145 	os_memcpy(entry->aa, aa, ETH_ALEN);
    146 	entry->network_ctx = network_ctx;
    147 
    148 	/* Replace an old entry for the same Authenticator (if found) with the
    149 	 * new entry */
    150 	pos = pmksa->pmksa;
    151 	prev = NULL;
    152 	while (pos) {
    153 		if (os_memcmp(aa, pos->aa, ETH_ALEN) == 0) {
    154 			if (pos->pmk_len == pmk_len &&
    155 			    os_memcmp(pos->pmk, pmk, pmk_len) == 0 &&
    156 			    os_memcmp(pos->pmkid, entry->pmkid, PMKID_LEN) ==
    157 			    0) {
    158 				wpa_printf(MSG_DEBUG, "WPA: reusing previous "
    159 					   "PMKSA entry");
    160 				os_free(entry);
    161 				return pos;
    162 			}
    163 			if (prev == NULL)
    164 				pmksa->pmksa = pos->next;
    165 			else
    166 				prev->next = pos->next;
    167 			if (pos == pmksa->sm->cur_pmksa) {
    168 				/* We are about to replace the current PMKSA
    169 				 * cache entry. This happens when the PMKSA
    170 				 * caching attempt fails, so we don't want to
    171 				 * force pmksa_cache_free_entry() to disconnect
    172 				 * at this point. Let's just make sure the old
    173 				 * PMKSA cache entry will not be used in the
    174 				 * future.
    175 				 */
    176 				wpa_printf(MSG_DEBUG, "RSN: replacing current "
    177 					   "PMKSA entry");
    178 				pmksa->sm->cur_pmksa = NULL;
    179 			}
    180 			wpa_printf(MSG_DEBUG, "RSN: Replace PMKSA entry for "
    181 				   "the current AP");
    182 			pmksa_cache_free_entry(pmksa, pos, 1);
    183 
    184 			/*
    185 			 * If OKC is used, there may be other PMKSA cache
    186 			 * entries based on the same PMK. These needs to be
    187 			 * flushed so that a new entry can be created based on
    188 			 * the new PMK.
    189 			 */
    190 			pmksa_cache_flush(pmksa, network_ctx);
    191 			break;
    192 		}
    193 		prev = pos;
    194 		pos = pos->next;
    195 	}
    196 
    197 	if (pmksa->pmksa_count >= pmksa_cache_max_entries && pmksa->pmksa) {
    198 		/* Remove the oldest entry to make room for the new entry */
    199 		pos = pmksa->pmksa;
    200 
    201 		if (pos == pmksa->sm->cur_pmksa) {
    202 			/*
    203 			 * Never remove the current PMKSA cache entry, since
    204 			 * it's in use, and removing it triggers a needless
    205 			 * deauthentication.
    206 			 */
    207 			pos = pos->next;
    208 			pmksa->pmksa->next = pos ? pos->next : NULL;
    209 		} else
    210 			pmksa->pmksa = pos->next;
    211 
    212 		if (pos) {
    213 			wpa_printf(MSG_DEBUG, "RSN: removed the oldest idle "
    214 				   "PMKSA cache entry (for " MACSTR ") to "
    215 				   "make room for new one",
    216 				   MAC2STR(pos->aa));
    217 			pmksa_cache_free_entry(pmksa, pos, 0);
    218 		}
    219 	}
    220 
    221 	/* Add the new entry; order by expiration time */
    222 	pos = pmksa->pmksa;
    223 	prev = NULL;
    224 	while (pos) {
    225 		if (pos->expiration > entry->expiration)
    226 			break;
    227 		prev = pos;
    228 		pos = pos->next;
    229 	}
    230 	if (prev == NULL) {
    231 		entry->next = pmksa->pmksa;
    232 		pmksa->pmksa = entry;
    233 		pmksa_cache_set_expiration(pmksa);
    234 	} else {
    235 		entry->next = prev->next;
    236 		prev->next = entry;
    237 	}
    238 	pmksa->pmksa_count++;
    239 	wpa_printf(MSG_DEBUG, "RSN: Added PMKSA cache entry for " MACSTR
    240 		   " network_ctx=%p", MAC2STR(entry->aa), network_ctx);
    241 	wpa_sm_add_pmkid(pmksa->sm, entry->aa, entry->pmkid);
    242 
    243 	return entry;
    244 }
    245 
    246 
    247 /**
    248  * pmksa_cache_flush - Flush PMKSA cache entries for a specific network
    249  * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
    250  * @network_ctx: Network configuration context or %NULL to flush all entries
    251  */
    252 void pmksa_cache_flush(struct rsn_pmksa_cache *pmksa, void *network_ctx)
    253 {
    254 	struct rsn_pmksa_cache_entry *entry, *prev = NULL, *tmp;
    255 	int removed = 0;
    256 
    257 	entry = pmksa->pmksa;
    258 	while (entry) {
    259 		if (entry->network_ctx == network_ctx || network_ctx == NULL) {
    260 			wpa_printf(MSG_DEBUG, "RSN: Flush PMKSA cache entry "
    261 				   "for " MACSTR, MAC2STR(entry->aa));
    262 			if (prev)
    263 				prev->next = entry->next;
    264 			else
    265 				pmksa->pmksa = entry->next;
    266 			tmp = entry;
    267 			entry = entry->next;
    268 			pmksa_cache_free_entry(pmksa, tmp, 0);
    269 			removed++;
    270 		} else {
    271 			prev = entry;
    272 			entry = entry->next;
    273 		}
    274 	}
    275 	if (removed)
    276 		pmksa_cache_set_expiration(pmksa);
    277 }
    278 
    279 
    280 /**
    281  * pmksa_cache_deinit - Free all entries in PMKSA cache
    282  * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
    283  */
    284 void pmksa_cache_deinit(struct rsn_pmksa_cache *pmksa)
    285 {
    286 	struct rsn_pmksa_cache_entry *entry, *prev;
    287 
    288 	if (pmksa == NULL)
    289 		return;
    290 
    291 	entry = pmksa->pmksa;
    292 	pmksa->pmksa = NULL;
    293 	while (entry) {
    294 		prev = entry;
    295 		entry = entry->next;
    296 		os_free(prev);
    297 	}
    298 	pmksa_cache_set_expiration(pmksa);
    299 	os_free(pmksa);
    300 }
    301 
    302 
    303 /**
    304  * pmksa_cache_get - Fetch a PMKSA cache entry
    305  * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
    306  * @aa: Authenticator address or %NULL to match any
    307  * @pmkid: PMKID or %NULL to match any
    308  * @network_ctx: Network context or %NULL to match any
    309  * Returns: Pointer to PMKSA cache entry or %NULL if no match was found
    310  */
    311 struct rsn_pmksa_cache_entry * pmksa_cache_get(struct rsn_pmksa_cache *pmksa,
    312 					       const u8 *aa, const u8 *pmkid,
    313 					       const void *network_ctx)
    314 {
    315 	struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;
    316 	while (entry) {
    317 		if ((aa == NULL || os_memcmp(entry->aa, aa, ETH_ALEN) == 0) &&
    318 		    (pmkid == NULL ||
    319 		     os_memcmp(entry->pmkid, pmkid, PMKID_LEN) == 0) &&
    320 		    (network_ctx == NULL || network_ctx == entry->network_ctx))
    321 			return entry;
    322 		entry = entry->next;
    323 	}
    324 	return NULL;
    325 }
    326 
    327 
    328 static struct rsn_pmksa_cache_entry *
    329 pmksa_cache_clone_entry(struct rsn_pmksa_cache *pmksa,
    330 			const struct rsn_pmksa_cache_entry *old_entry,
    331 			const u8 *aa)
    332 {
    333 	struct rsn_pmksa_cache_entry *new_entry;
    334 
    335 	new_entry = pmksa_cache_add(pmksa, old_entry->pmk, old_entry->pmk_len,
    336 				    aa, pmksa->sm->own_addr,
    337 				    old_entry->network_ctx, old_entry->akmp);
    338 	if (new_entry == NULL)
    339 		return NULL;
    340 
    341 	/* TODO: reorder entries based on expiration time? */
    342 	new_entry->expiration = old_entry->expiration;
    343 	new_entry->opportunistic = 1;
    344 
    345 	return new_entry;
    346 }
    347 
    348 
    349 /**
    350  * pmksa_cache_get_opportunistic - Try to get an opportunistic PMKSA entry
    351  * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
    352  * @network_ctx: Network configuration context
    353  * @aa: Authenticator address for the new AP
    354  * Returns: Pointer to a new PMKSA cache entry or %NULL if not available
    355  *
    356  * Try to create a new PMKSA cache entry opportunistically by guessing that the
    357  * new AP is sharing the same PMK as another AP that has the same SSID and has
    358  * already an entry in PMKSA cache.
    359  */
    360 struct rsn_pmksa_cache_entry *
    361 pmksa_cache_get_opportunistic(struct rsn_pmksa_cache *pmksa, void *network_ctx,
    362 			      const u8 *aa)
    363 {
    364 	struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;
    365 
    366 	wpa_printf(MSG_DEBUG, "RSN: Consider " MACSTR " for OKC", MAC2STR(aa));
    367 	if (network_ctx == NULL)
    368 		return NULL;
    369 	while (entry) {
    370 		if (entry->network_ctx == network_ctx) {
    371 			entry = pmksa_cache_clone_entry(pmksa, entry, aa);
    372 			if (entry) {
    373 				wpa_printf(MSG_DEBUG, "RSN: added "
    374 					   "opportunistic PMKSA cache entry "
    375 					   "for " MACSTR, MAC2STR(aa));
    376 			}
    377 			return entry;
    378 		}
    379 		entry = entry->next;
    380 	}
    381 	return NULL;
    382 }
    383 
    384 
    385 /**
    386  * pmksa_cache_get_current - Get the current used PMKSA entry
    387  * @sm: Pointer to WPA state machine data from wpa_sm_init()
    388  * Returns: Pointer to the current PMKSA cache entry or %NULL if not available
    389  */
    390 struct rsn_pmksa_cache_entry * pmksa_cache_get_current(struct wpa_sm *sm)
    391 {
    392 	if (sm == NULL)
    393 		return NULL;
    394 	return sm->cur_pmksa;
    395 }
    396 
    397 
    398 /**
    399  * pmksa_cache_clear_current - Clear the current PMKSA entry selection
    400  * @sm: Pointer to WPA state machine data from wpa_sm_init()
    401  */
    402 void pmksa_cache_clear_current(struct wpa_sm *sm)
    403 {
    404 	if (sm == NULL)
    405 		return;
    406 	sm->cur_pmksa = NULL;
    407 }
    408 
    409 
    410 /**
    411  * pmksa_cache_set_current - Set the current PMKSA entry selection
    412  * @sm: Pointer to WPA state machine data from wpa_sm_init()
    413  * @pmkid: PMKID for selecting PMKSA or %NULL if not used
    414  * @bssid: BSSID for PMKSA or %NULL if not used
    415  * @network_ctx: Network configuration context
    416  * @try_opportunistic: Whether to allow opportunistic PMKSA caching
    417  * Returns: 0 if PMKSA was found or -1 if no matching entry was found
    418  */
    419 int pmksa_cache_set_current(struct wpa_sm *sm, const u8 *pmkid,
    420 			    const u8 *bssid, void *network_ctx,
    421 			    int try_opportunistic)
    422 {
    423 	struct rsn_pmksa_cache *pmksa = sm->pmksa;
    424 	wpa_printf(MSG_DEBUG, "RSN: PMKSA cache search - network_ctx=%p "
    425 		   "try_opportunistic=%d", network_ctx, try_opportunistic);
    426 	if (pmkid)
    427 		wpa_hexdump(MSG_DEBUG, "RSN: Search for PMKID",
    428 			    pmkid, PMKID_LEN);
    429 	if (bssid)
    430 		wpa_printf(MSG_DEBUG, "RSN: Search for BSSID " MACSTR,
    431 			   MAC2STR(bssid));
    432 
    433 	sm->cur_pmksa = NULL;
    434 	if (pmkid)
    435 		sm->cur_pmksa = pmksa_cache_get(pmksa, NULL, pmkid,
    436 						network_ctx);
    437 	if (sm->cur_pmksa == NULL && bssid)
    438 		sm->cur_pmksa = pmksa_cache_get(pmksa, bssid, NULL,
    439 						network_ctx);
    440 	if (sm->cur_pmksa == NULL && try_opportunistic && bssid)
    441 		sm->cur_pmksa = pmksa_cache_get_opportunistic(pmksa,
    442 							      network_ctx,
    443 							      bssid);
    444 	if (sm->cur_pmksa) {
    445 		wpa_hexdump(MSG_DEBUG, "RSN: PMKSA cache entry found - PMKID",
    446 			    sm->cur_pmksa->pmkid, PMKID_LEN);
    447 		return 0;
    448 	}
    449 	wpa_printf(MSG_DEBUG, "RSN: No PMKSA cache entry found");
    450 	return -1;
    451 }
    452 
    453 
    454 /**
    455  * pmksa_cache_list - Dump text list of entries in PMKSA cache
    456  * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
    457  * @buf: Buffer for the list
    458  * @len: Length of the buffer
    459  * Returns: number of bytes written to buffer
    460  *
    461  * This function is used to generate a text format representation of the
    462  * current PMKSA cache contents for the ctrl_iface PMKSA command.
    463  */
    464 int pmksa_cache_list(struct rsn_pmksa_cache *pmksa, char *buf, size_t len)
    465 {
    466 	int i, ret;
    467 	char *pos = buf;
    468 	struct rsn_pmksa_cache_entry *entry;
    469 	struct os_time now;
    470 
    471 	os_get_time(&now);
    472 	ret = os_snprintf(pos, buf + len - pos,
    473 			  "Index / AA / PMKID / expiration (in seconds) / "
    474 			  "opportunistic\n");
    475 	if (ret < 0 || ret >= buf + len - pos)
    476 		return pos - buf;
    477 	pos += ret;
    478 	i = 0;
    479 	entry = pmksa->pmksa;
    480 	while (entry) {
    481 		i++;
    482 		ret = os_snprintf(pos, buf + len - pos, "%d " MACSTR " ",
    483 				  i, MAC2STR(entry->aa));
    484 		if (ret < 0 || ret >= buf + len - pos)
    485 			return pos - buf;
    486 		pos += ret;
    487 		pos += wpa_snprintf_hex(pos, buf + len - pos, entry->pmkid,
    488 					PMKID_LEN);
    489 		ret = os_snprintf(pos, buf + len - pos, " %d %d\n",
    490 				  (int) (entry->expiration - now.sec),
    491 				  entry->opportunistic);
    492 		if (ret < 0 || ret >= buf + len - pos)
    493 			return pos - buf;
    494 		pos += ret;
    495 		entry = entry->next;
    496 	}
    497 	return pos - buf;
    498 }
    499 
    500 
    501 /**
    502  * pmksa_cache_init - Initialize PMKSA cache
    503  * @free_cb: Callback function to be called when a PMKSA cache entry is freed
    504  * @ctx: Context pointer for free_cb function
    505  * @sm: Pointer to WPA state machine data from wpa_sm_init()
    506  * Returns: Pointer to PMKSA cache data or %NULL on failure
    507  */
    508 struct rsn_pmksa_cache *
    509 pmksa_cache_init(void (*free_cb)(struct rsn_pmksa_cache_entry *entry,
    510 				 void *ctx, int replace),
    511 		 void *ctx, struct wpa_sm *sm)
    512 {
    513 	struct rsn_pmksa_cache *pmksa;
    514 
    515 	pmksa = os_zalloc(sizeof(*pmksa));
    516 	if (pmksa) {
    517 		pmksa->free_cb = free_cb;
    518 		pmksa->ctx = ctx;
    519 		pmksa->sm = sm;
    520 	}
    521 
    522 	return pmksa;
    523 }
    524 
    525 #endif /* IEEE8021X_EAPOL and !CONFIG_NO_WPA2 */
    526