pmksa_cache.c

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/*
 * WPA Supplicant - RSN PMKSA cache
 * Copyright (c) 2004-2008, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "eloop.h"
#include "eapol_supp/eapol_supp_sm.h"
#include "wpa.h"
#include "wpa_i.h"
#include "pmksa_cache.h"

#if defined(IEEE8021X_EAPOL) && !defined(CONFIG_NO_WPA2)

static const int pmksa_cache_max_entries = 32;

struct rsn_pmksa_cache {
        struct rsn_pmksa_cache_entry *pmksa; /* PMKSA cache */
        int pmksa_count; /* number of entries in PMKSA cache */
        struct wpa_sm *sm; /* TODO: get rid of this reference(?) */

        void (*free_cb)(struct rsn_pmksa_cache_entry *entry, void *ctx,
                        int replace);
        void *ctx;
};


static void pmksa_cache_set_expiration(struct rsn_pmksa_cache *pmksa);


static void _pmksa_cache_free_entry(struct rsn_pmksa_cache_entry *entry)
{
        os_free(entry);
}


static void pmksa_cache_free_entry(struct rsn_pmksa_cache *pmksa,
                                   struct rsn_pmksa_cache_entry *entry,
                                   int replace)
{
        pmksa->pmksa_count--;
        pmksa->free_cb(entry, pmksa->ctx, replace);
        _pmksa_cache_free_entry(entry);
}


static void pmksa_cache_expire(void *eloop_ctx, void *timeout_ctx)
{
        struct rsn_pmksa_cache *pmksa = eloop_ctx;
        struct os_time now;

        os_get_time(&now);
        while (pmksa->pmksa && pmksa->pmksa->expiration <= now.sec) {
                struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;
                pmksa->pmksa = entry->next;
                wpa_printf(MSG_DEBUG, "RSN: expired PMKSA cache entry for "
                           MACSTR, MAC2STR(entry->aa));
                pmksa_cache_free_entry(pmksa, entry, 0);
        }

        pmksa_cache_set_expiration(pmksa);
}


static void pmksa_cache_reauth(void *eloop_ctx, void *timeout_ctx)
{
        struct rsn_pmksa_cache *pmksa = eloop_ctx;
        pmksa->sm->cur_pmksa = NULL;
        eapol_sm_request_reauth(pmksa->sm->eapol);
}


static void pmksa_cache_set_expiration(struct rsn_pmksa_cache *pmksa)
{
        int sec;
        struct rsn_pmksa_cache_entry *entry;
        struct os_time now;

        eloop_cancel_timeout(pmksa_cache_expire, pmksa, NULL);
        eloop_cancel_timeout(pmksa_cache_reauth, pmksa, NULL);
        if (pmksa->pmksa == NULL)
                return;
        os_get_time(&now);
        sec = pmksa->pmksa->expiration - now.sec;
        if (sec < 0)
                sec = 0;
        eloop_register_timeout(sec + 1, 0, pmksa_cache_expire, pmksa, NULL);

        entry = pmksa->sm->cur_pmksa ? pmksa->sm->cur_pmksa :
                pmksa_cache_get(pmksa, pmksa->sm->bssid, NULL);
        if (entry) {
                sec = pmksa->pmksa->reauth_time - now.sec;
                if (sec < 0)
                        sec = 0;
                eloop_register_timeout(sec, 0, pmksa_cache_reauth, pmksa,
                                       NULL);
        }
}


struct rsn_pmksa_cache_entry *
pmksa_cache_add(struct rsn_pmksa_cache *pmksa, const u8 *pmk, size_t pmk_len,
                const u8 *aa, const u8 *spa, void *network_ctx, int akmp)
{
        struct rsn_pmksa_cache_entry *entry, *pos, *prev;
        struct os_time now;

        if (pmk_len > PMK_LEN)
                return NULL;

        entry = os_zalloc(sizeof(*entry));
        if (entry == NULL)
                return NULL;
        os_memcpy(entry->pmk, pmk, pmk_len);
        entry->pmk_len = pmk_len;
        rsn_pmkid(pmk, pmk_len, aa, spa, entry->pmkid,
                  wpa_key_mgmt_sha256(akmp));
        os_get_time(&now);
        entry->expiration = now.sec + pmksa->sm->dot11RSNAConfigPMKLifetime;
        entry->reauth_time = now.sec + pmksa->sm->dot11RSNAConfigPMKLifetime *
                pmksa->sm->dot11RSNAConfigPMKReauthThreshold / 100;
        entry->akmp = akmp;
        os_memcpy(entry->aa, aa, ETH_ALEN);
        entry->network_ctx = network_ctx;

        /* Replace an old entry for the same Authenticator (if found) with the
         * new entry */
        pos = pmksa->pmksa;
        prev = NULL;
        while (pos) {
                if (os_memcmp(aa, pos->aa, ETH_ALEN) == 0) {
                        if (pos->pmk_len == pmk_len &&
                            os_memcmp(pos->pmk, pmk, pmk_len) == 0 &&
                            os_memcmp(pos->pmkid, entry->pmkid, PMKID_LEN) ==
                            0) {
                                wpa_printf(MSG_DEBUG, "WPA: reusing previous "
                                           "PMKSA entry");
                                os_free(entry);
                                return pos;
                        }
                        if (prev == NULL)
                                pmksa->pmksa = pos->next;
                        else
                                prev->next = pos->next;
                        if (pos == pmksa->sm->cur_pmksa) {
                                /* We are about to replace the current PMKSA
                                 * cache entry. This happens when the PMKSA
                                 * caching attempt fails, so we don't want to
                                 * force pmksa_cache_free_entry() to disconnect
                                 * at this point. Let's just make sure the old
                                 * PMKSA cache entry will not be used in the
                                 * future.
                                 */
                                wpa_printf(MSG_DEBUG, "RSN: replacing current "
                                           "PMKSA entry");
                                pmksa->sm->cur_pmksa = NULL;
                        }
                        wpa_printf(MSG_DEBUG, "RSN: Replace PMKSA entry for "
                                   "the current AP");
                        pmksa_cache_free_entry(pmksa, pos, 1);
                        break;
                }
                prev = pos;
                pos = pos->next;
        }

        if (pmksa->pmksa_count >= pmksa_cache_max_entries && pmksa->pmksa) {
                /* Remove the oldest entry to make room for the new entry */
                pos = pmksa->pmksa;
                pmksa->pmksa = pos->next;
                wpa_printf(MSG_DEBUG, "RSN: removed the oldest PMKSA cache "
                           "entry (for " MACSTR ") to make room for new one",
                           MAC2STR(pos->aa));
                wpa_sm_remove_pmkid(pmksa->sm, pos->aa, pos->pmkid);
                pmksa_cache_free_entry(pmksa, pos, 0);
        }

        /* Add the new entry; order by expiration time */
        pos = pmksa->pmksa;
        prev = NULL;
        while (pos) {
                if (pos->expiration > entry->expiration)
                        break;
                prev = pos;
                pos = pos->next;
        }
        if (prev == NULL) {
                entry->next = pmksa->pmksa;
                pmksa->pmksa = entry;
                pmksa_cache_set_expiration(pmksa);
        } else {
                entry->next = prev->next;
                prev->next = entry;
        }
        pmksa->pmksa_count++;
        wpa_printf(MSG_DEBUG, "RSN: added PMKSA cache entry for " MACSTR,
                   MAC2STR(entry->aa));
        wpa_sm_add_pmkid(pmksa->sm, entry->aa, entry->pmkid);

        return entry;
}


void pmksa_cache_deinit(struct rsn_pmksa_cache *pmksa)
{
        struct rsn_pmksa_cache_entry *entry, *prev;

        if (pmksa == NULL)
                return;

        entry = pmksa->pmksa;
        pmksa->pmksa = NULL;
        while (entry) {
                prev = entry;
                entry = entry->next;
                os_free(prev);
        }
        pmksa_cache_set_expiration(pmksa);
        os_free(pmksa);
}


struct rsn_pmksa_cache_entry * pmksa_cache_get(struct rsn_pmksa_cache *pmksa,
                                               const u8 *aa, const u8 *pmkid)
{
        struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;
        while (entry) {
                if ((aa == NULL || os_memcmp(entry->aa, aa, ETH_ALEN) == 0) &&
                    (pmkid == NULL ||
                     os_memcmp(entry->pmkid, pmkid, PMKID_LEN) == 0))
                        return entry;
                entry = entry->next;
        }
        return NULL;
}


void pmksa_cache_notify_reconfig(struct rsn_pmksa_cache *pmksa)
{
        struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;
        while (entry) {
                entry->network_ctx = NULL;
                entry = entry->next;
        }
}


static struct rsn_pmksa_cache_entry *
pmksa_cache_clone_entry(struct rsn_pmksa_cache *pmksa,
                        const struct rsn_pmksa_cache_entry *old_entry,
                        const u8 *aa)
{
        struct rsn_pmksa_cache_entry *new_entry;

        new_entry = pmksa_cache_add(pmksa, old_entry->pmk, old_entry->pmk_len,
                                    aa, pmksa->sm->own_addr,
                                    old_entry->network_ctx, old_entry->akmp);
        if (new_entry == NULL)
                return NULL;

        /* TODO: reorder entries based on expiration time? */
        new_entry->expiration = old_entry->expiration;
        new_entry->opportunistic = 1;

        return new_entry;
}


struct rsn_pmksa_cache_entry *
pmksa_cache_get_opportunistic(struct rsn_pmksa_cache *pmksa, void *network_ctx,
                              const u8 *aa)
{
        struct rsn_pmksa_cache_entry *entry = pmksa->pmksa;

        if (network_ctx == NULL)
                return NULL;
        while (entry) {
                if (entry->network_ctx == network_ctx) {
                        entry = pmksa_cache_clone_entry(pmksa, entry, aa);
                        if (entry) {
                                wpa_printf(MSG_DEBUG, "RSN: added "
                                           "opportunistic PMKSA cache entry "
                                           "for " MACSTR, MAC2STR(aa));
                        }
                        return entry;
                }
                entry = entry->next;
        }
        return NULL;
}


struct rsn_pmksa_cache_entry * pmksa_cache_get_current(struct wpa_sm *sm)
{
        if (sm == NULL)
                return NULL;
        return sm->cur_pmksa;
}


void pmksa_cache_clear_current(struct wpa_sm *sm)
{
        if (sm == NULL)
                return;
        sm->cur_pmksa = NULL;
}


int pmksa_cache_set_current(struct wpa_sm *sm, const u8 *pmkid,
                            const u8 *bssid, void *network_ctx,
                            int try_opportunistic)
{
        struct rsn_pmksa_cache *pmksa = sm->pmksa;
        sm->cur_pmksa = NULL;
        if (pmkid)
                sm->cur_pmksa = pmksa_cache_get(pmksa, NULL, pmkid);
        if (sm->cur_pmksa == NULL && bssid)
                sm->cur_pmksa = pmksa_cache_get(pmksa, bssid, NULL);
        if (sm->cur_pmksa == NULL && try_opportunistic && bssid)
                sm->cur_pmksa = pmksa_cache_get_opportunistic(pmksa,
                                                              network_ctx,
                                                              bssid);
        if (sm->cur_pmksa) {
                wpa_hexdump(MSG_DEBUG, "RSN: PMKID",
                            sm->cur_pmksa->pmkid, PMKID_LEN);
                return 0;
        }
        return -1;
}


int pmksa_cache_list(struct rsn_pmksa_cache *pmksa, char *buf, size_t len)
{
        int i, ret;
        char *pos = buf;
        struct rsn_pmksa_cache_entry *entry;
        struct os_time now;

        os_get_time(&now);
        ret = os_snprintf(pos, buf + len - pos,
                          "Index / AA / PMKID / expiration (in seconds) / "
                          "opportunistic\n");
        if (ret < 0 || ret >= buf + len - pos)
                return pos - buf;
        pos += ret;
        i = 0;
        entry = pmksa->pmksa;
        while (entry) {
                i++;
                ret = os_snprintf(pos, buf + len - pos, "%d " MACSTR " ",
                                  i, MAC2STR(entry->aa));
                if (ret < 0 || ret >= buf + len - pos)
                        return pos - buf;
                pos += ret;
                pos += wpa_snprintf_hex(pos, buf + len - pos, entry->pmkid,
                                        PMKID_LEN);
                ret = os_snprintf(pos, buf + len - pos, " %d %d\n",
                                  (int) (entry->expiration - now.sec),
                                  entry->opportunistic);
                if (ret < 0 || ret >= buf + len - pos)
                        return pos - buf;
                pos += ret;
                entry = entry->next;
        }
        return pos - buf;
}


struct rsn_pmksa_cache *
pmksa_cache_init(void (*free_cb)(struct rsn_pmksa_cache_entry *entry,
                                 void *ctx, int replace),
                 void *ctx, struct wpa_sm *sm)
{
        struct rsn_pmksa_cache *pmksa;

        pmksa = os_zalloc(sizeof(*pmksa));
        if (pmksa) {
                pmksa->free_cb = free_cb;
                pmksa->ctx = ctx;
                pmksa->sm = sm;
        }

        return pmksa;
}

#endif /* IEEE8021X_EAPOL and !CONFIG_NO_WPA2 */