src/rsn_supp/pmksa_cache.c

/*
 * WPA Supplicant - RSN PMKSA cache
 * Copyright (c) 2004-2009, 2011-2015, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"
#include "common.h"
#include "eloop.h"
#include "rsn_supp/wpa.h"
#include "rsn_supp/wpa_i.h"
#include "common/eapol_common.h"
#include "common/ieee802_11_defs.h"
#include "pmksa_cache.h"

#ifdef IEEE8021X_EAPOL

static const int pmksa_cache_max_entries = 10;
static const int dot11RSNAConfigPMKLifetime = 8640000; // 100 days = 3600 x 24 x 100 Seconds
static const int dot11RSNAConfigPMKReauthThreshold = 70;

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,
            enum pmksa_free_reason reason);
    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)
{
    bin_clear_free(entry, sizeof(*entry));
}


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


static void pmksa_cache_expire(void *eloop_ctx, void *user_data)
{
    struct rsn_pmksa_cache *pmksa = eloop_ctx;
    struct os_reltime now;

    os_get_reltime(&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, PMKSA_EXPIRE);
    }

    pmksa_cache_set_expiration(pmksa);
}

static void pmksa_cache_set_expiration(struct rsn_pmksa_cache *pmksa)
{
    int sec;
    struct os_reltime now;

    eloop_cancel_timeout(pmksa_cache_expire, pmksa, NULL);
    if (pmksa->pmksa == NULL)
        return;

    os_get_reltime(&now);
    sec = pmksa->pmksa->expiration - now.sec;
    if (sec < 0)
        sec = 0;

    eloop_register_timeout(sec + 1, 0, pmksa_cache_expire, pmksa, NULL);
}

/**
 * pmksa_cache_add - Add a PMKSA cache entry
 * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
 * @pmk: The new pairwise master key
 * @pmk_len: PMK length in bytes, usually PMK_LEN (32)
 * @kck: Key confirmation key or %NULL if not yet derived
 * @kck_len: KCK length in bytes
 * @aa: Authenticator address
 * @spa: Supplicant address
 * @network_ctx: Network configuration context for this PMK
 * @akmp: WPA_KEY_MGMT_* used in key derivation
 * Returns: Pointer to the added PMKSA cache entry or %NULL on error
 *
 * This function create a PMKSA entry for a new PMK and adds it to the PMKSA
 * cache. If an old entry is already in the cache for the same Authenticator,
 * this entry will be replaced with the new entry. PMKID will be calculated
 * based on the PMK and the driver interface is notified of the new PMKID.
 */
struct rsn_pmksa_cache_entry *
pmksa_cache_add(struct rsn_pmksa_cache *pmksa, const u8 *pmk, size_t pmk_len,
        const u8 *pmkid, const u8 *kck, size_t kck_len,
        const u8 *aa, const u8 *spa, void *network_ctx, int akmp)
{
    struct rsn_pmksa_cache_entry *entry, *pos, *prev;
    struct os_reltime now;

    if (pmk_len > PMK_LEN_MAX)
        return NULL;

    if (wpa_key_mgmt_suite_b(akmp) && !kck)
        return NULL;

    entry = os_zalloc(sizeof(*entry));
    if (entry == NULL)
        return NULL;
    os_memcpy(entry->pmk, pmk, pmk_len);
    entry->pmk_len = pmk_len;
    if (pmkid)
        os_memcpy(entry->pmkid, pmkid, PMKID_LEN);
    else if (akmp == WPA_KEY_MGMT_IEEE8021X_SUITE_B_192)
        rsn_pmkid_suite_b_192(kck, kck_len, aa, spa, entry->pmkid);
    else if (wpa_key_mgmt_suite_b(akmp))
        rsn_pmkid_suite_b(kck, kck_len, aa, spa, entry->pmkid);
    else
        rsn_pmkid(pmk, pmk_len, aa, spa, entry->pmkid, akmp);

    os_get_reltime(&now);
    entry->expiration = now.sec + dot11RSNAConfigPMKLifetime;
    entry->reauth_time = now.sec + dot11RSNAConfigPMKLifetime *
        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_const(pos->pmk, pmk, pmk_len) == 0 &&
                    os_memcmp_const(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 OKC is used, there may be other PMKSA cache
             * entries based on the same PMK. These needs to be
             * flushed so that a new entry can be created based on
             * the new PMK. Only clear other entries if they have a
             * matching PMK and this PMK has been used successfully
             * with the current AP, i.e., if opportunistic flag has
             * been cleared in wpa_supplicant_key_neg_complete().
             */
            wpa_printf(MSG_DEBUG, "RSN: Replace PMKSA entry for "
                    "the current AP and any PMKSA cache entry "
                    "that was based on the old PMK");
            if (!pos->opportunistic)
                pmksa_cache_flush(pmksa, network_ctx, pos->pmk,
                        pos->pmk_len);
            pmksa_cache_free_entry(pmksa, pos, PMKSA_REPLACE);
            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;

        if (pos == pmksa->sm->cur_pmksa) {
            /*
             * Never remove the current PMKSA cache entry, since
             * it's in use, and removing it triggers a needless
             * deauthentication.
             */
            pos = pos->next;
            pmksa->pmksa->next = pos ? pos->next : NULL;
        } else
            pmksa->pmksa = pos->next;

        if (pos) {
            wpa_printf(MSG_DEBUG, "RSN: removed the oldest idle "
                    "PMKSA cache entry (for " MACSTR ") to "
                    "make room for new one",
                    MAC2STR(pos->aa));
            pmksa_cache_free_entry(pmksa, pos, PMKSA_FREE);
        }
    }

    /* 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
            " network_ctx=%p", MAC2STR(entry->aa), network_ctx);

    return entry;
}


/**
 * pmksa_cache_flush - Flush PMKSA cache entries for a specific network
 * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
 * @network_ctx: Network configuration context or %NULL to flush all entries
 * @pmk: PMK to match for or %NYLL to match all PMKs
 * @pmk_len: PMK length
 */
void pmksa_cache_flush(struct rsn_pmksa_cache *pmksa, void *network_ctx,
        const u8 *pmk, size_t pmk_len)
{
    struct rsn_pmksa_cache_entry *entry, *prev = NULL, *tmp;
    int removed = 0;

    entry = pmksa->pmksa;
    while (entry) {
        if ((entry->network_ctx == network_ctx ||
                    network_ctx == NULL) &&
                (pmk == NULL ||
                 (pmk_len == entry->pmk_len &&
                  os_memcmp(pmk, entry->pmk, pmk_len) == 0))) {
            wpa_printf(MSG_DEBUG, "RSN: Flush PMKSA cache entry "
                    "for " MACSTR, MAC2STR(entry->aa));
            if (prev)
                prev->next = entry->next;
            else
                pmksa->pmksa = entry->next;
            tmp = entry;
            entry = entry->next;
            pmksa_cache_free_entry(pmksa, tmp, PMKSA_FREE);
            removed++;
        } else {
            prev = entry;
            entry = entry->next;
        }
    }
    /*if (removed)
      pmksa_cache_set_expiration(pmksa);*/
}


/**
 * pmksa_cache_deinit - Free all entries in PMKSA cache
 * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
 */
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);
    eloop_cancel_timeout(pmksa_cache_expire, pmksa, NULL);
    os_free(pmksa);
}


/**
 * pmksa_cache_get - Fetch a PMKSA cache entry
 * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
 * @aa: Authenticator address or %NULL to match any
 * @pmkid: PMKID or %NULL to match any
 * @network_ctx: Network context or %NULL to match any
 * Returns: Pointer to PMKSA cache entry or %NULL if no match was found
 */
struct rsn_pmksa_cache_entry * pmksa_cache_get(struct rsn_pmksa_cache *pmksa,
        const u8 *aa, const u8 *pmkid,
        const void *network_ctx)
{
    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) &&
                (network_ctx == NULL || network_ctx == entry->network_ctx))
            return entry;
        entry = entry->next;
    }
    return NULL;
}


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,
            NULL, NULL, 0,
            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;
}


/**
 * pmksa_cache_get_opportunistic - Try to get an opportunistic PMKSA entry
 * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
 * @network_ctx: Network configuration context
 * @aa: Authenticator address for the new AP
 * Returns: Pointer to a new PMKSA cache entry or %NULL if not available
 *
 * Try to create a new PMKSA cache entry opportunistically by guessing that the
 * new AP is sharing the same PMK as another AP that has the same SSID and has
 * already an entry in PMKSA cache.
 */
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;

    wpa_printf(MSG_DEBUG, "RSN: Consider " MACSTR " for OKC", MAC2STR(aa));
    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;
}


/**
 * pmksa_cache_get_current - Get the current used PMKSA entry
 * @sm: Pointer to WPA state machine data from wpa_sm_init()
 * Returns: Pointer to the current PMKSA cache entry or %NULL if not available
 */
struct rsn_pmksa_cache_entry * pmksa_cache_get_current(struct wpa_sm *sm)
{
    if (sm == NULL)
        return NULL;
    return sm->cur_pmksa;
}


/**
 * pmksa_cache_clear_current - Clear the current PMKSA entry selection
 * @sm: Pointer to WPA state machine data from wpa_sm_init()
 */
void pmksa_cache_clear_current(struct wpa_sm *sm)
{
    if (sm == NULL)
        return;
    sm->cur_pmksa = NULL;
}


/**
 * pmksa_cache_set_current - Set the current PMKSA entry selection
 * @sm: Pointer to WPA state machine data from wpa_sm_init()
 * @pmkid: PMKID for selecting PMKSA or %NULL if not used
 * @bssid: BSSID for PMKSA or %NULL if not used
 * @network_ctx: Network configuration context
 * @try_opportunistic: Whether to allow opportunistic PMKSA caching
 * Returns: 0 if PMKSA was found or -1 if no matching entry was found
 */
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;
    wpa_printf(MSG_DEBUG, "RSN: PMKSA cache search - network_ctx=%p "
            "try_opportunistic=%d", network_ctx, try_opportunistic);
    if (pmkid)
        wpa_hexdump(MSG_DEBUG, "RSN: Search for PMKID",
                pmkid, PMKID_LEN);
    if (bssid)
        wpa_printf(MSG_DEBUG, "RSN: Search for BSSID " MACSTR,
                MAC2STR(bssid));

    sm->cur_pmksa = NULL;
    if (pmkid)
        sm->cur_pmksa = pmksa_cache_get(pmksa, NULL, pmkid,
                network_ctx);
    if (sm->cur_pmksa == NULL && bssid)
        sm->cur_pmksa = pmksa_cache_get(pmksa, bssid, NULL,
                network_ctx);
    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: PMKSA cache entry found - PMKID",
                sm->cur_pmksa->pmkid, PMKID_LEN);
        return 0;
    }
    wpa_printf(MSG_DEBUG, "RSN: No PMKSA cache entry found");
    return -1;
}


/**
 * pmksa_cache_list - Dump text list of entries in PMKSA cache
 * @pmksa: Pointer to PMKSA cache data from pmksa_cache_init()
 * @buf: Buffer for the list
 * @len: Length of the buffer
 * Returns: number of bytes written to buffer
 *
 * This function is used to generate a text format representation of the
 * current PMKSA cache contents for the ctrl_iface PMKSA command.
 */
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_reltime now;
    ret = os_snprintf(pos, buf + len - pos,
            "Index / AA / PMKID / expiration (in seconds) / "
            "opportunistic\n");
    if (os_snprintf_error(buf + len - pos, ret))
        return pos - buf;
    pos += ret;
    i = 0;
    entry = pmksa->pmksa;
    os_get_reltime(&now);
    while (entry) {
        i++;
        ret = os_snprintf(pos, buf + len - pos, "%d " MACSTR " ",
                i, MAC2STR(entry->aa));
        if (os_snprintf_error(buf + len - pos, ret))
            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 (os_snprintf_error(buf + len - pos, ret))
            return pos - buf;
        pos += ret;
        entry = entry->next;
    }
    return pos - buf;
}


/**
 * pmksa_cache_init - Initialize PMKSA cache
 * @free_cb: Callback function to be called when a PMKSA cache entry is freed
 * @ctx: Context pointer for free_cb function
 * @sm: Pointer to WPA state machine data from wpa_sm_init()
 * Returns: Pointer to PMKSA cache data or %NULL on failure
 */
struct rsn_pmksa_cache *
pmksa_cache_init(void (*free_cb)(struct rsn_pmksa_cache_entry *entry,
            void *ctx, enum pmksa_free_reason reason),
        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;
        pmksa->pmksa_count = 0;
        pmksa->pmksa = NULL;
    }

    return pmksa;
}

#endif /* IEEE8021X_EAPOL */