preauth.c

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#include "includes.h"

#include "common.h"
#include "wpa.h"
#include "drivers/driver.h"
#include "eloop.h"
#include "l2_packet/l2_packet.h"
#include "eapol_supp/eapol_supp_sm.h"
#include "preauth.h"
#include "pmksa_cache.h"
#include "wpa_i.h"
#include "ieee802_11_defs.h"


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

#define PMKID_CANDIDATE_PRIO_SCAN 1000


struct rsn_pmksa_candidate {
        struct rsn_pmksa_candidate *next;
        u8 bssid[ETH_ALEN];
        int priority;
};


void pmksa_candidate_free(struct wpa_sm *sm)
{
        struct rsn_pmksa_candidate *entry, *prev;

        if (sm == NULL)
                return;

        entry = sm->pmksa_candidates;
        sm->pmksa_candidates = NULL;
        while (entry) {
                prev = entry;
                entry = entry->next;
                os_free(prev);
        }
}


static void rsn_preauth_receive(void *ctx, const u8 *src_addr,
                                const u8 *buf, size_t len)
{
        struct wpa_sm *sm = ctx;

        wpa_printf(MSG_DEBUG, "RX pre-auth from " MACSTR, MAC2STR(src_addr));
        wpa_hexdump(MSG_MSGDUMP, "RX pre-auth", buf, len);

        if (sm->preauth_eapol == NULL ||
            is_zero_ether_addr(sm->preauth_bssid) ||
            os_memcmp(sm->preauth_bssid, src_addr, ETH_ALEN) != 0) {
                wpa_printf(MSG_WARNING, "RSN pre-auth frame received from "
                           "unexpected source " MACSTR " - dropped",
                           MAC2STR(src_addr));
                return;
        }

        eapol_sm_rx_eapol(sm->preauth_eapol, src_addr, buf, len);
}


static void rsn_preauth_eapol_cb(struct eapol_sm *eapol, int success,
                                 void *ctx)
{
        struct wpa_sm *sm = ctx;
        u8 pmk[PMK_LEN];

        if (success) {
                int res, pmk_len;
                pmk_len = PMK_LEN;
                res = eapol_sm_get_key(eapol, pmk, PMK_LEN);
                if (res) {
                        /*
                         * EAP-LEAP is an exception from other EAP methods: it
                         * uses only 16-byte PMK.
                         */
                        res = eapol_sm_get_key(eapol, pmk, 16);
                        pmk_len = 16;
                }
                if (res == 0) {
                        wpa_hexdump_key(MSG_DEBUG, "RSN: PMK from pre-auth",
                                        pmk, pmk_len);
                        sm->pmk_len = pmk_len;
                        pmksa_cache_add(sm->pmksa, pmk, pmk_len,
                                        sm->preauth_bssid, sm->own_addr,
                                        sm->network_ctx,
                                        WPA_KEY_MGMT_IEEE8021X);
                } else {
                        wpa_msg(sm->ctx->msg_ctx, MSG_INFO,
                                "RSN: failed to get master session key from "
                                "pre-auth EAPOL state machines");
                        success = 0;
                }
        }

        wpa_msg(sm->ctx->msg_ctx, MSG_INFO, "RSN: pre-authentication with "
                MACSTR " %s", MAC2STR(sm->preauth_bssid),
                success ? "completed successfully" : "failed");

        rsn_preauth_deinit(sm);
        rsn_preauth_candidate_process(sm);
}


static void rsn_preauth_timeout(void *eloop_ctx, void *timeout_ctx)
{
        struct wpa_sm *sm = eloop_ctx;

        wpa_msg(sm->ctx->msg_ctx, MSG_INFO, "RSN: pre-authentication with "
                MACSTR " timed out", MAC2STR(sm->preauth_bssid));
        rsn_preauth_deinit(sm);
        rsn_preauth_candidate_process(sm);
}


static int rsn_preauth_eapol_send(void *ctx, int type, const u8 *buf,
                                  size_t len)
{
        struct wpa_sm *sm = ctx;
        u8 *msg;
        size_t msglen;
        int res;

        /* TODO: could add l2_packet_sendmsg that allows fragments to avoid
         * extra copy here */

        if (sm->l2_preauth == NULL)
                return -1;

        msg = wpa_sm_alloc_eapol(sm, type, buf, len, &msglen, NULL);
        if (msg == NULL)
                return -1;

        wpa_hexdump(MSG_MSGDUMP, "TX EAPOL (preauth)", msg, msglen);
        res = l2_packet_send(sm->l2_preauth, sm->preauth_bssid,
                             ETH_P_RSN_PREAUTH, msg, msglen);
        os_free(msg);
        return res;
}


int rsn_preauth_init(struct wpa_sm *sm, const u8 *dst,
                     struct eap_peer_config *eap_conf)
{
        struct eapol_config eapol_conf;
        struct eapol_ctx *ctx;

        if (sm->preauth_eapol)
                return -1;

        wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG,
                "RSN: starting pre-authentication with " MACSTR, MAC2STR(dst));

        sm->l2_preauth = l2_packet_init(sm->ifname, sm->own_addr,
                                        ETH_P_RSN_PREAUTH,
                                        rsn_preauth_receive, sm, 0);
        if (sm->l2_preauth == NULL) {
                wpa_printf(MSG_WARNING, "RSN: Failed to initialize L2 packet "
                           "processing for pre-authentication");
                return -2;
        }

        if (sm->bridge_ifname) {
                sm->l2_preauth_br = l2_packet_init(sm->bridge_ifname,
                                                   sm->own_addr,
                                                   ETH_P_RSN_PREAUTH,
                                                   rsn_preauth_receive, sm, 0);
                if (sm->l2_preauth_br == NULL) {
                        wpa_printf(MSG_WARNING, "RSN: Failed to initialize L2 "
                                   "packet processing (bridge) for "
                                   "pre-authentication");
                        return -2;
                }
        }

        ctx = os_zalloc(sizeof(*ctx));
        if (ctx == NULL) {
                wpa_printf(MSG_WARNING, "Failed to allocate EAPOL context.");
                return -4;
        }
        ctx->ctx = sm->ctx->ctx;
        ctx->msg_ctx = sm->ctx->ctx;
        ctx->preauth = 1;
        ctx->cb = rsn_preauth_eapol_cb;
        ctx->cb_ctx = sm;
        ctx->scard_ctx = sm->scard_ctx;
        ctx->eapol_send = rsn_preauth_eapol_send;
        ctx->eapol_send_ctx = sm;
        ctx->set_config_blob = sm->ctx->set_config_blob;
        ctx->get_config_blob = sm->ctx->get_config_blob;

        sm->preauth_eapol = eapol_sm_init(ctx);
        if (sm->preauth_eapol == NULL) {
                os_free(ctx);
                wpa_printf(MSG_WARNING, "RSN: Failed to initialize EAPOL "
                           "state machines for pre-authentication");
                return -3;
        }
        os_memset(&eapol_conf, 0, sizeof(eapol_conf));
        eapol_conf.accept_802_1x_keys = 0;
        eapol_conf.required_keys = 0;
        eapol_conf.fast_reauth = sm->fast_reauth;
        eapol_conf.workaround = sm->eap_workaround;
        eapol_sm_notify_config(sm->preauth_eapol, eap_conf, &eapol_conf);
        /*
         * Use a shorter startPeriod with preauthentication since the first
         * preauth EAPOL-Start frame may end up being dropped due to race
         * condition in the AP between the data receive and key configuration
         * after the 4-Way Handshake.
         */
        eapol_sm_configure(sm->preauth_eapol, -1, -1, 5, 6);
        os_memcpy(sm->preauth_bssid, dst, ETH_ALEN);

        eapol_sm_notify_portValid(sm->preauth_eapol, TRUE);
        /* 802.1X::portControl = Auto */
        eapol_sm_notify_portEnabled(sm->preauth_eapol, TRUE);

        eloop_register_timeout(sm->dot11RSNAConfigSATimeout, 0,
                               rsn_preauth_timeout, sm, NULL);

        return 0;
}


void rsn_preauth_deinit(struct wpa_sm *sm)
{
        if (sm == NULL || !sm->preauth_eapol)
                return;

        eloop_cancel_timeout(rsn_preauth_timeout, sm, NULL);
        eapol_sm_deinit(sm->preauth_eapol);
        sm->preauth_eapol = NULL;
        os_memset(sm->preauth_bssid, 0, ETH_ALEN);

        l2_packet_deinit(sm->l2_preauth);
        sm->l2_preauth = NULL;
        if (sm->l2_preauth_br) {
                l2_packet_deinit(sm->l2_preauth_br);
                sm->l2_preauth_br = NULL;
        }
}


void rsn_preauth_candidate_process(struct wpa_sm *sm)
{
        struct rsn_pmksa_candidate *candidate;

        if (sm->pmksa_candidates == NULL)
                return;

        /* TODO: drop priority for old candidate entries */

        wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: processing PMKSA candidate "
                "list");
        if (sm->preauth_eapol ||
            sm->proto != WPA_PROTO_RSN ||
            wpa_sm_get_state(sm) != WPA_COMPLETED ||
            (sm->key_mgmt != WPA_KEY_MGMT_IEEE8021X &&
             sm->key_mgmt != WPA_KEY_MGMT_IEEE8021X_SHA256)) {
                wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: not in suitable "
                        "state for new pre-authentication");
                return; /* invalid state for new pre-auth */
        }

        while (sm->pmksa_candidates) {
                struct rsn_pmksa_cache_entry *p = NULL;
                candidate = sm->pmksa_candidates;
                p = pmksa_cache_get(sm->pmksa, candidate->bssid, NULL);
                if (os_memcmp(sm->bssid, candidate->bssid, ETH_ALEN) != 0 &&
                    (p == NULL || p->opportunistic)) {
                        wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: PMKSA "
                                "candidate " MACSTR
                                " selected for pre-authentication",
                                MAC2STR(candidate->bssid));
                        sm->pmksa_candidates = candidate->next;
                        rsn_preauth_init(sm, candidate->bssid,
                                         sm->eap_conf_ctx);
                        os_free(candidate);
                        return;
                }
                wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: PMKSA candidate "
                        MACSTR " does not need pre-authentication anymore",
                        MAC2STR(candidate->bssid));
                /* Some drivers (e.g., NDIS) expect to get notified about the
                 * PMKIDs again, so report the existing data now. */
                if (p) {
                        wpa_sm_add_pmkid(sm, candidate->bssid, p->pmkid);
                }

                sm->pmksa_candidates = candidate->next;
                os_free(candidate);
        }
        wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: no more pending PMKSA "
                "candidates");
}


void pmksa_candidate_add(struct wpa_sm *sm, const u8 *bssid,
                         int prio, int preauth)
{
        struct rsn_pmksa_candidate *cand, *prev, *pos;

        if (sm->network_ctx && sm->proactive_key_caching)
                pmksa_cache_get_opportunistic(sm->pmksa, sm->network_ctx,
                                              bssid);

        if (!preauth) {
                wpa_printf(MSG_DEBUG, "RSN: Ignored PMKID candidate without "
                           "preauth flag");
                return;
        }

        /* If BSSID already on candidate list, update the priority of the old
         * entry. Do not override priority based on normal scan results. */
        prev = NULL;
        cand = sm->pmksa_candidates;
        while (cand) {
                if (os_memcmp(cand->bssid, bssid, ETH_ALEN) == 0) {
                        if (prev)
                                prev->next = cand->next;
                        else
                                sm->pmksa_candidates = cand->next;
                        break;
                }
                prev = cand;
                cand = cand->next;
        }

        if (cand) {
                if (prio < PMKID_CANDIDATE_PRIO_SCAN)
                        cand->priority = prio;
        } else {
                cand = os_zalloc(sizeof(*cand));
                if (cand == NULL)
                        return;
                os_memcpy(cand->bssid, bssid, ETH_ALEN);
                cand->priority = prio;
        }

        /* Add candidate to the list; order by increasing priority value. i.e.,
         * highest priority (smallest value) first. */
        prev = NULL;
        pos = sm->pmksa_candidates;
        while (pos) {
                if (cand->priority <= pos->priority)
                        break;
                prev = pos;
                pos = pos->next;
        }
        cand->next = pos;
        if (prev)
                prev->next = cand;
        else
                sm->pmksa_candidates = cand;

        wpa_msg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: added PMKSA cache "
                "candidate " MACSTR " prio %d", MAC2STR(bssid), prio);
        rsn_preauth_candidate_process(sm);
}


/* TODO: schedule periodic scans if current AP supports preauth */

void rsn_preauth_scan_results(struct wpa_sm *sm,
                              struct wpa_scan_results *results)
{
        struct wpa_scan_res *r;
        struct wpa_ie_data ie;
        int i;
        struct rsn_pmksa_cache_entry *pmksa;

        if (sm->ssid_len == 0)
                return;

        /*
         * TODO: is it ok to free all candidates? What about the entries
         * received from EVENT_PMKID_CANDIDATE?
         */
        pmksa_candidate_free(sm);

        for (i = results->num - 1; i >= 0; i--) {
                const u8 *ssid, *rsn;

                r = results->res[i];

                ssid = wpa_scan_get_ie(r, WLAN_EID_SSID);
                if (ssid == NULL || ssid[1] != sm->ssid_len ||
                    os_memcmp(ssid + 2, sm->ssid, ssid[1]) != 0)
                        continue;

                if (os_memcmp(r->bssid, sm->bssid, ETH_ALEN) == 0)
                        continue;

                rsn = wpa_scan_get_ie(r, WLAN_EID_RSN);
                if (rsn == NULL || wpa_parse_wpa_ie(rsn, 2 + rsn[1], &ie))
                        continue;

                pmksa = pmksa_cache_get(sm->pmksa, r->bssid, NULL);
                if (pmksa &&
                    (!pmksa->opportunistic ||
                     !(ie.capabilities & WPA_CAPABILITY_PREAUTH)))
                        continue;

                /*
                 * Give less priority to candidates found from normal
                 * scan results.
                 */
                pmksa_candidate_add(sm, r->bssid,
                                    PMKID_CANDIDATE_PRIO_SCAN,
                                    ie.capabilities & WPA_CAPABILITY_PREAUTH);
        }
}


#ifdef CONFIG_CTRL_IFACE

int rsn_preauth_get_status(struct wpa_sm *sm, char *buf, size_t buflen,
                           int verbose)
{
        char *pos = buf, *end = buf + buflen;
        int res, ret;

        if (sm->preauth_eapol) {
                ret = os_snprintf(pos, end - pos, "Pre-authentication "
                                  "EAPOL state machines:\n");
                if (ret < 0 || ret >= end - pos)
                        return pos - buf;
                pos += ret;
                res = eapol_sm_get_status(sm->preauth_eapol,
                                          pos, end - pos, verbose);
                if (res >= 0)
                        pos += res;
        }

        return pos - buf;
}
#endif /* CONFIG_CTRL_IFACE */


int rsn_preauth_in_progress(struct wpa_sm *sm)
{
        return sm->preauth_eapol != NULL;
}

#endif /* IEEE8021X_EAPOL and !CONFIG_NO_WPA2 */