eap_server_psk.c

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/*
 * hostapd / EAP-PSK (RFC 4764) server
 * Copyright (c) 2005-2007, 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.
 *
 * Note: EAP-PSK is an EAP authentication method and as such, completely
 * different from WPA-PSK. This file is not needed for WPA-PSK functionality.
 */

#include "includes.h"

#include "common.h"
#include "crypto/aes_wrap.h"
#include "eap_common/eap_psk_common.h"
#include "eap_server/eap_i.h"


struct eap_psk_data {
        enum { PSK_1, PSK_3, SUCCESS, FAILURE } state;
        u8 rand_s[EAP_PSK_RAND_LEN];
        u8 rand_p[EAP_PSK_RAND_LEN];
        u8 *id_p, *id_s;
        size_t id_p_len, id_s_len;
        u8 ak[EAP_PSK_AK_LEN], kdk[EAP_PSK_KDK_LEN], tek[EAP_PSK_TEK_LEN];
        u8 msk[EAP_MSK_LEN];
        u8 emsk[EAP_EMSK_LEN];
};


static void * eap_psk_init(struct eap_sm *sm)
{
        struct eap_psk_data *data;

        data = os_zalloc(sizeof(*data));
        if (data == NULL)
                return NULL;
        data->state = PSK_1;
        data->id_s = (u8 *) "hostapd";
        data->id_s_len = 7;

        return data;
}


static void eap_psk_reset(struct eap_sm *sm, void *priv)
{
        struct eap_psk_data *data = priv;
        os_free(data->id_p);
        os_free(data);
}


static struct wpabuf * eap_psk_build_1(struct eap_sm *sm,
                                       struct eap_psk_data *data, u8 id)
{
        struct wpabuf *req;
        struct eap_psk_hdr_1 *psk;

        wpa_printf(MSG_DEBUG, "EAP-PSK: PSK-1 (sending)");

        if (os_get_random(data->rand_s, EAP_PSK_RAND_LEN)) {
                wpa_printf(MSG_ERROR, "EAP-PSK: Failed to get random data");
                data->state = FAILURE;
                return NULL;
        }
        wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: RAND_S (server rand)",
                    data->rand_s, EAP_PSK_RAND_LEN);

        req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
                            sizeof(*psk) + data->id_s_len,
                            EAP_CODE_REQUEST, id);
        if (req == NULL) {
                wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory "
                           "request");
                data->state = FAILURE;
                return NULL;
        }

        psk = wpabuf_put(req, sizeof(*psk));
        psk->flags = EAP_PSK_FLAGS_SET_T(0); /* T=0 */
        os_memcpy(psk->rand_s, data->rand_s, EAP_PSK_RAND_LEN);
        wpabuf_put_data(req, data->id_s, data->id_s_len);

        return req;
}


static struct wpabuf * eap_psk_build_3(struct eap_sm *sm,
                                       struct eap_psk_data *data, u8 id)
{
        struct wpabuf *req;
        struct eap_psk_hdr_3 *psk;
        u8 *buf, *pchannel, nonce[16];
        size_t buflen;

        wpa_printf(MSG_DEBUG, "EAP-PSK: PSK-3 (sending)");

        req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
                            sizeof(*psk) + 4 + 16 + 1, EAP_CODE_REQUEST, id);
        if (req == NULL) {
                wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory "
                           "request");
                data->state = FAILURE;
                return NULL;
        }

        psk = wpabuf_put(req, sizeof(*psk));
        psk->flags = EAP_PSK_FLAGS_SET_T(2); /* T=2 */
        os_memcpy(psk->rand_s, data->rand_s, EAP_PSK_RAND_LEN);

        /* MAC_S = OMAC1-AES-128(AK, ID_S||RAND_P) */
        buflen = data->id_s_len + EAP_PSK_RAND_LEN;
        buf = os_malloc(buflen);
        if (buf == NULL)
                goto fail;

        os_memcpy(buf, data->id_s, data->id_s_len);
        os_memcpy(buf + data->id_s_len, data->rand_p, EAP_PSK_RAND_LEN);
        if (omac1_aes_128(data->ak, buf, buflen, psk->mac_s))
                goto fail;
        os_free(buf);

        if (eap_psk_derive_keys(data->kdk, data->rand_p, data->tek, data->msk,
                                data->emsk))
                goto fail;
        wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: TEK", data->tek, EAP_PSK_TEK_LEN);
        wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: MSK", data->msk, EAP_MSK_LEN);
        wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: EMSK", data->emsk, EAP_EMSK_LEN);

        os_memset(nonce, 0, sizeof(nonce));
        pchannel = wpabuf_put(req, 4 + 16 + 1);
        os_memcpy(pchannel, nonce + 12, 4);
        os_memset(pchannel + 4, 0, 16); /* Tag */
        pchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_SUCCESS << 6;
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL (plaintext)",
                    pchannel, 4 + 16 + 1);
        if (aes_128_eax_encrypt(data->tek, nonce, sizeof(nonce),
                                wpabuf_head(req), 22,
                                pchannel + 4 + 16, 1, pchannel + 4))
                goto fail;
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL (encrypted)",
                    pchannel, 4 + 16 + 1);

        return req;

fail:
        wpabuf_free(req);
        data->state = FAILURE;
        return NULL;
}


static struct wpabuf * eap_psk_buildReq(struct eap_sm *sm, void *priv, u8 id)
{
        struct eap_psk_data *data = priv;

        switch (data->state) {
        case PSK_1:
                return eap_psk_build_1(sm, data, id);
        case PSK_3:
                return eap_psk_build_3(sm, data, id);
        default:
                wpa_printf(MSG_DEBUG, "EAP-PSK: Unknown state %d in buildReq",
                           data->state);
                break;
        }
        return NULL;
}


static Boolean eap_psk_check(struct eap_sm *sm, void *priv,
                             struct wpabuf *respData)
{
        struct eap_psk_data *data = priv;
        size_t len;
        u8 t;
        const u8 *pos;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &len);
        if (pos == NULL || len < 1) {
                wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
                return TRUE;
        }
        t = EAP_PSK_FLAGS_GET_T(*pos);

        wpa_printf(MSG_DEBUG, "EAP-PSK: received frame: T=%d", t);

        if (data->state == PSK_1 && t != 1) {
                wpa_printf(MSG_DEBUG, "EAP-PSK: Expected PSK-2 - "
                           "ignore T=%d", t);
                return TRUE;
        }

        if (data->state == PSK_3 && t != 3) {
                wpa_printf(MSG_DEBUG, "EAP-PSK: Expected PSK-4 - "
                           "ignore T=%d", t);
                return TRUE;
        }

        if ((t == 1 && len < sizeof(struct eap_psk_hdr_2)) ||
            (t == 3 && len < sizeof(struct eap_psk_hdr_4))) {
                wpa_printf(MSG_DEBUG, "EAP-PSK: Too short frame");
                return TRUE;
        }

        return FALSE;
}


static void eap_psk_process_2(struct eap_sm *sm,
                              struct eap_psk_data *data,
                              struct wpabuf *respData)
{
        const struct eap_psk_hdr_2 *resp;
        u8 *pos, mac[EAP_PSK_MAC_LEN], *buf;
        size_t left, buflen;
        int i;
        const u8 *cpos;

        if (data->state != PSK_1)
                return;

        wpa_printf(MSG_DEBUG, "EAP-PSK: Received PSK-2");

        cpos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData,
                                &left);
        if (cpos == NULL || left < sizeof(*resp)) {
                wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
                return;
        }
        resp = (const struct eap_psk_hdr_2 *) cpos;
        cpos = (const u8 *) (resp + 1);
        left -= sizeof(*resp);

        os_free(data->id_p);
        data->id_p = os_malloc(left);
        if (data->id_p == NULL) {
                wpa_printf(MSG_INFO, "EAP-PSK: Failed to allocate memory for "
                           "ID_P");
                return;
        }
        os_memcpy(data->id_p, cpos, left);
        data->id_p_len = left;
        wpa_hexdump_ascii(MSG_MSGDUMP, "EAP-PSK: ID_P",
                          data->id_p, data->id_p_len);

        if (eap_user_get(sm, data->id_p, data->id_p_len, 0) < 0) {
                wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: unknown ID_P",
                                  data->id_p, data->id_p_len);
                data->state = FAILURE;
                return;
        }

        for (i = 0;
             i < EAP_MAX_METHODS &&
                     (sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
                      sm->user->methods[i].method != EAP_TYPE_NONE);
             i++) {
                if (sm->user->methods[i].vendor == EAP_VENDOR_IETF &&
                    sm->user->methods[i].method == EAP_TYPE_PSK)
                        break;
        }

        if (i >= EAP_MAX_METHODS ||
            sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
            sm->user->methods[i].method != EAP_TYPE_PSK) {
                wpa_hexdump_ascii(MSG_DEBUG,
                                  "EAP-PSK: EAP-PSK not enabled for ID_P",
                                  data->id_p, data->id_p_len);
                data->state = FAILURE;
                return;
        }

        if (sm->user->password == NULL ||
            sm->user->password_len != EAP_PSK_PSK_LEN) {
                wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: invalid password in "
                                  "user database for ID_P",
                                  data->id_p, data->id_p_len);
                data->state = FAILURE;
                return;
        }
        if (eap_psk_key_setup(sm->user->password, data->ak, data->kdk)) {
                data->state = FAILURE;
                return;
        }
        wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: AK", data->ak, EAP_PSK_AK_LEN);
        wpa_hexdump_key(MSG_DEBUG, "EAP-PSK: KDK", data->kdk, EAP_PSK_KDK_LEN);

        wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: RAND_P (client rand)",
                    resp->rand_p, EAP_PSK_RAND_LEN);
        os_memcpy(data->rand_p, resp->rand_p, EAP_PSK_RAND_LEN);

        /* MAC_P = OMAC1-AES-128(AK, ID_P||ID_S||RAND_S||RAND_P) */
        buflen = data->id_p_len + data->id_s_len + 2 * EAP_PSK_RAND_LEN;
        buf = os_malloc(buflen);
        if (buf == NULL) {
                data->state = FAILURE;
                return;
        }
        os_memcpy(buf, data->id_p, data->id_p_len);
        pos = buf + data->id_p_len;
        os_memcpy(pos, data->id_s, data->id_s_len);
        pos += data->id_s_len;
        os_memcpy(pos, data->rand_s, EAP_PSK_RAND_LEN);
        pos += EAP_PSK_RAND_LEN;
        os_memcpy(pos, data->rand_p, EAP_PSK_RAND_LEN);
        if (omac1_aes_128(data->ak, buf, buflen, mac)) {
                os_free(buf);
                data->state = FAILURE;
                return;
        }
        os_free(buf);
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", resp->mac_p, EAP_PSK_MAC_LEN);
        if (os_memcmp(mac, resp->mac_p, EAP_PSK_MAC_LEN) != 0) {
                wpa_printf(MSG_INFO, "EAP-PSK: Invalid MAC_P");
                wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Expected MAC_P",
                            mac, EAP_PSK_MAC_LEN);
                data->state = FAILURE;
                return;
        }

        data->state = PSK_3;
}


static void eap_psk_process_4(struct eap_sm *sm,
                              struct eap_psk_data *data,
                              struct wpabuf *respData)
{
        const struct eap_psk_hdr_4 *resp;
        u8 *decrypted, nonce[16];
        size_t left;
        const u8 *pos, *tag;

        if (data->state != PSK_3)
                return;

        wpa_printf(MSG_DEBUG, "EAP-PSK: Received PSK-4");

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &left);
        if (pos == NULL || left < sizeof(*resp)) {
                wpa_printf(MSG_INFO, "EAP-PSK: Invalid frame");
                return;
        }
        resp = (const struct eap_psk_hdr_4 *) pos;
        pos = (const u8 *) (resp + 1);
        left -= sizeof(*resp);

        wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Encrypted PCHANNEL", pos, left);

        if (left < 4 + 16 + 1) {
                wpa_printf(MSG_INFO, "EAP-PSK: Too short PCHANNEL data in "
                           "PSK-4 (len=%lu, expected 21)",
                           (unsigned long) left);
                return;
        }

        if (pos[0] == 0 && pos[1] == 0 && pos[2] == 0 && pos[3] == 0) {
                wpa_printf(MSG_DEBUG, "EAP-PSK: Nonce did not increase");
                return;
        }

        os_memset(nonce, 0, 12);
        os_memcpy(nonce + 12, pos, 4);
        pos += 4;
        left -= 4;
        tag = pos;
        pos += 16;
        left -= 16;

        decrypted = os_malloc(left);
        if (decrypted == NULL)
                return;
        os_memcpy(decrypted, pos, left);

        if (aes_128_eax_decrypt(data->tek, nonce, sizeof(nonce),
                                wpabuf_head(respData), 22, decrypted, left,
                                tag)) {
                wpa_printf(MSG_WARNING, "EAP-PSK: PCHANNEL decryption failed");
                os_free(decrypted);
                data->state = FAILURE;
                return;
        }
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: Decrypted PCHANNEL message",
                    decrypted, left);

        /* Verify R flag */
        switch (decrypted[0] >> 6) {
        case EAP_PSK_R_FLAG_CONT:
                wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - CONT - unsupported");
                data->state = FAILURE;
                break;
        case EAP_PSK_R_FLAG_DONE_SUCCESS:
                wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_SUCCESS");
                data->state = SUCCESS;
                break;
        case EAP_PSK_R_FLAG_DONE_FAILURE:
                wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_FAILURE");
                data->state = FAILURE;
                break;
        }
        os_free(decrypted);
}


static void eap_psk_process(struct eap_sm *sm, void *priv,
                            struct wpabuf *respData)
{
        struct eap_psk_data *data = priv;
        const u8 *pos;
        size_t len;

        if (sm->user == NULL || sm->user->password == NULL) {
                wpa_printf(MSG_INFO, "EAP-PSK: Plaintext password not "
                           "configured");
                data->state = FAILURE;
                return;
        }

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, respData, &len);
        if (pos == NULL || len < 1)
                return;

        switch (EAP_PSK_FLAGS_GET_T(*pos)) {
        case 1:
                eap_psk_process_2(sm, data, respData);
                break;
        case 3:
                eap_psk_process_4(sm, data, respData);
                break;
        }
}


static Boolean eap_psk_isDone(struct eap_sm *sm, void *priv)
{
        struct eap_psk_data *data = priv;
        return data->state == SUCCESS || data->state == FAILURE;
}


static u8 * eap_psk_getKey(struct eap_sm *sm, void *priv, size_t *len)
{
        struct eap_psk_data *data = priv;
        u8 *key;

        if (data->state != SUCCESS)
                return NULL;

        key = os_malloc(EAP_MSK_LEN);
        if (key == NULL)
                return NULL;
        os_memcpy(key, data->msk, EAP_MSK_LEN);
        *len = EAP_MSK_LEN;

        return key;
}


static u8 * eap_psk_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
{
        struct eap_psk_data *data = priv;
        u8 *key;

        if (data->state != SUCCESS)
                return NULL;

        key = os_malloc(EAP_EMSK_LEN);
        if (key == NULL)
                return NULL;
        os_memcpy(key, data->emsk, EAP_EMSK_LEN);
        *len = EAP_EMSK_LEN;

        return key;
}


static Boolean eap_psk_isSuccess(struct eap_sm *sm, void *priv)
{
        struct eap_psk_data *data = priv;
        return data->state == SUCCESS;
}


int eap_server_psk_register(void)
{
        struct eap_method *eap;
        int ret;

        eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
                                      EAP_VENDOR_IETF, EAP_TYPE_PSK, "PSK");
        if (eap == NULL)
                return -1;

        eap->init = eap_psk_init;
        eap->reset = eap_psk_reset;
        eap->buildReq = eap_psk_buildReq;
        eap->check = eap_psk_check;
        eap->process = eap_psk_process;
        eap->isDone = eap_psk_isDone;
        eap->getKey = eap_psk_getKey;
        eap->isSuccess = eap_psk_isSuccess;
        eap->get_emsk = eap_psk_get_emsk;

        ret = eap_server_method_register(eap);
        if (ret)
                eap_server_method_free(eap);
        return ret;
}