eap_psk.c

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/*
 * EAP peer method: EAP-PSK (RFC 4764)
 * 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.
 *
 * 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_i.h"


struct eap_psk_data {
        enum { PSK_INIT, PSK_MAC_SENT, PSK_DONE } state;
        u8 rand_p[EAP_PSK_RAND_LEN];
        u8 ak[EAP_PSK_AK_LEN], kdk[EAP_PSK_KDK_LEN], tek[EAP_PSK_TEK_LEN];
        u8 *id_s, *id_p;
        size_t id_s_len, id_p_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;
        const u8 *identity, *password;
        size_t identity_len, password_len;

        password = eap_get_config_password(sm, &password_len);
        if (!password || password_len != 16) {
                wpa_printf(MSG_INFO, "EAP-PSK: 16-octet pre-shared key not "
                           "configured");
                return NULL;
        }

        data = os_zalloc(sizeof(*data));
        if (data == NULL)
                return NULL;
        if (eap_psk_key_setup(password, data->ak, data->kdk)) {
                os_free(data);
                return NULL;
        }
        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);
        data->state = PSK_INIT;

        identity = eap_get_config_identity(sm, &identity_len);
        if (identity) {
                data->id_p = os_malloc(identity_len);
                if (data->id_p)
                        os_memcpy(data->id_p, identity, identity_len);
                data->id_p_len = identity_len;
        }
        if (data->id_p == NULL) {
                wpa_printf(MSG_INFO, "EAP-PSK: could not get own identity");
                os_free(data);
                return NULL;
        }

        return data;
}


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


static struct wpabuf * eap_psk_process_1(struct eap_psk_data *data,
                                         struct eap_method_ret *ret,
                                         const struct wpabuf *reqData)
{
        const struct eap_psk_hdr_1 *hdr1;
        struct eap_psk_hdr_2 *hdr2;
        struct wpabuf *resp;
        u8 *buf, *pos;
        size_t buflen, len;
        const u8 *cpos;

        wpa_printf(MSG_DEBUG, "EAP-PSK: in INIT state");

        cpos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, reqData, &len);
        hdr1 = (const struct eap_psk_hdr_1 *) cpos;
        if (cpos == NULL || len < sizeof(*hdr1)) {
                wpa_printf(MSG_INFO, "EAP-PSK: Invalid first message "
                           "length (%lu; expected %lu or more)",
                           (unsigned long) len,
                           (unsigned long) sizeof(*hdr1));
                ret->ignore = TRUE;
                return NULL;
        }
        wpa_printf(MSG_DEBUG, "EAP-PSK: Flags=0x%x", hdr1->flags);
        if (EAP_PSK_FLAGS_GET_T(hdr1->flags) != 0) {
                wpa_printf(MSG_INFO, "EAP-PSK: Unexpected T=%d (expected 0)",
                           EAP_PSK_FLAGS_GET_T(hdr1->flags));
                ret->methodState = METHOD_DONE;
                ret->decision = DECISION_FAIL;
                return NULL;
        }
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_S", hdr1->rand_s,
                    EAP_PSK_RAND_LEN);
        os_free(data->id_s);
        data->id_s_len = len - sizeof(*hdr1);
        data->id_s = os_malloc(data->id_s_len);
        if (data->id_s == NULL) {
                wpa_printf(MSG_ERROR, "EAP-PSK: Failed to allocate memory for "
                           "ID_S (len=%lu)", (unsigned long) data->id_s_len);
                ret->ignore = TRUE;
                return NULL;
        }
        os_memcpy(data->id_s, (u8 *) (hdr1 + 1), data->id_s_len);
        wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: ID_S",
                          data->id_s, data->id_s_len);

        if (os_get_random(data->rand_p, EAP_PSK_RAND_LEN)) {
                wpa_printf(MSG_ERROR, "EAP-PSK: Failed to get random data");
                ret->ignore = TRUE;
                return NULL;
        }

        resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK,
                             sizeof(*hdr2) + data->id_p_len, EAP_CODE_RESPONSE,
                             eap_get_id(reqData));
        if (resp == NULL)
                return NULL;
        hdr2 = wpabuf_put(resp, sizeof(*hdr2));
        hdr2->flags = EAP_PSK_FLAGS_SET_T(1); /* T=1 */
        os_memcpy(hdr2->rand_s, hdr1->rand_s, EAP_PSK_RAND_LEN);
        os_memcpy(hdr2->rand_p, data->rand_p, EAP_PSK_RAND_LEN);
        wpabuf_put_data(resp, data->id_p, data->id_p_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) {
                wpabuf_free(resp);
                return NULL;
        }
        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, hdr1->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, hdr2->mac_p)) {
                os_free(buf);
                wpabuf_free(resp);
                return NULL;
        }
        os_free(buf);
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_P", hdr2->rand_p,
                    EAP_PSK_RAND_LEN);
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", hdr2->mac_p, EAP_PSK_MAC_LEN);
        wpa_hexdump_ascii(MSG_DEBUG, "EAP-PSK: ID_P",
                          data->id_p, data->id_p_len);

        data->state = PSK_MAC_SENT;

        return resp;
}


static struct wpabuf * eap_psk_process_3(struct eap_psk_data *data,
                                         struct eap_method_ret *ret,
                                         const struct wpabuf *reqData)
{
        const struct eap_psk_hdr_3 *hdr3;
        struct eap_psk_hdr_4 *hdr4;
        struct wpabuf *resp;
        u8 *buf, *rpchannel, nonce[16], *decrypted;
        const u8 *pchannel, *tag, *msg;
        u8 mac[EAP_PSK_MAC_LEN];
        size_t buflen, left, data_len, len, plen;
        int failed = 0;
        const u8 *pos;

        wpa_printf(MSG_DEBUG, "EAP-PSK: in MAC_SENT state");

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK,
                               reqData, &len);
        hdr3 = (const struct eap_psk_hdr_3 *) pos;
        if (pos == NULL || len < sizeof(*hdr3)) {
                wpa_printf(MSG_INFO, "EAP-PSK: Invalid third message "
                           "length (%lu; expected %lu or more)",
                           (unsigned long) len,
                           (unsigned long) sizeof(*hdr3));
                ret->ignore = TRUE;
                return NULL;
        }
        left = len - sizeof(*hdr3);
        pchannel = (const u8 *) (hdr3 + 1);
        wpa_printf(MSG_DEBUG, "EAP-PSK: Flags=0x%x", hdr3->flags);
        if (EAP_PSK_FLAGS_GET_T(hdr3->flags) != 2) {
                wpa_printf(MSG_INFO, "EAP-PSK: Unexpected T=%d (expected 2)",
                           EAP_PSK_FLAGS_GET_T(hdr3->flags));
                ret->methodState = METHOD_DONE;
                ret->decision = DECISION_FAIL;
                return NULL;
        }
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: RAND_S", hdr3->rand_s,
                    EAP_PSK_RAND_LEN);
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_S", hdr3->mac_s, EAP_PSK_MAC_LEN);
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: PCHANNEL", pchannel, left);

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

        /* 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)
                return NULL;
        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, mac)) {
                os_free(buf);
                return NULL;
        }
        os_free(buf);
        if (os_memcmp(mac, hdr3->mac_s, EAP_PSK_MAC_LEN) != 0) {
                wpa_printf(MSG_WARNING, "EAP-PSK: Invalid MAC_S in third "
                           "message");
                ret->methodState = METHOD_DONE;
                ret->decision = DECISION_FAIL;
                return NULL;
        }
        wpa_printf(MSG_DEBUG, "EAP-PSK: MAC_S verified successfully");

        if (eap_psk_derive_keys(data->kdk, data->rand_p, data->tek,
                                data->msk, data->emsk)) {
                ret->methodState = METHOD_DONE;
                ret->decision = DECISION_FAIL;
                return NULL;
        }
        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, 12);
        os_memcpy(nonce + 12, pchannel, 4);
        pchannel += 4;
        left -= 4;

        tag = pchannel;
        pchannel += 16;
        left -= 16;

        msg = pchannel;

        wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - nonce",
                    nonce, sizeof(nonce));
        wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - hdr",
                    wpabuf_head(reqData), 5);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: PCHANNEL - cipher msg", msg, left);

        decrypted = os_malloc(left);
        if (decrypted == NULL) {
                ret->methodState = METHOD_DONE;
                ret->decision = DECISION_FAIL;
                return NULL;
        }
        os_memcpy(decrypted, msg, left);

        if (aes_128_eax_decrypt(data->tek, nonce, sizeof(nonce),
                                wpabuf_head(reqData),
                                sizeof(struct eap_hdr) + 1 +
                                sizeof(*hdr3) - EAP_PSK_MAC_LEN, decrypted,
                                left, tag)) {
                wpa_printf(MSG_WARNING, "EAP-PSK: PCHANNEL decryption failed");
                os_free(decrypted);
                return NULL;
        }
        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");
                failed = 1;
                break;
        case EAP_PSK_R_FLAG_DONE_SUCCESS:
                wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_SUCCESS");
                break;
        case EAP_PSK_R_FLAG_DONE_FAILURE:
                wpa_printf(MSG_DEBUG, "EAP-PSK: R flag - DONE_FAILURE");
                wpa_printf(MSG_INFO, "EAP-PSK: Authentication server rejected "
                           "authentication");
                failed = 1;
                break;
        }

        data_len = 1;
        if ((decrypted[0] & EAP_PSK_E_FLAG) && left > 1)
                data_len++;
        plen = sizeof(*hdr4) + 4 + 16 + data_len;
        resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PSK, plen,
                             EAP_CODE_RESPONSE, eap_get_id(reqData));
        if (resp == NULL) {
                os_free(decrypted);
                return NULL;
        }
        hdr4 = wpabuf_put(resp, sizeof(*hdr4));
        hdr4->flags = EAP_PSK_FLAGS_SET_T(3); /* T=3 */
        os_memcpy(hdr4->rand_s, hdr3->rand_s, EAP_PSK_RAND_LEN);
        rpchannel = wpabuf_put(resp, 4 + 16 + data_len);

        /* nonce++ */
        inc_byte_array(nonce, sizeof(nonce));
        os_memcpy(rpchannel, nonce + 12, 4);

        if (decrypted[0] & EAP_PSK_E_FLAG) {
                wpa_printf(MSG_DEBUG, "EAP-PSK: Unsupported E (Ext) flag");
                failed = 1;
                rpchannel[4 + 16] = (EAP_PSK_R_FLAG_DONE_FAILURE << 6) |
                        EAP_PSK_E_FLAG;
                if (left > 1) {
                        /* Add empty EXT_Payload with same EXT_Type */
                        rpchannel[4 + 16 + 1] = decrypted[1];
                }
        } else if (failed)
                rpchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_FAILURE << 6;
        else
                rpchannel[4 + 16] = EAP_PSK_R_FLAG_DONE_SUCCESS << 6;

        wpa_hexdump(MSG_DEBUG, "EAP-PSK: reply message (plaintext)",
                    rpchannel + 4 + 16, data_len);
        if (aes_128_eax_encrypt(data->tek, nonce, sizeof(nonce),
                                wpabuf_head(resp),
                                sizeof(struct eap_hdr) + 1 + sizeof(*hdr4),
                                rpchannel + 4 + 16, data_len, rpchannel + 4)) {
                os_free(decrypted);
                wpabuf_free(resp);
                return NULL;
        }
        wpa_hexdump(MSG_DEBUG, "EAP-PSK: reply message (PCHANNEL)",
                    rpchannel, 4 + 16 + data_len);

        wpa_printf(MSG_DEBUG, "EAP-PSK: Completed %ssuccessfully",
                   failed ? "un" : "");
        data->state = PSK_DONE;
        ret->methodState = METHOD_DONE;
        ret->decision = failed ? DECISION_FAIL : DECISION_UNCOND_SUCC;

        os_free(decrypted);

        return resp;
}


static struct wpabuf * eap_psk_process(struct eap_sm *sm, void *priv,
                                       struct eap_method_ret *ret,
                                       const struct wpabuf *reqData)
{
        struct eap_psk_data *data = priv;
        const u8 *pos;
        struct wpabuf *resp = NULL;
        size_t len;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PSK, reqData, &len);
        if (pos == NULL) {
                ret->ignore = TRUE;
                return NULL;
        }

        ret->ignore = FALSE;
        ret->methodState = METHOD_MAY_CONT;
        ret->decision = DECISION_FAIL;
        ret->allowNotifications = TRUE;

        switch (data->state) {
        case PSK_INIT:
                resp = eap_psk_process_1(data, ret, reqData);
                break;
        case PSK_MAC_SENT:
                resp = eap_psk_process_3(data, ret, reqData);
                break;
        case PSK_DONE:
                wpa_printf(MSG_DEBUG, "EAP-PSK: in DONE state - ignore "
                           "unexpected message");
                ret->ignore = TRUE;
                return NULL;
        }

        if (ret->methodState == METHOD_DONE) {
                ret->allowNotifications = FALSE;
        }

        return resp;
}


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


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 != PSK_DONE)
                return NULL;

        key = os_malloc(EAP_MSK_LEN);
        if (key == NULL)
                return NULL;

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

        key = os_malloc(EAP_EMSK_LEN);
        if (key == NULL)
                return NULL;

        *len = EAP_EMSK_LEN;
        os_memcpy(key, data->emsk, EAP_EMSK_LEN);

        return key;
}


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

        eap = eap_peer_method_alloc(EAP_PEER_METHOD_INTERFACE_VERSION,
                                    EAP_VENDOR_IETF, EAP_TYPE_PSK, "PSK");
        if (eap == NULL)
                return -1;

        eap->init = eap_psk_init;
        eap->deinit = eap_psk_deinit;
        eap->process = eap_psk_process;
        eap->isKeyAvailable = eap_psk_isKeyAvailable;
        eap->getKey = eap_psk_getKey;
        eap->get_emsk = eap_psk_get_emsk;

        ret = eap_peer_method_register(eap);
        if (ret)
                eap_peer_method_free(eap);
        return ret;
}