eap_pax.c

Go to the documentation of this file.

/*
 * EAP peer method: EAP-PAX (RFC 4746)
 * Copyright (c) 2005-2008, 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 "eap_common/eap_pax_common.h"
#include "eap_i.h"

/*
 * Note: only PAX_STD subprotocol is currently supported
 *
 * TODO: Add support with PAX_SEC with the mandatory to implement ciphersuite
 * (HMAC_SHA1_128, IANA DH Group 14 (2048 bits), RSA-PKCS1-V1_5) and
 * recommended ciphersuite (HMAC_SHA256_128, IANA DH Group 15 (3072 bits),
 * RSAES-OAEP).
 */

struct eap_pax_data {
        enum { PAX_INIT, PAX_STD_2_SENT, PAX_DONE } state;
        u8 mac_id, dh_group_id, public_key_id;
        union {
                u8 e[2 * EAP_PAX_RAND_LEN];
                struct {
                        u8 x[EAP_PAX_RAND_LEN]; /* server rand */
                        u8 y[EAP_PAX_RAND_LEN]; /* client rand */
                } r;
        } rand;
        char *cid;
        size_t cid_len;
        u8 ak[EAP_PAX_AK_LEN];
        u8 mk[EAP_PAX_MK_LEN];
        u8 ck[EAP_PAX_CK_LEN];
        u8 ick[EAP_PAX_ICK_LEN];
};


static void eap_pax_deinit(struct eap_sm *sm, void *priv);


static void * eap_pax_init(struct eap_sm *sm)
{
        struct eap_pax_data *data;
        const u8 *identity, *password;
        size_t identity_len, password_len;

        identity = eap_get_config_identity(sm, &identity_len);
        password = eap_get_config_password(sm, &password_len);
        if (!identity || !password) {
                wpa_printf(MSG_INFO, "EAP-PAX: CID (nai) or key (password) "
                           "not configured");
                return NULL;
        }

        if (password_len != EAP_PAX_AK_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: Invalid PSK length");
                return NULL;
        }

        data = os_zalloc(sizeof(*data));
        if (data == NULL)
                return NULL;
        data->state = PAX_INIT;

        data->cid = os_malloc(identity_len);
        if (data->cid == NULL) {
                eap_pax_deinit(sm, data);
                return NULL;
        }
        os_memcpy(data->cid, identity, identity_len);
        data->cid_len = identity_len;

        os_memcpy(data->ak, password, EAP_PAX_AK_LEN);

        return data;
}


static void eap_pax_deinit(struct eap_sm *sm, void *priv)
{
        struct eap_pax_data *data = priv;
        os_free(data->cid);
        os_free(data);
}


static struct wpabuf * eap_pax_alloc_resp(const struct eap_pax_hdr *req,
                                          u8 id, u8 op_code, size_t plen)
{
        struct wpabuf *resp;
        struct eap_pax_hdr *pax;

        resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PAX,
                             sizeof(*pax) + plen, EAP_CODE_RESPONSE, id);
        if (resp == NULL)
                return NULL;

        pax = wpabuf_put(resp, sizeof(*pax));
        pax->op_code = op_code;
        pax->flags = 0;
        pax->mac_id = req->mac_id;
        pax->dh_group_id = req->dh_group_id;
        pax->public_key_id = req->public_key_id;

        return resp;
}


static struct wpabuf * eap_pax_process_std_1(struct eap_pax_data *data,
                                             struct eap_method_ret *ret, u8 id,
                                             const struct eap_pax_hdr *req,
                                             size_t req_plen)
{
        struct wpabuf *resp;
        const u8 *pos;
        u8 *rpos;
        size_t left, plen;

        wpa_printf(MSG_DEBUG, "EAP-PAX: PAX_STD-1 (received)");

        if (data->state != PAX_INIT) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-1 received in "
                           "unexpected state (%d) - ignored", data->state);
                ret->ignore = TRUE;
                return NULL;
        }

        if (req->flags & EAP_PAX_FLAGS_CE) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-1 with CE flag set - "
                           "ignored");
                ret->ignore = TRUE;
                return NULL;
        }

        left = req_plen - sizeof(*req);

        if (left < 2 + EAP_PAX_RAND_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-1 with too short "
                           "payload");
                ret->ignore = TRUE;
                return NULL;
        }

        pos = (const u8 *) (req + 1);
        if (WPA_GET_BE16(pos) != EAP_PAX_RAND_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-1 with incorrect A "
                           "length %d (expected %d)",
                           WPA_GET_BE16(pos), EAP_PAX_RAND_LEN);
                ret->ignore = TRUE;
                return NULL;
        }

        pos += 2;
        left -= 2;
        os_memcpy(data->rand.r.x, pos, EAP_PAX_RAND_LEN);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: X (server rand)",
                    data->rand.r.x, EAP_PAX_RAND_LEN);
        pos += EAP_PAX_RAND_LEN;
        left -= EAP_PAX_RAND_LEN;

        if (left > 0) {
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ignored extra payload",
                            pos, left);
        }

        if (os_get_random(data->rand.r.y, EAP_PAX_RAND_LEN)) {
                wpa_printf(MSG_ERROR, "EAP-PAX: Failed to get random data");
                ret->ignore = TRUE;
                return NULL;
        }
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: Y (client rand)",
                    data->rand.r.y, EAP_PAX_RAND_LEN);

        if (eap_pax_initial_key_derivation(req->mac_id, data->ak, data->rand.e,
                                           data->mk, data->ck, data->ick) < 0)
        {
                ret->ignore = TRUE;
                return NULL;
        }

        wpa_printf(MSG_DEBUG, "EAP-PAX: PAX_STD-2 (sending)");

        plen = 2 + EAP_PAX_RAND_LEN + 2 + data->cid_len + 2 + EAP_PAX_MAC_LEN +
                EAP_PAX_ICV_LEN;
        resp = eap_pax_alloc_resp(req, id, EAP_PAX_OP_STD_2, plen);
        if (resp == NULL)
                return NULL;

        wpabuf_put_be16(resp, EAP_PAX_RAND_LEN);
        wpabuf_put_data(resp, data->rand.r.y, EAP_PAX_RAND_LEN);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: B = Y (client rand)",
                    data->rand.r.y, EAP_PAX_RAND_LEN);

        wpabuf_put_be16(resp, data->cid_len);
        wpabuf_put_data(resp, data->cid, data->cid_len);
        wpa_hexdump_ascii(MSG_MSGDUMP, "EAP-PAX: CID",
                          (u8 *) data->cid, data->cid_len);

        wpabuf_put_be16(resp, EAP_PAX_MAC_LEN);
        rpos = wpabuf_put(resp, EAP_PAX_MAC_LEN);
        eap_pax_mac(req->mac_id, data->ck, EAP_PAX_CK_LEN,
                    data->rand.r.x, EAP_PAX_RAND_LEN,
                    data->rand.r.y, EAP_PAX_RAND_LEN,
                    (u8 *) data->cid, data->cid_len, rpos);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: MAC_CK(A, B, CID)",
                    rpos, EAP_PAX_MAC_LEN);

        /* Optional ADE could be added here, if needed */

        rpos = wpabuf_put(resp, EAP_PAX_ICV_LEN);
        eap_pax_mac(req->mac_id, data->ick, EAP_PAX_ICK_LEN,
                    wpabuf_head(resp), wpabuf_len(resp) - EAP_PAX_ICV_LEN,
                    NULL, 0, NULL, 0, rpos);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ICV", rpos, EAP_PAX_ICV_LEN);

        data->state = PAX_STD_2_SENT;
        data->mac_id = req->mac_id;
        data->dh_group_id = req->dh_group_id;
        data->public_key_id = req->public_key_id;

        return resp;
}


static struct wpabuf * eap_pax_process_std_3(struct eap_pax_data *data,
                                             struct eap_method_ret *ret, u8 id,
                                             const struct eap_pax_hdr *req,
                                             size_t req_plen)
{
        struct wpabuf *resp;
        u8 *rpos, mac[EAP_PAX_MAC_LEN];
        const u8 *pos;
        size_t left;

        wpa_printf(MSG_DEBUG, "EAP-PAX: PAX_STD-3 (received)");

        if (data->state != PAX_STD_2_SENT) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-3 received in "
                           "unexpected state (%d) - ignored", data->state);
                ret->ignore = TRUE;
                return NULL;
        }

        if (req->flags & EAP_PAX_FLAGS_CE) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-3 with CE flag set - "
                           "ignored");
                ret->ignore = TRUE;
                return NULL;
        }

        left = req_plen - sizeof(*req);

        if (left < 2 + EAP_PAX_MAC_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-3 with too short "
                           "payload");
                ret->ignore = TRUE;
                return NULL;
        }

        pos = (const u8 *) (req + 1);
        if (WPA_GET_BE16(pos) != EAP_PAX_MAC_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: PAX_STD-3 with incorrect "
                           "MAC_CK length %d (expected %d)",
                           WPA_GET_BE16(pos), EAP_PAX_MAC_LEN);
                ret->ignore = TRUE;
                return NULL;
        }
        pos += 2;
        left -= 2;
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: MAC_CK(B, CID)",
                    pos, EAP_PAX_MAC_LEN);
        eap_pax_mac(data->mac_id, data->ck, EAP_PAX_CK_LEN,
                    data->rand.r.y, EAP_PAX_RAND_LEN,
                    (u8 *) data->cid, data->cid_len, NULL, 0, mac);
        if (os_memcmp(pos, mac, EAP_PAX_MAC_LEN) != 0) {
                wpa_printf(MSG_INFO, "EAP-PAX: Invalid MAC_CK(B, CID) "
                           "received");
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: expected MAC_CK(B, CID)",
                            mac, EAP_PAX_MAC_LEN);
                ret->methodState = METHOD_DONE;
                ret->decision = DECISION_FAIL;
                return NULL;
        }

        pos += EAP_PAX_MAC_LEN;
        left -= EAP_PAX_MAC_LEN;

        if (left > 0) {
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ignored extra payload",
                            pos, left);
        }

        wpa_printf(MSG_DEBUG, "EAP-PAX: PAX-ACK (sending)");

        resp = eap_pax_alloc_resp(req, id, EAP_PAX_OP_ACK, EAP_PAX_ICV_LEN);
        if (resp == NULL)
                return NULL;

        /* Optional ADE could be added here, if needed */

        rpos = wpabuf_put(resp, EAP_PAX_ICV_LEN);
        eap_pax_mac(data->mac_id, data->ick, EAP_PAX_ICK_LEN,
                    wpabuf_head(resp), wpabuf_len(resp) - EAP_PAX_ICV_LEN,
                    NULL, 0, NULL, 0, rpos);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ICV", rpos, EAP_PAX_ICV_LEN);

        data->state = PAX_DONE;
        ret->methodState = METHOD_DONE;
        ret->decision = DECISION_UNCOND_SUCC;
        ret->allowNotifications = FALSE;

        return resp;
}


static struct wpabuf * eap_pax_process(struct eap_sm *sm, void *priv,
                                       struct eap_method_ret *ret,
                                       const struct wpabuf *reqData)
{
        struct eap_pax_data *data = priv;
        const struct eap_pax_hdr *req;
        struct wpabuf *resp;
        u8 icvbuf[EAP_PAX_ICV_LEN], id;
        const u8 *icv, *pos;
        size_t len;
        u16 flen, mlen;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PAX, reqData, &len);
        if (pos == NULL || len < EAP_PAX_ICV_LEN) {
                ret->ignore = TRUE;
                return NULL;
        }
        id = eap_get_id(reqData);
        req = (const struct eap_pax_hdr *) pos;
        flen = len - EAP_PAX_ICV_LEN;
        mlen = wpabuf_len(reqData) - EAP_PAX_ICV_LEN;

        wpa_printf(MSG_DEBUG, "EAP-PAX: received frame: op_code 0x%x "
                   "flags 0x%x mac_id 0x%x dh_group_id 0x%x "
                   "public_key_id 0x%x",
                   req->op_code, req->flags, req->mac_id, req->dh_group_id,
                   req->public_key_id);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: received payload",
                    pos, len - EAP_PAX_ICV_LEN);

        if (data->state != PAX_INIT && data->mac_id != req->mac_id) {
                wpa_printf(MSG_INFO, "EAP-PAX: MAC ID changed during "
                           "authentication (was 0x%d, is 0x%d)",
                           data->mac_id, req->mac_id);
                ret->ignore = TRUE;
                return NULL;
        }

        if (data->state != PAX_INIT && data->dh_group_id != req->dh_group_id) {
                wpa_printf(MSG_INFO, "EAP-PAX: DH Group ID changed during "
                           "authentication (was 0x%d, is 0x%d)",
                           data->dh_group_id, req->dh_group_id);
                ret->ignore = TRUE;
                return NULL;
        }

        if (data->state != PAX_INIT &&
            data->public_key_id != req->public_key_id) {
                wpa_printf(MSG_INFO, "EAP-PAX: Public Key ID changed during "
                           "authentication (was 0x%d, is 0x%d)",
                           data->public_key_id, req->public_key_id);
                ret->ignore = TRUE;
                return NULL;
        }

        /* TODO: add support EAP_PAX_HMAC_SHA256_128 */
        if (req->mac_id != EAP_PAX_MAC_HMAC_SHA1_128) {
                wpa_printf(MSG_INFO, "EAP-PAX: Unsupported MAC ID 0x%x",
                           req->mac_id);
                ret->ignore = TRUE;
                return NULL;
        }

        if (req->dh_group_id != EAP_PAX_DH_GROUP_NONE) {
                wpa_printf(MSG_INFO, "EAP-PAX: Unsupported DH Group ID 0x%x",
                           req->dh_group_id);
                ret->ignore = TRUE;
                return NULL;
        }

        if (req->public_key_id != EAP_PAX_PUBLIC_KEY_NONE) {
                wpa_printf(MSG_INFO, "EAP-PAX: Unsupported Public Key ID 0x%x",
                           req->public_key_id);
                ret->ignore = TRUE;
                return NULL;
        }

        if (req->flags & EAP_PAX_FLAGS_MF) {
                /* TODO: add support for reassembling fragments */
                wpa_printf(MSG_INFO, "EAP-PAX: fragmentation not supported - "
                           "ignored packet");
                ret->ignore = TRUE;
                return NULL;
        }

        icv = pos + len - EAP_PAX_ICV_LEN;
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ICV", icv, EAP_PAX_ICV_LEN);
        if (req->op_code == EAP_PAX_OP_STD_1) {
                eap_pax_mac(req->mac_id, (u8 *) "", 0,
                            wpabuf_head(reqData), mlen, NULL, 0, NULL, 0,
                            icvbuf);
        } else {
                eap_pax_mac(req->mac_id, data->ick, EAP_PAX_ICK_LEN,
                            wpabuf_head(reqData), mlen, NULL, 0, NULL, 0,
                            icvbuf);
        }
        if (os_memcmp(icv, icvbuf, EAP_PAX_ICV_LEN) != 0) {
                wpa_printf(MSG_DEBUG, "EAP-PAX: invalid ICV - ignoring the "
                           "message");
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: expected ICV",
                            icvbuf, EAP_PAX_ICV_LEN);
                ret->ignore = TRUE;
                return NULL;
        }

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

        switch (req->op_code) {
        case EAP_PAX_OP_STD_1:
                resp = eap_pax_process_std_1(data, ret, id, req, flen);
                break;
        case EAP_PAX_OP_STD_3:
                resp = eap_pax_process_std_3(data, ret, id, req, flen);
                break;
        default:
                wpa_printf(MSG_DEBUG, "EAP-PAX: ignoring message with unknown "
                           "op_code %d", req->op_code);
                ret->ignore = TRUE;
                return NULL;
        }

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

        return resp;
}


static Boolean eap_pax_isKeyAvailable(struct eap_sm *sm, void *priv)
{
        struct eap_pax_data *data = priv;
        return data->state == PAX_DONE;
}


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

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

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

        *len = EAP_MSK_LEN;
        eap_pax_kdf(data->mac_id, data->mk, EAP_PAX_MK_LEN,
                    "Master Session Key", data->rand.e, 2 * EAP_PAX_RAND_LEN,
                    EAP_MSK_LEN, key);

        return key;
}


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

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

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

        *len = EAP_EMSK_LEN;
        eap_pax_kdf(data->mac_id, data->mk, EAP_PAX_MK_LEN,
                    "Extended Master Session Key",
                    data->rand.e, 2 * EAP_PAX_RAND_LEN,
                    EAP_EMSK_LEN, key);

        return key;
}


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

        eap = eap_peer_method_alloc(EAP_PEER_METHOD_INTERFACE_VERSION,
                                    EAP_VENDOR_IETF, EAP_TYPE_PAX, "PAX");
        if (eap == NULL)
                return -1;

        eap->init = eap_pax_init;
        eap->deinit = eap_pax_deinit;
        eap->process = eap_pax_process;
        eap->isKeyAvailable = eap_pax_isKeyAvailable;
        eap->getKey = eap_pax_getKey;
        eap->get_emsk = eap_pax_get_emsk;

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