eap_server_sake.c

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/*
 * hostapd / EAP-SAKE (RFC 4763) server
 * Copyright (c) 2006-2007, 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.
 */

#include "includes.h"

#include "common.h"
#include "eap_server/eap_i.h"
#include "eap_common/eap_sake_common.h"


struct eap_sake_data {
        enum { IDENTITY, CHALLENGE, CONFIRM, SUCCESS, FAILURE } state;
        u8 rand_s[EAP_SAKE_RAND_LEN];
        u8 rand_p[EAP_SAKE_RAND_LEN];
        struct {
                u8 auth[EAP_SAKE_TEK_AUTH_LEN];
                u8 cipher[EAP_SAKE_TEK_CIPHER_LEN];
        } tek;
        u8 msk[EAP_MSK_LEN];
        u8 emsk[EAP_EMSK_LEN];
        u8 session_id;
        u8 *peerid;
        size_t peerid_len;
        u8 *serverid;
        size_t serverid_len;
};


static const char * eap_sake_state_txt(int state)
{
        switch (state) {
        case IDENTITY:
                return "IDENTITY";
        case CHALLENGE:
                return "CHALLENGE";
        case CONFIRM:
                return "CONFIRM";
        case SUCCESS:
                return "SUCCESS";
        case FAILURE:
                return "FAILURE";
        default:
                return "?";
        }
}


static void eap_sake_state(struct eap_sake_data *data, int state)
{
        wpa_printf(MSG_DEBUG, "EAP-SAKE: %s -> %s",
                   eap_sake_state_txt(data->state),
                   eap_sake_state_txt(state));
        data->state = state;
}


static void * eap_sake_init(struct eap_sm *sm)
{
        struct eap_sake_data *data;

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

        if (os_get_random(&data->session_id, 1)) {
                wpa_printf(MSG_ERROR, "EAP-SAKE: Failed to get random data");
                os_free(data);
                return NULL;
        }
        wpa_printf(MSG_DEBUG, "EAP-SAKE: Initialized Session ID %d",
                   data->session_id);

        /* TODO: add support for configuring SERVERID */
        data->serverid = (u8 *) os_strdup("hostapd");
        if (data->serverid)
                data->serverid_len = os_strlen((char *) data->serverid);

        return data;
}


static void eap_sake_reset(struct eap_sm *sm, void *priv)
{
        struct eap_sake_data *data = priv;
        os_free(data->serverid);
        os_free(data->peerid);
        os_free(data);
}


static struct wpabuf * eap_sake_build_msg(struct eap_sake_data *data,
                                          u8 id, size_t length, u8 subtype)
{
        struct eap_sake_hdr *sake;
        struct wpabuf *msg;
        size_t plen;

        plen = sizeof(struct eap_sake_hdr) + length;

        msg = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_SAKE, plen,
                            EAP_CODE_REQUEST, id);
        if (msg == NULL) {
                wpa_printf(MSG_ERROR, "EAP-SAKE: Failed to allocate memory "
                           "request");
                return NULL;
        }

        sake = wpabuf_put(msg, sizeof(*sake));
        sake->version = EAP_SAKE_VERSION;
        sake->session_id = data->session_id;
        sake->subtype = subtype;

        return msg;
}


static struct wpabuf * eap_sake_build_identity(struct eap_sm *sm,
                                               struct eap_sake_data *data,
                                               u8 id)
{
        struct wpabuf *msg;
        size_t plen;

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Request/Identity");

        plen = 4;
        if (data->serverid)
                plen += 2 + data->serverid_len;
        msg = eap_sake_build_msg(data, id, plen, EAP_SAKE_SUBTYPE_IDENTITY);
        if (msg == NULL) {
                data->state = FAILURE;
                return NULL;
        }

        wpa_printf(MSG_DEBUG, "EAP-SAKE: * AT_PERM_ID_REQ");
        eap_sake_add_attr(msg, EAP_SAKE_AT_PERM_ID_REQ, NULL, 2);

        if (data->serverid) {
                wpa_printf(MSG_DEBUG, "EAP-SAKE: * AT_SERVERID");
                eap_sake_add_attr(msg, EAP_SAKE_AT_SERVERID,
                                  data->serverid, data->serverid_len);
        }

        return msg;
}


static struct wpabuf * eap_sake_build_challenge(struct eap_sm *sm,
                                                struct eap_sake_data *data,
                                                u8 id)
{
        struct wpabuf *msg;
        size_t plen;

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Request/Challenge");

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

        plen = 2 + EAP_SAKE_RAND_LEN;
        if (data->serverid)
                plen += 2 + data->serverid_len;
        msg = eap_sake_build_msg(data, id, plen, EAP_SAKE_SUBTYPE_CHALLENGE);
        if (msg == NULL) {
                data->state = FAILURE;
                return NULL;
        }

        wpa_printf(MSG_DEBUG, "EAP-SAKE: * AT_RAND_S");
        eap_sake_add_attr(msg, EAP_SAKE_AT_RAND_S,
                          data->rand_s, EAP_SAKE_RAND_LEN);

        if (data->serverid) {
                wpa_printf(MSG_DEBUG, "EAP-SAKE: * AT_SERVERID");
                eap_sake_add_attr(msg, EAP_SAKE_AT_SERVERID,
                                  data->serverid, data->serverid_len);
        }

        return msg;
}


static struct wpabuf * eap_sake_build_confirm(struct eap_sm *sm,
                                              struct eap_sake_data *data,
                                              u8 id)
{
        struct wpabuf *msg;
        u8 *mic;

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Request/Confirm");

        msg = eap_sake_build_msg(data, id, 2 + EAP_SAKE_MIC_LEN,
                                 EAP_SAKE_SUBTYPE_CONFIRM);
        if (msg == NULL) {
                data->state = FAILURE;
                return NULL;
        }

        wpa_printf(MSG_DEBUG, "EAP-SAKE: * AT_MIC_S");
        wpabuf_put_u8(msg, EAP_SAKE_AT_MIC_S);
        wpabuf_put_u8(msg, 2 + EAP_SAKE_MIC_LEN);
        mic = wpabuf_put(msg, EAP_SAKE_MIC_LEN);
        if (eap_sake_compute_mic(data->tek.auth, data->rand_s, data->rand_p,
                                 data->serverid, data->serverid_len,
                                 data->peerid, data->peerid_len, 0,
                                 wpabuf_head(msg), wpabuf_len(msg), mic, mic))
        {
                wpa_printf(MSG_INFO, "EAP-SAKE: Failed to compute MIC");
                data->state = FAILURE;
                os_free(msg);
                return NULL;
        }

        return msg;
}


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

        switch (data->state) {
        case IDENTITY:
                return eap_sake_build_identity(sm, data, id);
        case CHALLENGE:
                return eap_sake_build_challenge(sm, data, id);
        case CONFIRM:
                return eap_sake_build_confirm(sm, data, id);
        default:
                wpa_printf(MSG_DEBUG, "EAP-SAKE: Unknown state %d in buildReq",
                           data->state);
                break;
        }
        return NULL;
}


static Boolean eap_sake_check(struct eap_sm *sm, void *priv,
                              struct wpabuf *respData)
{
        struct eap_sake_data *data = priv;
        struct eap_sake_hdr *resp;
        size_t len;
        u8 version, session_id, subtype;
        const u8 *pos;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_SAKE, respData, &len);
        if (pos == NULL || len < sizeof(struct eap_sake_hdr)) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Invalid frame");
                return TRUE;
        }

        resp = (struct eap_sake_hdr *) pos;
        version = resp->version;
        session_id = resp->session_id;
        subtype = resp->subtype;

        if (version != EAP_SAKE_VERSION) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Unknown version %d", version);
                return TRUE;
        }

        if (session_id != data->session_id) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Session ID mismatch (%d,%d)",
                           session_id, data->session_id);
                return TRUE;
        }

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Received frame: subtype=%d", subtype);

        if (data->state == IDENTITY && subtype == EAP_SAKE_SUBTYPE_IDENTITY)
                return FALSE;

        if (data->state == CHALLENGE && subtype == EAP_SAKE_SUBTYPE_CHALLENGE)
                return FALSE;

        if (data->state == CONFIRM && subtype == EAP_SAKE_SUBTYPE_CONFIRM)
                return FALSE;

        if (subtype == EAP_SAKE_SUBTYPE_AUTH_REJECT)
                return FALSE;

        wpa_printf(MSG_INFO, "EAP-SAKE: Unexpected subtype=%d in state=%d",
                   subtype, data->state);

        return TRUE;
}


static void eap_sake_process_identity(struct eap_sm *sm,
                                      struct eap_sake_data *data,
                                      const struct wpabuf *respData,
                                      const u8 *payload, size_t payloadlen)
{
        if (data->state != IDENTITY)
                return;

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Received Response/Identity");
        /* TODO: update identity and select new user data */
        eap_sake_state(data, CHALLENGE);
}


static void eap_sake_process_challenge(struct eap_sm *sm,
                                       struct eap_sake_data *data,
                                       const struct wpabuf *respData,
                                       const u8 *payload, size_t payloadlen)
{
        struct eap_sake_parse_attr attr;
        u8 mic_p[EAP_SAKE_MIC_LEN];

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

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Received Response/Challenge");

        if (eap_sake_parse_attributes(payload, payloadlen, &attr))
                return;

        if (!attr.rand_p || !attr.mic_p) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Response/Challenge did not "
                           "include AT_RAND_P or AT_MIC_P");
                return;
        }

        os_memcpy(data->rand_p, attr.rand_p, EAP_SAKE_RAND_LEN);

        os_free(data->peerid);
        data->peerid = NULL;
        data->peerid_len = 0;
        if (attr.peerid) {
                data->peerid = os_malloc(attr.peerid_len);
                if (data->peerid == NULL)
                        return;
                os_memcpy(data->peerid, attr.peerid, attr.peerid_len);
                data->peerid_len = attr.peerid_len;
        }

        if (sm->user == NULL || sm->user->password == NULL ||
            sm->user->password_len != 2 * EAP_SAKE_ROOT_SECRET_LEN) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Plaintext password with "
                           "%d-byte key not configured",
                           2 * EAP_SAKE_ROOT_SECRET_LEN);
                data->state = FAILURE;
                return;
        }
        eap_sake_derive_keys(sm->user->password,
                             sm->user->password + EAP_SAKE_ROOT_SECRET_LEN,
                             data->rand_s, data->rand_p,
                             (u8 *) &data->tek, data->msk, data->emsk);

        eap_sake_compute_mic(data->tek.auth, data->rand_s, data->rand_p,
                             data->serverid, data->serverid_len,
                             data->peerid, data->peerid_len, 1,
                             wpabuf_head(respData), wpabuf_len(respData),
                             attr.mic_p, mic_p);
        if (os_memcmp(attr.mic_p, mic_p, EAP_SAKE_MIC_LEN) != 0) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Incorrect AT_MIC_P");
                eap_sake_state(data, FAILURE);
                return;
        }

        eap_sake_state(data, CONFIRM);
}


static void eap_sake_process_confirm(struct eap_sm *sm,
                                     struct eap_sake_data *data,
                                     const struct wpabuf *respData,
                                     const u8 *payload, size_t payloadlen)
{
        struct eap_sake_parse_attr attr;
        u8 mic_p[EAP_SAKE_MIC_LEN];

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

        wpa_printf(MSG_DEBUG, "EAP-SAKE: Received Response/Confirm");

        if (eap_sake_parse_attributes(payload, payloadlen, &attr))
                return;

        if (!attr.mic_p) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Response/Confirm did not "
                           "include AT_MIC_P");
                return;
        }

        eap_sake_compute_mic(data->tek.auth, data->rand_s, data->rand_p,
                             data->serverid, data->serverid_len,
                             data->peerid, data->peerid_len, 1,
                             wpabuf_head(respData), wpabuf_len(respData),
                             attr.mic_p, mic_p);
        if (os_memcmp(attr.mic_p, mic_p, EAP_SAKE_MIC_LEN) != 0) {
                wpa_printf(MSG_INFO, "EAP-SAKE: Incorrect AT_MIC_P");
                eap_sake_state(data, FAILURE);
        } else
                eap_sake_state(data, SUCCESS);
}


static void eap_sake_process_auth_reject(struct eap_sm *sm,
                                         struct eap_sake_data *data,
                                         const struct wpabuf *respData,
                                         const u8 *payload, size_t payloadlen)
{
        wpa_printf(MSG_DEBUG, "EAP-SAKE: Received Response/Auth-Reject");
        eap_sake_state(data, FAILURE);
}


static void eap_sake_process(struct eap_sm *sm, void *priv,
                             struct wpabuf *respData)
{
        struct eap_sake_data *data = priv;
        struct eap_sake_hdr *resp;
        u8 subtype;
        size_t len;
        const u8 *pos, *end;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_SAKE, respData, &len);
        if (pos == NULL || len < sizeof(struct eap_sake_hdr))
                return;

        resp = (struct eap_sake_hdr *) pos;
        end = pos + len;
        subtype = resp->subtype;
        pos = (u8 *) (resp + 1);

        wpa_hexdump(MSG_DEBUG, "EAP-SAKE: Received attributes",
                    pos, end - pos);

        switch (subtype) {
        case EAP_SAKE_SUBTYPE_IDENTITY:
                eap_sake_process_identity(sm, data, respData, pos, end - pos);
                break;
        case EAP_SAKE_SUBTYPE_CHALLENGE:
                eap_sake_process_challenge(sm, data, respData, pos, end - pos);
                break;
        case EAP_SAKE_SUBTYPE_CONFIRM:
                eap_sake_process_confirm(sm, data, respData, pos, end - pos);
                break;
        case EAP_SAKE_SUBTYPE_AUTH_REJECT:
                eap_sake_process_auth_reject(sm, data, respData, pos,
                                             end - pos);
                break;
        }
}


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


static u8 * eap_sake_getKey(struct eap_sm *sm, void *priv, size_t *len)
{
        struct eap_sake_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_sake_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
{
        struct eap_sake_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_sake_isSuccess(struct eap_sm *sm, void *priv)
{
        struct eap_sake_data *data = priv;
        return data->state == SUCCESS;
}


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

        eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
                                      EAP_VENDOR_IETF, EAP_TYPE_SAKE, "SAKE");
        if (eap == NULL)
                return -1;

        eap->init = eap_sake_init;
        eap->reset = eap_sake_reset;
        eap->buildReq = eap_sake_buildReq;
        eap->check = eap_sake_check;
        eap->process = eap_sake_process;
        eap->isDone = eap_sake_isDone;
        eap->getKey = eap_sake_getKey;
        eap->isSuccess = eap_sake_isSuccess;
        eap->get_emsk = eap_sake_get_emsk;

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