eap_pax.c

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#include "includes.h"

#include "common.h"
#include "eap_server/eap_i.h"
#include "eap_common/eap_pax_common.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_STD_1, PAX_STD_3, SUCCESS, FAILURE } state;
        u8 mac_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;
        u8 ak[EAP_PAX_AK_LEN];
        u8 mk[EAP_PAX_MK_LEN];
        u8 ck[EAP_PAX_CK_LEN];
        u8 ick[EAP_PAX_ICK_LEN];
        int keys_set;
        char *cid;
        size_t cid_len;
};


static void * eap_pax_init(struct eap_sm *sm)
{
        struct eap_pax_data *data;

        data = os_zalloc(sizeof(*data));
        if (data == NULL)
                return NULL;
        data->state = PAX_STD_1;
        /*
         * TODO: make this configurable once EAP_PAX_HMAC_SHA256_128 is
         * supported
         */
        data->mac_id = EAP_PAX_MAC_HMAC_SHA1_128;

        return data;
}


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


static struct wpabuf * eap_pax_build_std_1(struct eap_sm *sm,
                                           struct eap_pax_data *data, u8 id)
{
        struct wpabuf *req;
        struct eap_pax_hdr *pax;
        u8 *pos;

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

        if (os_get_random(data->rand.r.x, EAP_PAX_RAND_LEN)) {
                wpa_printf(MSG_ERROR, "EAP-PAX: Failed to get random data");
                data->state = FAILURE;
                return NULL;
        }

        req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PAX,
                            sizeof(*pax) + 2 + EAP_PAX_RAND_LEN +
                            EAP_PAX_ICV_LEN, EAP_CODE_REQUEST, id);
        if (req == NULL) {
                wpa_printf(MSG_ERROR, "EAP-PAX: Failed to allocate memory "
                           "request");
                data->state = FAILURE;
                return NULL;
        }

        pax = wpabuf_put(req, sizeof(*pax));
        pax->op_code = EAP_PAX_OP_STD_1;
        pax->flags = 0;
        pax->mac_id = data->mac_id;
        pax->dh_group_id = EAP_PAX_DH_GROUP_NONE;
        pax->public_key_id = EAP_PAX_PUBLIC_KEY_NONE;

        wpabuf_put_be16(req, EAP_PAX_RAND_LEN);
        wpabuf_put_data(req, data->rand.r.x, EAP_PAX_RAND_LEN);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: A = X (server rand)",
                    data->rand.r.x, EAP_PAX_RAND_LEN);

        pos = wpabuf_put(req, EAP_PAX_MAC_LEN);
        eap_pax_mac(data->mac_id, (u8 *) "", 0,
                    wpabuf_mhead(req), wpabuf_len(req) - EAP_PAX_ICV_LEN,
                    NULL, 0, NULL, 0, pos);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ICV", pos, EAP_PAX_ICV_LEN);

        return req;
}


static struct wpabuf * eap_pax_build_std_3(struct eap_sm *sm,
                                           struct eap_pax_data *data, u8 id)
{
        struct wpabuf *req;
        struct eap_pax_hdr *pax;
        u8 *pos;

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

        req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PAX,
                            sizeof(*pax) + 2 + EAP_PAX_MAC_LEN +
                            EAP_PAX_ICV_LEN, EAP_CODE_REQUEST, id);
        if (req == NULL) {
                wpa_printf(MSG_ERROR, "EAP-PAX: Failed to allocate memory "
                           "request");
                data->state = FAILURE;
                return NULL;
        }

        pax = wpabuf_put(req, sizeof(*pax));
        pax->op_code = EAP_PAX_OP_STD_3;
        pax->flags = 0;
        pax->mac_id = data->mac_id;
        pax->dh_group_id = EAP_PAX_DH_GROUP_NONE;
        pax->public_key_id = EAP_PAX_PUBLIC_KEY_NONE;

        wpabuf_put_be16(req, EAP_PAX_MAC_LEN);
        pos = wpabuf_put(req, 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, pos);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: MAC_CK(B, CID)",
                    pos, EAP_PAX_MAC_LEN);
        pos += EAP_PAX_MAC_LEN;

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

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

        return req;
}


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

        switch (data->state) {
        case PAX_STD_1:
                return eap_pax_build_std_1(sm, data, id);
        case PAX_STD_3:
                return eap_pax_build_std_3(sm, data, id);
        default:
                wpa_printf(MSG_DEBUG, "EAP-PAX: Unknown state %d in buildReq",
                           data->state);
                break;
        }
        return NULL;
}


static Boolean eap_pax_check(struct eap_sm *sm, void *priv,
                             struct wpabuf *respData)
{
        struct eap_pax_data *data = priv;
        struct eap_pax_hdr *resp;
        const u8 *pos;
        size_t len, mlen;
        u8 icvbuf[EAP_PAX_ICV_LEN], *icv;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PAX, respData, &len);
        if (pos == NULL || len < sizeof(*resp)) {
                wpa_printf(MSG_INFO, "EAP-PAX: Invalid frame");
                return TRUE;
        }

        mlen = sizeof(struct eap_hdr) + 1 + len;
        resp = (struct eap_pax_hdr *) pos;

        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",
                   resp->op_code, resp->flags, resp->mac_id, resp->dh_group_id,
                   resp->public_key_id);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: received payload",
                    (u8 *) (resp + 1), len - sizeof(*resp) - EAP_PAX_ICV_LEN);

        if (data->state == PAX_STD_1 &&
            resp->op_code != EAP_PAX_OP_STD_2) {
                wpa_printf(MSG_DEBUG, "EAP-PAX: Expected PAX_STD-2 - "
                           "ignore op %d", resp->op_code);
                return TRUE;
        }

        if (data->state == PAX_STD_3 &&
            resp->op_code != EAP_PAX_OP_ACK) {
                wpa_printf(MSG_DEBUG, "EAP-PAX: Expected PAX-ACK - "
                           "ignore op %d", resp->op_code);
                return TRUE;
        }

        if (resp->op_code != EAP_PAX_OP_STD_2 &&
            resp->op_code != EAP_PAX_OP_ACK) {
                wpa_printf(MSG_DEBUG, "EAP-PAX: Unknown op_code 0x%x",
                           resp->op_code);
        }

        if (data->mac_id != resp->mac_id) {
                wpa_printf(MSG_DEBUG, "EAP-PAX: Expected MAC ID 0x%x, "
                           "received 0x%x", data->mac_id, resp->mac_id);
                return TRUE;
        }

        if (resp->dh_group_id != EAP_PAX_DH_GROUP_NONE) {
                wpa_printf(MSG_INFO, "EAP-PAX: Expected DH Group ID 0x%x, "
                           "received 0x%x", EAP_PAX_DH_GROUP_NONE,
                           resp->dh_group_id);
                return TRUE;
        }

        if (resp->public_key_id != EAP_PAX_PUBLIC_KEY_NONE) {
                wpa_printf(MSG_INFO, "EAP-PAX: Expected Public Key ID 0x%x, "
                           "received 0x%x", EAP_PAX_PUBLIC_KEY_NONE,
                           resp->public_key_id);
                return TRUE;
        }

        if (resp->flags & EAP_PAX_FLAGS_MF) {
                /* TODO: add support for reassembling fragments */
                wpa_printf(MSG_INFO, "EAP-PAX: fragmentation not supported");
                return TRUE;
        }

        if (resp->flags & EAP_PAX_FLAGS_CE) {
                wpa_printf(MSG_INFO, "EAP-PAX: Unexpected CE flag");
                return TRUE;
        }

        if (data->keys_set) {
                if (len - sizeof(*resp) < EAP_PAX_ICV_LEN) {
                        wpa_printf(MSG_INFO, "EAP-PAX: No ICV in the packet");
                        return TRUE;
                }
                icv = wpabuf_mhead_u8(respData) + mlen - EAP_PAX_ICV_LEN;
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ICV", icv, EAP_PAX_ICV_LEN);
                eap_pax_mac(data->mac_id, data->ick, EAP_PAX_ICK_LEN,
                            wpabuf_mhead(respData),
                            wpabuf_len(respData) - EAP_PAX_ICV_LEN,
                            NULL, 0, NULL, 0, icvbuf);
                if (os_memcmp(icvbuf, icv, EAP_PAX_ICV_LEN) != 0) {
                        wpa_printf(MSG_INFO, "EAP-PAX: Invalid ICV");
                        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: Expected ICV",
                                    icvbuf, EAP_PAX_ICV_LEN);
                        return TRUE;
                }
        }

        return FALSE;
}


static void eap_pax_process_std_2(struct eap_sm *sm,
                                  struct eap_pax_data *data,
                                  struct wpabuf *respData)
{
        struct eap_pax_hdr *resp;
        u8 mac[EAP_PAX_MAC_LEN], icvbuf[EAP_PAX_ICV_LEN];
        const u8 *pos;
        size_t len, left;
        int i;

        if (data->state != PAX_STD_1)
                return;

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

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PAX, respData, &len);
        if (pos == NULL || len < sizeof(*resp) + EAP_PAX_ICV_LEN)
                return;

        resp = (struct eap_pax_hdr *) pos;
        pos = (u8 *) (resp + 1);
        left = len - sizeof(*resp);

        if (left < 2 + EAP_PAX_RAND_LEN ||
            WPA_GET_BE16(pos) != EAP_PAX_RAND_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: Too short PAX_STD-2 (B)");
                return;
        }
        pos += 2;
        left -= 2;
        os_memcpy(data->rand.r.y, pos, EAP_PAX_RAND_LEN);
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: Y (client rand)",
                    data->rand.r.y, EAP_PAX_RAND_LEN);
        pos += EAP_PAX_RAND_LEN;
        left -= EAP_PAX_RAND_LEN;

        if (left < 2 || (size_t) 2 + WPA_GET_BE16(pos) > left) {
                wpa_printf(MSG_INFO, "EAP-PAX: Too short PAX_STD-2 (CID)");
                return;
        }
        data->cid_len = WPA_GET_BE16(pos);
        os_free(data->cid);
        data->cid = os_malloc(data->cid_len);
        if (data->cid == NULL) {
                wpa_printf(MSG_INFO, "EAP-PAX: Failed to allocate memory for "
                           "CID");
                return;
        }
        os_memcpy(data->cid, pos + 2, data->cid_len);
        pos += 2 + data->cid_len;
        left -= 2 + data->cid_len;
        wpa_hexdump_ascii(MSG_MSGDUMP, "EAP-PAX: CID",
                          (u8 *) data->cid, data->cid_len);

        if (left < 2 + EAP_PAX_MAC_LEN ||
            WPA_GET_BE16(pos) != EAP_PAX_MAC_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: Too short PAX_STD-2 (MAC_CK)");
                return;
        }
        pos += 2;
        left -= 2;
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: MAC_CK(A, B, CID)",
                    pos, EAP_PAX_MAC_LEN);

        if (eap_user_get(sm, (u8 *) data->cid, data->cid_len, 0) < 0) {
                wpa_hexdump_ascii(MSG_DEBUG, "EAP-PAX: unknown CID",
                                  (u8 *) data->cid, data->cid_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_PAX)
                        break;
        }

        if (i >= EAP_MAX_METHODS ||
            sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
            sm->user->methods[i].method != EAP_TYPE_PAX) {
                wpa_hexdump_ascii(MSG_DEBUG,
                                  "EAP-PAX: EAP-PAX not enabled for CID",
                                  (u8 *) data->cid, data->cid_len);
                data->state = FAILURE;
                return;
        }

        if (sm->user->password == NULL ||
            sm->user->password_len != EAP_PAX_AK_LEN) {
                wpa_hexdump_ascii(MSG_DEBUG, "EAP-PAX: invalid password in "
                                  "user database for CID",
                                  (u8 *) data->cid, data->cid_len);
                data->state = FAILURE;
                return;
        }
        os_memcpy(data->ak, sm->user->password, EAP_PAX_AK_LEN);

        if (eap_pax_initial_key_derivation(data->mac_id, data->ak,
                                           data->rand.e, data->mk, data->ck,
                                           data->ick) < 0) {
                wpa_printf(MSG_INFO, "EAP-PAX: Failed to complete initial "
                           "key derivation");
                data->state = FAILURE;
                return;
        }
        data->keys_set = 1;

        eap_pax_mac(data->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, mac);
        if (os_memcmp(mac, pos, EAP_PAX_MAC_LEN) != 0) {
                wpa_printf(MSG_INFO, "EAP-PAX: Invalid MAC_CK(A, B, CID) in "
                           "PAX_STD-2");
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: Expected MAC_CK(A, B, CID)",
                            mac, EAP_PAX_MAC_LEN);
                data->state = FAILURE;
                return;
        }

        pos += EAP_PAX_MAC_LEN;
        left -= EAP_PAX_MAC_LEN;

        if (left < EAP_PAX_ICV_LEN) {
                wpa_printf(MSG_INFO, "EAP-PAX: Too short ICV (%lu) in "
                           "PAX_STD-2", (unsigned long) left);
                return;
        }
        wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: ICV", pos, EAP_PAX_ICV_LEN);
        eap_pax_mac(data->mac_id, data->ick, EAP_PAX_ICK_LEN,
                    wpabuf_head(respData),
                    wpabuf_len(respData) - EAP_PAX_ICV_LEN, NULL, 0, NULL, 0,
                    icvbuf);
        if (os_memcmp(icvbuf, pos, EAP_PAX_ICV_LEN) != 0) {
                wpa_printf(MSG_INFO, "EAP-PAX: Invalid ICV in PAX_STD-2");
                wpa_hexdump(MSG_MSGDUMP, "EAP-PAX: Expected ICV",
                            icvbuf, EAP_PAX_ICV_LEN);
                return;
        }
        pos += EAP_PAX_ICV_LEN;
        left -= EAP_PAX_ICV_LEN;

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

        data->state = PAX_STD_3;
}


static void eap_pax_process_ack(struct eap_sm *sm,
                                struct eap_pax_data *data,
                                struct wpabuf *respData)
{
        if (data->state != PAX_STD_3)
                return;

        wpa_printf(MSG_DEBUG, "EAP-PAX: Received PAX-ACK - authentication "
                   "completed successfully");
        data->state = SUCCESS;
}


static void eap_pax_process(struct eap_sm *sm, void *priv,
                            struct wpabuf *respData)
{
        struct eap_pax_data *data = priv;
        struct eap_pax_hdr *resp;
        const u8 *pos;
        size_t len;

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

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PAX, respData, &len);
        if (pos == NULL || len < sizeof(*resp))
                return;

        resp = (struct eap_pax_hdr *) pos;

        switch (resp->op_code) {
        case EAP_PAX_OP_STD_2:
                eap_pax_process_std_2(sm, data, respData);
                break;
        case EAP_PAX_OP_ACK:
                eap_pax_process_ack(sm, data, respData);
                break;
        }
}


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


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 != SUCCESS)
                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 != SUCCESS)
                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;
}


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


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

        eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
                                      EAP_VENDOR_IETF, EAP_TYPE_PAX, "PAX");
        if (eap == NULL)
                return -1;

        eap->init = eap_pax_init;
        eap->reset = eap_pax_reset;
        eap->buildReq = eap_pax_buildReq;
        eap->check = eap_pax_check;
        eap->process = eap_pax_process;
        eap->isDone = eap_pax_isDone;
        eap->getKey = eap_pax_getKey;
        eap->isSuccess = eap_pax_isSuccess;
        eap->get_emsk = eap_pax_get_emsk;

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