/*

 * Copyright (c) 2010-2012 Frank Morgner and Dominik Oepen

 *

 * This file is part of OpenPACE.

 *

 * OpenPACE is free software: you can redistribute it and/or modify it under

 * the terms of the GNU General Public License as published by the Free

 * Software Foundation, either version 3 of the License, or (at your option)

 * any later version.

 *

 * OpenPACE is distributed in the hope that it will be useful, but WITHOUT ANY

 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more

 * details.

 *

 * You should have received a copy of the GNU General Public License along with

 * OpenPACE.  If not, see <http://www.gnu.org/licenses/>.

 *

 * Additional permission under GNU GPL version 3 section 7

 *

 * If you modify this Program, or any covered work, by linking or combining it

 * with OpenSSL (or a modified version of that library), containing

 * parts covered by the terms of OpenSSL's license, the licensors of

 * this Program grant you additional permission to convey the resulting work.

 * Corresponding Source for a non-source form of such a combination shall include

 * the source code for the parts of OpenSSL used as well as that of the

 * covered work.

 *

 * If you modify this Program, or any covered work, by linking or combining it

 * with OpenSC (or a modified version of that library), containing

 * parts covered by the terms of OpenSC's license, the licensors of

 * this Program grant you additional permission to convey the resulting work. 

 * Corresponding Source for a non-source form of such a combination shall include

 * the source code for the parts of OpenSC used as well as that of the

 * covered work.

 */

/**

 * @file ta.c

 * @brief Protocol steps for the terminal authentication version 2

 *

 * @date 2011-04-03

 *

 * @author Frank Morgner <frankmorgner@gmail.com>

 * @author Dominik Oepen <oepen@informatik.hu-berlin.de>

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "eac_err.h"

#include "eac_lib.h"

#include "eac_util.h"

#include "misc.h"

#include "ta_lib.h"

#include <eac/cv_cert.h>

#include <eac/ta.h>

#include <openssl/bio.h>

#include <openssl/ecdsa.h>

#include <openssl/evp.h>

#include <openssl/rsa.h>

#include <string.h>

void TA_disable_checks(EAC_CTX *ctx)

{

    if (ctx && ctx->ta_ctx)

        ctx->ta_ctx->flags = TA_FLAG_SKIP_TIMECHECK;

}

int

TA_STEP2_import_certificate(const EAC_CTX *ctx,

           const unsigned char *cert, size_t cert_len)

{

    CVC_CERT *ta_cert = NULL;

    int r = 0;

    check(ctx, "Invalid arguments");

    ta_cert = CVC_d2i_CVC_CERT(&ta_cert, &cert, cert_len);

    r = TA_CTX_import_certificate(ctx->ta_ctx, ta_cert, ctx->bn_ctx);

err:

    if (ta_cert)

        CVC_CERT_free(ta_cert);

    return r;

}

/**

 * @brief gets the data, which is signed in the process of TA

 *

 * @param[in] pcd_ta_comp_eph_pubkey compressed ephemeral CA public key of PCD

 * @param[in] id_picc compressed ephemeral PACE public key of PICC

 * @param[in] nonce nonce from PICC

 * @param[in] (optional) auxdata auxiliary data from PCD

 *

 * @return A buffer containing the data to be signed or NULL in case of an error

 */

static BUF_MEM *

get_ta_sigdata(const BUF_MEM *pcd_ta_comp_eph_pubkey,

        const BUF_MEM *id_picc, const BUF_MEM *nonce,

        const BUF_MEM *auxdata)

{

    size_t len;

    BUF_MEM *data = NULL;

    check_return(nonce && pcd_ta_comp_eph_pubkey, "Invalid arguments");

    /* Data to be signed: ID PICC || r PICC || Comp(~PK_PCD) || APCD */

    /* Authenticated auxiliary data are optional (only necessary if special

     * functions will be used later on) */

    if (auxdata) {

        len = id_picc->length + nonce->length +

            pcd_ta_comp_eph_pubkey->length + auxdata->length;

    } else {

        len = id_picc->length + nonce->length +

            pcd_ta_comp_eph_pubkey->length;

    }

    data = BUF_MEM_create(len);

    if (!data)

        return NULL;

    /* Concatenate the data */

    memcpy(data->data, id_picc->data, id_picc->length);

    memcpy(data->data + id_picc->length, nonce->data, nonce->length);

    memcpy(data->data + id_picc->length + nonce->length, pcd_ta_comp_eph_pubkey->data,

            pcd_ta_comp_eph_pubkey->length);

    if (auxdata)

        memcpy(data->data + id_picc->length + nonce->length +

                pcd_ta_comp_eph_pubkey->length, auxdata->data, auxdata->length);

    return data;

}

BUF_MEM *

TA_STEP3_generate_ephemeral_key(const EAC_CTX *ctx)

{

    BUF_MEM *comp_pub_key, *pub_key = NULL;

    check_return(ctx && ctx->ca_ctx && ctx->ca_ctx->ka_ctx,

            "Invalid arguments");

    pub_key = KA_CTX_generate_key(ctx->ca_ctx->ka_ctx, ctx->bn_ctx);

    comp_pub_key = Comp(ctx->ca_ctx->ka_ctx->key, pub_key, ctx->bn_ctx,

            ctx->md_ctx);

    if (pub_key)

        BUF_MEM_free(pub_key);

    return comp_pub_key;

}

/* Nonce for TA is always 8 bytes long */

#define TA_NONCE_SIZE 8

BUF_MEM *

TA_STEP4_get_nonce(const EAC_CTX *ctx)

{

    check_return(ctx && ctx->ta_ctx, "Invalid arguments");

    BUF_MEM_clear_free(ctx->ta_ctx->nonce);

    ctx->ta_ctx->nonce = randb(TA_NONCE_SIZE);

    check_return(ctx->ta_ctx->nonce, "Failed to generate nonce");

    return BUF_MEM_dup(ctx->ta_ctx->nonce);

}

int

TA_STEP4_set_nonce(const EAC_CTX *ctx, const BUF_MEM *nonce) {

    int r = 0;

    check(ctx && ctx->ta_ctx && nonce, "Invalid arguments");

    if (ctx->ta_ctx->nonce)

      BUF_MEM_free(ctx->ta_ctx->nonce);

    ctx->ta_ctx->nonce = BUF_MEM_dup(nonce);

    check(ctx->ta_ctx->nonce, "Failed to copy nonce");

    r = 1;

err:

    return r;

}

BUF_MEM *

TA_STEP5_sign(const EAC_CTX *ctx, const BUF_MEM *my_ta_comp_eph_pubkey,

           const BUF_MEM *opp_pace_comp_eph_pubkey, const BUF_MEM *auxdata)

{

    BUF_MEM *data = NULL, *signature = NULL;

    check(ctx && ctx->ta_ctx, "Invalid arguments");

    /* Get the data to be signed */

    data = get_ta_sigdata(my_ta_comp_eph_pubkey, opp_pace_comp_eph_pubkey,

            ctx->ta_ctx->nonce, auxdata);

    signature = EAC_sign(ctx->ta_ctx->protocol, ctx->ta_ctx->priv_key, data);

err:

    if (data)

        BUF_MEM_free(data);

    return signature;

}

int

TA_STEP6_verify(const EAC_CTX *ctx, const BUF_MEM *opp_ta_comp_eph_pubkey,

           const BUF_MEM *my_pace_comp_eph_pubkey, const BUF_MEM *auxdata,

           const BUF_MEM *signature)

{

    BUF_MEM *data = NULL;

    int r = -1;

    check(ctx && ctx->ta_ctx, "Invalid arguments");

    check(ctx->ta_ctx->nonce, "Conditions not satisfied");

    /* Get the data to be verified */

    data = get_ta_sigdata(opp_ta_comp_eph_pubkey, my_pace_comp_eph_pubkey,

            ctx->ta_ctx->nonce, auxdata);

    r = EAC_verify(ctx->ta_ctx->protocol, ctx->ta_ctx->pub_key, signature, data);

err:

    if (data)

        BUF_MEM_free(data);

    return r;

}