#include "includes.h"

#include "algo.h"

#include "buffer.h"

#include "session.h"

#include "dbrandom.h"

#include "crypto_desc.h"

#include "ecc.h"

#include "kex.h"

#if DROPBEAR_ECDH

struct kex_ecdh_param *gen_kexecdh_param() {

    struct kex_ecdh_param *param = m_malloc(sizeof(*param));

    const struct dropbear_ecc_curve *curve = ses.newkeys->algo_kex->details;

    if (ecc_make_key_ex(NULL, dropbear_ltc_prng, 

        &param->key, curve->dp) != CRYPT_OK) {

        dropbear_exit("ECC error");

    }

    return param;

}

void free_kexecdh_param(struct kex_ecdh_param *param) {

    ecc_free(&param->key);

    m_free(param);

}

void kexecdh_comb_key(struct kex_ecdh_param *param, buffer *pub_them,

        sign_key *hostkey) {

    const struct dropbear_ecc_curve *curve

        = ses.newkeys->algo_kex->details;

    /* public keys from client and server */

    ecc_key *Q_C, *Q_S, *Q_them;

    Q_them = buf_get_ecc_raw_pubkey(pub_them, curve);

    if (Q_them == NULL) {

        dropbear_exit("ECC error");

    }

    ses.dh_K = dropbear_ecc_shared_secret(Q_them, &param->key);

    /* Create the remainder of the hash buffer, to generate the exchange hash

       See RFC5656 section 4 page 7 */

    if (IS_DROPBEAR_CLIENT) {

        Q_C = &param->key;

        Q_S = Q_them;

    } else {

        Q_C = Q_them;

        Q_S = &param->key;

    } 

    /* K_S, the host key */

    buf_put_pub_key(ses.kexhashbuf, hostkey, ses.newkeys->algo_hostkey);

    /* Q_C, client's ephemeral public key octet string */

    buf_put_ecc_raw_pubkey_string(ses.kexhashbuf, Q_C);

    /* Q_S, server's ephemeral public key octet string */

    buf_put_ecc_raw_pubkey_string(ses.kexhashbuf, Q_S);

    /* K, the shared secret */

    buf_putmpint(ses.kexhashbuf, ses.dh_K);

    ecc_free(Q_them);

    m_free(Q_them);

    /* calculate the hash H to sign */

    finish_kexhashbuf();

}

#endif /* DROPBEAR_ECDH */