/*      $OpenBSD: bn_mont.c,v 1.2 2022/12/06 18:23:29 tb Exp $  */

/*
 * Copyright (c) 2014 Miodrag Vallat.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <err.h>
#include <stdio.h>
#include <stdlib.h>

#include <openssl/bn.h>
#include <openssl/crypto.h>
#include <openssl/dh.h>
#include <openssl/err.h>

/*
 * Test for proper bn_mul_mont behaviour when operands are of vastly different
 * sizes.
 */

int
main(int argc, char *argv[])
{
        DH *dh = NULL;
        BIGNUM *priv_key = NULL;
        unsigned char *key = NULL;
        unsigned char r[32 + 16 * 8];
        size_t privsz;

        arc4random_buf(r, sizeof(r));

        for (privsz = 32; privsz <= sizeof(r); privsz += 8) {
                dh = DH_new();
                if (dh == NULL)
                        goto err;
                if (DH_generate_parameters_ex(dh, 32, DH_GENERATOR_2,
                    NULL) == 0)
                        goto err;

                /* force private key to be much larger than public one */
                priv_key = BN_bin2bn(r, privsz, NULL);
                if (priv_key == NULL)
                        goto err;

                if (!DH_set0_key(dh, NULL, priv_key))
                        goto err;
                priv_key = NULL;

                if (DH_generate_key(dh) == 0)
                        goto err;
                key = malloc(DH_size(dh));
                if (key == NULL)
                        err(1, "malloc");
                if (DH_compute_key(key, DH_get0_pub_key(dh), dh) == -1)
                        goto err;

                free(key);
                key = NULL;
                DH_free(dh);
                dh = NULL;
        }

        return 0;

 err:
        ERR_print_errors_fp(stderr);
        free(key);
        BN_free(priv_key);
        DH_free(dh);
        return 1;
}