/*

 * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 * https://www.openssl.org/source/license.html

 * or in the file LICENSE in the source distribution.

 */

/*

 * Confirm that if (d, r) = a / b, then b * d + r == a, and that sign(d) ==

 * sign(a), and 0 <= r <= b

 */

#include <stdio.h>

#include <openssl/bn.h>

#include <openssl/err.h>

#include "fuzzer.h"

/* 256 kB */

#define MAX_LEN (256 * 1000)

static BN_CTX *ctx;

static BIGNUM *b1;

static BIGNUM *b2;

static BIGNUM *b3;

static BIGNUM *b4;

static BIGNUM *b5;

int FuzzerInitialize(int *argc, char ***argv)

{

    b1 = BN_new();

    b2 = BN_new();

    b3 = BN_new();

    b4 = BN_new();

    b5 = BN_new();

    ctx = BN_CTX_new();

    OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CRYPTO_STRINGS, NULL);

    ERR_clear_error();

    return 1;

}

int FuzzerTestOneInput(const uint8_t *buf, size_t len)

{

    int success = 0;

    size_t l1 = 0, l2 = 0;

    /* s1 and s2 will be the signs for b1 and b2. */

    int s1 = 0, s2 = 0;

    /* limit the size of the input to avoid timeout */

    if (len > MAX_LEN)

        len = MAX_LEN;

    /* We are going to split the buffer in two, sizes l1 and l2, giving b1 and

     * b2.

     */

    if (len > 0) {

        --len;

        /* Use first byte to divide the remaining buffer into 3Fths. I admit

         * this disallows some number sizes. If it matters, better ideas are

         * welcome (Ben).

         */

        l1 = ((buf[0] & 0x3f) * len) / 0x3f;

        s1 = buf[0] & 0x40;

        s2 = buf[0] & 0x80;

        ++buf;

        l2 = len - l1;

    }

    OPENSSL_assert(BN_bin2bn(buf, l1, b1) == b1);

    BN_set_negative(b1, s1);

    OPENSSL_assert(BN_bin2bn(buf + l1, l2, b2) == b2);

    BN_set_negative(b2, s2);

    /* divide by 0 is an error */

    if (BN_is_zero(b2)) {

        success = 1;

        goto done;

    }

    OPENSSL_assert(BN_div(b3, b4, b1, b2, ctx));

    if (BN_is_zero(b1))

        success = BN_is_zero(b3) && BN_is_zero(b4);

    else if (BN_is_negative(b1))

        success = (BN_is_negative(b3) != BN_is_negative(b2) || BN_is_zero(b3))

            && (BN_is_negative(b4) || BN_is_zero(b4));

    else

        success = (BN_is_negative(b3) == BN_is_negative(b2)  || BN_is_zero(b3))

            && (!BN_is_negative(b4) || BN_is_zero(b4));

    OPENSSL_assert(BN_mul(b5, b3, b2, ctx));

    OPENSSL_assert(BN_add(b5, b5, b4));

    success = success && BN_cmp(b5, b1) == 0;

    if (!success) {

        BN_print_fp(stdout, b1);

        putchar('\n');

        BN_print_fp(stdout, b2);

        putchar('\n');

        BN_print_fp(stdout, b3);

        putchar('\n');

        BN_print_fp(stdout, b4);

        putchar('\n');

        BN_print_fp(stdout, b5);

        putchar('\n');

        printf("%d %d %d %d %d %d %d\n", BN_is_negative(b1),

               BN_is_negative(b2),

               BN_is_negative(b3), BN_is_negative(b4), BN_is_zero(b4),

               BN_is_negative(b3) != BN_is_negative(b2)

               && (BN_is_negative(b4) || BN_is_zero(b4)),

               BN_cmp(b5, b1));

        puts("----\n");

    }

 done:

    OPENSSL_assert(success);

    ERR_clear_error();

    return 0;

}

void FuzzerCleanup(void)

{

    BN_free(b1);

    BN_free(b2);

    BN_free(b3);

    BN_free(b4);

    BN_free(b5);

    BN_CTX_free(ctx);

}