/*

 * Copyright 1995-2026 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 can obtain a copy

 * in the file LICENSE in the source distribution or at

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

 */

#include <stdio.h>

#include <openssl/err.h>

#include "crypto/ctype.h"

#include "bn_local.h"

/* Must 'OPENSSL_free' the returned data */

char *BN_bn2hex(const BIGNUM *a)

{

    int i, j, v, z = 0;

    char *buf;

    char *p;

    if (BN_is_zero(a))

        return OPENSSL_strdup("0");

    buf = OPENSSL_malloc(a->top * BN_BYTES * 2 + 2);

    if (buf == NULL)

        goto err;

    p = buf;

    if (a->neg)

        *p++ = '-';

    for (i = a->top - 1; i >= 0; i--) {

        for (j = BN_BITS2 - 8; j >= 0; j -= 8) {

            /* strip leading zeros */

            v = (int)((a->d[i] >> j) & 0xff);

            if (z || v != 0) {

                p += ossl_to_hex(p, v);

                z = 1;

            }

        }

    }

    *p = '\0';

err:

    return buf;

}

#ifndef FIPS_MODULE

/* No BIO_snprintf in FIPS_MODULE */

/* Must 'OPENSSL_free' the returned data */

char *BN_bn2dec(const BIGNUM *a)

{

    int i = 0, num, ok = 0, n, tbytes;

    char *buf = NULL;

    char *p;

    BIGNUM *t = NULL;

    BN_ULONG *bn_data = NULL, *lp;

    int bn_data_num;

    /*-

     * get an upper bound for the length of the decimal integer

     * num <= (BN_num_bits(a) + 1) * log(2)

     *     <= 3 * BN_num_bits(a) * 0.101 + log(2) + 1     (rounding error)

     *     <= 3 * BN_num_bits(a) / 10 + 3 * BN_num_bits / 1000 + 1 + 1

     */

    i = BN_num_bits(a) * 3;

    num = (i / 10 + i / 1000 + 1) + 1;

    tbytes = num + 3; /* negative and terminator and one spare? */

    bn_data_num = num / BN_DEC_NUM + 1;

    bn_data = OPENSSL_malloc_array(bn_data_num, sizeof(BN_ULONG));

    buf = OPENSSL_malloc(tbytes);

    if (buf == NULL || bn_data == NULL)

        goto err;

    if ((t = BN_dup(a)) == NULL)

        goto err;

    p = buf;

    lp = bn_data;

    if (BN_is_zero(t)) {

        *p++ = '0';

        *p++ = '\0';

    } else {

        if (BN_is_negative(t))

            *p++ = '-';

        while (!BN_is_zero(t)) {

            if (lp - bn_data >= bn_data_num)

                goto err;

            *lp = BN_div_word(t, BN_DEC_CONV);

            if (*lp == (BN_ULONG)-1)

                goto err;

            lp++;

        }

        lp--;

        /*

         * We now have a series of blocks, BN_DEC_NUM chars in length, where

         * the last one needs truncation. The blocks need to be reversed in

         * order.

         */

        n = snprintf(p, tbytes - (size_t)(p - buf), BN_DEC_FMT1, *lp);

        if (n < 0 || (size_t)n >= tbytes - (size_t)(p - buf))

            goto err;

        p += n;

        while (lp != bn_data) {

            lp--;

            n = snprintf(p, tbytes - (size_t)(p - buf), BN_DEC_FMT2, *lp);

            if (n < 0 || (size_t)n >= tbytes - (size_t)(p - buf))

                goto err;

            p += n;

        }

    }

    ok = 1;

err:

    OPENSSL_free(bn_data);

    BN_free(t);

    if (ok)

        return buf;

    OPENSSL_free(buf);

    return NULL;

}

#endif

int BN_hex2bn(BIGNUM **bn, const char *a)

{

    BIGNUM *ret = NULL;

    BN_ULONG l = 0;

    int neg = 0, h, m, i, j, k, c;

    int num;

    if (a == NULL || *a == '\0')

        return 0;

    if (*a == '-') {

        neg = 1;

        a++;

    }

    for (i = 0; i <= INT_MAX / 4 && ossl_isxdigit(a[i]); i++)

        continue;

    if (i == 0 || i > INT_MAX / 4)

        return 0;

    num = i + neg;

    if (bn == NULL)

        return num;

    /* a is the start of the hex digits, and it is 'i' long */

    if (*bn == NULL) {

        if ((ret = BN_new()) == NULL)

            return 0;

    } else {

        ret = *bn;

        if (BN_get_flags(ret, BN_FLG_STATIC_DATA)) {

            ERR_raise(ERR_LIB_BN, ERR_R_PASSED_INVALID_ARGUMENT);

            return 0;

        }

        BN_zero(ret);

    }

    /* i is the number of hex digits */

    if (bn_expand(ret, i * 4) == NULL)

        goto err;

    j = i; /* least significant 'hex' */

    m = 0;

    h = 0;

    while (j > 0) {

        m = (BN_BYTES * 2 <= j) ? BN_BYTES * 2 : j;

        l = 0;

        for (;;) {

            c = a[j - m];

            k = OPENSSL_hexchar2int(c);

            if (k < 0)

                k = 0; /* paranoia */

            l = (l << 4) | k;

            if (--m <= 0) {

                ret->d[h++] = l;

                break;

            }

        }

        j -= BN_BYTES * 2;

    }

    ret->top = h;

    bn_correct_top(ret);

    *bn = ret;

    bn_check_top(ret);

    /* Don't set the negative flag if it's zero. */

    if (ret->top != 0)

        ret->neg = neg;

    return num;

err:

    if (*bn == NULL)

        BN_free(ret);

    return 0;

}

int BN_dec2bn(BIGNUM **bn, const char *a)

{

    BIGNUM *ret = NULL;

    BN_ULONG l = 0;

    int neg = 0, i, j;

    int num;

    if (a == NULL || *a == '\0')

        return 0;

    if (*a == '-') {

        neg = 1;

        a++;

    }

    for (i = 0; i <= INT_MAX / 4 && ossl_isdigit(a[i]); i++)

        continue;

    if (i == 0 || i > INT_MAX / 4)

        goto err;

    num = i + neg;

    if (bn == NULL)

        return num;

    /*

     * a is the start of the digits, and it is 'i' long. We chop it into

     * BN_DEC_NUM digits at a time

     */

    if (*bn == NULL) {

        if ((ret = BN_new()) == NULL)

            return 0;

    } else {

        ret = *bn;

        BN_zero(ret);

    }

    /* i is the number of digits, a bit of an over expand */

    if (bn_expand(ret, i * 4) == NULL)

        goto err;

    j = BN_DEC_NUM - i % BN_DEC_NUM;

    if (j == BN_DEC_NUM)

        j = 0;

    l = 0;

    while (--i >= 0) {

        l *= 10;

        l += *a - '0';

        a++;

        if (++j == BN_DEC_NUM) {

            if (!BN_mul_word(ret, BN_DEC_CONV)

                || !BN_add_word(ret, l))

                goto err;

            l = 0;

            j = 0;

        }

    }

    bn_correct_top(ret);

    *bn = ret;

    bn_check_top(ret);

    /* Don't set the negative flag if it's zero. */

    if (ret->top != 0)

        ret->neg = neg;

    return num;

err:

    if (*bn == NULL)

        BN_free(ret);

    return 0;

}

int BN_asc2bn(BIGNUM **bn, const char *a)

{

    const char *p = a;

    if (*p == '-')

        p++;

    if (p[0] == '0' && (p[1] == 'X' || p[1] == 'x')) {

        if (!BN_hex2bn(bn, p + 2))

            return 0;

    } else {

        if (!BN_dec2bn(bn, p))

            return 0;

    }

    /* Don't set the negative flag if it's zero. */

    if (*a == '-' && (*bn)->top != 0)

        (*bn)->neg = 1;

    return 1;

}