path: root/src/bn.c

/**
 * XML Security Library (http://www.aleksey.com/xmlsec).
 *
 * Big Numbers.
 *
 * This is free software; see Copyright file in the source
 * distribution for preciese wording.
 *
 * Copyright (C) 2002-2016 Aleksey Sanin <aleksey@aleksey.com>. All Rights Reserved.
 * Copyright (C) 2003 Cordys R&D BV, All rights reserved.
 */
#include "globals.h"

#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include <libxml/tree.h>

#include <xmlsec/xmlsec.h>
#include <xmlsec/xmltree.h>
#include <xmlsec/base64.h>
#include <xmlsec/bn.h>
#include <xmlsec/errors.h>

/* table for converting hex digits back to bytes */
static const int xmlSecBnLookupTable[] =
{
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
     0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};

static const char xmlSecBnRevLookupTable[] =
{
    '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
};

/*****************************************************************************
 *
 * xmlSecBn
 *
 ****************************************************************************/
/**
 * xmlSecBnCreate:
 * @size:       the initial allocated BN size.
 *
 * Creates a new BN object. Caller is responsible for destroying it
 * by calling @xmlSecBnDestroy function.
 *
 * Returns: the newly BN or a NULL if an error occurs.
 */
xmlSecBnPtr
xmlSecBnCreate(xmlSecSize size) {
    return(xmlSecBufferCreate(size));
}

/**
 * xmlSecBnDestroy:
 * @bn:         the pointer to BN.
 *
 * Destroys @bn object created with @xmlSecBnCreate function.
 */
void
xmlSecBnDestroy(xmlSecBnPtr bn) {
    xmlSecBufferDestroy(bn);
}

/**
 * xmlSecBnInitialize:
 * @bn:         the pointer to BN.
 * @size:       the initial allocated BN size.
 *
 * Initializes a BN object. Caller is responsible for destroying it
 * by calling @xmlSecBnFinalize function.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnInitialize(xmlSecBnPtr bn, xmlSecSize size) {
    return(xmlSecBufferInitialize(bn, size));
}

/**
 * xmlSecBnFinalize:
 * @bn:         the pointer to BN.
 *
 * Destroys @bn object created with @xmlSecBnInitialize function.
 */
void
xmlSecBnFinalize(xmlSecBnPtr bn) {
    xmlSecBufferFinalize(bn);
}

/**
 * xmlSecBnGetData:
 * @bn:         the pointer to BN.
 *
 * Gets pointer to the binary @bn representation.
 *
 * Returns: pointer to binary BN data or NULL if an error occurs.
 */
xmlSecByte*
xmlSecBnGetData(xmlSecBnPtr bn) {
    return(xmlSecBufferGetData(bn));
}

/**
 * xmlSecBnSetData:
 * @bn:         the pointer to BN.
 * @data:       the pointer to new BN binary data.
 * @size:       the size of new BN data.
 *
 * Sets the value of @bn to @data.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnSetData(xmlSecBnPtr bn, const xmlSecByte* data, xmlSecSize size) {
    return(xmlSecBufferSetData(bn, data, size));
}

/**
 * xmlSecBnGetSize:
 * @bn:         the pointer to BN.
 *
 * Gets the size of binary data in @bn.
 *
 * Returns: the size of binary data.
 */
xmlSecSize
xmlSecBnGetSize(xmlSecBnPtr bn) {
    return(xmlSecBufferGetSize(bn));
}

/**
 * xmlSecBnZero:
 * @bn:         the pointer to BN.
 *
 * Sets the value of @bn to zero.
 */
void
xmlSecBnZero(xmlSecBnPtr bn) {
    xmlSecBufferEmpty(bn);
}

/**
 * xmlSecBnFromString:
 * @bn:         the pointer to BN.
 * @str:        the string with BN.
 * @base:       the base for @str.
 *
 * Reads @bn from string @str assuming it has base @base.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnFromString(xmlSecBnPtr bn, const xmlChar* str, xmlSecSize base) {
    xmlSecSize i, len, size;
    xmlSecByte ch;
    xmlSecByte* data;
    int positive;
    int nn;
    int ret;

    xmlSecAssert2(bn != NULL, -1);
    xmlSecAssert2(str != NULL, -1);
    xmlSecAssert2(base > 1, -1);
    xmlSecAssert2(base <= sizeof(xmlSecBnRevLookupTable), -1);

    /* trivial case */
    len = xmlStrlen(str);
    if(len == 0) {
        return(0);
    }

    /* The result size could not exceed the input string length
     * because each char fits inside a byte in all cases :)
     * In truth, it would be likely less than 1/2 input string length
     * because each byte is represented by 2 chars. If needed,
     * buffer size would be increased by Mul/Add functions.
     * Finally, we can add one byte for 00 or 10 prefix.
     */
    ret = xmlSecBufferSetMaxSize(bn, xmlSecBufferGetSize(bn) + len / 2 + 1 + 1);
    if(ret < 0) {
        xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnRevLookupTable",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "size=%d", len / 2 + 1);
        return (-1);
    }

    /* figure out if it is positive or negative number */
    positive = 1;
    i = 0;
    while(i < len) {
        ch = str[i++];

        /* skip spaces */
        if(isspace(ch)) {
                continue;
        }

        /* check if it is + or - */
        if(ch == '+') {
            positive = 1;
            break;
        } else if(ch == '-') {
            positive = 0;
            break;
        }

        /* otherwise, it must be start of the number */
        nn = xmlSecBnLookupTable[ch];
        if((nn >= 0) && ((xmlSecSize)nn < base)) {
            xmlSecAssert2(i > 0, -1);

            /* no sign, positive by default */
            positive = 1;
            --i; /* make sure that we will look at this character in next loop */
            break;
        } else {
                xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        NULL,
                        XMLSEC_ERRORS_R_INVALID_DATA,
                        "char=%c;base=%d",
                        ch, base);
                return (-1);
        }
    }

    /* now parse the number itself */
    while(i < len) {
        ch = str[i++];
        if(isspace(ch)) {
                continue;
        }

        xmlSecAssert2(ch < sizeof(xmlSecBnLookupTable) / sizeof(xmlSecBnLookupTable[0]), -1);
        nn = xmlSecBnLookupTable[ch];
        if((nn < 0) || ((xmlSecSize)nn > base)) {
                xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        NULL,
                        XMLSEC_ERRORS_R_INVALID_DATA,
                        "char=%c;base=%d",
                        ch, base);
                return (-1);
        }

        ret = xmlSecBnMul(bn, base);
        if(ret < 0) {
                xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnMul",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "base=%d", base);
                return (-1);
        }

        ret = xmlSecBnAdd(bn, nn);
        if(ret < 0) {
                xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnAdd",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "base=%d", base);
                return (-1);
}
    }

    /* check if we need to add 00 prefix, do this for empty bn too */
    data = xmlSecBufferGetData(bn);
    size = xmlSecBufferGetSize(bn);
    if(((size > 0) && (data[0] > 127)) || (size == 0))  {
        ch = 0;
        ret = xmlSecBufferPrepend(bn, &ch, 1);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                NULL,
                "xmlSecBufferPrepend",
                XMLSEC_ERRORS_R_XMLSEC_FAILED,
                "base=%d", base);
            return (-1);
        }
    }

    /* do 2's compliment and add 1 to represent negative value */
    if(positive == 0) {
        data = xmlSecBufferGetData(bn);
        size = xmlSecBufferGetSize(bn);
        for(i = 0; i < size; ++i) {
            data[i] ^= 0xFF;
        }

        ret = xmlSecBnAdd(bn, 1);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                NULL,
                "xmlSecBnAdd",
                XMLSEC_ERRORS_R_XMLSEC_FAILED,
                "base=%d", base);
            return (-1);
        }
    }

    return(0);
}

/**
 * xmlSecBnToString:
 * @bn:         the pointer to BN.
 * @base:       the base for returned string.
 *
 * Writes @bn to string with base @base. Caller is responsible for
 * freeing returned string with @xmlFree.
 *
 * Returns: the string represenataion if BN or a NULL if an error occurs.
 */
xmlChar*
xmlSecBnToString(xmlSecBnPtr bn, xmlSecSize base) {
    xmlSecBn bn2;
    int positive = 1;
    xmlChar* res;
    xmlSecSize i, len, size;
    xmlSecByte* data;
    int ret;
    int nn;
    xmlChar ch;

    xmlSecAssert2(bn != NULL, NULL);
    xmlSecAssert2(base > 1, NULL);
    xmlSecAssert2(base <= sizeof(xmlSecBnRevLookupTable), NULL);


    /* copy bn */
    data = xmlSecBufferGetData(bn);
    size = xmlSecBufferGetSize(bn);
    ret = xmlSecBnInitialize(&bn2, size);
    if(ret < 0) {
        xmlSecError(XMLSEC_ERRORS_HERE,
            NULL,
            "xmlSecBnCreate",
            XMLSEC_ERRORS_R_XMLSEC_FAILED,
            "size=%d", size);
        return (NULL);
    }

    ret = xmlSecBnSetData(&bn2, data, size);
    if(ret < 0) {
        xmlSecError(XMLSEC_ERRORS_HERE,
            NULL,
            "xmlSecBnSetData",
            XMLSEC_ERRORS_R_XMLSEC_FAILED,
            "size=%d", size);
        xmlSecBnFinalize(&bn2);
        return (NULL);
    }

    /* check if it is a negative number or not */
    data = xmlSecBufferGetData(&bn2);
    size = xmlSecBufferGetSize(&bn2);
    if((size > 0) && (data[0] > 127)) {
        /* subtract 1 and do 2's compliment */
        ret = xmlSecBnAdd(&bn2, -1);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnAdd",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "size=%d", size);
            xmlSecBnFinalize(&bn2);
            return (NULL);
        }
        for(i = 0; i < size; ++i) {
            data[i] ^= 0xFF;
        }

        positive = 0;
    } else {
        positive = 1;
    }

    /* Result string len is
     *      len = log base (256) * <bn size>
     * Since the smallest base == 2 then we can get away with
     *      len = 8 * <bn size>
     */
    len = 8 * size + 1 + 1;
    res = (xmlChar*)xmlMalloc(len + 1);
    if(res == NULL) {
        xmlSecError(XMLSEC_ERRORS_HERE,
                            NULL,
                            NULL,
                            XMLSEC_ERRORS_R_MALLOC_FAILED,
                            "len=%d", len);
        xmlSecBnFinalize(&bn2);
        return (NULL);
    }
    memset(res, 0, len + 1);

    for(i = 0; (xmlSecBufferGetSize(&bn2) > 0) && (i < len); i++) {
        if(xmlSecBnDiv(&bn2, base, &nn) < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnDiv",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "base=%d", base);
            xmlFree(res);
            xmlSecBnFinalize(&bn2);
            return (NULL);
        }
        xmlSecAssert2((size_t)nn < sizeof(xmlSecBnRevLookupTable), NULL);
        res[i] = xmlSecBnRevLookupTable[nn];
    }
    xmlSecAssert2(i < len, NULL);

    /* we might have '0' at the beggining, remove it but keep one zero */
    for(len = i; (len > 1) && (res[len - 1] == '0'); len--);
    res[len] = '\0';

    /* add "-" for negative numbers */
    if(positive == 0) {
        res[len] = '-';
        res[++len] = '\0';
    }

    /* swap the string because we wrote it in reverse order */
    for(i = 0; i < len / 2; i++) {
        ch = res[i];
        res[i] = res[len - i - 1];
        res[len - i - 1] = ch;
    }

    xmlSecBnFinalize(&bn2);
    return(res);
}

/**
 * xmlSecBnFromHexString:
 * @bn:         the pointer to BN.
 * @str:        the string with BN.
 *
 * Reads @bn from hex string @str.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnFromHexString(xmlSecBnPtr bn, const xmlChar* str) {
    return(xmlSecBnFromString(bn, str, 16));
}

/**
 * xmlSecBnToHexString:
 * @bn:         the pointer to BN.
 *
 * Writes @bn to hex string. Caller is responsible for
 * freeing returned string with @xmlFree.
 *
 * Returns: the string represenataion if BN or a NULL if an error occurs.
 */
xmlChar*
xmlSecBnToHexString(xmlSecBnPtr bn) {
    return(xmlSecBnToString(bn, 16));
}

/**
 * xmlSecBnFromDecString:
 * @bn:         the pointer to BN.
 * @str:        the string with BN.
 *
 * Reads @bn from decimal string @str.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnFromDecString(xmlSecBnPtr bn, const xmlChar* str) {
    return(xmlSecBnFromString(bn, str, 10));
}

/**
 * xmlSecBnToDecString:
 * @bn:         the pointer to BN.
 *
 * Writes @bn to decimal string. Caller is responsible for
 * freeing returned string with @xmlFree.
 *
 * Returns: the string represenataion if BN or a NULL if an error occurs.
 */
xmlChar*
xmlSecBnToDecString(xmlSecBnPtr bn) {
    return(xmlSecBnToString(bn, 10));
}

/**
 * xmlSecBnMul:
 * @bn:                 the pointer to BN.
 * @multiplier:         the multiplier.
 *
 * Multiplies @bn with @multiplier.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnMul(xmlSecBnPtr bn, int multiplier) {
    xmlSecByte* data;
    int over;
    xmlSecSize i;
    xmlSecByte ch;
    int ret;

    xmlSecAssert2(bn != NULL, -1);
    xmlSecAssert2(multiplier > 0, -1);

    if(multiplier == 1) {
        return(0);
    }

    data = xmlSecBufferGetData(bn);
    i = xmlSecBufferGetSize(bn);
    over = 0;
    while(i > 0) {
        xmlSecAssert2(data != NULL, -1);

        over    = over + multiplier * data[--i];
        data[i] = over % 256;
        over    = over / 256;
    }

    while(over > 0) {
        ch      = over % 256;
        over    = over / 256;

        ret = xmlSecBufferPrepend(bn, &ch, 1);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBufferPrepend",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "size=1");
            return (-1);
        }
    }

    return(0);
}

/**
 * xmlSecBnDiv:
 * @bn:         the pointer to BN.
 * @divider:    the divider
 * @mod:        the pointer for modulus result.
 *
 * Divides @bn by @divider and places modulus into @mod.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnDiv(xmlSecBnPtr bn, int divider, int* mod) {
    int over;
    xmlSecSize i, size;
    xmlSecByte* data;
    int ret;

    xmlSecAssert2(bn != NULL, -1);
    xmlSecAssert2(divider > 0, -1);
    xmlSecAssert2(mod != NULL, -1);

    if(divider == 1) {
        return(0);
    }

    data = xmlSecBufferGetData(bn);
    size = xmlSecBufferGetSize(bn);
    for(over = 0, i = 0; i < size; i++) {
        xmlSecAssert2(data != NULL, -1);

        over    = over * 256 + data[i];
        data[i] = over / divider;
        over    = over % divider;
    }
    (*mod) = over;

    /* remove leading zeros */
    for(i = 0; i < size; i++) {
        xmlSecAssert2(data != NULL, -1);

        if(data[i] != 0) {
            break;
        }
    }
    if(i > 0) {
        ret = xmlSecBufferRemoveHead(bn, i);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBufferRemoveHead",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        "size=%d", i);
            return (-1);
        }
    }
    return(0);
}

/**
 * xmlSecBnAdd:
 * @bn:         the pointer to BN.
 * @delta:      the delta.
 *
 * Adds @delta to @bn.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnAdd(xmlSecBnPtr bn, int delta) {
    int over, tmp;
    xmlSecByte* data;
    xmlSecSize i;
    xmlSecByte ch;
    int ret;

    xmlSecAssert2(bn != NULL, -1);

    if(delta == 0) {
        return(0);
    }

    data = xmlSecBufferGetData(bn);
    if(delta > 0) {
        for(over = delta, i = xmlSecBufferGetSize(bn); (i > 0) && (over > 0) ;) {
                xmlSecAssert2(data != NULL, -1);

            tmp     = data[--i];
                over   += tmp;
                data[i] = over % 256;
                over    = over / 256;
        }

        while(over > 0) {
                ch      = over % 256;
                over    = over / 256;

                ret = xmlSecBufferPrepend(bn, &ch, 1);
                if(ret < 0) {
                    xmlSecError(XMLSEC_ERRORS_HERE,
                                NULL,
                                "xmlSecBufferPrepend",
                                XMLSEC_ERRORS_R_XMLSEC_FAILED,
                                "size=1");
                    return (-1);
                }
        }
    } else {
        for(over = -delta, i = xmlSecBufferGetSize(bn); (i > 0) && (over > 0);) {
                xmlSecAssert2(data != NULL, -1);

            tmp     = data[--i];
            if(tmp < over) {
                data[i] = 0;
                over = (over - tmp) / 256;
            } else {
                data[i] = tmp - over;
                over = 0;
            }
        }
    }
    return(0);
}

/**
 * xmlSecBnReverse:
 * @bn:         the pointer to BN.
 *
 * Reverses bytes order in @bn.
 *
 * Returns: 0 on success or a negative value if an error occurs.
 */
int
xmlSecBnReverse(xmlSecBnPtr bn) {
    xmlSecByte* data;
    xmlSecSize i, j, size;
    xmlSecByte ch;

    xmlSecAssert2(bn != NULL, -1);

    data = xmlSecBufferGetData(bn);
    size = xmlSecBufferGetSize(bn);
    for(i = 0, j = size - 1; i < size / 2; ++i, --j) {
        xmlSecAssert2(data != NULL, -1);

        ch       = data[i];
        data[i]  = data[j];
        data[j]  = ch;
    }

    return(0);
}

/**
 * xmlSecBnCompare:
 * @bn:         the pointer to BN.
 * @data:       the data to compare BN to.
 * @dataSize:   the @data size.
 *
 * Compares the @bn with @data.
 *
 * Returns: 0 if data is equal, negative value if @bn is less or positive value if @bn
 * is greater than @data.
 */
int
xmlSecBnCompare(xmlSecBnPtr bn, const xmlSecByte* data, xmlSecSize dataSize) {
    xmlSecByte* bnData;
    xmlSecSize bnSize;

    xmlSecAssert2(bn != NULL, -1);

    bnData = xmlSecBnGetData(bn);
    bnSize = xmlSecBnGetSize(bn);

    /* skip zeros in the beggining */
    while((dataSize > 0) && (data != 0) && (data[0] == 0)) {
        ++data;
        --dataSize;
    }
    while((bnSize > 0) && (bnData != 0) && (bnData[0] == 0)) {
        ++bnData;
        --bnSize;
    }

    if(((bnData == NULL) || (bnSize == 0)) && ((data == NULL) || (dataSize == 0))) {
        return(0);
    } else if((bnData == NULL) || (bnSize == 0)) {
        return(-1);
    } else if((data == NULL) || (dataSize == 0)) {
        return(1);
    } else if(bnSize < dataSize) {
        return(-1);
    } else if(bnSize > dataSize) {
        return(-1);
    }

    xmlSecAssert2(bnData != NULL, -1);
    xmlSecAssert2(data != NULL, -1);
    xmlSecAssert2(bnSize == dataSize, -1);

    return(memcmp(bnData, data, dataSize));
}

/**
 * xmlSecBnCompareReverse:
 * @bn:         the pointer to BN.
 * @data:       the data to compare BN to.
 * @dataSize:   the @data size.
 *
 * Compares the @bn with reverse @data.
 *
 * Returns: 0 if data is equal, negative value if @bn is less or positive value if @bn
 * is greater than @data.
 */
int
xmlSecBnCompareReverse(xmlSecBnPtr bn, const xmlSecByte* data, xmlSecSize dataSize) {
    xmlSecByte* bnData;
    xmlSecSize bnSize;
    xmlSecSize i, j;

    xmlSecAssert2(bn != NULL, -1);

    bnData = xmlSecBnGetData(bn);
    bnSize = xmlSecBnGetSize(bn);

    /* skip zeros in the beggining */
    while((dataSize > 0) && (data != 0) && (data[dataSize - 1] == 0)) {
        --dataSize;
    }
    while((bnSize > 0) && (bnData != 0) && (bnData[0] == 0)) {
        ++bnData;
        --bnSize;
    }

    if(((bnData == NULL) || (bnSize == 0)) && ((data == NULL) || (dataSize == 0))) {
        return(0);
    } else if((bnData == NULL) || (bnSize == 0)) {
        return(-1);
    } else if((data == NULL) || (dataSize == 0)) {
        return(1);
    } else if(bnSize < dataSize) {
        return(-1);
    } else if(bnSize > dataSize) {
        return(-1);
    }

    xmlSecAssert2(bnData != NULL, -1);
    xmlSecAssert2(data != NULL, -1);
    xmlSecAssert2(bnSize == dataSize, -1);
    for(i = 0, j = dataSize - 1; i < dataSize; ++i, --j) {
        if(bnData[i] < data[j]) {
            return(-1);
        } else if(data[j] < bnData[i]) {
            return(1);
        }
    }

    return(0);
}

/**
 * xmlSecBnGetNodeValue:
 * @bn:         the pointer to BN.
 * @cur:        the poitner to an XML node.
 * @format:     the BN format.
 * @reverse:    if set then reverse read buffer after reading.
 *
 * Converts the node content from @format to @bn.
 *
 * Returns: 0 on success and a negative values if an error occurs.
 */
int
xmlSecBnGetNodeValue(xmlSecBnPtr bn, xmlNodePtr cur, xmlSecBnFormat format, int reverse) {
    xmlChar* content;
    int ret;

    xmlSecAssert2(bn != NULL, -1);
    xmlSecAssert2(cur != NULL, -1);

    switch(format) {
    case xmlSecBnBase64:
        ret = xmlSecBufferBase64NodeContentRead(bn, cur);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBufferBase64NodeContentRead",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            return(-1);
        }
        break;
    case xmlSecBnHex:
        content = xmlNodeGetContent(cur);
        if(content == NULL) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlNodeGetContent",
                        XMLSEC_ERRORS_R_XML_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            return(-1);
        }
        ret = xmlSecBnFromHexString(bn, content);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnFromHexString",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            xmlFree(content);
            return(-1);
        }
        xmlFree(content);
        break;
    case xmlSecBnDec:
        content = xmlNodeGetContent(cur);
        if(content == NULL) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlNodeGetContent",
                        XMLSEC_ERRORS_R_XML_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            return(-1);
        }
        ret = xmlSecBnFromDecString(bn, content);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnFromDecString",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            xmlFree(content);
            return(-1);
        }
        xmlFree(content);
        break;
    }

    if(reverse != 0) {
        ret = xmlSecBnReverse(bn);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnReverse",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            return(-1);
        }
    }
    return(0);
}

/**
 * xmlSecBnSetNodeValue:
 * @bn:                 the pointer to BN.
 * @cur:                the poitner to an XML node.
 * @format:             the BN format.
 * @reverse:            the flag that indicates whether to reverse the buffer before writing.
 * @addLineBreaks:      the flag; it is equal to 1 then linebreaks will be added before and after new buffer content.
 *
 * Converts the @bn and sets it to node content.
 *
 * Returns: 0 on success and a negative values if an error occurs.
 */
int
xmlSecBnSetNodeValue(xmlSecBnPtr bn, xmlNodePtr cur, xmlSecBnFormat format, int reverse, int addLineBreaks) {
    xmlChar* content;
    int ret;

    xmlSecAssert2(bn != NULL, -1);
    xmlSecAssert2(cur != NULL, -1);

    if(reverse != 0) {
        ret = xmlSecBnReverse(bn);
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnReverse",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            return(-1);
        }
    }

    if(addLineBreaks) {
        xmlNodeAddContent(cur, xmlSecStringCR);
    }

    switch(format) {
    case xmlSecBnBase64:
        ret = xmlSecBufferBase64NodeContentWrite(bn, cur, xmlSecBase64GetDefaultLineSize());
        if(ret < 0) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBufferBase64NodeContentWrite",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            return(-1);
        }
        break;
    case xmlSecBnHex:
        content = xmlSecBnToHexString(bn);
        if(content == NULL) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnToHexString",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            xmlFree(content);
            return(-1);
        }
        xmlNodeSetContent(cur, content);
        xmlFree(content);
        break;
    case xmlSecBnDec:
        content = xmlSecBnToDecString(bn);
        if(content == NULL) {
            xmlSecError(XMLSEC_ERRORS_HERE,
                        NULL,
                        "xmlSecBnToDecString",
                        XMLSEC_ERRORS_R_XMLSEC_FAILED,
                        XMLSEC_ERRORS_NO_MESSAGE);
            xmlFree(content);
            return(-1);
        }
        xmlNodeSetContent(cur, content);
        xmlFree(content);
        break;
    }

    if(addLineBreaks) {
        xmlNodeAddContent(cur, xmlSecStringCR);
    }

    return(0);
}

/**
 * xmlSecBnBlobSetNodeValue:
 * @data:       the pointer to BN blob.
 * @dataSize:   the size of BN blob.
 * @cur:        the poitner to an XML node.
 * @format:     the BN format.
 * @reverse:    the flag that indicates whether to reverse the buffer before writing.
 * @addLineBreaks:  if the flag is equal to 1 then
 *              linebreaks will be added before and after
 *              new buffer content.
 *
 * Converts the @blob and sets it to node content.
 *
 * Returns: 0 on success and a negative values if an error occurs.
 */
int
xmlSecBnBlobSetNodeValue(const xmlSecByte* data, xmlSecSize dataSize,
                         xmlNodePtr cur, xmlSecBnFormat format, int reverse,
                         int addLineBreaks) {
    xmlSecBn bn;
    int ret;

    xmlSecAssert2(data != NULL, -1);
    xmlSecAssert2(cur != NULL, -1);

    ret = xmlSecBnInitialize(&bn, dataSize);
    if(ret < 0) {
        xmlSecError(XMLSEC_ERRORS_HERE,
                    NULL,
                    "xmlSecBnInitialize",
                    XMLSEC_ERRORS_R_XMLSEC_FAILED,
                    XMLSEC_ERRORS_NO_MESSAGE);
        return(-1);
    }

    ret = xmlSecBnSetData(&bn, data, dataSize);
    if(ret < 0) {
        xmlSecError(XMLSEC_ERRORS_HERE,
                    NULL,
                    "xmlSecBnSetData",
                    XMLSEC_ERRORS_R_XMLSEC_FAILED,
                    XMLSEC_ERRORS_NO_MESSAGE);
        xmlSecBnFinalize(&bn);
        return(-1);
    }

    ret = xmlSecBnSetNodeValue(&bn, cur, format, reverse, addLineBreaks);
    if(ret < 0) {
        xmlSecError(XMLSEC_ERRORS_HERE,
                    NULL,
                    "xmlSecBnSetNodeValue",
                    XMLSEC_ERRORS_R_XMLSEC_FAILED,
                    XMLSEC_ERRORS_NO_MESSAGE);
        xmlSecBnFinalize(&bn);
        return(-1);
    }

    xmlSecBnFinalize(&bn);
    return(0);
}