Beesnest/Windows/DcCrypto.cpp

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/*
Copyright 2007 Erez Bibi (erezbibi@users.sourceforge.net)
This file is part of Beesnest.

Beesnest is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

Beesnest is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Beesnest; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/


/**
 * DcCrypto.cpp: implementation of the CdcCrypto class.
 * for documentation see the header file.
 */
#include "DcCrypto.h"

#define NUM_OF_DIGITS   10
#define NUM_OF_LETTERS  26

HCRYPTPROV CdcCrypto::hProv;

void CdcCrypto::Init ()
{
    /* Get a handle to the default provider. */
    if (!CryptAcquireContext (&hProv, NULL, NULL, PROV_RSA_FULL,
        CRYPT_VERIFYCONTEXT))
        throw CdcException ("Cannot get a handle to the default provider.");

}


void CdcCrypto::Destroy ()
{
    CryptReleaseContext (hProv, 0);
}


CdcString CdcCrypto::GetRandomString (int len)
{
    if (len >= BUFF_LEN) len = BUFF_LEN - 1;
    unsigned char temp [BUFF_LEN];

    /* Get a random buffer. */
    if (!CryptGenRandom (hProv, len, temp))
            throw CdcException ("Cannot generate random string.");

    /* Convert a to valid string. */
    for (int i = 0; i < len; ++i)
    {   /* I want upper case letters, lower case and digit. */
        temp[i] = temp[i] % ((NUM_OF_LETTERS * 2) + NUM_OF_DIGITS);
        if (temp[i] < NUM_OF_DIGITS) temp[i] += '0';
        else if (temp[i] < (NUM_OF_DIGITS + NUM_OF_LETTERS))
            temp[i] += 'A' - NUM_OF_DIGITS;
        else temp[i] += 'a' - (NUM_OF_DIGITS + NUM_OF_LETTERS);
    }

    temp[len] = '\0';
    return CdcString ((char*)temp);
}

CdcString  CdcCrypto::MakeHash (const CdcString& buff)
{
    HCRYPTHASH hHash = 0;

    /* Create a hash object. */
    if (!CryptCreateHash (hProv, CALG_MD5, 0, 0, &hHash))
        throw CdcException ("Cannot create hash object.");

    /* Put the hash in a buffer. */
    if (!CryptHashData (hHash, (unsigned char*)buff.GetBuffer (),
        buff.GetLength (), 0))
        throw CdcException ("Cannot put the buffer into hash object.");

    /* Read the hash value. */
    unsigned char hash_buff [BUFF_LEN];
    DWORD len = BUFF_LEN;
    if (!CryptGetHashParam (hHash, HP_HASHVAL, hash_buff, &len, 0))
        throw CdcException ("Cannot read the hash value.");

    /* Destroy the hash object. */
    if (hHash) CryptDestroyHash(hHash);

    /* Convert hash to hex. */
    CdcString hex_hash;
    char temp[10];
    for (int i = 0; i < len; ++i)
    {
        sprintf (temp, "%2x", hash_buff[i]);
        if (temp[0] == ' ') temp[0] = '0';
        hex_hash += temp;
    }
    return hex_hash;
}