Question

I tried to read a REG_BINARY value of the Windows registry, but I don’t know how… I’m really new to the c++ world and I hope that you’ll be cool and help me with that problem.

I found that code on this website, I know this is not doing the job, but just for let you know what I’m trying to do.

#include <iostream>
#include <windows.h>

using namespace std;

int main()
{
    HKEY hKey;
    DWORD dwDisp = REG_BINARY;
    DWORD dwSize = sizeof(dwDisp);
    DWORD dwValue = 0;
    DWORD dwReturn;
    DWORD dwBufSize = sizeof(dwDisp);

    if( RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",0, KEY_ALL_ACCESS, &hKey) == ERROR_SUCCESS)
    {
        DWORD error = RegQueryValueEx(hKey,"DigitalProductId",0,0, (LPBYTE)&dwReturn, &dwBufSize);
        if(error == ERROR_SUCCESS)
        {
            cout << "Key value is :" << dwReturn << endl;
        }
        else
        {
           cout << "Cannot query for key value; Error is : " << error << endl;
        }
    }

    RegCloseKey(hKey);

    return 0;
}

P.S. I’m using gcc without .net.

Thanks for your help it will be very appreciated.

---

Thanks all!
There is the fully functional code:

#include <iostream>
#include <windows.h>

using namespace std;

int main()
{
    HKEY hKey;
    DWORD dwBufSize = 200;
    UCHAR dwReturn[200];
    UCHAR digits[] = {'B','C','D','F','G','H','J','K','M','P','Q','R','T','V','W','X','Y','2','3','4','6','7','8','9'};
    UCHAR strresult[26];

    if( RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",0, KEY_QUERY_VALUE, &hKey) == ERROR_SUCCESS)
    {
        DWORD error = RegQueryValueEx(hKey,"DigitalProductId",0,0, (LPBYTE)dwReturn, &dwBufSize);
        if(error == ERROR_SUCCESS)
        {

            for (int i=24;i>=0;i--) {
                int x=0;

                for (int j=14;j>=0;j--) {
                x = (x<<8) + (dwReturn+0x34)[j];
                (dwReturn+0x34)[j] = x / 24;
                x = x % 24;
                }
                strresult[i]=digits[x];
            }

            string part1, part2, part3, part4, part5;
            string str;
            string strRetVal;

            for(int i = 0; strresult[i] != 0; i++)
            {
                str += strresult[i];
            }

            part1 = str.substr(0,5) + "-";
            part2 = str.substr(5,5) + "-";
            part3 = str.substr(10,5) + "-";
            part4 = str.substr(15,5) + "-";
            part5 = str.substr(20,5);

            strRetVal = part1 + part2 + part3 + part4 + part5;

            cout << "Windows Key : " << strRetVal << endl;
        }
        else
        {
           cout << "Cannot query for key value; Error is : " << error << ", dwBufSize="<<dwBufSize<<endl;
        }
    }

    RegCloseKey(hKey);

    return 0;
}

Answer 1

There are two problems with the code you posted – the buffer for the binary value is too small and
KEY_ALL_ACCESS could be too much to ask for, KEY_QUERY_VALUE is enough.

Here is the code that has this mistakes corrected. You can change dwReturn[1000] to dwReturn[1] and see that RegQueryValueEx returns an error and the required buffer size.

int main()
{
    HKEY hKey;
    DWORD dwReturn[1000];  //dwReturn[1]
    DWORD dwBufSize = sizeof(dwReturn);

    if( RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",0, KEY_QUERY_VALUE, &hKey) == ERROR_SUCCESS)
    {
        DWORD error = RegQueryValueEx(hKey,"DigitalProductId",0,0, (LPBYTE)dwReturn, &dwBufSize);
        if(error == ERROR_SUCCESS)
        {
            cout << "dwReturn[0]=" << dwReturn[0] << ", dwBufSize=" << dwBufSize <<endl;
        }
        else
        {
           cout << "Cannot query for key value; Error is : " << error << ", dwBufSize="<<dwBufSize<<endl;
        }
    }

    RegCloseKey(hKey);

    return 0;
}

Note that in the case of “DigitalProductId” the first DWORD contains the length so dwReturn[0] and dwBufSize are the same.