Redirect stdin to pipe

I got a VB script template to invoke a runas command as a privileged user. The script uses Sendkeys to pass the plain admin password to the runas command like that:

    objShell.AppActivate(RunAsCommand)
    objShell.Sendkeys AdminPassword

I was told to encode my VB scripts based on that template by Microsoft Script Encoder. It turns a .vbs file to a .vbe file that can be started using cscript or wsript. The use of this tool is to be able to prevent people from looking at, or modifying, VB scripts.

However, it took me one minute to find tools in Internet that were able to decode these vbe scripts. So, i am looking for an alternative.

My first approach is to write a VC program that does the same as the VB script. I learned about redirecting standard io handles and pipes and finally got two programs. The 'startxp' prog invokes 'testchild' and tries to send a password to the input stream of testchild by using a pipe. All worked perfectly - no errors - but testchild  doesn't get any input from the pipe and i was still able to enter from keyboard.

Any idea what i made wrong?

---------------- startxp.cpp -----------------------
#pragma warning ( disable : 4786 )

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

#include <conio.h>

using namespace std;

#define MAX_LEN_CMD                     512
#define MAX_LEN_PW                      32
                                       
#define DEF_PROC_ATTR_SEC_DESC_NULL     NULL
#define DEF_THRD_ATTR_SEC_DESC_NULL     NULL
#define DEF_ENV_BLOCK_NULL              NULL
#define DEF_CUR_DIR_NULL                NULL
#define INHERIT_HANDLES_FALSE           FALSE
#define INHERIT_HANDLES_TRUE            TRUE

static char         szCmdLine[MAX_LEN_CMD] = { '\0' };

 
int main(int nArgs, char* szArgs[])
{
    if (nArgs < 2)
    {
        cout << endl << "syntax: " << szArgs[0] << " <prog_to_exec> <argument1> ..." << endl;
        return 1;
    }

    string strCmdLine;

    for (int n = 1; n < nArgs; n++)
    {
        strCmdLine += szArgs[n];
        strCmdLine += ' ';
    }

    char szPassword[MAX_LEN_PW];
    cout << "Please Enter Password ==>";
    int           j = 0;
    unsigned char c;

    while (j < MAX_LEN_PW-1 && (c = (unsigned char)getch()) != VK_RETURN )
    {
         szPassword[j++] = c;
         cout << '*';
    }
    szPassword[j] = '\0';

    strCmdLine = /*RUN_AS_KW_TEST_BSHTOP + */ strCmdLine;
    memcpy(szCmdLine, strCmdLine.c_str(), strCmdLine.size());
    szCmdLine[strCmdLine.size()] = '\0';  
   
    SECURITY_ATTRIBUTES sa;
    sa.nLength              = sizeof(sa);
    sa.lpSecurityDescriptor = NULL;
    sa.bInheritHandle       = TRUE;

    HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
    HANDLE hStdErr = GetStdHandle(STD_ERROR_HANDLE);

    HANDLE hReadPipe;
    HANDLE hWritePipe;

    if (!CreatePipe(&hReadPipe, &hWritePipe, &sa, 0))
    {
        cout << "CreatePipe failed " << GetLastError() << endl;
        return 4;
    }

    STARTUPINFO         si;
    memset(&si, 0, sizeof(STARTUPINFO));

    si.cb           = sizeof(STARTUPINFO);
    si.dwFlags      = STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
    si.wShowWindow  = SW_SHOWMINIMIZED;
    si.hStdInput    = hReadPipe;
    si.hStdOutput   = hStdOut;
    si.hStdError    = hStdErr;

    PROCESS_INFORMATION pi;
    memset(&pi, 0, sizeof(PROCESS_INFORMATION));

    if (!CreateProcess(NULL,
                       szCmdLine,
                       DEF_PROC_ATTR_SEC_DESC_NULL,
                       DEF_THRD_ATTR_SEC_DESC_NULL,
                       INHERIT_HANDLES_TRUE,
                       CREATE_NEW_CONSOLE,
                       DEF_ENV_BLOCK_NULL,
                       DEF_CUR_DIR_NULL,
                       &si,
                       &pi)
       )
    {
        return GetLastError();
    }

    Sleep(500);
    strPwd += "\r\n";
    DWORD  lenWritten;
    if (!WriteFile(hWritePipe, strPwd.c_str(), strPwd.length(), &lenWritten, NULL))
    {
        cout << "WritePipe failed " << GetLastError() << endl;
        CloseHandle(hWritePipe);
        return 5;
    }
    CloseHandle(hWritePipe);

    // Wait until child process exits.
    WaitForSingleObject( pi.hProcess, INFINITE );

    CloseHandle(hReadPipe);
    CloseHandle(hWritePipe);

    // Close process and thread handles.
    CloseHandle( pi.hProcess );
    CloseHandle( pi.hThread );

    return 0;
}
-------------------- end startxp.cpp ---------------------------------------

-------------------- begin testchild.cpp -----------------------------------
#pragma warning ( disable : 4786 )

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

#include <conio.h>

using namespace std;

#define MAX_LEN_PW                      32

void main()
{
    char szPassword[MAX_LEN_PW];
    cout << "Please Enter Password ==>";
    int           j = 0;
    unsigned char c;

    while (j < MAX_LEN_PW-1 && (c = (unsigned char)getch()) != VK_RETURN )
    {
        szPassword[j++] = c;
        cout << '*';
    }
    szPassword[j] = '\0';
    ofstream ofs("testchild.out");
    ofs << szPassword;
    ofs.close();
}
-------------------- end testchild.cpp -----------------------------------


Regards, Alex