Appending Strings to lpCmdLine WinMain - c++

Question

Trying to create a loader for an executable, it fails to execute when the length of string supplied in the Parameters is more than some length. But the Parameters are completely read from the initialization file. It also crashes when the Parameters=Null.
typedef int (__cdecl *ExecMain_t)(HINSTANCE, HINSTANCE, LPSTR, int);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
HMODULE Loader = LoadLibraryExA(".\\library.dll", NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
char* Parameters;
CIniFile iniReader(".\\Configure.ini");
Parameters = iniReader.IniReadValue("App", "Parameters");
char xCommand[MAX_PATH] = {0};
_snprintf_s(xCommand, _TRUNCATE, "-verify "); //parameter from exe
strcat_s(xCommand, _TRUNCATE, Parameters);
strcpy_s(lpCmdLine, _TRUNCATE, xCommand);
delete[] Parameters;
Parameters = NULL;
ExecMain_t procExecMain = (ExecMain_t)GetProcAddress(Loader,"ExecMain");
procExecMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
return 1;
}
Crash description:
Problem Event Name: APPCRASH
Application Name: exec.exe
Application Version: 0.0.0.0
Application Timestamp: 530df50a
Fault Module Name: KERNELBASE.dll
Fault Module Version: 6.2.9200.16384
EDIT: Trying to figure out why it crashes when the Parameter string length is increases.
Even crashes if I pass more characters along with "-verify " (passing parameter from exe)
EDIT2: Modified the code by replacing MAX_PATH by _TRUNCATE. Seems to work for some characters in the parameters but when exceeded, crashes.

Answer 1

Here are several problems:
char xCommand[MAX_PATH] = {0};
_snprintf_s(xCommand, _TRUNCATE, "-verify "); //parameter from exe
strcat_s(xCommand, _TRUNCATE, Parameters);
strcpy_s(lpCmdLine, _TRUNCATE, xCommand);
I think you should use strcpy_s instead of _snprintf_s, after all I don't see you printing any format in xCommand.
Then, the second parameter, _TRUNCATE should actually be MAX_PATH since the second parameter of this functions is the number of elements of the destination buffer.
But most important, the third line is completely wrong, because you're trying to write into the input buffer lpCmdLine and that will overwrite the memory beyond the buffer bounds. What you need is to copy the content of the original buffer into your new command buffer. Something like this (notice I wrote this code in the browser so it may contain errors):
char xCommand[MAX_PATH] = {0};
strcpy_s(xCommand, MAX_PATH, lpCmdLine); // copy the original command line
strcat_s(xCommand, MAX_PATH, " -verify "); // append
strcat_s(xCommand, MAX_PATH, Parameters); // append
and then pass this buffer to your ExecMain function:
procExecMain(hInstance, hPrevInstance, xCommand, nCmdShow);