Anyone know why this POST with WinHttp is failing

Question

I am trying to send a POST request to a PHP script. I have got GET to work but am having some issues with POST. The result is always blank when it should show the value of the post parameter.

#include <windows.h>
#include <wininet.h>

#pragma comment(lib, "Crypt32.lib")
#pragma comment(lib, "wininet.lib")

void PrintError(char *szFunc)
{
char szErr[128];
wsprintf(szErr, "%s: %d\n", szFunc, GetLastError());
OutputDebugString(szErr);
}

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{   
BOOL bCookie;
DWORD dwFlags;
DWORD dwReadSize;
DWORD dwBuffLen = sizeof(dwFlags);
HINTERNET hInternet, hSession, hRequest;  
char szBuffer[256 * 1024] = ""; 
SIZE_T nBufferSize = 0; 

hInternet = InternetOpen("Mozilla/5.0 (Windows NT 6.1; WOW64; rv:23.0) Gecko/20100101 Firefox/23.0", INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0);
if(hInternet == NULL)
{
    PrintError("InternetOpen");
    return 0;

}

hSession = InternetConnect(hInternet, "localhost", 443, NULL, NULL, INTERNET_SERVICE_HTTP, 0, NULL);
if(hSession == NULL)
{
    PrintError("InternetConnet");
    return 0;
}

hRequest = HttpOpenRequest(hSession, "GET", "/index.php", "HTTP/1.1", NULL, NULL, INTERNET_FLAG_SECURE|INTERNET_FLAG_RELOAD|INTERNET_FLAG_NO_CACHE_WRITE|INTERNET_FLAG_NO_COOKIES, NULL);
if(hRequest == NULL)
{   
    PrintError("HttpOpenRequest");
    return 0;
}

// Need to do this to support self signed SSL certificates          
InternetQueryOption(hRequest, INTERNET_OPTION_SECURITY_FLAGS, (LPVOID)&dwFlags, &dwBuffLen);
dwFlags = INTERNET_FLAG_IGNORE_CERT_CN_INVALID|SECURITY_FLAG_IGNORE_UNKNOWN_CA;
InternetSetOption (hRequest, INTERNET_OPTION_SECURITY_FLAGS, &dwFlags, sizeof(dwFlags));    

// Set cookie data
if(!HttpAddRequestHeaders(hRequest, "Cookie: my_cookie=chocolate_chip\r\n", -1L, HTTP_ADDREQ_FLAG_ADD))
{                   
    PrintError("HttpAddRequestHeaders"); 
    return 0;
}   

if(!HttpSendRequest(hRequest, NULL, 0, NULL, 0))
{   
    PrintError("HttpSendRequest"); 
    return 0;
}

for(;;)
{
    dwReadSize = 0;
    InternetReadFile(hRequest, szBuffer + nBufferSize, sizeof(szBuffer) - nBufferSize - 1, &dwReadSize);
    if(!dwReadSize)
    {
        break;
    }                       
    szBuffer[nBufferSize + dwReadSize] = 0;                       
    nBufferSize += dwReadSize;
}

if(strstr(szBuffer, "chocolate_chip"))
{
    bCookie = true;
    OutputDebugString("Cookie Is Working...\n");            
}

hRequest = HttpOpenRequest(hSession, "POST", "/index.php", "HTTP/1.1", NULL, NULL, INTERNET_FLAG_SECURE|INTERNET_FLAG_RELOAD|INTERNET_FLAG_NO_CACHE_WRITE|INTERNET_FLAG_NO_COOKIES, NULL);
if(hRequest == NULL)
{   
    PrintError("HttpOpenRequest");
    return 0;
}

// Need to do this to support self signed SSL certificates          
InternetQueryOption(hRequest, INTERNET_OPTION_SECURITY_FLAGS, (LPVOID)&dwFlags, &dwBuffLen);
dwFlags = INTERNET_FLAG_IGNORE_CERT_CN_INVALID|SECURITY_FLAG_IGNORE_UNKNOWN_CA;
InternetSetOption (hRequest, INTERNET_OPTION_SECURITY_FLAGS, &dwFlags, sizeof(dwFlags));    

// Should be at the top, just for debug..
char *szPostData = "my_post=HelloWorld!";   
if(!HttpSendRequest(hRequest, "Content-Type: application/x-www-form-urlencoded", -1, (LPVOID)szPostData, sizeof(szPostData)))
{
    PrintError("HttpOpenRequest");
    return 0;
}   

// Clear the buffer from before
memset(szBuffer, 0, sizeof(szBuffer));

// Maybe there is a better way to read data?
for(;;)
{
    dwReadSize = 0;
    InternetReadFile(hRequest, szBuffer + nBufferSize, sizeof(szBuffer) - nBufferSize - 1, &dwReadSize);
    if(!dwReadSize)
    {
        break;
    }                       
    szBuffer[nBufferSize + dwReadSize] = 0;                       
    nBufferSize += dwReadSize;
}

MessageBox(0, szBuffer, 0, 0); // Always empty for post 

InternetCloseHandle(hRequest);
InternetCloseHandle(hSession);
InternetCloseHandle(hInternet);
return 0;
}

The PHP code i am using just so you can see what i am trying to do here.

<?php   

if(isset($_COOKIE['my_cookie']))
{
    echo $_COOKIE['my_cookie'];
}

if(isset($_POST['my_post']))
{           
        echo $_POST['my_post'];         
}   

?>

Been at this for a few hours. Anyone know whats up?

Answer 1

char *szPostData = "my_post=HelloWorld!";   
if(!HttpSendRequest(hRequest, "Content-Type: application/x-www-form-urlencoded", -1, (LPVOID)szPostData, sizeof(szPostData)))

sizeof(szPostData) doesn't do what you think it does. It calculates the size in bytes of a char* pointer, not the data it points to.