Question

I am working on an application that will trigger a UAC prompt in whatever program is opened by ShellExecute.

I can’t figure out how to hard-code a path for the ShellExecute to run. As of now this program uses whatever path is in arg[0]. How can I build a string to put in the place of arg[0] on the line sinfo.lpFile = arg[0];?

I am very new so if you can’t see why making a string to put in that line will solve my problem then you are most likely right.

#include "stdafx.h"

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <shellapi.h>
#include <process.h>

#include "uac-example.h"

int WINAPI WinMain(HINSTANCE inst, HINSTANCE prevInst,LPSTR cmdLine, int nCmdShow){
    LPWSTR *arg;
    int argc = 0;
    HRESULT ret = SUCCESS;
    WCHAR imagePath[MAXPATHLEN];
    WCHAR workingDir[MAXPATHLEN];
    WCHAR uacDir[MAXPATHLEN];
    WCHAR uacRunningLockFilePath[MAXPATHLEN];
    HANDLE uacRunningLockFileHandle = INVALID_HANDLE_VALUE;
    WCHAR elevatedLockFilePath[MAXPATHLEN];
    HANDLE elevatedLockFileHandle = INVALID_HANDLE_VALUE;
    arg = CommandLineToArgvW(GetCommandLineW(),&argc);
    //if(arg == NULL || argc < 2) {
    //  ERRORBOX("Missing required program arguments.\n\nUsage:\nuac-example.exe <working directory>");
    //  return FAILURE;
    //}
    GetModuleFileName(NULL, imagePath, MAXPATHLEN);
    arg[0] = imagePath;
    wcscpy_s((wchar_t *)uacDir, MAXPATHLEN, arg[1]);
    _snwprintf_s(uacRunningLockFilePath, MAXPATHLEN, MAXPATHLEN,
                    _T("%s/") _T(RUNNING_LOCK_FILE), uacDir);
    wcscpy_s(workingDir, MAXPATHLEN, imagePath);
    WCHAR *slash = wcsrchr(workingDir, '\\');
    wcscpy_s(slash, MAXPATHLEN, _T(""));
    _snwprintf_s(elevatedLockFilePath, MAXPATHLEN, MAXPATHLEN,_T("%s/") _T(ELEVATE_LOCK_FILE), workingDir);
    uacRunningLockFileHandle = CreateFileW(uacRunningLockFilePath,(GENERIC_READ | GENERIC_WRITE),0,NULL,OPEN_ALWAYS,FILE_FLAG_DELETE  _ON_CLOSE,NULL);
    if (uacRunningLockFileHandle == INVALID_HANDLE_VALUE) {
        if (_waccess(elevatedLockFilePath, F_OK) == 0 &&
                _wremove(elevatedLockFilePath) != 0) {
            return FAILURE;
        }
        elevatedLockFileHandle = CreateFileW(elevatedLockFilePath,(GENERIC_READ | GENERIC_WRITE),0,NULL,OPEN_ALWAYS,FILE_FLAG_DELETE  _ON_CLOSE,NULL);
        if(elevatedLockFileHandle == INVALID_HANDLE_VALUE){
            ERRORBOX("Unable to acquire the necessary permissions to run demo app.");
            return FAILURE;
        }
        LPWSTR spawnCmdLine = BuildCommandLine(argc - 1, arg + 1);
        if(!spawnCmdLine){
            CloseHandle(elevatedLockFileHandle);
            ERRORBOX("An error occured while respawning self.");
            return FAILURE;
        }
        SHELLEXECUTEINFO sinfo;
        memset(&sinfo, 0, sizeof(SHELLEXECUTEINFO));
        sinfo.cbSize = sizeof(SHELLEXECUTEINFO);
        sinfo.fMask = SEE_MASK_FLAG_DDEWAIT | SEE_MASK_NOCLOSEPROCESS;
        sinfo.hwnd = NULL;
        sinfo.lpFile = arg[0];
        sinfo.lpParameters = spawnCmdLine;
        sinfo.lpVerb = L"runas"; // <<-- this is what makes a UAC prompt show up
        sinfo.nShow = SW_SHOWMAXIMIZED;
        BOOL result = ShellExecuteEx(&sinfo);
        LocalFree(spawnCmdLine);
        if(result){
            WaitForSingleObject(sinfo.hProcess, INFINITE);
            CloseHandle(sinfo.hProcess);
            return SUCCESS;
        }else{
            return FAILURE;
        }
    }
    EXIT_IF_ELEVATED(elevatedLockFilePath,uacRunningLo  ckFileHandle,SUCCESS);
    LocalFree(arg);
    return SUCCESS;
}

// ----------------------------------------------------------------------
// The following code was taken directly from the Mozilla Firefox Updater
// source tree, and slightly modified to support "Wide" strings in
// Visual C++.
// ----------------------------------------------------------------------

LPWSTR
BuildCommandLine(int argc, LPWSTR *argv){
    int i;
    int len = 0;
    // The + 1 of the last argument handles the
    // allocation for null termination
    for (i = 0; i < argc; ++i) {
        len += ArgStrLen(argv[i]) + 1;
    }
    // Protect against callers that pass 0 arguments
    if (len == 0) {
        len = 1;
    }
    LPWSTR s = (LPWSTR)malloc(len * sizeof(LPWSTR));
    if (!s) {
        return NULL;
    }
    LPWSTR c = s;
    for (i = 0; i < argc; ++i) {
        c = ArgToString(c, argv[i]);
        if (i + 1 != argc) {
            *c = ' ';
            ++c;
        }
    }
    *c = '\0';
    return s;
}
int
ArgStrLen(LPWSTR s) {
  int backslashes = 0;
  int i = wcslen(s);
  BOOL hasDoubleQuote = wcschr(s, L'"') != NULL;
  // Only add doublequotes if the string contains a space or a tab
  BOOL addDoubleQuotes = wcspbrk(s, L" \t") != NULL;
  if (addDoubleQuotes) {
    i += 2; // initial and final duoblequote
  }
  if (hasDoubleQuote) {
    while (*s) {
      if (*s == '\\') {
        ++backslashes;
      } else {
        if (*s == '"') {
          // Escape the doublequote and all backslashes preceding the doublequote
          i += backslashes + 1;
        }
        backslashes = 0;
      }

      ++s;
    }
  }

  return i;
}
LPWSTR
ArgToString(LPWSTR d, LPWSTR s) {
  int backslashes = 0;
  BOOL hasDoubleQuote = wcschr(s, L'"') != NULL;
  // Only add doublequotes if the string contains a space or a tab
  BOOL addDoubleQuotes = wcspbrk(s, L" \t") != NULL;
  if (addDoubleQuotes) {
    *d = '"'; // initial doublequote
    ++d;
  }
  if (hasDoubleQuote) {
    int i;
    while (*s) {
      if (*s == '\\') {
        ++backslashes;
      } else {
        if (*s == '"') {
        // Escape the doublequote and all backslashes\
        // preceding the doublequote
          for (i = 0; i <= backslashes; ++i) {
            *d = '\\';
            ++d;
          }
        }
        backslashes = 0;
      }
      *d = *s;
      ++d; ++s;
    }
  } else {
    wcscpy(d, s);
    d += wcslen(s);
  }
  if (addDoubleQuotes) {
    *d = '"'; // final doublequote
    ++d;
  }
  return d;
}

Answer 1

Simply as:

char path[] = "C:\\program.exe";
sinfo.lpFile = path;