Patched-Code-(Post-Patch).cpp

Patched Code (Post-Patch)
The fix introduces the FILE_FLAG_OPEN_REPARSE_POINT flag to prevent following malicious directory junctions, and utilizes ImpersonateLoggedOnUser to ensure the operation is bound to the permissions of the user requesting the scan, rather than NT AUTHORITY\SYSTEM.

// SECURE: Prevents symlink abuse and impersonates the requesting user.

// 1. Impersonate the user who triggered the Defender action
if (ImpersonateLoggedOnUser(hUserToken)) {
    
    // 2. Open the file strictly WITHOUT following reparse points/junctions
    HANDLE hFile = CreateFile(
        userProvidedPath, 
        GENERIC_WRITE, 
        0, 
        NULL, 
        CREATE_ALWAYS, 
        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OPEN_REPARSE_POINT, // Fails if it's a symlink
        NULL
    );

    if (hFile != INVALID_HANDLE_VALUE) {
        // 3. Verify the file isn't a malicious link before writing
        DWORD fileAttributes = GetFileAttributes(userProvidedPath);
        if (!(fileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)) {
            WriteDataToFile(hFile, data);
        }
        CloseHandle(hFile);
    }
    
    // 4. Revert back to SYSTEM privileges after the risky operation is done
    RevertToSelf();
} else {
    // Handle impersonation failure securely
    LogSecurityEvent("Failed to impersonate user during file operation.");
}