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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Diagnostics;
using Microsoft.Win32.SafeHandles;
namespace System.IO
{
public partial class FileStream : Stream
{
private SafeFileHandle OpenHandle(FileMode mode, FileShare share, FileOptions options)
{
return CreateFileOpenHandle(mode, share, options);
}
private unsafe SafeFileHandle CreateFileOpenHandle(FileMode mode, FileShare share, FileOptions options)
{
Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = GetSecAttrs(share);
int fAccess =
((_access & FileAccess.Read) == FileAccess.Read ? GENERIC_READ : 0) |
((_access & FileAccess.Write) == FileAccess.Write ? GENERIC_WRITE : 0);
// Our Inheritable bit was stolen from Windows, but should be set in
// the security attributes class. Don't leave this bit set.
share &= ~FileShare.Inheritable;
// Must use a valid Win32 constant here...
if (mode == FileMode.Append)
mode = FileMode.OpenOrCreate;
int flagsAndAttributes = (int)options;
// For mitigating local elevation of privilege attack through named pipes
// make sure we always call CreateFile with SECURITY_ANONYMOUS so that the
// named pipe server can't impersonate a high privileged client security context
// (note that this is the effective default on CreateFile2)
flagsAndAttributes |= (Interop.Kernel32.SecurityOptions.SECURITY_SQOS_PRESENT | Interop.Kernel32.SecurityOptions.SECURITY_ANONYMOUS);
using (DisableMediaInsertionPrompt.Create())
{
return ValidateFileHandle(
Interop.Kernel32.CreateFile(_path, fAccess, share, ref secAttrs, mode, flagsAndAttributes, IntPtr.Zero));
}
}
private static bool GetDefaultIsAsync(SafeFileHandle handle)
{
return handle.IsAsync ?? !IsHandleSynchronous(handle, ignoreInvalid: true) ?? DefaultIsAsync;
}
private static unsafe bool? IsHandleSynchronous(SafeFileHandle fileHandle, bool ignoreInvalid)
{
if (fileHandle.IsInvalid)
return null;
uint fileMode;
int status = Interop.NtDll.NtQueryInformationFile(
FileHandle: fileHandle,
IoStatusBlock: out Interop.NtDll.IO_STATUS_BLOCK ioStatus,
FileInformation: &fileMode,
Length: sizeof(uint),
FileInformationClass: Interop.NtDll.FileModeInformation);
switch (status)
{
case 0:
// We we're successful
break;
case Interop.NtDll.STATUS_INVALID_HANDLE:
if (!ignoreInvalid)
{
throw Win32Marshal.GetExceptionForWin32Error(Interop.Errors.ERROR_INVALID_HANDLE);
}
else
{
return null;
}
default:
// Something else is preventing access
Debug.Fail("Unable to get the file mode information, status was" + status.ToString());
return null;
}
// If either of these two flags are set, the file handle is synchronous (not overlapped)
return (fileMode & (Interop.NtDll.FILE_SYNCHRONOUS_IO_ALERT | Interop.NtDll.FILE_SYNCHRONOUS_IO_NONALERT)) > 0;
}
private static void VerifyHandleIsSync(SafeFileHandle handle, int fileType, FileAccess access)
{
// As we can accurately check the handle type when we have access to NtQueryInformationFile we don't need to skip for
// any particular file handle type.
// If the handle was passed in without an explicit async setting, we already looked it up in GetDefaultIsAsync
if (!handle.IsAsync.HasValue)
return;
// If we can't check the handle, just assume it is ok.
if (!(IsHandleSynchronous(handle, ignoreInvalid: false) ?? true))
throw new ArgumentException(SR.Arg_HandleNotSync, nameof(handle));
}
}
}
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