1 files changed, 77 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/IO/FileStream.Win32.cs b/src/mscorlib/shared/System/IO/FileStream.Win32.cs
new file mode 100644
index 0000000000..0045ebeaf8
--- /dev/null
+++ b/src/mscorlib/shared/System/IO/FileStream.Win32.cs
@@ -0,0 +1,77 @@
+// 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.Buffers;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.CompilerServices;
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        private SafeFileHandle OpenHandle(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
+            flagsAndAttributes |= (Interop.Kernel32.SecurityOptions.SECURITY_SQOS_PRESENT | Interop.Kernel32.SecurityOptions.SECURITY_ANONYMOUS);
+
+            // Don't pop up a dialog for reading from an empty floppy drive
+            uint oldMode = Interop.Kernel32.SetErrorMode(Interop.Kernel32.SEM_FAILCRITICALERRORS);
+            try
+            {
+                SafeFileHandle fileHandle = Interop.Kernel32.CreateFile(_path, fAccess, share, ref secAttrs, mode, flagsAndAttributes, IntPtr.Zero);
+                fileHandle.IsAsync = _useAsyncIO;
+
+                if (fileHandle.IsInvalid)
+                {
+                    // Return a meaningful exception with the full path.
+
+                    // NT5 oddity - when trying to open "C:\" as a Win32FileStream,
+                    // we usually get ERROR_PATH_NOT_FOUND from the OS.  We should
+                    // probably be consistent w/ every other directory.
+                    int errorCode = Marshal.GetLastWin32Error();
+
+                    if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && _path.Length == PathInternal.GetRootLength(_path))
+                        errorCode = Interop.Errors.ERROR_ACCESS_DENIED;
+
+                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                }
+                
+                int fileType = Interop.Kernel32.GetFileType(fileHandle);
+                if (fileType != Interop.Kernel32.FileTypes.FILE_TYPE_DISK)
+                {
+                    fileHandle.Dispose();
+                    throw new NotSupportedException(SR.NotSupported_FileStreamOnNonFiles);
+                }
+
+                return fileHandle;
+            }
+            finally
+            {
+                Interop.Kernel32.SetErrorMode(oldMode);
+            }
+        }
+    }
+}