[FileStream] handle UNC and device paths #54483

adamsitnik · 2021-06-21T12:13:53Z

ghost · 2021-06-21T12:13:57Z

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Issue Details

Author:	adamsitnik
Assignees:	-
Labels:	`area-System.IO`
Milestone:	6.0.0

src/libraries/System.Private.CoreLib/src/System/IO/PathInternal.Windows.cs

jozkee · 2021-06-22T06:01:37Z

src/libraries/System.Private.CoreLib/src/System/IO/PathInternal.Windows.cs

+
+        // this method works only for `fullPath` returned by Path.GetFullPath
+        // currently we don't have interest in supporting relative paths
+        internal static void DosToNtPath(ReadOnlySpan<char> fullPath, ref ValueStringBuilder vsb)


I assume for the opposite, translate NT to DOS, a helper like this should be needed, right?
For context #54253 (comment) , a Symlinks API uses DeviceIoControl which returns an NT path that I need to translate to DOS.

This is my silly attempt on doing it:
https://github.com/dotnet/runtime/blob/908530a70613af1172138e48d041d6c5d710d866/src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Windows.cs#L513-L518
Also, I think I mixed the names (DOS and NT) in the comments.

@jozkee You could use RtlNtPathNameToDosPathName, but the problem is that it's internal and not documented, so we should not be using that.

The mapping that you have pointed to seems to be missing a few translations:

\??\UNC\ to \\ (files located on a remote machine)

\??\ to \\.\ for devices like names pipes: \\.\pipe\$pipeName

But the question is: are they valid in this context? Can someone create a link to a named pipe or a file located on a network share?

FWIW the best doc about the paths I've found so far: https://googleprojectzero.blogspot.com/2016/02/the-definitive-guide-on-win32-to-nt.html

Symbolic links to files on network shares are possible; fsutil behavior set symlinkevaluation can enable or disable them. I don't know about symbolic links to named pipes.

The mapping that you have pointed to seems to be missing a few translations:

The first example you pointed should still work, as far as I know: Converting \??\UNC\ to \\?\UNC, should be equivalent. The difference is that you do not want to pass a path prefixed with \??\ to the user, and should always translate it to \\?\.

Regarding the second example: Have you seen cases where Windows gives you a path prefixed with \??\ but you were expecting it to start with \\.\? And how would you know this?

src/libraries/System.Private.CoreLib/src/System/IO/PathInternal.Windows.cs

src/libraries/Common/tests/Tests/System/IO/PathInternal.Windows.Tests.cs

…ping DOS to NT paths

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs

stephentoub

Thanks!

carlossanlop

LGTM

carlossanlop · 2021-06-23T03:00:05Z

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs

        {
-            uint ntStatus;
-            IntPtr fileHandle;
+            Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = default;


default isn't really needed, right?

jozkee · 2021-06-23T03:34:58Z

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs

+                // probably be consistent w/ every other directory.
+                int errorCode = Marshal.GetLastPInvokeError();
+
+                if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && fullPath!.Length == PathInternal.GetRootLength(fullPath))


Suggested change

if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && fullPath!.Length == PathInternal.GetRootLength(fullPath))

if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && fullPath.Length == PathInternal.GetRootLength(fullPath))

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs

adamsitnik · 2021-06-23T07:19:57Z

/backport to release/6.0-preview6

github-actions · 2021-06-23T07:20:10Z

Started backporting to release/6.0-preview6: https://github.com/dotnet/runtime/actions/runs/963422709

…nitial_config * origin/main: (362 commits) [wasm][debugger] Reuse debugger-agent on wasm debugger (dotnet#52300) Put Crossgen2 in sync with dotnet#54235 (dotnet#54438) Move System.Object serialization to ObjectConverter (dotnet#54436) Move setting fHasVirtualStaticMethods out of sanity check section (dotnet#54574) [wasm] Compile .bc->.o in parallel, before passing to the linker (dotnet#54053) Change PathInternal.IsCaseSensitive to a constant (dotnet#54340) Make mono_polling_required a public symbol (dotnet#54592) Respect EventSource::IsSupported setting in more codepaths (dotnet#51977) Root ComActivator for hosting (dotnet#54524) Add ILLink annotations to S.D.Common related to DbConnectionStringBuilder (dotnet#54280) Fix finalizer issue with regions (dotnet#54550) Add support for multi-arch install locations (dotnet#53763) Update library testing docs page to reduce confusion (dotnet#54324) [FileStream] handle UNC and device paths (dotnet#54483) Update NetAnalyzers version (dotnet#54511) Added runtime dependency to fix the intermittent test failures (dotnet#54587) Disable failing System.Reflection.Tests.ModuleTests.GetMethods (dotnet#54564) [wasm] Move AOT builds from `runtime-staging` to `runtime` (dotnet#54577) Keep obj node for ArrayIndex. (dotnet#54584) Disable another failing MemoryCache test (dotnet#54578) ...

handle UNC and device paths

48e8e5f

adamsitnik added the area-System.IO label Jun 21, 2021

adamsitnik added this to the 6.0.0 milestone Jun 21, 2021

adamsitnik requested review from carlossanlop, stephentoub and jozkee June 21, 2021 12:13

adamsitnik linked an issue Jun 21, 2021 that may be closed by this pull request

A System.NullReferenceException was throwing when get a **gif** image using Image.FromFile() method #54475

Closed

adamsitnik mentioned this pull request Jun 21, 2021

A System.NullReferenceException was throwing when get a **gif** image using Image.FromFile() method #54475

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stephentoub reviewed Jun 21, 2021

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src/libraries/System.Private.CoreLib/src/System/IO/PathInternal.Windows.cs Outdated Show resolved Hide resolved

jozkee reviewed Jun 22, 2021

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stop using NtCreateFile as there is no public and reliable way of map…

c763c89

…ping DOS to NT paths

adamsitnik mentioned this pull request Jun 22, 2021

[FileStream] add tests for device and UNC paths #54545

Merged

adamsitnik requested review from jozkee and stephentoub June 22, 2021 14:41

stephentoub reviewed Jun 22, 2021

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src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs Show resolved Hide resolved

stephentoub reviewed Jun 22, 2021

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src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs Show resolved Hide resolved

stephentoub approved these changes Jun 22, 2021

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carlossanlop approved these changes Jun 23, 2021

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danmoseley mentioned this pull request Jun 23, 2021

Sporadic failure in file enumeration tests on Unix #54589

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jozkee reviewed Jun 23, 2021

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adamsitnik merged commit 0aafceb into dotnet:main Jun 23, 2021

github-actions bot mentioned this pull request Jun 23, 2021

[release/6.0-preview6] [FileStream] handle UNC and device paths #54595

Merged

adamsitnik mentioned this pull request Jun 25, 2021

Throws an exception when opening an existing file #54474

Closed

adamsitnik mentioned this pull request Jun 25, 2021

Add symbolic link APIs #54253

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adamsitnik deleted the issue54474 branch July 2, 2021 11:09

karelz mentioned this pull request Jul 28, 2021

[WinHttpHandler] Long running test: ResponseHeadersRead_SynchronizationContextNotUsedByHandler on Win7/Win8 #54034

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[FileStream] handle UNC and device paths #54483

[FileStream] handle UNC and device paths #54483

adamsitnik commented Jun 21, 2021 •

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ghost commented Jun 21, 2021

jozkee Jun 22, 2021

adamsitnik Jun 22, 2021

KalleOlaviNiemitalo Jun 22, 2021

carlossanlop Jun 23, 2021

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carlossanlop Jun 23, 2021

jozkee Jun 23, 2021

adamsitnik commented Jun 23, 2021

github-actions bot commented Jun 23, 2021

	if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && fullPath!.Length == PathInternal.GetRootLength(fullPath))
	if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && fullPath.Length == PathInternal.GetRootLength(fullPath))

[FileStream] handle UNC and device paths #54483

[FileStream] handle UNC and device paths #54483

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adamsitnik commented Jun 21, 2021 •

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