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[FileStream] handle UNC and device paths #54483

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merged 2 commits into from
Jun 23, 2021
Merged

[FileStream] handle UNC and device paths #54483

merged 2 commits into from
Jun 23, 2021

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adamsitnik
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@adamsitnik adamsitnik commented Jun 21, 2021 •
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Fixes #54474
Fixes #54475
Fixes #54337

@adamsitnik adamsitnik added this to the 6.0.0 milestone Jun 21, 2021
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Issue Details

Fixes #54474

Author: adamsitnik
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area-System.IO
Milestone: 6.0.0

@adamsitnik 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
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@adamsitnik adamsitnik mentioned this pull request Jun 21, 2021
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jozkee
jozkee reviewed Jun 22, 2021
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src/libraries/System.Private.CoreLib/src/System/IO/PathInternal.Windows.cs Outdated

// 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)
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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.

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@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

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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.

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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 Outdated Show resolved Hide resolved
src/libraries/Common/tests/Tests/System/IO/PathInternal.Windows.Tests.cs Outdated Show resolved Hide resolved
@adamsitnik adamsitnik mentioned this pull request Jun 22, 2021
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stephentoub
stephentoub approved these changes Jun 22, 2021
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Thanks!

carlossanlop
carlossanlop approved these changes Jun 23, 2021
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LGTM

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs
{
uint ntStatus;
IntPtr fileHandle;
Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = default;
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default isn't really needed, right?

@danmoseley danmoseley mentioned this pull request Jun 23, 2021
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jozkee
jozkee reviewed Jun 23, 2021
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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))
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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 Show resolved Hide resolved
@adamsitnik adamsitnik merged commit 0aafceb into dotnet:main Jun 23, 2021
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/backport to release/6.0-preview6

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

@github-actions github-actions bot mentioned this pull request Jun 23, 2021
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thaystg added a commit to thaystg/runtime that referenced this pull request Jun 23, 2021
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Merge remote-tracking branch 'origin/main' into thays_fix_exception_i…
ae2a17c 
…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)
  ...
@adamsitnik adamsitnik mentioned this pull request Jun 25, 2021
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@adamsitnik adamsitnik mentioned this pull request Jun 25, 2021
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@adamsitnik adamsitnik deleted the issue54474 branch July 2, 2021 11:09
@karelz karelz mentioned this pull request Jul 28, 2021
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@jozkee jozkee jozkee left review comments

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@carlossanlop carlossanlop carlossanlop approved these changes

@stephentoub stephentoub stephentoub approved these changes

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