From 91bf34679c85e4417318573440bf5450ce193fa9 Mon Sep 17 00:00:00 2001
From: Ilya <darpa@yandex.ru>
Date: Thu, 3 Oct 2019 19:41:18 +0500
Subject: [PATCH] Read special reparse points without accessing it (#10662)

* Enhance enum FileDesiredAccess with zero value GenericZero
* Use the GenericZero as desired access mode to read reparse point without access it

From docs:
If desired access is zero, the application can query certain metadata such as file, directory, or device attributes without accessing that file or device, even if GENERIC_READ access would have been denied
---
 .../namespaces/FileSystemProvider.cs                | 13 +++++++++++--
 .../Get-Item.Tests.ps1                              |  9 +++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/System.Management.Automation/namespaces/FileSystemProvider.cs b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
index f731a32273..88f2eb51ec 100644
--- a/src/System.Management.Automation/namespaces/FileSystemProvider.cs
+++ b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
@@ -7712,6 +7712,7 @@ namespace Microsoft.PowerShell.Commands
         // dwDesiredAccess of CreateFile
         internal enum FileDesiredAccess : uint
         {
+            GenericZero = 0,
             GenericRead = 0x80000000,
             GenericWrite = 0x40000000,
             GenericExecute = 0x20000000,
@@ -7917,7 +7918,11 @@ namespace Microsoft.PowerShell.Commands
             if (instance.BaseObject is FileSystemInfo fileSysInfo)
             {
 #if !UNIX
-                using (SafeFileHandle handle = OpenReparsePoint(fileSysInfo.FullName, FileDesiredAccess.GenericRead))
+                // We set accessMode parameter to zero because documentation says:
+                // If this parameter is zero, the application can query certain metadata
+                // such as file, directory, or device attributes without accessing
+                // that file or device, even if GENERIC_READ access would have been denied.
+                using (SafeFileHandle handle = OpenReparsePoint(fileSysInfo.FullName, FileDesiredAccess.GenericZero))
                 {
                     string linkTarget = WinInternalGetTarget(handle);
 
@@ -7982,7 +7987,11 @@ namespace Microsoft.PowerShell.Commands
                 throw new PlatformNotSupportedException();
             }
 
-            using (SafeFileHandle handle = OpenReparsePoint(filePath, FileDesiredAccess.GenericRead))
+            // We set accessMode parameter to zero because documentation says:
+            // If this parameter is zero, the application can query certain metadata
+            // such as file, directory, or device attributes without accessing
+            // that file or device, even if GENERIC_READ access would have been denied.
+            using (SafeFileHandle handle = OpenReparsePoint(filePath, FileDesiredAccess.GenericZero))
             {
                 int outBufferSize = Marshal.SizeOf<REPARSE_DATA_BUFFER_SYMBOLICLINK>();
 
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Management/Get-Item.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Management/Get-Item.Tests.ps1
index d1e37919d8..c9be5e10f8 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Management/Get-Item.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Management/Get-Item.Tests.ps1
@@ -52,6 +52,15 @@ Describe "Get-Item" -Tags "CI" {
         ${result}.FullName | Should -BeExactly ${item}.FullName
     }
 
+    It "Should get properties for special reparse points" -skip:$skipNotWindows {
+        $result = Get-Item -Path $HOME/Cookies -Force
+        $result.LinkType | Should -BeExactly "Junction"
+        $result.Target | Should -Not -BeNullOrEmpty
+        $result.Name | Should -BeExactly "Cookies"
+        $result.Mode | Should -BeExactly "l--hs"
+        $result.Exists | Should -BeTrue
+    }
+
     Context "Test for Include, Exclude, and Filter" {
         BeforeAll {
             ${testBaseDir} = "${TESTDRIVE}/IncludeExclude"