From d0e823797f1bbac8c256a4f607bc97812ca0fdb6 Mon Sep 17 00:00:00 2001
From: Steve Lee <slee@microsoft.com>
Date: Tue, 12 Oct 2021 14:16:32 -0700
Subject: [PATCH] Don't allow `Move-Item` with FileSystemProvider to move a
 directory into itself (#16198)

---
 .../namespaces/FileSystemProvider.cs               |  9 +++++++++
 .../resources/FileSystemProviderStrings.resx       |  3 +++
 .../FileSystem.Tests.ps1                           | 14 ++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/src/System.Management.Automation/namespaces/FileSystemProvider.cs b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
index 7e6d302b22..37229a18db 100644
--- a/src/System.Management.Automation/namespaces/FileSystemProvider.cs
+++ b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
@@ -5851,6 +5851,15 @@ namespace Microsoft.PowerShell.Commands
                         destination = MakePath(destination, dir.Name);
                     }
 
+                    // Don't allow moving a directory into itself
+                    if (destination.StartsWith(Path.TrimEndingDirectorySeparator(path) + Path.DirectorySeparatorChar))
+                    {
+                        string error = StringUtil.Format(FileSystemProviderStrings.TargetCannotBeSubdirectoryOfSource, destination);
+                        var e = new IOException(error);
+                        WriteError(new ErrorRecord(e, "MoveItemArgumentError", ErrorCategory.InvalidArgument, destination));
+                        return;
+                    }
+
                     // Get the confirmation text
                     string action = FileSystemProviderStrings.MoveItemActionDirectory;
 
diff --git a/src/System.Management.Automation/resources/FileSystemProviderStrings.resx b/src/System.Management.Automation/resources/FileSystemProviderStrings.resx
index 1b4d1159e5..9c232ae836 100644
--- a/src/System.Management.Automation/resources/FileSystemProviderStrings.resx
+++ b/src/System.Management.Automation/resources/FileSystemProviderStrings.resx
@@ -345,4 +345,7 @@
   <data name="AlreadyListedDirectory" xml:space="preserve">
     <value>Skip already-visited directory {0}.</value>
   </data>
+  <data name="TargetCannotBeSubdirectoryOfSource" xml:space="preserve">
+    <value>Destination path cannot be a subdirectory of the source: {0}.</value>
+  </data>
 </root>
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1
index 10ec92b6be..bec4ad83b8 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1
@@ -187,6 +187,20 @@ Describe "Basic FileSystem Provider Tests" -Tags "CI" {
             $e.Exception | Should -BeOfType System.IO.IOException
         }
 
+        It 'Verify Move-Item fails for destination that is subdir of source with trailing: <trailingChar>' -TestCases @(
+            @{ trailingChar = [System.IO.Path]::DirectorySeparatorChar }
+            @{ trailingChar = [System.IO.Path]::AltDirectorySeparatorChar }
+            @{ trailingChar = '' }
+        ) {
+            param($trailingChar)
+
+            $dest = Join-Path -Path $TestDrive -ChildPath dest
+            $null = New-item -ItemType Directory -Path $dest -Force -ErrorAction Stop
+            $src = "$TestDrive$trailingChar"
+
+            { Move-Item -Path $src -Destination $dest -ErrorAction Stop } | Should -Throw -ErrorId 'MoveItemArgumentError,Microsoft.PowerShell.Commands.MoveItemCommand'
+        }
+
         It "Verify Move-Item throws correct error for non-existent source" {
             { Move-Item -Path /does/not/exist -Destination $testFile -ErrorAction Stop } | Should -Throw -ErrorId 'PathNotFound,Microsoft.PowerShell.Commands.MoveItemCommand'
         }