From 452213c833008bec139f571c238aad5857c70550 Mon Sep 17 00:00:00 2001
From: Steve Lee <slee@microsoft.com>
Date: Tue, 2 Apr 2024 09:42:40 -0700
Subject: [PATCH] Fix `Test-Path -IsValid` to check for invalid path and
 filename characters (#21358)

---
 .../namespaces/FileSystemProvider.cs          | 15 +++++++
 .../Test-Path.Tests.ps1                       | 42 +++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/src/System.Management.Automation/namespaces/FileSystemProvider.cs b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
index 9337b466805..372e106ce61 100644
--- a/src/System.Management.Automation/namespaces/FileSystemProvider.cs
+++ b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
@@ -1080,6 +1080,21 @@ protected override bool IsValidPath(string path)
                 }
             }
 
+            // .NET introduced a change where invalid characters are accepted https://learn.microsoft.com/en-us/dotnet/core/compatibility/2.1#path-apis-dont-throw-an-exception-for-invalid-characters
+            // We need to check for invalid characters ourselves.  `Path.GetInvalidFileNameChars()` is a supserset of `Path.GetInvalidPathChars()`
+
+            // Remove drive root first
+            string pathWithoutDriveRoot = path.Substring(Path.GetPathRoot(path).Length);
+            char[] invalidFileChars = Path.GetInvalidFileNameChars();
+
+            foreach (string segment in pathWithoutDriveRoot.Split(Path.DirectorySeparatorChar))
+            {
+                if (segment.IndexOfAny(invalidFileChars) != -1)
+                {
+                    return false;
+                }
+            }
+
             return true;
         }
 
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Management/Test-Path.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Management/Test-Path.Tests.ps1
index edad763fe71..a2619877f6d 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Management/Test-Path.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Management/Test-Path.Tests.ps1
@@ -110,6 +110,48 @@ Describe "Test-Path" -Tags "CI" {
         Test-Path -Path $badPath -IsValid | Should -BeFalse
     }
 
+    It 'Windows paths should be valid: <path>' -skip:(!$IsWindows) -TestCases @(
+        @{ path = "C:\Program Files" }
+        @{ path = "C:\Program Files (x86)\" }
+        @{ path = "filesystem::z:\foo" }
+        @{ path = "filesystem::z:\foo\" }
+        @{ path = "variable::psversiontable" }
+        @{ path = "c:\windows\cmd.exe:test" }
+    ) {
+        param($path)
+        Test-Path -Path $path -IsValid | Should -BeTrue
+    }
+
+    It 'Windows paths should be inavlid: <variant>' -Skip:(!$IsWindows) -TestCases @(
+        @{ variant = "wildcard"; path = "C:\Program Files\foo*" }
+        @{ variant = "pipe symbol"; path = "C:\Program Files|p\foo" }
+        @{ variant = "null char"; path = "C:\Win`u{0000}dows\System32" }
+    ) {
+        param($path)
+        Test-Path -Path $path -IsValid | Should -BeFalse
+    }
+
+    It 'Unix paths should be valid: <path>' -Skip:($IsWindows) -TestCases @(
+        @{ path = "/usr/bin" }
+        @{ path = "/usr/bin/" }
+        @{ path = "filesystem::/usr/bin" }
+        @{ path = "filesystem::/usr/bin/" }
+        @{ path = "variable::psversiontable" }
+        @{ path = "/usr/bi*n/test" }
+        @{ path = "/usr/bin/tes*t" }
+    ) {
+        param($path)
+        Test-Path -Path $path -IsValid | Should -BeTrue
+    }
+
+    It 'Unix paths should be invalid: <variant>' -Skip:($IsWindows) -TestCases @(
+        @{ variant = "null in path"; path = "/usr/bi`u{0000}n/test" }
+        @{ variant = "null in filename"; path = "/usr/bin/t`u{0000}est" }
+    ) {
+        param($path)
+        Test-Path -Path $path -IsValid | Should -BeFalse
+    }
+
     It "Should return true on paths containing spaces when the path is surrounded in quotes" {
         Test-Path -Path "/totally a valid/path" -IsValid | Should -BeTrue
     }