Guard against null or blank path components when adding to module p…

…ath (#19922)
PowerShell · Jul 31, 2023 · 3710671 · 3710671
1 parent 2c6777b
commit 3710671
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Showing 3 changed files with 39 additions and 14 deletions.
diff --git a/src/System.Management.Automation/engine/Modules/ModuleIntrinsics.cs b/src/System.Management.Automation/engine/Modules/ModuleIntrinsics.cs
@@ -967,7 +967,7 @@ internal static string GetPersonalModulePath()
 #if UNIX
             return Platform.SelectProductNameForDirectory(Platform.XDG_Type.USER_MODULES);
 #else
-            string myDocumentsPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
+            string myDocumentsPath = InternalTestHooks.SetMyDocumentsSpecialFolderToBlank ? string.Empty : Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
             return string.IsNullOrEmpty(myDocumentsPath) ? null : Path.Combine(myDocumentsPath, Utils.ModuleDirectory);
 #endif
         }
@@ -1259,26 +1259,30 @@ public static string GetModulePath(string currentProcessModulePath, string hklmM
                 // personalModulePath
                 // sharedModulePath
                 // systemModulePath
-                currentProcessModulePath = AddToPath(currentProcessModulePath, personalModulePathToUse, 0);
-                int insertIndex = currentProcessModulePath.IndexOf(Path.PathSeparator, PathContainsSubstring(currentProcessModulePath, personalModulePathToUse));
-                if (insertIndex != -1)
-                {
-                    // advance past the path separator
-                    insertIndex++;
-                }
 
-                currentProcessModulePath = AddToPath(currentProcessModulePath, sharedModulePath, insertIndex);
-                insertIndex = currentProcessModulePath.IndexOf(Path.PathSeparator, PathContainsSubstring(currentProcessModulePath, sharedModulePath));
+                int insertIndex = 0;
+
+                currentProcessModulePath = UpdatePath(currentProcessModulePath, personalModulePathToUse, ref insertIndex);
+                currentProcessModulePath = UpdatePath(currentProcessModulePath, sharedModulePath, ref insertIndex);
+                currentProcessModulePath = UpdatePath(currentProcessModulePath, systemModulePathToUse, ref insertIndex);
+            }
+
+            return currentProcessModulePath;
+        }
+
+        private static string UpdatePath(string path, string pathToAdd, ref int insertIndex)
+        {
+            if (!string.IsNullOrEmpty(pathToAdd))
+            {
+                path = AddToPath(path, pathToAdd, insertIndex);
+                insertIndex = path.IndexOf(Path.PathSeparator, PathContainsSubstring(path, pathToAdd));
                 if (insertIndex != -1)
                 {
                     // advance past the path separator
                     insertIndex++;
                 }
-
-                currentProcessModulePath = AddToPath(currentProcessModulePath, systemModulePathToUse, insertIndex);
             }
-
-            return currentProcessModulePath;
+            return path;
         }
 
         /// <summary>

diff --git a/src/System.Management.Automation/engine/Utils.cs b/src/System.Management.Automation/engine/Utils.cs
@@ -1559,6 +1559,9 @@ public static class InternalTestHooks
         internal static bool SetConsoleWidthToZero;
         internal static bool SetConsoleHeightToZero;
 
+        // Simulate 'MyDocuments' returning empty string
+        internal static bool SetMyDocumentsSpecialFolderToBlank;
+
         internal static bool SetDate;
 
         // A location to test PSEdition compatibility functionality for Windows PowerShell modules with

diff --git a/test/powershell/engine/Module/ModulePath.Tests.ps1 b/test/powershell/engine/Module/ModulePath.Tests.ps1
@@ -247,3 +247,21 @@ Describe "ModuleIntrinsics.GetPSModulePath API tests" -tag @('CI', 'RequireAdmin
         $currentModulePathElements | Should -Contain $mPath
     }
 }
+
+Describe 'ModuleIntrinsics.GetModulePath environment interaction' -tag @('CI') {
+
+    It "GetModulePath does not crash when MyDocuments special folder is empty" {
+        try {
+            [System.Management.Automation.Internal.InternalTestHooks]::SetTestHook('SetMyDocumentsSpecialFolderToBlank', $true)
+            [System.Management.Automation.ModuleIntrinsics]::GetModulePath($null, $null, $null)
+        }
+        finally {
+            [System.Management.Automation.Internal.InternalTestHooks]::SetTestHook('SetMyDocumentsSpecialFolderToBlank', $false)
+        }
+    }
+
+    It "GetModulePath does not crash when MyDocuments special folder is not empty" {
+        [System.Management.Automation.ModuleIntrinsics]::GetModulePath($null, $null, $null)
+    }
+
+}