Fix NullReferenceException when the native enumerator returns null

src/Orc.SystemInfo.Tests/Orc.SystemInfo.Tests.csproj

@@ -18,6 +18,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
+    <PackageReference Include="Moq" Version="4.20.69" />
     <PackageReference Include="NUnit" Version="3.13.3" PrivateAssets="all" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" PrivateAssets="all" />
     <PackageReference Include="PublicApiGenerator" Version="11.0.0" PrivateAssets="all" />

src/Orc.SystemInfo.Tests/PublicApiFacts.Orc_SystemInfo_HasNoBreakingChanges_Async.verified.txt

@@ -1,4 +1,5 @@
 [assembly: System.Resources.NeutralResourcesLanguage("en-US")]
+[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("DynamicProxyGenAssembly2")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("Orc.SystemInfo.Tests")]
 [assembly: System.Runtime.InteropServices.ComVisible(false)]
 [assembly: System.Runtime.Versioning.TargetFramework(".NETCoreApp,Version=v6.0", FrameworkDisplayName=".NET 6.0")]

src/Orc.SystemInfo.Tests/Wmi/WindowsManagementObjectEnumeratorFacts.cs

@@ -0,0 +1,40 @@
+namespace Orc.SystemInfo.Tests
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Text;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Moq;
+    using NUnit.Framework;
+    using Orc.SystemInfo.Win32;
+    using Orc.SystemInfo.Wmi;
+
+    public class WindowsManagementObjectEnumeratorFacts
+    {
+        [Test]
+        public async Task Returns_False_When_Enumerator_Returns_Null_Async()
+        {
+            IWbemClassObject objects;
+            uint returnedCount;
+
+            var wbemClassObjectEnumeratorMock = new Mock<IWbemClassObjectEnumerator>();
+
+            wbemClassObjectEnumeratorMock.Setup(x => x.Next(It.IsAny<int>(), It.IsAny<uint>(), out objects, out returnedCount))
+                .Returns((int to, uint c, out IWbemClassObject o, out uint rc) =>
+                {
+                    o = null;
+                    rc = 0;
+
+                    return new HResult(0);
+                });
+
+            using var enumerator = new WindowsManagementObjectEnumerator(wbemClassObjectEnumeratorMock.Object);
+
+            var moveNextResult = enumerator.MoveNext();
+
+            Assert.That(moveNextResult, Is.False);
+        }
+    }
+}

src/Orc.SystemInfo/Properties/AssemblyInfo.cs

@@ -17,3 +17,4 @@
 [assembly: ComVisible(false)]
 
 [assembly: InternalsVisibleTo("Orc.SystemInfo.Tests")]
+[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")]

src/Orc.SystemInfo/Win32/HResult.cs

@@ -94,4 +94,9 @@ public void ThrowIfFailed()
             throw ex;
         }
     }
-}
+
+    public override string ToString()
+    {
+        return $"{_value} (Failed = {Failed})";
+    }
+}

src/Orc.SystemInfo/Win32/Wbem/Extensions/IWbemClassObjectEnumeratorExtensions.cs

@@ -1,11 +1,10 @@
 namespace Orc.SystemInfo.Win32;
 
-using System;
 using System.Threading;
 
 public static class IWbemClassObjectEnumeratorExtensions
 {
-    internal static IWbemClassObject Next(this IWbemClassObjectEnumerator wbemClassObjectEnumerator)
+    internal static IWbemClassObject? Next(this IWbemClassObjectEnumerator wbemClassObjectEnumerator)
     {
         const uint count = 1;
         var hresult = wbemClassObjectEnumerator.Next(Timeout.Infinite, count, out var current, out _);

src/Orc.SystemInfo/Win32/Wbem/Extensions/IWbemLocatorExtensions.cs

@@ -9,12 +9,12 @@ internal static class IWbemLocatorExtensions
     /// <param name="resource"></param>
     /// <param name="ctx"></param>
     /// <returns></returns>
-    internal static IWbemServices ConnectServer(this IWbemLocator wbemLocator, string resource, IWbemContext? ctx)
+    internal static IWbemServices? ConnectServer(this IWbemLocator wbemLocator, string resource, IWbemContext? ctx)
     {
         var hr = wbemLocator.ConnectServer(resource, null, null, null, WbemConnectOption.None, null, ctx, out var services);
 
         hr.ThrowIfFailed();
 
         return services;
     }
-}
+}

src/Orc.SystemInfo/Win32/Wbem/Interfaces/IWbemClassObject.cs

@@ -32,31 +32,31 @@ HResult GetNames([In, MarshalAs(UnmanagedType.LPWStr)] string? qualifierName, [I
     HResult EndEnumeration();
 
     [PreserveSig]
-    HResult GetPropertyQualifierSet([In, MarshalAs(UnmanagedType.LPWStr)] string property, [Out] out IWbemQualifierSet qualifierSet);
+    HResult GetPropertyQualifierSet([In, MarshalAs(UnmanagedType.LPWStr)] string property, [Out] out IWbemQualifierSet? qualifierSet);
 
     [PreserveSig]
     HResult Clone([Out] out IWbemClassObject copy);
 
     [PreserveSig]
-    HResult GetObjectText([In] int flags, [Out, MarshalAs(UnmanagedType.BStr)] out string objectText);
+    HResult GetObjectText([In] int flags, [Out, MarshalAs(UnmanagedType.BStr)] out string? objectText);
 
     [PreserveSig]
-    HResult SpawnDerivedClass([In] int flags, [Out] out IWbemClassObject newClass);
+    HResult SpawnDerivedClass([In] int flags, [Out] out IWbemClassObject? newClass);
 
     [PreserveSig]
-    HResult SpawnInstance([In] int flags, [Out] out IWbemClassObject newInstance);
+    HResult SpawnInstance([In] int flags, [Out] out IWbemClassObject? newInstance);
 
     [PreserveSig]
     HResult CompareTo([In] WbemClassObjectComparisonOptions compareOption, [In] IWbemClassObject compareTo);
 
     [PreserveSig]
-    HResult GetPropertyOrigin([In, MarshalAs(UnmanagedType.LPWStr)] string name, [Out, MarshalAs(UnmanagedType.BStr)] out string className);
+    HResult GetPropertyOrigin([In, MarshalAs(UnmanagedType.LPWStr)] string name, [Out, MarshalAs(UnmanagedType.BStr)] out string? className);
 
     [PreserveSig]
     HResult InheritsFrom([In, MarshalAs(UnmanagedType.LPWStr)] string ancestor);
 
     [PreserveSig]
-    HResult GetMethod([In, MarshalAs(UnmanagedType.LPWStr)] string name, [In] int flags, [Out] out IWbemClassObject inSignature, [Out] out IWbemClassObject outSignature);
+    HResult GetMethod([In, MarshalAs(UnmanagedType.LPWStr)] string name, [In] int flags, [Out] out IWbemClassObject? inSignature, [Out] out IWbemClassObject? outSignature);
 
     [PreserveSig]
     HResult PutMethod([In, MarshalAs(UnmanagedType.LPWStr)] string name, [In] int flags, [In] IWbemClassObject inSignature, [In] IWbemClassObject outSignature);
@@ -68,14 +68,14 @@ HResult GetNames([In, MarshalAs(UnmanagedType.LPWStr)] string? qualifierName, [I
     HResult BeginMethodEnumeration([In] int enumFlags);
 
     [PreserveSig]
-    HResult NextMethod([In] int flags, [Out, MarshalAs(UnmanagedType.BStr)] string name, [Out] out IWbemClassObject inSignature, [Out] out IWbemClassObject outSignature);
+    HResult NextMethod([In] int flags, [Out, MarshalAs(UnmanagedType.BStr)] string name, [Out] out IWbemClassObject? inSignature, [Out] out IWbemClassObject? outSignature);
 
     [PreserveSig]
     HResult EndMethodEnumeration();
 
     [PreserveSig]
-    HResult GetMethodQualifierSet([In, MarshalAs(UnmanagedType.LPWStr)] string method, [Out] out IWbemQualifierSet qualifierSet);
+    HResult GetMethodQualifierSet([In, MarshalAs(UnmanagedType.LPWStr)] string method, [Out] out IWbemQualifierSet? qualifierSet);
 
     [PreserveSig]
-    HResult GetMethodOrigin([In, MarshalAs(UnmanagedType.LPWStr)] string methodName, [Out, MarshalAs(UnmanagedType.BStr)] out string className);
-}
+    HResult GetMethodOrigin([In, MarshalAs(UnmanagedType.LPWStr)] string methodName, [Out, MarshalAs(UnmanagedType.BStr)] out string? className);
+}

src/Orc.SystemInfo/Win32/Wbem/Interfaces/IWbemClassObjectEnumerator.cs

@@ -18,7 +18,7 @@ HResult Next(
         [In]
         uint count,
         [Out]
-        out IWbemClassObject objects,
+        out IWbemClassObject? objects,
         [Out]
         out uint returnedCount);
 
@@ -38,4 +38,4 @@ HResult Skip(
         int timeOut,
         [In]
         uint count);
-}
+}

src/Orc.SystemInfo/Win32/Wbem/Interfaces/IWbemContext.cs

@@ -29,9 +29,9 @@ HResult Next(
         [In]
         uint flags,
         [Out, MarshalAs(UnmanagedType.BStr)]
-        out string name,
+        out string? name,
         [Out]
-        out object value);
+        out object? value);
 
     [PreserveSig]
     HResult EndEnumeration();
@@ -43,7 +43,7 @@ HResult SetValue(
         [In]
         uint flags,
         [In]
-        object value);
+        object? value);
 
     [PreserveSig]
     HResult GetValue(
@@ -52,7 +52,7 @@ HResult GetValue(
         [In]
         uint flags,
         [Out]
-        out object value);
+        out object? value);
 
     [PreserveSig]
     HResult DeleteValue(
@@ -63,4 +63,4 @@ HResult DeleteValue(
 
     [PreserveSig]
     HResult DeleteAll();
-}
+}

src/Orc.SystemInfo/Win32/Wbem/Interfaces/IWbemLocator.cs

@@ -25,5 +25,5 @@ HResult ConnectServer(
         [In, MarshalAs(UnmanagedType.Interface)]
         IWbemContext? ctx,
         [Out, MarshalAs(UnmanagedType.Interface)]
-        out IWbemServices wbemServices);
-}
+        out IWbemServices? wbemServices);
+}

src/Orc.SystemInfo/Win32/Wbem/Interfaces/IWbemQualifierSet.cs

@@ -26,7 +26,7 @@ HResult Get(
         [In]
         int flags,
         [Out]
-        out object value,
+        out object? value,
         [Out]
         out int flavor);
 
@@ -42,9 +42,9 @@ HResult Next(
         [In]
         int flags,
         [Out, MarshalAs(UnmanagedType.BStr)]
-        out string name,
+        out string? name,
         [Out]
-        out object value,
+        out object? value,
         [Out]
         out int flavor);
 
@@ -53,7 +53,7 @@ HResult Put(
         [In, MarshalAs(UnmanagedType.LPWStr)]
         string name,
         [In]
-        object value,
+        object? value,
         [In]
         int flavor);
-}
+}

src/Orc.SystemInfo/Wmi/WindowsManagementConnection.cs

@@ -41,9 +41,13 @@ public void Open()
                 const WbemAuthenticationLevel authLevel = WbemAuthenticationLevel.PacketIntegrity;
 
                 _wbemServices = locator.ConnectServer(DefaultLocalRootPath, _context);
-                _wbemServices.SetProxy(WbemImpersonationLevel.Impersonate, authLevel);
 
-                _connected = true;
+                if (_wbemServices is not null)
+                {
+                    _wbemServices.SetProxy(WbemImpersonationLevel.Impersonate, authLevel);
+
+                    _connected = true;
+                }
             }
         }
         catch (Exception ex)
@@ -61,7 +65,11 @@ protected override void DisposeUnmanaged()
         {
             if (_wbemServices is not null)
             {
-                Marshal.ReleaseComObject(_wbemServices);
+                if (Marshal.IsComObject(_wbemServices))
+                {
+                    Marshal.ReleaseComObject(_wbemServices);
+                }
+
                 _wbemServices = null;
             }
 

src/Orc.SystemInfo/Wmi/WindowsManagementObjectEnumerator.cs

@@ -42,10 +42,15 @@ public bool MoveNext()
         ThrowIfDisposed();
 
         var currentWmiObject = _wbemClassObjectEnumerator.Next();
+        if (currentWmiObject is null)
+        {
+            return false;
+        }
 
 #pragma warning disable IDISP003 // Dispose previous before re-assigning
         Current = new WindowsManagementObject(currentWmiObject);
 #pragma warning restore IDISP003 // Dispose previous before re-assigning
+
         return true;
     }
 
@@ -70,7 +75,10 @@ public void Dispose()
             return;
         }
 
-        Marshal.ReleaseComObject(_wbemClassObjectEnumerator);
+        if (Marshal.IsComObject(_wbemClassObjectEnumerator))
+        {
+            Marshal.ReleaseComObject(_wbemClassObjectEnumerator);
+        }
 
         _disposed = true;
     }