Fix credential event callback reference lifetime

2026-08-30 15:42:48 +10:00
parent b0a9886708
commit 7fad9cb351
18 changed files with 1105 additions and 8 deletions
@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [ComVisible(true)]
+    [ClassInterface(ClassInterfaceType.None)]
+    [Guid("2C87FFBB-6497-4D1A-8291-74B5DB3A0C3A")]
+    internal sealed class AbiTestCredentialProvider3 : CredentialProviderBase
+    {
+        public AbiTestCredentialProvider3()
+        {
+            this.Field = new SmallLabelControl("message", "Callback ABI test");
+            this.Logo = new CredentialProviderLogoControl("logo", "Callback ABI logo");
+        }
+
+        public SmallLabelControl Field { get; }
+
+        public CredentialProviderLogoControl Logo { get; }
+
+        public AbiTestCredentialTile3 Tile { get; private set; }
+
+        public override bool IsUsageScenarioSupported(UsageScenario cpus, CredUIWinFlags dwFlags)
+        {
+            return cpus == UsageScenario.CredUI;
+        }
+
+        public override IEnumerable<ControlBase> GetControls(UsageScenario cpus)
+        {
+            return new ControlBase[] { this.Field, this.Logo };
+        }
+
+        public override bool ShouldIncludeUserTile(CredentialProviderUser user)
+        {
+            return false;
+        }
+
+        public override bool ShouldIncludeGenericTile()
+        {
+            return true;
+        }
+
+        public override CredentialTile CreateGenericTile()
+        {
+            this.Tile = new AbiTestCredentialTile3(this);
+            return this.Tile;
+        }
+
+        public override CredentialTile2 CreateUserTile(CredentialProviderUser user)
+        {
+            return null;
+        }
+    }
+}
@@ -0,0 +1,26 @@
+using System;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    internal sealed class AbiTestCredentialTile3 : CredentialTile3
+    {
+        public AbiTestCredentialTile3(CredentialProviderBase credentialProvider) : base(credentialProvider)
+        {
+        }
+
+        public bool ThrowOnLoad { get; set; }
+
+        public override void OnLoad()
+        {
+            if (this.ThrowOnLoad)
+            {
+                throw new InvalidOperationException("Callback ABI test OnLoad failure");
+            }
+        }
+
+        protected override CredentialResponseBase GetCredentials()
+        {
+            return null;
+        }
+    }
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int CredentialAdviseDelegate(IntPtr instance, IntPtr credentialEvents);
+}
@@ -0,0 +1,295 @@
+using System;
+using System.Drawing;
+using System.Runtime.InteropServices;
+using System.Threading;
+using NUnit.Framework;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [TestFixture]
+    [NonParallelizable]
+    [Apartment(ApartmentState.STA)]
+    public class CredentialCallbackAbiTests
+    {
+        [Test]
+        public void RawEventInterfacesPreserveQueryInterfaceIdentityAndReferenceCounts()
+        {
+            RawCredentialEvents events = new RawCredentialEvents(3);
+
+            try
+            {
+                AssertIUnknownIdentity(events, events.Events1Interface);
+                AssertIUnknownIdentity(events, events.Events2Interface);
+                AssertIUnknownIdentity(events, events.Events3Interface);
+
+                RawQueryInterfaceDelegate queryInterface = GetRawMethod<RawQueryInterfaceDelegate>(events.Events1Interface, 0);
+                Guid events2Id = RawCredentialEventAbi.ICredentialProviderCredentialEvents2;
+                int beforeEvents2Query = events.CurrentReferenceCount;
+
+                Assert.That(queryInterface(events.Events1Interface, ref events2Id, out IntPtr events2Pointer), Is.EqualTo(CredentialProviderAbi.S_OK));
+                Assert.That(events2Pointer, Is.EqualTo(events.Events2Interface));
+                Assert.That(events.CurrentReferenceCount, Is.EqualTo(beforeEvents2Query + 1));
+                ReleaseRaw(events2Pointer);
+                Assert.That(events.CurrentReferenceCount, Is.EqualTo(beforeEvents2Query));
+
+                Guid unsupportedId = new Guid("757DA58F-742C-4840-9692-10A9D6392E93");
+                int beforeUnsupportedQuery = events.CurrentReferenceCount;
+
+                Assert.That(queryInterface(events.Events1Interface, ref unsupportedId, out IntPtr unsupportedPointer), Is.EqualTo(RawCredentialEventAbi.E_NOINTERFACE));
+                Assert.That(unsupportedPointer, Is.EqualTo(IntPtr.Zero));
+                Assert.That(events.CurrentReferenceCount, Is.EqualTo(beforeUnsupportedQuery));
+            }
+            finally
+            {
+                events.Dispose();
+            }
+
+            CollectComWrappers();
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void FailedAdviseReleasesCallbackState()
+        {
+            RawCredentialEvents events = ExerciseFailedAdvise();
+
+            CollectComWrappers();
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void RepeatedAdviseReplacesTheExistingCallbackReference()
+        {
+            RawCredentialEvents events;
+
+            using (CredentialCallbackScenario scenario = new CredentialCallbackScenario(2))
+            {
+                events = scenario.Events;
+
+                Assert.That(scenario.Advise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterFirstAdvise = events.CurrentReferenceCount;
+
+                Assert.That(scenario.Advise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterSecondAdvise = events.CurrentReferenceCount;
+
+                Assert.That(afterSecondAdvise, Is.EqualTo(afterFirstAdvise));
+                Assert.That(scenario.UnAdvise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                Assert.That(events.CurrentReferenceCount, Is.LessThan(afterSecondAdvise));
+            }
+
+            CollectComWrappers();
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(0));
+        }
+
+        private static RawCredentialEvents ExerciseFailedAdvise()
+        {
+            RawCredentialEvents events;
+
+            using (CredentialCallbackScenario scenario = new CredentialCallbackScenario(2))
+            {
+                events = scenario.Events;
+                scenario.Provider.Tile.ThrowOnLoad = true;
+                int releaseCallsBeforeAdvise = events.ReleaseCallCount;
+
+                Assert.That(scenario.Advise(), Is.EqualTo(CredentialProviderAbi.E_FAIL));
+                Assert.That(events.ReleaseCallCount, Is.GreaterThan(releaseCallsBeforeAdvise));
+
+                scenario.Provider.Field.Label = "No callback after failed Advise";
+                Assert.That(events.SetFieldStringCallCount, Is.EqualTo(0));
+            }
+
+            return events;
+        }
+
+        [Test]
+        public void Events1SetFieldStringPreservesSlotArgumentsAndLifetimePhases()
+        {
+            RawCredentialEvents events;
+
+            using (CredentialCallbackScenario scenario = new CredentialCallbackScenario(1))
+            {
+                events = scenario.Events;
+                int beforeAdvise = scenario.Events.CurrentReferenceCount;
+
+                Assert.That(scenario.Advise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterAdvise = scenario.Events.CurrentReferenceCount;
+
+                SmallLabelControl field = scenario.Provider.Tile.Controls.GetControl<SmallLabelControl>("message");
+                field.Label = "Updated through Events1";
+                int duringUpdate = scenario.Events.CurrentReferenceCount;
+
+                Assert.Multiple(() =>
+                {
+                    Assert.That(scenario.Events.SetFieldStringCallCount, Is.EqualTo(1));
+                    Assert.That(scenario.Events.LastCredential, Is.Not.EqualTo(IntPtr.Zero));
+                    Assert.That(scenario.Events.LastFieldId, Is.EqualTo(field.Id));
+                    Assert.That(scenario.Events.LastString, Is.EqualTo("Updated through Events1"));
+                    Assert.That(scenario.Events.Events2QueryCount, Is.GreaterThan(0));
+                    Assert.That(scenario.Events.Events3QueryCount, Is.EqualTo(0));
+                });
+
+                int releaseCallsBeforeUnAdvise = scenario.Events.ReleaseCallCount;
+                Assert.That(scenario.UnAdvise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterUnAdvise = scenario.Events.CurrentReferenceCount;
+
+                AssertLifetimePhases(scenario.Events, beforeAdvise, afterAdvise, duringUpdate, afterUnAdvise, releaseCallsBeforeUnAdvise);
+            }
+
+            CollectComWrappers();
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void Events2FieldUpdatesPreserveSlotsArgumentsAndLifetimePhases()
+        {
+            RawCredentialEvents events;
+
+            using (CredentialCallbackScenario scenario = new CredentialCallbackScenario(2))
+            {
+                events = scenario.Events;
+                int beforeAdvise = scenario.Events.CurrentReferenceCount;
+
+                Assert.That(scenario.Advise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterAdvise = scenario.Events.CurrentReferenceCount;
+
+                SmallLabelControl field = scenario.Provider.Tile.Controls.GetControl<SmallLabelControl>("message");
+                scenario.Provider.Tile.BeginBulkFieldUpdate();
+                field.Options = FieldOptions.Email;
+                scenario.Provider.Tile.EndBulkFieldUpdate();
+                int duringUpdate = scenario.Events.CurrentReferenceCount;
+
+                Assert.Multiple(() =>
+                {
+                    Assert.That(scenario.Events.BeginFieldUpdatesCallCount, Is.EqualTo(1));
+                    Assert.That(scenario.Events.EndFieldUpdatesCallCount, Is.EqualTo(1));
+                    Assert.That(scenario.Events.SetFieldOptionsCallCount, Is.EqualTo(1));
+                    Assert.That(scenario.Events.LastCredential, Is.Not.EqualTo(IntPtr.Zero));
+                    Assert.That(scenario.Events.LastFieldId, Is.EqualTo(field.Id));
+                    Assert.That(scenario.Events.LastUIntValue, Is.EqualTo((uint)FieldOptions.Email));
+                    Assert.That(scenario.Events.Events2QueryCount, Is.GreaterThan(0));
+                    Assert.That(scenario.Events.Events3QueryCount, Is.EqualTo(0));
+                });
+
+                int releaseCallsBeforeUnAdvise = scenario.Events.ReleaseCallCount;
+                Assert.That(scenario.UnAdvise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterUnAdvise = scenario.Events.CurrentReferenceCount;
+
+                AssertLifetimePhases(scenario.Events, beforeAdvise, afterAdvise, duringUpdate, afterUnAdvise, releaseCallsBeforeUnAdvise);
+            }
+
+            CollectComWrappers();
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void Events3BitmapBufferPreservesSlotArgumentsCallShapeAndLifetimePhases()
+        {
+            RawCredentialEvents events = ExerciseEvents3BitmapBuffer();
+
+            CollectComWrappers();
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(0));
+        }
+
+        private static RawCredentialEvents ExerciseEvents3BitmapBuffer()
+        {
+            RawCredentialEvents events;
+
+            using (CredentialCallbackScenario scenario = new CredentialCallbackScenario(3))
+            {
+                events = scenario.Events;
+                int beforeAdvise = scenario.Events.CurrentReferenceCount;
+
+                Assert.That(scenario.Advise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterAdvise = scenario.Events.CurrentReferenceCount;
+
+                CredentialProviderLogoControl logo = scenario.Provider.Tile.Controls.GetControl<CredentialProviderLogoControl>("logo");
+                using (Bitmap bitmap = new Bitmap(2, 2))
+                {
+                    bitmap.SetPixel(0, 0, Color.Transparent);
+                    bitmap.SetPixel(1, 0, Color.Red);
+                    logo.Bitmap = bitmap;
+                }
+
+                int duringUpdate = scenario.Events.CurrentReferenceCount;
+                byte[] buffer = scenario.Events.LastBitmapBuffer;
+
+                Assert.Multiple(() =>
+                {
+                    Assert.That(scenario.Events.SetFieldBitmapBufferCallCount, Is.EqualTo(1));
+                    Assert.That(scenario.Events.LastCredential, Is.Not.EqualTo(IntPtr.Zero));
+                    Assert.That(scenario.Events.LastFieldId, Is.EqualTo(logo.Id));
+                    Assert.That(buffer, Is.Not.Null);
+                    Assert.That(buffer.Length, Is.GreaterThan(8));
+                    Assert.That(buffer[0], Is.EqualTo(0x89));
+                    Assert.That(buffer[1], Is.EqualTo(0x50));
+                    Assert.That(buffer[2], Is.EqualTo(0x4E));
+                    Assert.That(buffer[3], Is.EqualTo(0x47));
+                    Assert.That(buffer[4], Is.EqualTo(0x0D));
+                    Assert.That(buffer[5], Is.EqualTo(0x0A));
+                    Assert.That(buffer[6], Is.EqualTo(0x1A));
+                    Assert.That(buffer[7], Is.EqualTo(0x0A));
+                    Assert.That(scenario.Events.BitmapBufferReturnValuePointerWasPresent, Is.True);
+                    Assert.That(scenario.Events.Events2QueryCount, Is.GreaterThan(0));
+                    Assert.That(scenario.Events.Events3QueryCount, Is.GreaterThan(0));
+                });
+
+                int releaseCallsBeforeUnAdvise = scenario.Events.ReleaseCallCount;
+                Assert.That(scenario.UnAdvise(), Is.EqualTo(CredentialProviderAbi.S_OK));
+                int afterUnAdvise = scenario.Events.CurrentReferenceCount;
+
+                AssertLifetimePhases(scenario.Events, beforeAdvise, afterAdvise, duringUpdate, afterUnAdvise, releaseCallsBeforeUnAdvise);
+            }
+
+            return events;
+        }
+
+        private static void AssertLifetimePhases(RawCredentialEvents events, int beforeAdvise, int afterAdvise, int duringUpdate, int afterUnAdvise, int releaseCallsBeforeUnAdvise)
+        {
+            TestContext.WriteLine($"Callback reference counts: before Advise={beforeAdvise}, after Advise={afterAdvise}, during update={duringUpdate}, after UnAdvise={afterUnAdvise}; AddRef calls={events.AddRefCallCount}, Release calls={events.ReleaseCallCount}");
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beforeAdvise, Is.EqualTo(1));
+                Assert.That(afterAdvise, Is.GreaterThan(beforeAdvise));
+                Assert.That(duringUpdate, Is.GreaterThanOrEqualTo(afterAdvise));
+                Assert.That(afterUnAdvise, Is.LessThan(duringUpdate));
+                Assert.That(afterUnAdvise, Is.GreaterThanOrEqualTo(beforeAdvise));
+                Assert.That(events.ReleaseCallCount, Is.GreaterThan(releaseCallsBeforeUnAdvise));
+            });
+        }
+
+        private static void AssertIUnknownIdentity(RawCredentialEvents events, IntPtr source)
+        {
+            RawQueryInterfaceDelegate queryInterface = GetRawMethod<RawQueryInterfaceDelegate>(source, 0);
+            Guid unknownId = RawCredentialEventAbi.IUnknown;
+            int beforeQuery = events.CurrentReferenceCount;
+
+            Assert.That(queryInterface(source, ref unknownId, out IntPtr unknown), Is.EqualTo(CredentialProviderAbi.S_OK));
+            Assert.That(unknown, Is.EqualTo(events.Events1Interface));
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(beforeQuery + 1));
+
+            ReleaseRaw(unknown);
+            Assert.That(events.CurrentReferenceCount, Is.EqualTo(beforeQuery));
+        }
+
+        private static TDelegate GetRawMethod<TDelegate>(IntPtr interfacePointer, int slot) where TDelegate : class
+        {
+            IntPtr vtable = Marshal.ReadIntPtr(interfacePointer);
+            IntPtr method = Marshal.ReadIntPtr(vtable, checked(slot * IntPtr.Size));
+            return (TDelegate)(object)Marshal.GetDelegateForFunctionPointer(method, typeof(TDelegate));
+        }
+
+        private static void ReleaseRaw(IntPtr interfacePointer)
+        {
+            RawReferenceDelegate release = GetRawMethod<RawReferenceDelegate>(interfacePointer, 2);
+            release(interfacePointer);
+        }
+
+        private static void CollectComWrappers()
+        {
+            GC.Collect();
+            GC.WaitForPendingFinalizers();
+            GC.Collect();
+        }
+    }
+}
@@ -0,0 +1,148 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    internal sealed class CredentialCallbackScenario : IDisposable
+    {
+        private readonly TestCredentialProviderUserArray users;
+        private readonly ComInterfacePointer credential;
+        private readonly CredentialAdviseDelegate advise;
+        private readonly CredentialUnAdviseDelegate unAdvise;
+        private bool advised;
+        private bool disposed;
+
+        public CredentialCallbackScenario(int maximumEventsVersion)
+        {
+            this.Provider = new AbiTestCredentialProvider3();
+            this.users = new TestCredentialProviderUserArray();
+            this.Events = new RawCredentialEvents(maximumEventsVersion);
+
+            try
+            {
+                this.InitializeProvider();
+                this.credential = this.CreateCredentialInterface();
+                this.advise = this.credential.GetMethod<CredentialAdviseDelegate>(RawCredentialEventAbi.CredentialAdviseSlot);
+                this.unAdvise = this.credential.GetMethod<CredentialUnAdviseDelegate>(RawCredentialEventAbi.CredentialUnAdviseSlot);
+            }
+            catch
+            {
+                this.credential?.Dispose();
+                this.Events.Dispose();
+                throw;
+            }
+        }
+
+        public AbiTestCredentialProvider3 Provider { get; }
+
+        public RawCredentialEvents Events { get; }
+
+        public int Advise()
+        {
+            this.ThrowIfDisposed();
+            int hresult = this.advise(this.credential.Value, this.Events.Events1Interface);
+            if (hresult == CredentialProviderAbi.S_OK)
+            {
+                this.advised = true;
+            }
+
+            return hresult;
+        }
+
+        public int UnAdvise()
+        {
+            this.ThrowIfDisposed();
+            int hresult = this.unAdvise(this.credential.Value);
+            if (hresult == CredentialProviderAbi.S_OK)
+            {
+                this.advised = false;
+            }
+
+            return hresult;
+        }
+
+        public void Dispose()
+        {
+            if (this.disposed)
+            {
+                return;
+            }
+
+            if (this.advised)
+            {
+                this.unAdvise(this.credential.Value);
+                this.advised = false;
+            }
+
+            this.credential.Dispose();
+            this.Events.Dispose();
+            this.disposed = true;
+            GC.KeepAlive(this.users);
+            GC.KeepAlive(this.Provider);
+        }
+
+        private void InitializeProvider()
+        {
+            using (ComInterfacePointer providerInterface = ComInterfacePointer.Create(this.Provider, CredentialProviderAbi.ICredentialProvider))
+            {
+                SetUsageScenarioDelegate setUsageScenario = providerInterface.GetMethod<SetUsageScenarioDelegate>(CredentialProviderAbi.SetUsageScenarioSlot);
+                this.ThrowIfFailed(setUsageScenario(providerInterface.Value, (int)UsageScenario.CredUI, 0), "SetUsageScenario");
+            }
+
+            using (ComInterfacePointer setUserArrayInterface = ComInterfacePointer.Create(this.Provider, CredentialProviderAbi.ICredentialProviderSetUserArray))
+            using (ComInterfacePointer userArrayInterface = ComInterfacePointer.Create(this.users, CredentialProviderAbi.ICredentialProviderUserArray))
+            {
+                SetUserArrayDelegate setUserArray = setUserArrayInterface.GetMethod<SetUserArrayDelegate>(CredentialProviderAbi.SetUserArraySlot);
+                this.ThrowIfFailed(setUserArray(setUserArrayInterface.Value, userArrayInterface.Value), "SetUserArray");
+            }
+        }
+
+        private ComInterfacePointer CreateCredentialInterface()
+        {
+            using (ComInterfacePointer providerInterface = ComInterfacePointer.Create(this.Provider, CredentialProviderAbi.ICredentialProvider))
+            {
+                GetCredentialCountDelegate getCredentialCount = providerInterface.GetMethod<GetCredentialCountDelegate>(CredentialProviderAbi.GetCredentialCountSlot);
+                GetCredentialAtDelegate getCredentialAt = providerInterface.GetMethod<GetCredentialAtDelegate>(CredentialProviderAbi.GetCredentialAtSlot);
+
+                this.ThrowIfFailed(getCredentialCount(providerInterface.Value, out uint count, out uint defaultCredential, out int autoLogonWithDefault), "GetCredentialCount");
+                if (count != 1)
+                {
+                    throw new InvalidOperationException($"The callback ABI provider returned {count} credentials instead of one");
+                }
+
+                IntPtr credentialPointer = IntPtr.Zero;
+
+                try
+                {
+                    this.ThrowIfFailed(getCredentialAt(providerInterface.Value, 0, out credentialPointer), "GetCredentialAt");
+                    ComInterfacePointer result = ComInterfacePointer.TakeOwnership(credentialPointer);
+                    credentialPointer = IntPtr.Zero;
+                    return result;
+                }
+                finally
+                {
+                    if (credentialPointer != IntPtr.Zero)
+                    {
+                        Marshal.Release(credentialPointer);
+                    }
+                }
+            }
+        }
+
+        private void ThrowIfFailed(int hresult, string operation)
+        {
+            if (hresult != CredentialProviderAbi.S_OK)
+            {
+                throw new COMException($"{operation} failed", hresult);
+            }
+        }
+
+        private void ThrowIfDisposed()
+        {
+            if (this.disposed)
+            {
+                throw new ObjectDisposedException(nameof(CredentialCallbackScenario));
+            }
+        }
+    }
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int CredentialUnAdviseDelegate(IntPtr instance);
+}
@@ -0,0 +1,39 @@
+using System;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    internal static class RawCredentialEventAbi
+    {
+        public static readonly Guid IUnknown = new Guid("00000000-0000-0000-C000-000000000046");
+
+        public static readonly Guid ICredentialProviderCredentialEvents = new Guid("FA6FA76B-66B7-4B11-95F1-86171118E816");
+
+        public static readonly Guid ICredentialProviderCredentialEvents2 = new Guid("B53C00B6-9922-4B78-B1F4-DDFE774DC39B");
+
+        public static readonly Guid ICredentialProviderCredentialEvents3 = new Guid("2D8DEEB8-1322-4973-8DF9-B282F2468290");
+
+        public const int CredentialAdviseSlot = 3;
+
+        public const int CredentialUnAdviseSlot = 4;
+
+        public const int SetFieldStringSlot = 5;
+
+        public const int BeginFieldUpdatesSlot = 13;
+
+        public const int EndFieldUpdatesSlot = 14;
+
+        public const int SetFieldOptionsSlot = 15;
+
+        public const int SetFieldBitmapBufferSlot = 16;
+
+        public const int Events1SlotCount = 13;
+
+        public const int Events2SlotCount = 16;
+
+        public const int Events3SlotCount = 17;
+
+        public const int E_NOINTERFACE = unchecked((int)0x80004002);
+
+        public const int E_POINTER = unchecked((int)0x80004003);
+    }
+}
@@ -0,0 +1,10 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    // The trailing returnValue pointer characterizes the current CLR projection without PreserveSig.
+    // It does not establish the native ABI of the undocumented Windows Events3 interface.
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawCredentialEventBitmapBufferDelegate(IntPtr instance, IntPtr credential, uint fieldId, uint imageBufferSize, IntPtr imageBuffer, IntPtr returnValue);
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawCredentialEventFieldCheckboxDelegate(IntPtr instance, IntPtr credential, uint fieldId, int isChecked, IntPtr label);
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawCredentialEventFieldPointerDelegate(IntPtr instance, IntPtr credential, uint fieldId, IntPtr value);
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawCredentialEventFieldUIntDelegate(IntPtr instance, IntPtr credential, uint fieldId, uint value);
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawCredentialEventNoArgumentsDelegate(IntPtr instance);
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawCredentialEventOnCreatingWindowDelegate(IntPtr instance, out IntPtr ownerWindow);
+}
@@ -0,0 +1,430 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    internal sealed class RawCredentialEvents : IDisposable
+    {
+        private static readonly object RegistryLock = new object();
+        private static readonly HashSet<RawCredentialEvents> Registry = new HashSet<RawCredentialEvents>();
+
+        private readonly object observationLock = new object();
+        private readonly int maximumVersion;
+        private readonly RawQueryInterfaceDelegate queryInterfaceDelegate;
+        private readonly RawReferenceDelegate addRefDelegate;
+        private readonly RawReferenceDelegate releaseDelegate;
+        private readonly RawCredentialEventFieldUIntDelegate fieldUIntStubDelegate;
+        private readonly RawCredentialEventFieldPointerDelegate fieldPointerStubDelegate;
+        private readonly RawCredentialEventFieldCheckboxDelegate fieldCheckboxStubDelegate;
+        private readonly RawCredentialEventFieldPointerDelegate setFieldStringDelegate;
+        private readonly RawCredentialEventNoArgumentsDelegate beginFieldUpdatesDelegate;
+        private readonly RawCredentialEventNoArgumentsDelegate endFieldUpdatesDelegate;
+        private readonly RawCredentialEventFieldUIntDelegate setFieldOptionsDelegate;
+        private readonly RawCredentialEventOnCreatingWindowDelegate onCreatingWindowDelegate;
+        private readonly RawCredentialEventBitmapBufferDelegate setFieldBitmapBufferDelegate;
+
+        private IntPtr events1Vtable;
+        private IntPtr events2Vtable;
+        private IntPtr events3Vtable;
+        private IntPtr events1Interface;
+        private IntPtr events2Interface;
+        private IntPtr events3Interface;
+        private int referenceCount;
+        private int addRefCallCount;
+        private int releaseCallCount;
+        private int events2QueryCount;
+        private int events3QueryCount;
+        private int setFieldStringCallCount;
+        private int beginFieldUpdatesCallCount;
+        private int endFieldUpdatesCallCount;
+        private int setFieldOptionsCallCount;
+        private int setFieldBitmapBufferCallCount;
+        private int ownerReferenceReleased;
+        private IntPtr lastCredential;
+        private uint lastFieldId;
+        private uint lastUIntValue;
+        private string lastString;
+        private byte[] lastBitmapBuffer;
+        private bool bitmapBufferReturnValuePointerWasPresent;
+
+        public RawCredentialEvents(int maximumVersion)
+        {
+            if (maximumVersion < 1 || maximumVersion > 3)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maximumVersion));
+            }
+
+            this.maximumVersion = maximumVersion;
+            this.referenceCount = 1;
+            this.queryInterfaceDelegate = this.QueryInterface;
+            this.addRefDelegate = this.AddRef;
+            this.releaseDelegate = this.Release;
+            this.fieldUIntStubDelegate = this.FieldUIntStub;
+            this.fieldPointerStubDelegate = this.FieldPointerStub;
+            this.fieldCheckboxStubDelegate = this.FieldCheckboxStub;
+            this.setFieldStringDelegate = this.SetFieldString;
+            this.beginFieldUpdatesDelegate = this.BeginFieldUpdates;
+            this.endFieldUpdatesDelegate = this.EndFieldUpdates;
+            this.setFieldOptionsDelegate = this.SetFieldOptions;
+            this.onCreatingWindowDelegate = this.OnCreatingWindow;
+            this.setFieldBitmapBufferDelegate = this.SetFieldBitmapBuffer;
+
+            try
+            {
+                this.events1Vtable = this.CreateVtable(RawCredentialEventAbi.Events1SlotCount);
+                this.events1Interface = this.CreateInterface(this.events1Vtable);
+
+                if (maximumVersion >= 2)
+                {
+                    this.events2Vtable = this.CreateVtable(RawCredentialEventAbi.Events2SlotCount);
+                    this.events2Interface = this.CreateInterface(this.events2Vtable);
+                }
+
+                if (maximumVersion >= 3)
+                {
+                    this.events3Vtable = this.CreateVtable(RawCredentialEventAbi.Events3SlotCount);
+                    this.events3Interface = this.CreateInterface(this.events3Vtable);
+                }
+
+                lock (RegistryLock)
+                {
+                    Registry.Add(this);
+                }
+            }
+            catch
+            {
+                this.FreeNativeMemory();
+                throw;
+            }
+        }
+
+        public IntPtr Events1Interface => this.events1Interface;
+
+        public IntPtr Events2Interface => this.events2Interface;
+
+        public IntPtr Events3Interface => this.events3Interface;
+
+        public int CurrentReferenceCount => Volatile.Read(ref this.referenceCount);
+
+        public int AddRefCallCount => Volatile.Read(ref this.addRefCallCount);
+
+        public int ReleaseCallCount => Volatile.Read(ref this.releaseCallCount);
+
+        public int Events2QueryCount => Volatile.Read(ref this.events2QueryCount);
+
+        public int Events3QueryCount => Volatile.Read(ref this.events3QueryCount);
+
+        public int SetFieldStringCallCount => Volatile.Read(ref this.setFieldStringCallCount);
+
+        public int BeginFieldUpdatesCallCount => Volatile.Read(ref this.beginFieldUpdatesCallCount);
+
+        public int EndFieldUpdatesCallCount => Volatile.Read(ref this.endFieldUpdatesCallCount);
+
+        public int SetFieldOptionsCallCount => Volatile.Read(ref this.setFieldOptionsCallCount);
+
+        public int SetFieldBitmapBufferCallCount => Volatile.Read(ref this.setFieldBitmapBufferCallCount);
+
+        public IntPtr LastCredential
+        {
+            get
+            {
+                lock (this.observationLock)
+                {
+                    return this.lastCredential;
+                }
+            }
+        }
+
+        public uint LastFieldId
+        {
+            get
+            {
+                lock (this.observationLock)
+                {
+                    return this.lastFieldId;
+                }
+            }
+        }
+
+        public uint LastUIntValue
+        {
+            get
+            {
+                lock (this.observationLock)
+                {
+                    return this.lastUIntValue;
+                }
+            }
+        }
+
+        public string LastString
+        {
+            get
+            {
+                lock (this.observationLock)
+                {
+                    return this.lastString;
+                }
+            }
+        }
+
+        public byte[] LastBitmapBuffer
+        {
+            get
+            {
+                lock (this.observationLock)
+                {
+                    return this.lastBitmapBuffer == null ? null : (byte[])this.lastBitmapBuffer.Clone();
+                }
+            }
+        }
+
+        public bool BitmapBufferReturnValuePointerWasPresent
+        {
+            get
+            {
+                lock (this.observationLock)
+                {
+                    return this.bitmapBufferReturnValuePointerWasPresent;
+                }
+            }
+        }
+
+        public void Dispose()
+        {
+            if (Interlocked.Exchange(ref this.ownerReferenceReleased, 1) == 0)
+            {
+                this.Release(IntPtr.Zero);
+            }
+        }
+
+        private IntPtr CreateVtable(int slotCount)
+        {
+            IntPtr vtable = Marshal.AllocHGlobal(checked(slotCount * IntPtr.Size));
+
+            for (int slot = 0; slot < slotCount; slot++)
+            {
+                Marshal.WriteIntPtr(vtable, checked(slot * IntPtr.Size), IntPtr.Zero);
+            }
+
+            this.WriteMethod(vtable, 0, this.queryInterfaceDelegate);
+            this.WriteMethod(vtable, 1, this.addRefDelegate);
+            this.WriteMethod(vtable, 2, this.releaseDelegate);
+            this.WriteMethod(vtable, 3, this.fieldUIntStubDelegate);
+            this.WriteMethod(vtable, 4, this.fieldUIntStubDelegate);
+            this.WriteMethod(vtable, RawCredentialEventAbi.SetFieldStringSlot, this.setFieldStringDelegate);
+            this.WriteMethod(vtable, 6, this.fieldCheckboxStubDelegate);
+            this.WriteMethod(vtable, 7, this.fieldPointerStubDelegate);
+            this.WriteMethod(vtable, 8, this.fieldUIntStubDelegate);
+            this.WriteMethod(vtable, 9, this.fieldUIntStubDelegate);
+            this.WriteMethod(vtable, 10, this.fieldPointerStubDelegate);
+            this.WriteMethod(vtable, 11, this.fieldUIntStubDelegate);
+            this.WriteMethod(vtable, 12, this.onCreatingWindowDelegate);
+
+            if (slotCount >= RawCredentialEventAbi.Events2SlotCount)
+            {
+                this.WriteMethod(vtable, RawCredentialEventAbi.BeginFieldUpdatesSlot, this.beginFieldUpdatesDelegate);
+                this.WriteMethod(vtable, RawCredentialEventAbi.EndFieldUpdatesSlot, this.endFieldUpdatesDelegate);
+                this.WriteMethod(vtable, RawCredentialEventAbi.SetFieldOptionsSlot, this.setFieldOptionsDelegate);
+            }
+
+            if (slotCount >= RawCredentialEventAbi.Events3SlotCount)
+            {
+                this.WriteMethod(vtable, RawCredentialEventAbi.SetFieldBitmapBufferSlot, this.setFieldBitmapBufferDelegate);
+            }
+
+            return vtable;
+        }
+
+        private IntPtr CreateInterface(IntPtr vtable)
+        {
+            IntPtr result = Marshal.AllocHGlobal(IntPtr.Size);
+            Marshal.WriteIntPtr(result, vtable);
+            return result;
+        }
+
+        private void WriteMethod(IntPtr vtable, int slot, Delegate method)
+        {
+            Marshal.WriteIntPtr(vtable, checked(slot * IntPtr.Size), Marshal.GetFunctionPointerForDelegate(method));
+        }
+
+        private int QueryInterface(IntPtr instance, ref Guid interfaceId, out IntPtr interfacePointer)
+        {
+            interfacePointer = IntPtr.Zero;
+
+            if (interfaceId == RawCredentialEventAbi.IUnknown || interfaceId == RawCredentialEventAbi.ICredentialProviderCredentialEvents)
+            {
+                interfacePointer = this.events1Interface;
+            }
+            else if (interfaceId == RawCredentialEventAbi.ICredentialProviderCredentialEvents2)
+            {
+                Interlocked.Increment(ref this.events2QueryCount);
+                if (this.maximumVersion >= 2)
+                {
+                    interfacePointer = this.events2Interface;
+                }
+            }
+            else if (interfaceId == RawCredentialEventAbi.ICredentialProviderCredentialEvents3)
+            {
+                Interlocked.Increment(ref this.events3QueryCount);
+                if (this.maximumVersion >= 3)
+                {
+                    interfacePointer = this.events3Interface;
+                }
+            }
+
+            if (interfacePointer == IntPtr.Zero)
+            {
+                return RawCredentialEventAbi.E_NOINTERFACE;
+            }
+
+            this.AddRef(instance);
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private uint AddRef(IntPtr instance)
+        {
+            Interlocked.Increment(ref this.addRefCallCount);
+            return checked((uint)Interlocked.Increment(ref this.referenceCount));
+        }
+
+        private uint Release(IntPtr instance)
+        {
+            Interlocked.Increment(ref this.releaseCallCount);
+            int result = Interlocked.Decrement(ref this.referenceCount);
+
+            if (result == 0)
+            {
+                lock (RegistryLock)
+                {
+                    Registry.Remove(this);
+                }
+
+                this.FreeNativeMemory();
+            }
+
+            return checked((uint)result);
+        }
+
+        private int SetFieldString(IntPtr instance, IntPtr credential, uint fieldId, IntPtr value)
+        {
+            try
+            {
+                lock (this.observationLock)
+                {
+                    this.lastCredential = credential;
+                    this.lastFieldId = fieldId;
+                    this.lastString = value == IntPtr.Zero ? null : Marshal.PtrToStringUni(value);
+                }
+
+                Interlocked.Increment(ref this.setFieldStringCallCount);
+                return CredentialProviderAbi.S_OK;
+            }
+            catch
+            {
+                return CredentialProviderAbi.E_FAIL;
+            }
+        }
+
+        private int BeginFieldUpdates(IntPtr instance)
+        {
+            Interlocked.Increment(ref this.beginFieldUpdatesCallCount);
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private int EndFieldUpdates(IntPtr instance)
+        {
+            Interlocked.Increment(ref this.endFieldUpdatesCallCount);
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private int SetFieldOptions(IntPtr instance, IntPtr credential, uint fieldId, uint value)
+        {
+            lock (this.observationLock)
+            {
+                this.lastCredential = credential;
+                this.lastFieldId = fieldId;
+                this.lastUIntValue = value;
+            }
+
+            Interlocked.Increment(ref this.setFieldOptionsCallCount);
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private int SetFieldBitmapBuffer(IntPtr instance, IntPtr credential, uint fieldId, uint imageBufferSize, IntPtr imageBuffer, IntPtr returnValue)
+        {
+            try
+            {
+                if (returnValue == IntPtr.Zero)
+                {
+                    return RawCredentialEventAbi.E_POINTER;
+                }
+
+                byte[] buffer = new byte[checked((int)imageBufferSize)];
+                if (buffer.Length > 0)
+                {
+                    Marshal.Copy(imageBuffer, buffer, 0, buffer.Length);
+                }
+
+                Marshal.WriteInt32(returnValue, CredentialProviderAbi.S_OK);
+
+                lock (this.observationLock)
+                {
+                    this.lastCredential = credential;
+                    this.lastFieldId = fieldId;
+                    this.lastBitmapBuffer = buffer;
+                    this.bitmapBufferReturnValuePointerWasPresent = true;
+                }
+
+                Interlocked.Increment(ref this.setFieldBitmapBufferCallCount);
+                return CredentialProviderAbi.S_OK;
+            }
+            catch
+            {
+                return CredentialProviderAbi.E_FAIL;
+            }
+        }
+
+        private int FieldUIntStub(IntPtr instance, IntPtr credential, uint fieldId, uint value)
+        {
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private int FieldPointerStub(IntPtr instance, IntPtr credential, uint fieldId, IntPtr value)
+        {
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private int FieldCheckboxStub(IntPtr instance, IntPtr credential, uint fieldId, int isChecked, IntPtr label)
+        {
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private int OnCreatingWindow(IntPtr instance, out IntPtr ownerWindow)
+        {
+            ownerWindow = IntPtr.Zero;
+            return CredentialProviderAbi.S_OK;
+        }
+
+        private void FreeNativeMemory()
+        {
+            this.FreeNativeMemory(ref this.events1Interface);
+            this.FreeNativeMemory(ref this.events2Interface);
+            this.FreeNativeMemory(ref this.events3Interface);
+            this.FreeNativeMemory(ref this.events1Vtable);
+            this.FreeNativeMemory(ref this.events2Vtable);
+            this.FreeNativeMemory(ref this.events3Vtable);
+        }
+
+        private void FreeNativeMemory(ref IntPtr pointer)
+        {
+            if (pointer != IntPtr.Zero)
+            {
+                Marshal.FreeHGlobal(pointer);
+                pointer = IntPtr.Zero;
+            }
+        }
+    }
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate int RawQueryInterfaceDelegate(IntPtr instance, ref Guid interfaceId, out IntPtr interfacePointer);
+}
@@ -0,0 +1,8 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Lithnet.CredentialProvider.UnitTests.ComInterop
+{
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    internal delegate uint RawReferenceDelegate(IntPtr instance);
+}
@@ -12,14 +12,17 @@ namespace Lithnet.CredentialProvider
            {
                this.logger.LogTrace("Advise");

+                if (this.eventsUnknown != IntPtr.Zero)
+                {
+                    this.ReleaseCredentialEvents();
+                }
+
                if (pcpce != null)
                {
+                    this.eventsUnknown = Marshal.GetIUnknownForObject(pcpce);
                    this.Controls.AssignEvents(pcpce);
                    this.events = pcpce;
                    this.events2 = pcpce as ICredentialProviderCredentialEvents2;
-
-                    var intPtr = Marshal.GetIUnknownForObject(pcpce);
-                    Marshal.AddRef(intPtr);
                }

                this.OnLoad();
@@ -28,6 +31,7 @@ namespace Lithnet.CredentialProvider
            }
            catch (Exception ex)
            {
+                this.ReleaseCredentialEvents();
                this.logger.LogError(ex, "Advise failed");
                return HRESULT.E_FAIL;
            }
@@ -39,12 +43,9 @@ namespace Lithnet.CredentialProvider
            {
                this.logger.LogTrace("Unadvise");

-                if (this.events != null)
+                if (this.eventsUnknown != IntPtr.Zero)
                {
-                    this.Controls.UnassignEvents();
-                    var intPtr = Marshal.GetIUnknownForObject(this.events);
-                    Marshal.Release(intPtr);
-                    this.events = null;
+                    this.ReleaseCredentialEvents();
                }

                this.OnUnload();
@@ -58,6 +59,26 @@ namespace Lithnet.CredentialProvider
            }
        }

+        private void ReleaseCredentialEvents()
+        {
+            try
+            {
+                this.Controls.UnassignEvents();
+            }
+            finally
+            {
+                this.events2 = null;
+                this.events = null;
+
+                if (this.eventsUnknown != IntPtr.Zero)
+                {
+                    IntPtr unknown = this.eventsUnknown;
+                    this.eventsUnknown = IntPtr.Zero;
+                    Marshal.Release(unknown);
+                }
+            }
+        }
+
        int ICredentialProviderCredential.SetSelected(out int pbAutoLogon)
        {
            pbAutoLogon = 0;
@@ -11,6 +11,7 @@ namespace Lithnet.CredentialProvider
    public abstract partial class CredentialTile
    {
        private protected readonly ICredentialProviderLogger logger;
+        private IntPtr eventsUnknown;
        private protected ICredentialProviderCredentialEvents events;
        private protected ICredentialProviderCredentialEvents2 events2;
        private protected ControlCollection controls;