Do not use AllocHGlobal in Pkcs12Reader

src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj

@@ -27,6 +27,8 @@
   <ItemGroup Condition="'$(GeneratePlatformNotSupportedAssemblyMessage)' == ''">
     <Compile Include="$(CommonPath)DisableRuntimeMarshalling.cs"
              Link="Common\DisableRuntimeMarshalling.cs" />
+    <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeCrypt32Handle.cs"
+             Link="Common\Microsoft\Win32\SafeHandles\SafeCrypt32Handle.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeHandleCache.cs"
              Link="Common\Microsoft\Win32\SafeHandles\SafeHandleCache.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeX509ChainHandle.cs"
@@ -902,10 +904,12 @@
     <Compile Include="System\Security\Cryptography\X509Certificates\OpenSslX509ChainEventSource.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\OpenSslX509ChainProcessor.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\OpenSslX509Encoder.cs" />
+    <Compile Include="System\Security\Cryptography\X509Certificates\SafeLocalAllocWithClearOnDisposeHandle.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\StorePal.OpenSsl.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixChainVerifier.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixExportProvider.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixPkcs12Reader.cs" />
+    <Compile Include="System\Security\Cryptography\X509Certificates\UnmanagedCryptoBufferMemoryManager.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnsupportedDisallowedStore.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X500NameEncoder.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X500NameEncoder.ManagedDecode.cs" />
@@ -1036,6 +1040,7 @@
     <Compile Include="System\Security\Cryptography\X509Certificates\ManagedX509ExtensionProcessor.cs" />
     <Compile Include="System\Security\Cryptography\Shake128.NonWindows.cs" />
     <Compile Include="System\Security\Cryptography\Shake256.NonWindows.cs" />
+    <Compile Include="System\Security\Cryptography\X509Certificates\SafeLocalAllocWithClearOnDisposeHandle.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\StorePal.Android.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\StorePal.Android.AndroidKeyStore.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\StorePal.Android.ExportPal.cs" />
@@ -1044,6 +1049,7 @@
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixChainVerifier.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixExportProvider.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixPkcs12Reader.cs" />
+    <Compile Include="System\Security\Cryptography\X509Certificates\UnmanagedCryptoBufferMemoryManager.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnsupportedDisallowedStore.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X500NameEncoder.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X500NameEncoder.ManagedDecode.cs" />
@@ -1157,9 +1163,11 @@
     <Compile Include="System\Security\Cryptography\X509Certificates\FindPal.Apple.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\ManagedCertificateFinder.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\ManagedX509ExtensionProcessor.cs" />
+    <Compile Include="System\Security\Cryptography\X509Certificates\SafeLocalAllocWithClearOnDisposeHandle.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixChainVerifier.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixExportProvider.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\UnixPkcs12Reader.cs" />
+    <Compile Include="System\Security\Cryptography\X509Certificates\UnmanagedCryptoBufferMemoryManager.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X500NameEncoder.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X500NameEncoder.ManagedDecode.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X509Pal.Apple.ECKey.cs" />
@@ -1633,8 +1641,6 @@
              Link="Common\Microsoft\Win32\SafeHandles\SafeCertStoreHandle.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeChainEngineHandle.cs"
              Link="Common\Microsoft\Win32\SafeHandles\SafeChainEngineHandle.cs" />
-    <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeCrypt32Handle.cs"
-             Link="Common\Microsoft\Win32\SafeHandles\SafeCrypt32Handle.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeCryptMsgHandle.cs"
              Link="Common\Microsoft\Win32\SafeHandles\SafeCryptMsgHandle.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeUnicodeStringHandle.cs"

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/SafeLocalAllocWithClearOnDisposeHandle.cs

@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+namespace System.Security.Cryptography.X509Certificates
+{
+    /// <summary>
+    /// SafeHandle for LocalAlloc'd memory which calls ZeroMemory when releasing handle.
+    /// </summary>
+    internal sealed class SafeLocalAllocWithClearOnDisposeHandle : SafeCrypt32Handle<SafeLocalAllocWithClearOnDisposeHandle>
+    {
+        internal int Length { get; private set; }
+
+        public static SafeLocalAllocWithClearOnDisposeHandle Create(int cb)
+        {
+            var h = new SafeLocalAllocWithClearOnDisposeHandle();
+            h.SetHandle(Marshal.AllocHGlobal(cb));
+            h.Length = cb;
+            return h;
+        }
+
+        internal unsafe Span<byte> DangerousGetSpan()
+            => new Span<byte>((void*)handle, Length);
+
+        protected sealed override unsafe bool ReleaseHandle()
+        {
+            CryptographicOperations.ZeroMemory(DangerousGetSpan());
+            Marshal.FreeHGlobal(handle);
+            return true;
+        }
+    }
+}

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/UnixPkcs12Reader.cs

@@ -24,7 +24,7 @@ internal abstract class UnixPkcs12Reader : IDisposable
         private ContentInfoAsn[]? _safeContentsValues;
         private CertAndKey[]? _certs;
         private int _certCount;
-        private PointerMemoryManager<byte>? _tmpManager;
+        private UnmanagedCryptoBufferMemoryManager? _tmpManager;
         private bool _allowDoubleBind;
 
         protected abstract ICertificatePalCore ReadX509Der(ReadOnlyMemory<byte> data);
@@ -40,13 +40,10 @@ protected void ParsePkcs12(ReadOnlySpan<byte> data)
                 // Windows compatibility: Ignore trailing data.
                 ReadOnlySpan<byte> encodedData = reader.PeekEncodedValue();
 
-                unsafe
-                {
-                    IntPtr tmpPtr = Marshal.AllocHGlobal(encodedData.Length);
-                    Span<byte> tmpSpan = new Span<byte>((byte*)tmpPtr, encodedData.Length);
-                    encodedData.CopyTo(tmpSpan);
-                    _tmpManager = new PointerMemoryManager<byte>((void*)tmpPtr, encodedData.Length);
-                }
+                // We use unmanaged buffer to avoid GC compaction clones of the private key material
+                _tmpManager = new UnmanagedCryptoBufferMemoryManager(encodedData.Length);
+                Span<byte> tmpSpan = _tmpManager.GetSpan();
+                encodedData.CopyTo(tmpSpan);
 
                 ReadOnlyMemory<byte> tmpMemory = _tmpManager.Memory;
                 reader = new AsnValueReader(tmpMemory.Span, AsnEncodingRules.BER);
@@ -112,26 +109,8 @@ internal IEnumerable<CertAndKey> EnumerateAll()
 
         public void Dispose()
         {
-            // Generally, having a MemoryManager cleaned up in a Dispose is a bad practice.
-            // In this case, the UnixPkcs12Reader is only ever created in a using statement,
-            // never accessed by a second thread, and there isn't a manual call to Dispose
-            // mixed in anywhere.
-            if (_tmpManager != null)
-            {
-                unsafe
-                {
-                    Span<byte> tmp = _tmpManager.GetSpan();
-                    CryptographicOperations.ZeroMemory(tmp);
-
-                    fixed (byte* ptr = tmp)
-                    {
-                        Marshal.FreeHGlobal((IntPtr)ptr);
-                    }
-                }
-
-                ((IDisposable)_tmpManager).Dispose();
-                _tmpManager = null;
-            }
+            ((IDisposable?)_tmpManager)?.Dispose();
+            _tmpManager = null;
 
             ContentInfoAsn[]? rentedContents = Interlocked.Exchange(ref _safeContentsValues, null);
             CertAndKey[]? rentedCerts = Interlocked.Exchange(ref _certs, null);

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/UnmanagedCryptoBufferMemoryManager.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Buffers;
+
+namespace System.Security.Cryptography.X509Certificates
+{
+    /// <summary>
+    /// Unmanaged memory manager backed by buffer allocated with Marshal.AllocHGlobal ensuring memory is cleared on Dispose.
+    /// </summary>
+    internal sealed unsafe class UnmanagedCryptoBufferMemoryManager : MemoryManager<byte>
+    {
+        private readonly SafeLocalAllocWithClearOnDisposeHandle _handle;
+
+        internal UnmanagedCryptoBufferMemoryManager(int length)
+        {
+            _handle = SafeLocalAllocWithClearOnDisposeHandle.Create(length);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                _handle.Dispose();
+            }
+        }
+
+        public override Span<byte> GetSpan()
+            => _handle.DangerousGetSpan();
+
+        public override MemoryHandle Pin(int elementIndex = 0)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void Unpin()
+        {
+        }
+    }
+}