Fixing HashCode Seed Initialization on BCL package (#43004)

* Fixing HashCode Seed Initialization on BCL package

* Adding Branding and building of HashCode package

* Addressing PR Feedback

* Adding Unit Test

* Address PR feedback

* Adding test for appcontext switch too

* Disable EnsureSeedReturnsEqualValuesWhenAppContextSwitchIsSet on netcoreapp

* Adding retry helper in case the test fails in Linux due to timing

Co-authored-by: Eric StJohn <ericstj@microsoft.com>

src/Microsoft.Bcl.HashCode/Directory.Build.props

@@ -2,7 +2,7 @@
  <Import Project="..\Directory.Build.props" />
  <PropertyGroup>
  <AssemblyVersion>1.0.0.0</AssemblyVersion>
- <PackageVersion>1.1.0</PackageVersion>
+ <PackageVersion>1.1.1</PackageVersion>
  <StrongNameKeyId>Open</StrongNameKeyId>
  <!-- This assembly should never be placed inbox as it is only for downlevel compatibility. -->
  </PropertyGroup>

src/Microsoft.Bcl.HashCode/src/Interop.GetRandomBytes.cs

@@ -3,12 +3,21 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
 
 internal partial class Interop
 {
  internal static unsafe void GetRandomBytes(byte* buffer, int length)
  {
- byte[] bytes = Guid.NewGuid().ToByteArray();
- buffer = (byte*)BitConverter.ToUInt32(bytes, 0);
+ if (!LocalAppContextSwitches.UseNonRandomizedHashSeed)
+ {
+ using (RandomNumberGenerator rng = RandomNumberGenerator.Create())
+ {
+ byte[] tmp = new byte[length];
+ rng.GetBytes(tmp);
+ Marshal.Copy(tmp, 0, (IntPtr)buffer, length);
+ }
+ }
  }
 }

src/Microsoft.Bcl.HashCode/src/LocalAppContextSwitches.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ private static int s_useNonRandomizedHashSeed;
+ public static bool UseNonRandomizedHashSeed
+ {
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ get => GetCachedSwitchValue("Switch.System.Data.UseNonRandomizedHashSeed", ref s_useNonRandomizedHashSeed);
+ }
+ }
+}

src/Microsoft.Bcl.HashCode/src/Microsoft.Bcl.HashCode.csproj

@@ -4,7 +4,7 @@
  <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  <IsPartialFacadeAssembly Condition="'$(TargetFramework)' != 'netstandard2.0' AND '$(TargetsNetFx)' != 'true'">true</IsPartialFacadeAssembly>
  <OmitResources>$(IsPartialFacadeAssembly)</OmitResources>
- <Configurations>net461-Debug;net461-Release;netcoreapp-Debug;netcoreapp-Release;netcoreapp2.1-Debug;netcoreapp2.1-Release;netfx-Debug;netfx-Release;netstandard-Debug;netstandard-Release;netstandard2.1-Debug;netstandard2.1-Release</Configurations>
+ <Configurations>netstandard-Debug;netstandard-Release;net461-Debug;net461-Release;netcoreapp-Debug;netcoreapp-Release;netcoreapp2.1-Debug;netcoreapp2.1-Release;netfx-Debug;netfx-Release;netstandard2.1-Debug;netstandard2.1-Release</Configurations>
  <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup Condition="'$(IsPartialFacadeAssembly)' != 'true'">
@@ -13,6 +13,10 @@
  </Compile>
  <Compile Include="BitOperations.cs" />
  <Compile Include="Interop.GetRandomBytes.cs" />
+ <Compile Include="LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)\CoreLib\System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\CoreLib\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Reference Include="mscorlib" />
  <Reference Include="System" />
  </ItemGroup>

src/Microsoft.Bcl.HashCode/tests/Configurations.props

@@ -0,0 +1,8 @@
+<Project DefaultTargets="Build">
+ <PropertyGroup>
+ <BuildConfigurations>
+ netfx;
+ netcoreapp;
+ </BuildConfigurations>
+ </PropertyGroup>
+</Project>

src/Microsoft.Bcl.HashCode/tests/HashCodeSeedInitializerTests.cs

@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.DotNet.RemoteExecutor;
+using System;
+using System.Reflection;
+using Xunit;
+
+namespace Microsoft.Bcl.HashCode.Tests
+{
+ public class HashCodeSeedInitializerTests
+ {
+ [Fact]
+ public void EnsureSeedReturnsDifferentValuesTest()
+ {
+ // Adding 5 retries since in Netcoreapp-Linux the seed that is generated is time-dependant so
+ // this test might fail there. This will ensure we reduce flakiness while still providing
+ // regression coverage.
+ RetryHelper.Execute(() =>
+ {
+ int FirstSeed = CalculateHashCodeInRemoteProcess(setAppContextSwitch: false);
+ int SecondSeed = CalculateHashCodeInRemoteProcess(setAppContextSwitch: false);
+
+ Assert.NotEqual(FirstSeed, SecondSeed);
+ });
+ }
+
+ [Fact]
+ [SkipOnTargetFramework(TargetFrameworkMonikers.Netcoreapp, "AppContextSwitch is not supported on .NETCore")]
+ public void EnsureSeedReturnsEqualValuesWhenAppContextSwitchIsSet()
+ {
+ int FirstSeed = CalculateHashCodeInRemoteProcess(setAppContextSwitch: true);
+ int SecondSeed = CalculateHashCodeInRemoteProcess(setAppContextSwitch: true);
+
+ Assert.Equal(FirstSeed, SecondSeed);
+ }
+
+ private int CalculateHashCodeInRemoteProcess(bool setAppContextSwitch)
+ {
+ RemoteInvokeOptions options = new RemoteInvokeOptions()
+ {
+ CheckExitCode = false
+ };
+ var executor = (setAppContextSwitch) ?
+ RemoteExecutor.Invoke(() =>
+ {
+ AppContext.SetSwitch("Switch.System.Data.UseNonRandomizedHashSeed", true);
+ return GetHashCodeSeed(); 
+ }, options) : 
+ RemoteExecutor.Invoke(GetHashCodeSeed, options);
+
+ int hashedResult = executor.ExitCode;
+ executor.Dispose();
+
+ return hashedResult;
+
+ int GetHashCodeSeed()
+ {
+ System.HashCode hc = new System.HashCode();
+ hc.Add(5);
+ return hc.ToHashCode();
+ };
+ }
+
+ }
+
+}

src/Microsoft.Bcl.HashCode/tests/Microsoft.Bcl.HashCode.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <Configurations>netfx-Debug;netfx-Release;netcoreapp-Debug;netcoreapp-Release</Configurations>
+ <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="HashCodeSeedInitializerTests.cs" />
+ </ItemGroup>
+</Project>

src/packages.builds

@@ -26,6 +26,9 @@
  <AdditionalProperties>$(AdditionalProperties)</AdditionalProperties>
  </Project>
  <!-- add specific builds / pkgproj's here to include in servicing builds -->
+ <Project Include="$(MSBuildThisFileDirectory)Microsoft.Bcl.HashCode\pkg\Microsoft.Bcl.HashCode.pkgproj">
+ <AdditionalProperties>$(AdditionalProperties)</AdditionalProperties>
+ </Project>
  </ItemGroup>
 
  <ItemGroup>