From d060188b123315bd0275e05a6d6c111551f892d7 Mon Sep 17 00:00:00 2001
From: Frans van Dorsselaer <17404029+dorssel@users.noreply.github.com>
Date: Wed, 8 Jan 2025 16:18:17 +0100
Subject: [PATCH] Prepare for Span

---
 .github/linters/vs-spell-exclusion.txt |  1 +
 AesExtra/AesExtra.csproj               |  8 ++++++--
 AesExtra/AesSiv.cs                     |  2 +-
 AesExtra/CryptographicOperations.cs    | 10 +++++++---
 AesExtra/GlobalSuppressions.cs         |  2 ++
 Directory.Packages.props               |  2 ++
 UnitTests/UnitTests.csproj             |  4 +++-
 7 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/.github/linters/vs-spell-exclusion.txt b/.github/linters/vs-spell-exclusion.txt
index 1a17389..b6e3af2 100644
--- a/.github/linters/vs-spell-exclusion.txt
+++ b/.github/linters/vs-spell-exclusion.txt
@@ -8,5 +8,6 @@ dotnet
 Encryptor
 inliner
 IntelliSense
+netstandard
 NIST
 xorend
diff --git a/AesExtra/AesExtra.csproj b/AesExtra/AesExtra.csproj
index e46d95a..17ee546 100644
--- a/AesExtra/AesExtra.csproj
+++ b/AesExtra/AesExtra.csproj
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <!--
 SPDX-FileCopyrightText: 2022 Frans van Dorsselaer
 
@@ -7,7 +7,7 @@ SPDX-License-Identifier: MIT
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
     <RootNamespace>Dorssel.Security.Cryptography</RootNamespace>
     <AssemblyName>Dorssel.Security.Cryptography.AesExtra</AssemblyName>
 
@@ -21,4 +21,8 @@ SPDX-License-Identifier: MIT
     <None Include="..\README.md" Pack="true" PackagePath="" Visible="false" />
   </ItemGroup>
 
+  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+    <PackageReference Include="Microsoft.Bcl.Memory" />
+  </ItemGroup>
+
 </Project>
diff --git a/AesExtra/AesSiv.cs b/AesExtra/AesSiv.cs
index 2d5889a..16a7c07 100644
--- a/AesExtra/AesSiv.cs
+++ b/AesExtra/AesSiv.cs
@@ -65,7 +65,7 @@ byte[] S2V(byte[][] associatedData, byte[] plaintext)
             _ = Cmac.TransformBlock(plaintext, 0, plaintext.Length - BLOCKSIZE, null, 0);
             _ = Cmac.TransformBlock(D, 0, BLOCKSIZE, null, 0);
             _ = Cmac.TransformFinalBlock([], 0, 0);
-            return Cmac.Hash;
+            return Cmac.Hash!;
         }
         else
         {
diff --git a/AesExtra/CryptographicOperations.cs b/AesExtra/CryptographicOperations.cs
index dae58ea..b53efc0 100644
--- a/AesExtra/CryptographicOperations.cs
+++ b/AesExtra/CryptographicOperations.cs
@@ -3,12 +3,14 @@
 //
 // SPDX-License-Identifier: MIT
 
+#if NETSTANDARD2_0
+
 using System.Runtime.CompilerServices;
 
 namespace Dorssel.Security.Cryptography;
 
 /// <summary>
-/// This is a backport of .NET 9. Since this library is for .NET Standard 2.0 it uses <see cref="byte"/>[] instead of Span.
+/// This is a backport of .NET 9.
 /// <para/>
 /// See:
 /// <see href="https://github.com/dotnet/runtime/blob/main/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CryptographicOperations.cs"/>
@@ -16,7 +18,7 @@ namespace Dorssel.Security.Cryptography;
 static class CryptographicOperations
 {
     [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
-    public static bool FixedTimeEquals(byte[] left, byte[] right)
+    public static bool FixedTimeEquals(ReadOnlySpan<byte> left, ReadOnlySpan<byte> right)
     {
         // NoOptimization because we want this method to be exactly as non-short-circuiting
         // as written.
@@ -40,7 +42,7 @@ public static bool FixedTimeEquals(byte[] left, byte[] right)
     }
 
     [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
-    public static void ZeroMemory(byte[] buffer)
+    public static void ZeroMemory(Span<byte> buffer)
     {
         // NoOptimize to prevent the optimizer from deciding this call is unnecessary
         // NoInlining to prevent the inliner from forgetting that the method was no-optimize
@@ -50,3 +52,5 @@ public static void ZeroMemory(byte[] buffer)
         }
     }
 }
+
+#endif
diff --git a/AesExtra/GlobalSuppressions.cs b/AesExtra/GlobalSuppressions.cs
index fad0ac1..da9b987 100644
--- a/AesExtra/GlobalSuppressions.cs
+++ b/AesExtra/GlobalSuppressions.cs
@@ -11,3 +11,5 @@
 
 [assembly: SuppressMessage("Security", "CA5358:Review cipher mode usage with cryptography experts", Justification = "Done :)")]
 [assembly: SuppressMessage("Security", "CA5401:Do not use CreateEncryptor with non-default IV", Justification = "We only use ECB, which does not use an IV")] // DevSkim: ignore DS187371
+[assembly: SuppressMessage("Maintainability", "CA1512:Use ArgumentOutOfRangeException throw helper", Justification = "Not available in netstandard2.0.")]
+[assembly: SuppressMessage("Maintainability", "CA1513:Use ObjectDisposedException throw helper", Justification = "Not available in netstandard2.0.")]
diff --git a/Directory.Packages.props b/Directory.Packages.props
index 41f25e6..b5ab572 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -8,6 +8,8 @@ SPDX-License-Identifier: MIT
   <ItemGroup>
     <!-- all -->
     <PackageVersion Include="Dorssel.GitVersion.MsBuild" Version="1.1.0" />
+    <!-- netstandard2.0 -->
+    <PackageVersion Include="Microsoft.Bcl.Memory" Version="9.0.0" />
     <!-- UnitTests -->
     <PackageVersion Include="Moq" Version="4.20.72" />
   </ItemGroup>
diff --git a/UnitTests/UnitTests.csproj b/UnitTests/UnitTests.csproj
index 2e0397c..cc7cd9f 100644
--- a/UnitTests/UnitTests.csproj
+++ b/UnitTests/UnitTests.csproj
@@ -17,7 +17,9 @@ SPDX-License-Identifier: MIT
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\AesExtra\AesExtra.csproj" />
+    <ProjectReference Include="..\AesExtra\AesExtra.csproj">
+      <SetTargetFramework>TargetFramework=netstandard2.0</SetTargetFramework>
+    </ProjectReference>
   </ItemGroup>
 
 </Project>