From cd2b8edfa8a92fbbb444ca18200d519ef6494319 Mon Sep 17 00:00:00 2001
From: Alex Barney <thealexbarney@gmail.com>
Date: Wed, 2 Mar 2022 11:09:17 -0700
Subject: [PATCH] Skeleton AesXtsStorage

---
 src/LibHac/FsSystem/AesXtsStorage.cs | 115 +++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/LibHac/FsSystem/AesXtsStorage.cs

diff --git a/src/LibHac/FsSystem/AesXtsStorage.cs b/src/LibHac/FsSystem/AesXtsStorage.cs
new file mode 100644
index 00000000..229f2161
--- /dev/null
+++ b/src/LibHac/FsSystem/AesXtsStorage.cs
@@ -0,0 +1,115 @@
+// ReSharper disable NotAccessedField.Local
+using System;
+using System.Buffers.Binary;
+using LibHac.Common;
+using LibHac.Common.FixedArrays;
+using LibHac.Crypto;
+using LibHac.Diag;
+using LibHac.Fs;
+using LibHac.Os;
+
+namespace LibHac.FsSystem;
+
+/// <summary>
+/// Reads and writes to an <see cref="IStorage"/> that's encrypted with AES-XTS-128.
+/// </summary>
+/// <remarks>Based on FS 13.1.0 (nnSdk 13.4.0)</remarks>
+public class AesXtsStorage : IStorage
+{
+    public static readonly int AesBlockSize = Aes.BlockSize;
+    public static readonly int KeySize = Aes.KeySize128;
+    public static readonly int IvSize = Aes.KeySize128;
+
+    private IStorage _baseStorage;
+    private Array16<byte> _key1;
+    private Array16<byte> _key2;
+    private Array16<byte> _iv;
+    private int _blockSize;
+    private SdkMutexType _mutex;
+
+    // LibHac addition: This field goes unused if initialized with a plain IStorage.
+    // The original class uses a template for both the shared and non-shared IStorage which avoids needing this field.
+    private SharedRef<IStorage> _baseStorageShared;
+
+    public static void MakeAesXtsIv(Span<byte> outIv, long offset, int blockSize)
+    {
+        Assert.Equal(outIv.Length, IvSize);
+        Assert.SdkRequiresGreaterEqual(offset, 0);
+        Assert.SdkRequiresAligned((ulong)blockSize, AesBlockSize);
+
+        BinaryPrimitives.WriteInt64BigEndian(outIv.Slice(sizeof(long)), offset / blockSize);
+    }
+
+    public AesXtsStorage(IStorage baseStorage, ReadOnlySpan<byte> key1, ReadOnlySpan<byte> key2, ReadOnlySpan<byte> iv,
+        int blockSize)
+    {
+        _baseStorage = baseStorage;
+        _blockSize = blockSize;
+        _mutex = new SdkMutexType();
+
+        Assert.SdkRequiresEqual(KeySize, key1.Length);
+        Assert.SdkRequiresEqual(KeySize, key2.Length);
+        Assert.SdkRequiresEqual(IvSize, iv.Length);
+        Assert.SdkRequiresAligned((ulong)blockSize, AesBlockSize);
+
+        key1.CopyTo(_key1.Items);
+        key2.CopyTo(_key2.Items);
+        iv.CopyTo(_iv.Items);
+    }
+
+    public AesXtsStorage(ref SharedRef<IStorage> baseStorage, ReadOnlySpan<byte> key1, ReadOnlySpan<byte> key2,
+        ReadOnlySpan<byte> iv, int blockSize)
+    {
+        _baseStorageShared = SharedRef<IStorage>.CreateMove(ref baseStorage);
+        _baseStorage = _baseStorageShared.Get;
+        _blockSize = blockSize;
+        _mutex = new SdkMutexType();
+
+        Assert.SdkRequiresEqual(KeySize, key1.Length);
+        Assert.SdkRequiresEqual(KeySize, key2.Length);
+        Assert.SdkRequiresEqual(IvSize, iv.Length);
+        Assert.SdkRequiresAligned((ulong)blockSize, AesBlockSize);
+
+        key1.CopyTo(_key1.Items);
+        key2.CopyTo(_key2.Items);
+        iv.CopyTo(_iv.Items);
+    }
+
+    public override void Dispose()
+    {
+        _baseStorageShared.Destroy();
+
+        base.Dispose();
+    }
+
+    public override Result Read(long offset, Span<byte> destination)
+    {
+        throw new NotImplementedException();
+    }
+
+    public override Result Write(long offset, ReadOnlySpan<byte> source)
+    {
+        throw new NotImplementedException();
+    }
+
+    public override Result Flush()
+    {
+        throw new NotImplementedException();
+    }
+
+    public override Result GetSize(out long size)
+    {
+        throw new NotImplementedException();
+    }
+
+    public override Result SetSize(long size)
+    {
+        throw new NotImplementedException();
+    }
+
+    public override Result OperateRange(Span<byte> outBuffer, OperationId operationId, long offset, long size,
+        ReadOnlySpan<byte> inBuffer)
+    {
+        throw new NotImplementedException();
+    }
+}
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