Support NCAs with sparse partitions

src/LibHac/Common/FixedArrays/Array6.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace LibHac.Common.FixedArrays;
+
+[StructLayout(LayoutKind.Sequential)]
+public struct Array6<T>
+{
+    public const int Length = 6;
+
+    private T _1;
+    private T _2;
+    private T _3;
+    private T _4;
+    private T _5;
+    private T _6;
+
+    public ref T this[int i] => ref Items[i];
+
+    public Span<T> Items => SpanHelpers.CreateSpan(ref _1, Length);
+    public readonly ReadOnlySpan<T> ItemsRo => SpanHelpers.CreateReadOnlySpan(in _1, Length);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator ReadOnlySpan<T>(in Array6<T> value) => value.ItemsRo;
+}

src/LibHac/FsSystem/NcaUtils/Nca.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
+using System.Runtime.CompilerServices;
 using LibHac.Common;
 using LibHac.Common.Keys;
 using LibHac.Crypto;
@@ -148,12 +149,71 @@ public class Nca
         long offset = Header.GetSectionStartOffset(index);
         long size = Header.GetSectionSize(index);
 
-        BaseStorage.GetSize(out long baseSize).ThrowIfFailure();
+        BaseStorage.GetSize(out long ncaStorageSize).ThrowIfFailure();
 
-        if (!IsSubRange(offset, size, baseSize))
+        NcaFsHeader fsHeader = Header.GetFsHeader(index);
+
+        if (fsHeader.ExistsSparseLayer())
+        {
+            ref NcaSparseInfo sparseInfo = ref fsHeader.GetSparseInfo();
+
+            Unsafe.SkipInit(out BucketTree.Header header);
+            sparseInfo.MetaHeader.ItemsRo.CopyTo(SpanHelpers.AsByteSpan(ref header));
+            header.Verify().ThrowIfFailure();
+
+            var sparseStorage = new SparseStorage();
+
+            if (header.EntryCount == 0)
+            {
+                sparseStorage.Initialize(size);
+            }
+            else
+            {
+                long dataSize = sparseInfo.GetPhysicalSize();
+
+                if (!IsSubRange(sparseInfo.PhysicalOffset, dataSize, ncaStorageSize))
+                {
+                    throw new InvalidDataException(
+                        $"Section offset (0x{offset:x}) and length (0x{size:x}) fall outside the total NCA length (0x{ncaStorageSize:x}).");
+                }
+
+                IStorage baseStorage = BaseStorage.Slice(sparseInfo.PhysicalOffset, dataSize);
+                baseStorage.GetSize(out long baseStorageSize).ThrowIfFailure();
+
+                long metaOffset = sparseInfo.MetaOffset;
+                long metaSize = sparseInfo.MetaSize;
+
+                if (metaOffset - sparseInfo.PhysicalOffset + metaSize > baseStorageSize)
+                    ResultFs.NcaBaseStorageOutOfRangeB.Value.ThrowIfFailure();
+
+                IStorage metaStorageEncrypted = baseStorage.Slice(metaOffset, metaSize);
+
+                ulong upperCounter = sparseInfo.MakeAesCtrUpperIv(new NcaAesCtrUpperIv(fsHeader.Counter)).Value;
+                IStorage metaStorage = OpenAesCtrStorage(metaStorageEncrypted, index, sparseInfo.PhysicalOffset + metaOffset, upperCounter);
+
+                long nodeOffset = 0;
+                long nodeSize = IndirectStorage.QueryNodeStorageSize(header.EntryCount);
+                long entryOffset = nodeOffset + nodeSize;
+                long entrySize = IndirectStorage.QueryEntryStorageSize(header.EntryCount);
+
+                using var nodeStorage = new ValueSubStorage(metaStorage, nodeOffset, nodeSize);
+                using var entryStorage = new ValueSubStorage(metaStorage, entryOffset, entrySize);
+
+                new SubStorage(metaStorage, nodeOffset, nodeSize).WriteAllBytes("nodeStorage");
+
+                sparseStorage.Initialize(new ArrayPoolMemoryResource(), in nodeStorage, in entryStorage, header.EntryCount).ThrowIfFailure();
+
+                using var dataStorage = new ValueSubStorage(baseStorage, 0, sparseInfo.GetPhysicalSize());
+                sparseStorage.SetDataStorage(in dataStorage);
+            }
+
+            return sparseStorage;
+        }
+
+        if (!IsSubRange(offset, size, ncaStorageSize))
         {
             throw new InvalidDataException(
-                $"Section offset (0x{offset:x}) and length (0x{size:x}) fall outside the total NCA length (0x{baseSize:x}).");
+                $"Section offset (0x{offset:x}) and length (0x{size:x}) fall outside the total NCA length (0x{ncaStorageSize:x}).");
         }
 
         return BaseStorage.Slice(offset, size);
@@ -170,7 +230,7 @@ public class Nca
             case NcaEncryptionType.XTS:
                 return OpenAesXtsStorage(baseStorage, index, decrypting);
             case NcaEncryptionType.AesCtr:
-                return OpenAesCtrStorage(baseStorage, index);
+                return OpenAesCtrStorage(baseStorage, index, Header.GetSectionStartOffset(index), header.Counter);
             case NcaEncryptionType.AesCtrEx:
                 return OpenAesCtrExStorage(baseStorage, index, decrypting);
             default:
@@ -191,13 +251,12 @@ public class Nca
     }
     // ReSharper restore UnusedParameter.Local
 
-    private IStorage OpenAesCtrStorage(IStorage baseStorage, int index)
+    private IStorage OpenAesCtrStorage(IStorage baseStorage, int index, long offset, ulong upperCounter)
     {
-        NcaFsHeader fsHeader = GetFsHeader(index);
         byte[] key = GetContentKey(NcaKeyType.AesCtr);
-        byte[] counter = Aes128CtrStorage.CreateCounter(fsHeader.Counter, Header.GetSectionStartOffset(index));
+        byte[] counter = Aes128CtrStorage.CreateCounter(upperCounter, Header.GetSectionStartOffset(index));
 
-        var aesStorage = new Aes128CtrStorage(baseStorage, key, Header.GetSectionStartOffset(index), counter, true);
+        var aesStorage = new Aes128CtrStorage(baseStorage, key, offset, counter, true);
         return new CachedStorage(aesStorage, 0x4000, 4, true);
     }
 

src/LibHac/FsSystem/NcaUtils/NcaFsHeader.cs

@@ -61,6 +61,17 @@ public struct NcaFsHeader
         return GetPatchInfo().RelocationTreeSize != 0;
     }
 
+    public ref NcaSparseInfo GetSparseInfo()
+    {
+        return ref MemoryMarshal.Cast<byte, NcaSparseInfo>(_header.Span.Slice(FsHeaderStruct.SparseInfoOffset,
+            FsHeaderStruct.SparseInfoSize))[0];
+    }
+
+    public bool ExistsSparseLayer()
+    {
+        return GetSparseInfo().Generation != 0;
+    }
+
     public ulong Counter
     {
         get => Header.UpperCounter;
@@ -86,6 +97,8 @@ public struct NcaFsHeader
         public const int IntegrityInfoSize = 0xF8;
         public const int PatchInfoOffset = 0x100;
         public const int PatchInfoSize = 0x40;
+        public const int SparseInfoOffset = 0x148;
+        public const int SparseInfoSize = 0x30;
 
         [FieldOffset(0)] public short Version;
         [FieldOffset(2)] public byte FormatType;

src/LibHac/FsSystem/NcaUtils/NcaKeyType.cs

@@ -2,9 +2,9 @@
 
 internal enum NcaKeyType
 {
-    AesXts0,
+    AesXts0 = 0,
-    AesXts1,
+    AesXts1 = 1,
-    AesCtr,
+    AesCtr = 2,
-    Type3,
+    AesCtrEx = 3,
-    Type4
+    AesCtrHw = 4
 }

src/LibHac/FsSystem/NcaUtils/NcaStructs.cs

@@ -1,4 +1,8 @@
-namespace LibHac.FsSystem.NcaUtils;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using LibHac.Common.FixedArrays;
+
+namespace LibHac.FsSystem.NcaUtils;
 
 public class TitleVersion
 {
@@ -34,6 +38,42 @@ public class TitleVersion
     }
 }
 
+public struct NcaSparseInfo
+{
+    public long MetaOffset;
+    public long MetaSize;
+    public Array16<byte> MetaHeader;
+    public long PhysicalOffset;
+    public ushort Generation;
+    private Array6<byte> _reserved;
+
+    public readonly uint GetGeneration() => (uint)(Generation << 16);
+    public readonly long GetPhysicalSize() => MetaOffset + MetaSize;
+
+    public readonly NcaAesCtrUpperIv MakeAesCtrUpperIv(NcaAesCtrUpperIv upperIv)
+    {
+        NcaAesCtrUpperIv sparseUpperIv = upperIv;
+        sparseUpperIv.Generation = GetGeneration();
+        return sparseUpperIv;
+    }
+}
+
+[StructLayout(LayoutKind.Explicit)]
+public struct NcaAesCtrUpperIv
+{
+    [FieldOffset(0)] public ulong Value;
+
+    [FieldOffset(0)] public uint Generation;
+    [FieldOffset(4)] public uint SecureValue;
+
+    internal NcaAesCtrUpperIv(ulong value)
+    {
+        Unsafe.SkipInit(out Generation);
+        Unsafe.SkipInit(out SecureValue);
+        Value = value;
+    }
+}
+
 public enum NcaSectionType
 {
     Code,