LibHac/libhac/Nca.cs

using System;
using System.Collections.Generic;
using System.IO;
using libhac.XTSSharp;

namespace libhac
{
    public class Nca : IDisposable
    {
        public NcaHeader Header { get; private set; }
        public string NcaId { get; set; }
        public string Filename { get; set; }
        public bool HasRightsId { get; private set; }
        public int CryptoType { get; private set; }
        public byte[][] DecryptedKeys { get; } = Util.CreateJaggedArray<byte[][]>(4, 0x10);
        public Stream Stream { get; private set; }
        private bool KeepOpen { get; }

        public List<NcaSection> Sections = new List<NcaSection>();

        public Nca(Keyset keyset, Stream stream, bool keepOpen)
        {
            stream.Position = 0;
            KeepOpen = keepOpen;
            Stream = stream;
            DecryptHeader(keyset, stream);

            CryptoType = Math.Max(Header.CryptoType, Header.CryptoType2);
            if (CryptoType > 0) CryptoType--;

            HasRightsId = !Header.RightsId.IsEmpty();

            if (!HasRightsId)
            {
                DecryptKeyArea(keyset);
            }

            for (int i = 0; i < 4; i++)
            {
                var section = ParseSection(i);
                if (section != null) Sections.Add(section);
            }
        }

        public Stream OpenSection(int index)
        {
            if (index >= Sections.Count) throw new ArgumentOutOfRangeException(nameof(index));
            var sect = Sections[index];

            long offset = sect.Offset;
            long size = sect.Size;

            switch (sect.Header.FsType)
            {
                case SectionFsType.Pfs0:
                    offset = sect.Offset + sect.Pfs0.Pfs0Offset;
                    size = sect.Pfs0.Pfs0Size;
                    break;
                case SectionFsType.Romfs:
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }

            Stream.Position = offset;

            switch (sect.Header.CryptType)
            {
                case SectionCryptType.None:
                    break;
                case SectionCryptType.XTS:
                    break;
                case SectionCryptType.CTR:
                    return new RandomAccessSectorStream(new AesCtrStream(Stream, DecryptedKeys[2], offset, size, offset), false);
                case SectionCryptType.BKTR:
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }

            return Stream;
        }

        private void DecryptHeader(Keyset keyset, Stream stream)
        {
            byte[] headerBytes = new byte[0xC00];
            var xts = XtsAes128.Create(keyset.header_key);
            using (var headerDec = new RandomAccessSectorStream(new XtsSectorStream(stream, xts, 0x200)))
            {
                headerDec.Read(headerBytes, 0, headerBytes.Length);
            }

            var reader = new BinaryReader(new MemoryStream(headerBytes));

            Header = NcaHeader.Read(reader);
        }

        private void DecryptKeyArea(Keyset keyset)
        {
            for (int i = 0; i < 4; i++)
            {
                Crypto.DecryptEcb(keyset.key_area_keys[CryptoType][Header.KaekInd], Header.EncryptedKeys[i],
                    DecryptedKeys[i], 0x10);
            }
        }

        private NcaSection ParseSection(int index)
        {
            var entry = Header.SectionEntries[index];
            var header = Header.FsHeaders[index];
            if (entry.MediaStartOffset == 0) return null;

            var sect = new NcaSection();

            sect.SectionNum = index;
            sect.Offset = Util.MediaToReal(entry.MediaStartOffset);
            sect.Size = Util.MediaToReal(entry.MediaEndOffset) - sect.Offset;
            sect.Header = header;
            sect.Type = header.Type;

            if (sect.Type == SectionType.Pfs0)
            {
                sect.Pfs0 = header.Pfs0;
            }

            return sect;
        }

        public void Dispose()
        {
            if (!KeepOpen)
            {
                Stream?.Dispose();
            }
        }
    }

    public class NcaSection
    {
        public Stream Stream { get; set; }
        public NcaFsHeader Header { get; set; }
        public SectionType Type { get; set; }
        public int SectionNum { get; set; }
        public long Offset { get; set; }
        public long Size { get; set; }

        public Pfs0Superblock Pfs0 { get; set; }
    }
}