public static void AddIfExists(this List <NCCHRegion> list, NCCHRegion region)
{
if (region.Size != 0)
{
list.Add(region);
}
}
private void ExtractExeFS(Stream output, NCCHRegion region, Keyslot secondaryKeyslot, bool close = true)
{
if (secondaryKeyslot == Keyslot.NCCH)
{
//if the secondary keyslot is also the original 0x2C NCCH Keyslot, don't bother decrypting anything in parts, and just shove the entire ExeFS through a CryptoStream
Tools.CryptFileStreamPart(this.NCCHMemoryMappedFile, output, new AesCtrCryptoTransform(this.Cryptor.NormalKey[(int)Keyslot.NCCH], region.CTR), region.Offset, region.Size, close);
return;
}
//here we go, i don't like this part
byte[] header = new byte[0x200];
using (MemoryMappedViewStream headerViewStream = this.NCCHMemoryMappedFile.CreateViewStream(region.Offset, 0x200))
{
header = Tools.CryptBytes(headerViewStream.ReadBytes(0x200), new AesCtrCryptoTransform(this.Cryptor.NormalKey[0x2C], region.CTR));
}
output.Write(header);
//create dummy ExeFS class instance to figure out the locations of each file in the ExeFS
ExeFS exefs = new ExeFS(header);
//write decrypted header to output file
foreach (ExeFSEntry entry in exefs.Entries)
{
byte[] CTR = (region.CTRInt + (entry.Offset / 16)).ToCTRBytes();
AesCtrCryptoTransform transform = (NormalCryptoExeFSFiles.Contains(entry.Name)) ? new AesCtrCryptoTransform(this.Cryptor.NormalKey[(int)Keyslot.NCCH], CTR) : new AesCtrCryptoTransform(this.Cryptor.NormalKey[(int)secondaryKeyslot], CTR);
using (MemoryMappedViewStream fileViewStream = this.NCCHMemoryMappedFile.CreateViewStream(region.Offset + entry.Offset, entry.Size))
{
CryptoStream cs = new CryptoStream(output, transform, CryptoStreamMode.Write);
output.Seek(entry.Offset, SeekOrigin.Begin);
fileViewStream.CopyTo(cs);
cs.FlushFinalBlock();
}
}
//sneaky way to make it gm9-like
if (!(output.GetType() == typeof(MemoryMappedViewStream)))
{
output.SetLength(Tools.RoundUp(output.Length, 0x200));
}
if (close)
{
output.Dispose();
}
}
public void ExtractSection(NCCHSection section, Stream outputStream, bool decrypt = true, bool close = true)
{
if (this.Info.Flags.UsesEncryption && this.Cryptor == null && decrypt == true)
{
throw new ArgumentException("This NCCH is encrypted, and no Crypto Engine was provided to perform decryption.");
}
if (!this.Regions.Any(region => region.Type == section))
{
throw new ArgumentException($"The requested section ({Enum.GetName(typeof(NCCHSection), section)}) was not found inside this NCCH.");
}
NCCHRegion region = this.Regions.Find(region => region.Type == section);
if (this.Info.Flags.UsesEncryption && decrypt && !NoCryptoSections.Contains(region.Type)) //if encrypted, user wants to decrypt, and the selected region is known to use encryption
{
Keyslot primaryKeyslot;
Keyslot secondaryKeyslot;
byte[] secondaryKeyY = new byte[16];
if (this.Info.Flags.UsesFixedKey)
{
primaryKeyslot = ((this.Info.TitleID & (0x10 << 32)) > 0) ? Keyslot.FixedSystemKey : Keyslot.ZeroKey;
secondaryKeyslot = primaryKeyslot;
}
else
{
primaryKeyslot = Keyslot.NCCH;
secondaryKeyslot = secondaryKeyslot = this.Info.Flags.CryptoMethod switch
{
0x00 => Keyslot.NCCH,
0x01 => Keyslot.NCCH70,
0x0A => Keyslot.NCCH93,
0x0B => Keyslot.NCCH96,
_ => throw new Exception("Could not determine crypto type. This should NOT happen.")
};
if (this.Info.Flags.UsesSeed)
{
this.Info.LoadSeed(this.SeedDB);
secondaryKeyY = this.Info.SeededKeyY;
}
else
{
secondaryKeyY = this.Info.KeyY;
}
}
this.Cryptor.SetKeyslot("y", (int)primaryKeyslot, this.Info.KeyY.ToUnsignedBigInt()); //load primary key into keyslot
this.Cryptor.SetKeyslot("y", (int)secondaryKeyslot, secondaryKeyY.ToUnsignedBigInt()); //load secondary key into keyslot
//decrypts based on section
switch (region.Type)
{
case NCCHSection.ExHeader:
Tools.CryptFileStreamPart(this.NCCHMemoryMappedFile, outputStream, new AesCtrCryptoTransform(this.Cryptor.NormalKey[(int)primaryKeyslot], region.CTR), region.Offset, region.Size, close);
break;
case NCCHSection.RomFS:
//uses secondary keyslot for it's entirety
Tools.CryptFileStreamPart(this.NCCHMemoryMappedFile, outputStream, new AesCtrCryptoTransform(this.Cryptor.NormalKey[(int)secondaryKeyslot], region.CTR), region.Offset, region.Size, close);
break;
case NCCHSection.ExeFS:
//can use two keyslots. because of this, I separated the ExeFS decryption into another method
ExtractExeFS(outputStream, region, secondaryKeyslot, close);
break;
}
}
else //just extract the raw section, because no crypto is used or the user did not request decryption
{
Tools.ExtractFileStreamPart(this.NCCHMemoryMappedFile, outputStream, region.Offset, region.Size, close);
}
}
