LibHac/src/hactoolnet/ProcessNax0.cs

using System;
using System.Linq;
using System.Text;
using LibHac.Common;
using LibHac.Crypto;
using LibHac.Fs;
using LibHac.Fs.Fsa;
using LibHac.FsSystem;
using LibHac.Tools.FsSystem;
using LibHac.Util;
using static hactoolnet.Print;

namespace hactoolnet;

internal static class ProcessNax0
{
    public static void Process(Context ctx)
    {
        if (ctx.Options.SdPath == null)
        {
            ctx.Logger.LogMessage("SD path must be specified.");
            return;
        }

        Span<AesXtsKey> keys = ctx.KeySet.SdCardEncryptionKeys;

        using var baseFile = new UniqueRef<IFile>(new LocalFile(ctx.Options.InFile, OpenMode.Read));

        AesXtsFile xtsFile = null;
        int contentType = 0;

        for (int i = 0; i < keys.Length; i++)
        {
            byte[] kekSource = keys[i].SubKeys[0].DataRo.ToArray();
            byte[] validationKey = keys[i].SubKeys[1].DataRo.ToArray();

            try
            {
                xtsFile = new AesXtsFile(OpenMode.Read, ref baseFile.Ref(), ctx.Options.SdPath.ToU8String(), kekSource, validationKey, 0x4000);
                contentType = i;

                break;
            }
            catch (HorizonResultException) { }
        }

        if (xtsFile == null)
        {
            ctx.Logger.LogMessage("Error: NAX0 key derivation failed. Check SD card seed and relative path.");
            return;
        }

        ctx.Logger.LogMessage(xtsFile.Print(contentType));

        if (string.IsNullOrWhiteSpace(ctx.Options.PlaintextOut)) return;

        xtsFile.AsStorage().WriteAllBytes(ctx.Options.PlaintextOut, ctx.Logger);
        ctx.Logger.LogMessage($"Saved Decrypted NAX0 Content to {ctx.Options.PlaintextOut}...");
    }

    private static string Print(this AesXtsFile xtsFile, int contentType)
    {
        int colLen = 36;
        var sb = new StringBuilder();
        sb.AppendLine();

        sb.AppendLine("NAX0:");

        AesXtsFileHeader header = xtsFile.Header;
        uint magic = header.Magic;

        PrintItem(sb, colLen, "    Magic:", StringUtils.Utf8ToString(SpanHelpers.AsReadOnlyByteSpan(in magic)));
        PrintItem(sb, colLen, "    Content Type:", GetContentType(contentType));
        PrintItem(sb, colLen, "    Content Size:", $"{header.Size:x12}");
        PrintItem(sb, colLen, "    Header HMAC:", header.Signature);
        PrintItem(sb, colLen, "    Encrypted Keys:", header.EncryptedKey1.Concat(header.EncryptedKey2).ToArray());
        PrintItem(sb, colLen, "    Decrypted Keys:", header.DecryptedKey1.Concat(header.DecryptedKey2).ToArray());

        return sb.ToString();
    }

    private static string GetContentType(int type) => type switch
    {
        0 => "Save",
        1 => "NCA",
        2 => "Custom storage",
        _ => "Unknown"
    };
}