BizHawk/BizHawk.Client.Common/SharpCompress/Common/Rar/RarCryptoBinaryReader.cs

#if !NO_CRYPTO
using System.Collections.Generic;
using System.IO;

namespace SharpCompress.Common.Rar
{
    internal class RarCryptoBinaryReader : RarCrcBinaryReader
    {
        private RarRijndael _rijndael;
        private byte[] _salt;
        private readonly string _password;
        private readonly Queue<byte> _data = new Queue<byte>();
        private long _readCount;

        public RarCryptoBinaryReader(Stream stream, string password)
            : base(stream)
        {
            _password = password;

            // coderb: not sure why this was being done at this logical point
            //SkipQueue();
            byte[] salt = ReadBytes(8);
            InitializeAes(salt);
        }

        // track read count ourselves rather than using the underlying stream since we buffer
        public override long CurrentReadByteCount
        {
            get => _readCount;
            protected set
            {
                // ignore
            }
        }

        public override void Mark()
        {
            _readCount = 0;
        }

        private bool UseEncryption => _salt != null;

        internal void InitializeAes(byte[] salt)
        {
            _salt = salt;
            _rijndael = RarRijndael.InitializeFrom(_password, salt);
        }

        public override byte ReadByte()
        {
            if (UseEncryption)
            {
                return ReadAndDecryptBytes(1)[0];
            }

            _readCount++;
            return base.ReadByte();
        }

        public override byte[] ReadBytes(int count)
        {
            if (UseEncryption)
            {
                return ReadAndDecryptBytes(count);
            }

            _readCount += count;
            return base.ReadBytes(count);
        }

        private byte[] ReadAndDecryptBytes(int count)
        {
            int queueSize = _data.Count;
            int sizeToRead = count - queueSize;

            if (sizeToRead > 0)
            {
                int alignedSize = sizeToRead + ((~sizeToRead + 1) & 0xf);
                for (int i = 0; i < alignedSize / 16; i++)
                {
                    //long ax = System.currentTimeMillis();
                    byte[] cipherText = ReadBytesNoCrc(16);
                    var readBytes = _rijndael.ProcessBlock(cipherText);
                    foreach (var readByte in readBytes)
                        _data.Enqueue(readByte);
                }
            }

            var decryptedBytes = new byte[count];

            for (int i = 0; i < count; i++)
            {
                var b = _data.Dequeue();
                decryptedBytes[i] = b;
                UpdateCrc(b);
            }

            _readCount += count;
            return decryptedBytes;
        }

        public void ClearQueue()
        {
            _data.Clear();
        }

        public void SkipQueue()
        {
            var position = BaseStream.Position;
            BaseStream.Position = position + _data.Count;
            ClearQueue();
        }
    }
}
#endif