using System;
using System.IO;
using System.Security.Cryptography;
using Gurock.SmartInspect;

public class CryptoProtocol : FileProtocol
{
	private string fIVOption;
	private string fKeyOption;
	private byte[] fKey;
	private byte[] fIV;

	protected override Stream GetStream(Stream stream)
	{
		if (this.fKey == null || this.fIV == null)
		{
			ThrowException("Invalid key or initialization vector");
		}

		Rijndael rijndael = Rijndael.Create();

		return new CryptoStream(
			stream,
			rijndael.CreateEncryptor(this.fKey, this.fIV),
			CryptoStreamMode.Write
		);
	}

	protected byte[] GetHexadecimalBytes(string s)
	{
		if (s == null)
		{
			return null;
		}

		sbyte[] LOOKUP = 
			{
				-1, -1, -1, -1, -1, -1, -1, -1,
				-1, -1, -1, -1, -1, -1, -1, -1,
				-1, -1, -1, -1, -1, -1, -1, -1,
				-1, -1, -1, -1, -1, -1, -1, -1,
				-1, -1, -1, -1, -1, -1, -1, -1,
				-1, -1, -1, -1, -1, -1, -1, -1,
				 0,  1,  2,  3,  4,  5,  6,  7,
				 8,  9, -1, -1, -1, -1, -1, -1,
				-1, 10, 11, 12, 13, 14, 15
			};

		s = s.ToUpper();
		if ((s.Length & 1) != 0)
		{
			return null;
		}

		byte[] b = new byte[s.Length / 2];

		for (int i = 0; i < b.Length; i++)
		{
			char hiChar = s[i * 2];
			char loChar = s[i * 2 + 1];

			if (hiChar >= LOOKUP.Length ||
				loChar >= LOOKUP.Length)
			{
				return null;
			}

			sbyte hi = LOOKUP[hiChar];
			sbyte lo = LOOKUP[loChar];

			if (hi == -1 || lo == -1)
			{
				return null;
			}

			b[i] = (byte)
				((byte)hi << 4 | (byte)lo);
		}

		return b;
	}

	protected override string Name
	{
		get { return "crypto"; }
	}

	protected override bool IsValidOption(string name)
	{
		return
			name.Equals("key") ||
			name.Equals("iv") ||
			base.IsValidOption(name);
	}

	protected override void LoadOptions()
	{
		base.LoadOptions();
		this.fKeyOption = GetStringOption("key", null);
		this.fKey = GetHexadecimalBytes(this.fKeyOption);
		this.fIVOption = GetStringOption("iv", null);
		this.fIV = GetHexadecimalBytes(this.fIVOption);
	}

	protected override void BuildOptions(ConnectionsBuilder builder)
	{
		base.BuildOptions(builder);
		builder.AddOption("key", this.fKeyOption);
		builder.AddOption("iv", this.fIVOption);
	}
}