Redmine

# = net/smtp.rb

# 

# Copyright (c) 1999-2007 Yukihiro Matsumoto.

#

# Copyright (c) 1999-2007 Minero Aoki.

# 

# Written & maintained by Minero Aoki <aamine@loveruby.net>.

#

# Documented by William Webber and Minero Aoki.

# 

# This program is free software. You can re-distribute and/or

# modify this program under the same terms as Ruby itself.

# 

# NOTE: You can find Japanese version of this document at:

# http://www.ruby-lang.org/ja/man/html/net_smtp.html

# 

# $Id: smtp.rb 28208 2010-06-08 06:14:59Z shyouhei $

#

# See Net::SMTP for documentation. 

# 

require 'net/protocol'

require 'digest/md5'

require 'timeout'

require 'net/ntlm'

begin

  require 'openssl'

rescue LoadError

end

module Net

  # Module mixed in to all SMTP error classes

  module SMTPError

    # This *class* is a module for backward compatibility.

    # In later release, this module becomes a class.

  end

  # Represents an SMTP authentication error.

  class SMTPAuthenticationError < ProtoAuthError

    include SMTPError

  end

  # Represents SMTP error code 420 or 450, a temporary error.

  class SMTPServerBusy < ProtoServerError

    include SMTPError

  end

  # Represents an SMTP command syntax error (error code 500)

  class SMTPSyntaxError < ProtoSyntaxError

    include SMTPError

  end

  # Represents a fatal SMTP error (error code 5xx, except for 500)

  class SMTPFatalError < ProtoFatalError

    include SMTPError

  end

  # Unexpected reply code returned from server.

  class SMTPUnknownError < ProtoUnknownError

    include SMTPError

  end

  # Command is not supported on server.

  class SMTPUnsupportedCommand < ProtocolError

    include SMTPError

  end

  #

  # = Net::SMTP

  #

  # == What is This Library?

  # 

  # This library provides functionality to send internet

  # mail via SMTP, the Simple Mail Transfer Protocol. For details of

  # SMTP itself, see [RFC2821] (http://www.ietf.org/rfc/rfc2821.txt).

  # 

  # == What is This Library NOT?

  # 

  # This library does NOT provide functions to compose internet mails.

  # You must create them by yourself. If you want better mail support,

  # try RubyMail or TMail. You can get both libraries from RAA.

  # (http://www.ruby-lang.org/en/raa.html)

  # 

  # FYI: the official documentation on internet mail is: [RFC2822] (http://www.ietf.org/rfc/rfc2822.txt).

  # 

  # == Examples

  # 

  # === Sending Messages

  # 

  # You must open a connection to an SMTP server before sending messages.

  # The first argument is the address of your SMTP server, and the second 

  # argument is the port number. Using SMTP.start with a block is the simplest 

  # way to do this. This way, the SMTP connection is closed automatically 

  # after the block is executed.

  # 

  #     require 'net/smtp'

  #     Net::SMTP.start('your.smtp.server', 25) do |smtp|

  #       # Use the SMTP object smtp only in this block.

  #     end

  # 

  # Replace 'your.smtp.server' with your SMTP server. Normally

  # your system manager or internet provider supplies a server

  # for you.

  # 

  # Then you can send messages.

  # 

  #     msgstr = <<END_OF_MESSAGE

  #     From: Your Name <your@mail.address>

  #     To: Destination Address <someone@example.com>

  #     Subject: test message

  #     Date: Sat, 23 Jun 2001 16:26:43 +0900

  #     Message-Id: <unique.message.id.string@example.com>

  # 

  #     This is a test message.

  #     END_OF_MESSAGE

  # 

  #     require 'net/smtp'

  #     Net::SMTP.start('your.smtp.server', 25) do |smtp|

  #       smtp.send_message msgstr,

  #                         'your@mail.address',

  #                         'his_addess@example.com'

  #     end

  # 

  # === Closing the Session

  # 

  # You MUST close the SMTP session after sending messages, by calling 

  # the #finish method:

  # 

  #     # using SMTP#finish

  #     smtp = Net::SMTP.start('your.smtp.server', 25)

  #     smtp.send_message msgstr, 'from@address', 'to@address'

  #     smtp.finish

  # 

  # You can also use the block form of SMTP.start/SMTP#start.  This closes

  # the SMTP session automatically:

  # 

  #     # using block form of SMTP.start

  #     Net::SMTP.start('your.smtp.server', 25) do |smtp|

  #       smtp.send_message msgstr, 'from@address', 'to@address'

  #     end

  # 

  # I strongly recommend this scheme.  This form is simpler and more robust.

  # 

  # === HELO domain

  # 

  # In almost all situations, you must provide a third argument

  # to SMTP.start/SMTP#start. This is the domain name which you are on

  # (the host to send mail from). It is called the "HELO domain".

  # The SMTP server will judge whether it should send or reject

  # the SMTP session by inspecting the HELO domain.

  # 

  #     Net::SMTP.start('your.smtp.server', 25,

  #                     'mail.from.domain') { |smtp| ... }

  # 

  # === SMTP Authentication

  # 

  # The Net::SMTP class supports three authentication schemes;

  # PLAIN, LOGIN, and CRAM MD5.  (SMTP Authentication: [RFC2554])

  # To use SMTP authentication, pass extra arguments to 

  # SMTP.start/SMTP#start.

  # 

  #     # PLAIN

  #     Net::SMTP.start('your.smtp.server', 25, 'mail.from.domain',

  #                     'Your Account', 'Your Password', :plain)

  #     # LOGIN

  #     Net::SMTP.start('your.smtp.server', 25, 'mail.from.domain',

  #                     'Your Account', 'Your Password', :login)

  # 

  #     # CRAM MD5

  #     Net::SMTP.start('your.smtp.server', 25, 'mail.from.domain',

  #                     'Your Account', 'Your Password', :cram_md5)

  #

  class SMTP

    Revision = %q$Revision: 28208 $.split[1]

    # The default SMTP port number, 25.

    def SMTP.default_port

      25

    end

    # The default mail submission port number, 587.

    def SMTP.default_submission_port

      587

    end

    # The default SMTPS port number, 465.

    def SMTP.default_tls_port

      465

    end

    class << self

      alias default_ssl_port default_tls_port

    end

    def SMTP.default_ssl_context

      OpenSSL::SSL::SSLContext.new

    end

    #

    # Creates a new Net::SMTP object.

    #

    # +address+ is the hostname or ip address of your SMTP

    # server.  +port+ is the port to connect to; it defaults to

    # port 25.

    #

    # This method does not open the TCP connection.  You can use

    # SMTP.start instead of SMTP.new if you want to do everything

    # at once.  Otherwise, follow SMTP.new with SMTP#start.

    #

    def initialize(address, port = nil)

      @address = address

      @port = (port || SMTP.default_port)

      @esmtp = true

      @capabilities = nil

      @socket = nil

      @started = false

      @open_timeout = 30

      @read_timeout = 60

      @error_occured = false

      @debug_output = nil

      @tls = false

      @starttls = false

      @ssl_context = nil

    end

    # Provide human-readable stringification of class state.

    def inspect

      "#<#{self.class} #{@address}:#{@port} started=#{@started}>"

    end

    # +true+ if the SMTP object uses ESMTP (which it does by default).

    def esmtp?

      @esmtp

    end

    #

    # Set whether to use ESMTP or not.  This should be done before 

    # calling #start.  Note that if #start is called in ESMTP mode,

    # and the connection fails due to a ProtocolError, the SMTP

    # object will automatically switch to plain SMTP mode and

    # retry (but not vice versa).

    #

    def esmtp=(bool)

      @esmtp = bool

    end

    alias esmtp esmtp?

    # true if server advertises STARTTLS.

    # You cannot get valid value before opening SMTP session.

    def capable_starttls?

      capable?('STARTTLS')

    end

    def capable?(key)

      return nil unless @capabilities

      @capabilities[key] ? true : false

    end

    private :capable?

    # true if server advertises AUTH PLAIN.

    # You cannot get valid value before opening SMTP session.

    def capable_plain_auth?

      auth_capable?('PLAIN')

    end

    # true if server advertises AUTH LOGIN.

    # You cannot get valid value before opening SMTP session.

    def capable_login_auth?

      auth_capable?('LOGIN')

    end

    # true if server advertises AUTH NTLM.

    # You cannot get valid value before opening SMTP session.

    def capable_login_auth?

      auth_capable?('NTLM')

    end

    # true if server advertises AUTH CRAM-MD5.

    # You cannot get valid value before opening SMTP session.

    def capable_cram_md5_auth?

      auth_capable?('CRAM-MD5')

    end

    def auth_capable?(type)

      return nil unless @capabilities

      return false unless @capabilities['AUTH']

      @capabilities['AUTH'].include?(type)

    end

    private :auth_capable?

    # Returns supported authentication methods on this server.

    # You cannot get valid value before opening SMTP session.

    def capable_auth_types

      return [] unless @capabilities

      return [] unless @capabilities['AUTH']

      @capabilities['AUTH']

    end

    # true if this object uses SMTP/TLS (SMTPS).

    def tls?

      @tls

    end

    alias ssl? tls?

    # Enables SMTP/TLS (SMTPS: SMTP over direct TLS connection) for

    # this object.  Must be called before the connection is established

    # to have any effect.  +context+ is a OpenSSL::SSL::SSLContext object.

    def enable_tls(context = SMTP.default_ssl_context)

      raise 'openssl library not installed' unless defined?(OpenSSL)

      raise ArgumentError, "SMTPS and STARTTLS is exclusive" if @starttls

      @tls = true

      @ssl_context = context

    end

    alias enable_ssl enable_tls

    # Disables SMTP/TLS for this object.  Must be called before the

    # connection is established to have any effect.

    def disable_tls

      @tls = false

      @ssl_context = nil

    end

    alias disable_ssl disable_tls

    # Returns truth value if this object uses STARTTLS.

    # If this object always uses STARTTLS, returns :always.

    # If this object uses STARTTLS when the server support TLS, returns :auto.

    def starttls?

      @starttls

    end

    # true if this object uses STARTTLS.

    def starttls_always?

      @starttls == :always

    end

    # true if this object uses STARTTLS when server advertises STARTTLS.

    def starttls_auto?

      @starttls == :auto

    end

    # Enables SMTP/TLS (STARTTLS) for this object.

    # +context+ is a OpenSSL::SSL::SSLContext object.

    def enable_starttls(context = SMTP.default_ssl_context)

      raise 'openssl library not installed' unless defined?(OpenSSL)

      raise ArgumentError, "SMTPS and STARTTLS is exclusive" if @tls

      @starttls = :always

      @ssl_context = context

    end

    # Enables SMTP/TLS (STARTTLS) for this object if server accepts.

    # +context+ is a OpenSSL::SSL::SSLContext object.

    def enable_starttls_auto(context = SMTP.default_ssl_context)

      raise 'openssl library not installed' unless defined?(OpenSSL)

      raise ArgumentError, "SMTPS and STARTTLS is exclusive" if @tls

      @starttls = :auto

      @ssl_context = context

    end

    # Disables SMTP/TLS (STARTTLS) for this object.  Must be called

    # before the connection is established to have any effect.

    def disable_starttls

      @starttls = false

      @ssl_context = nil

    end

    # The address of the SMTP server to connect to.

    attr_reader :address

    # The port number of the SMTP server to connect to.

    attr_reader :port

    # Seconds to wait while attempting to open a connection.

    # If the connection cannot be opened within this time, a

    # TimeoutError is raised.

    attr_accessor :open_timeout

    # Seconds to wait while reading one block (by one read(2) call).

    # If the read(2) call does not complete within this time, a

    # TimeoutError is raised.

    attr_reader :read_timeout

    # Set the number of seconds to wait until timing-out a read(2)

    # call.

    def read_timeout=(sec)

      @socket.read_timeout = sec if @socket

      @read_timeout = sec

    end

    #

    # WARNING: This method causes serious security holes.

    # Use this method for only debugging.

    #

    # Set an output stream for debug logging.

    # You must call this before #start.

    #

    #   # example

    #   smtp = Net::SMTP.new(addr, port)

    #   smtp.set_debug_output $stderr

    #   smtp.start do |smtp|

    #     ....

    #   end

    #

    def debug_output=(arg)

      @debug_output = arg

    end

    alias set_debug_output debug_output=

    #

    # SMTP session control

    #

    #

    # Creates a new Net::SMTP object and connects to the server.

    #

    # This method is equivalent to:

    # 

    #   Net::SMTP.new(address, port).start(helo_domain, account, password, authtype)

    #

    # === Example

    #

    #     Net::SMTP.start('your.smtp.server') do |smtp|

    #       smtp.send_message msgstr, 'from@example.com', ['dest@example.com']

    #     end

    #

    # === Block Usage

    #

    # If called with a block, the newly-opened Net::SMTP object is yielded

    # to the block, and automatically closed when the block finishes.  If called

    # without a block, the newly-opened Net::SMTP object is returned to

    # the caller, and it is the caller's responsibility to close it when

    # finished.

    #

    # === Parameters

    #

    # +address+ is the hostname or ip address of your smtp server.

    #

    # +port+ is the port to connect to; it defaults to port 25.

    #

    # +helo+ is the _HELO_ _domain_ provided by the client to the

    # server (see overview comments); it defaults to 'localhost.localdomain'. 

    #

    # The remaining arguments are used for SMTP authentication, if required

    # or desired.  +user+ is the account name; +secret+ is your password

    # or other authentication token; and +authtype+ is the authentication

    # type, one of :plain, :login, or :cram_md5.  See the discussion of

    # SMTP Authentication in the overview notes.

    #

    # === Errors

    #

    # This method may raise:

    #

    # * Net::SMTPAuthenticationError

    # * Net::SMTPServerBusy

    # * Net::SMTPSyntaxError

    # * Net::SMTPFatalError

    # * Net::SMTPUnknownError

    # * IOError

    # * TimeoutError

    #

    def SMTP.start(address, port = nil, helo = 'localhost.localdomain',

                   user = nil, secret = nil, authtype = nil,

                   &block)   # :yield: smtp

      new(address, port).start(helo, user, secret, authtype, &block)

    end

    # +true+ if the SMTP session has been started.

    def started?

      @started

    end

    #

    # Opens a TCP connection and starts the SMTP session.

    #

    # === Parameters

    #

    # +helo+ is the _HELO_ _domain_ that you'll dispatch mails from; see

    # the discussion in the overview notes.

    #

    # If both of +user+ and +secret+ are given, SMTP authentication 

    # will be attempted using the AUTH command.  +authtype+ specifies 

    # the type of authentication to attempt; it must be one of

    # :login, :plain, and :cram_md5.  See the notes on SMTP Authentication

    # in the overview. 

    #

    # === Block Usage

    #

    # When this methods is called with a block, the newly-started SMTP

    # object is yielded to the block, and automatically closed after

    # the block call finishes.  Otherwise, it is the caller's 

    # responsibility to close the session when finished.

    #

    # === Example

    #

    # This is very similar to the class method SMTP.start.

    #

    #     require 'net/smtp' 

    #     smtp = Net::SMTP.new('smtp.mail.server', 25)

    #     smtp.start(helo_domain, account, password, authtype) do |smtp|

    #       smtp.send_message msgstr, 'from@example.com', ['dest@example.com']

    #     end 

    #

    # The primary use of this method (as opposed to SMTP.start)

    # is probably to set debugging (#set_debug_output) or ESMTP

    # (#esmtp=), which must be done before the session is

    # started.  

    #

    # === Errors

    #

    # If session has already been started, an IOError will be raised.

    #

    # This method may raise:

    #

    # * Net::SMTPAuthenticationError

    # * Net::SMTPServerBusy

    # * Net::SMTPSyntaxError

    # * Net::SMTPFatalError

    # * Net::SMTPUnknownError

    # * IOError

    # * TimeoutError

    #

    def start(helo = 'localhost.localdomain',

              user = nil, secret = nil, authtype = nil)   # :yield: smtp

      if block_given?

        begin

          do_start helo, user, secret, authtype

          return yield(self)

        ensure

          do_finish

        end

      else

        do_start helo, user, secret, authtype

        return self

      end

    end

    # Finishes the SMTP session and closes TCP connection.

    # Raises IOError if not started.

    def finish

      raise IOError, 'not yet started' unless started?

      do_finish

    end

    private

    def do_start(helo_domain, user, secret, authtype)

      raise IOError, 'SMTP session already started' if @started

      if user or secret

        check_auth_method(authtype || DEFAULT_AUTH_TYPE)

        check_auth_args user, secret

      end

      s = timeout(@open_timeout) { TCPSocket.open(@address, @port) }   

      logging "Connection opened: #{@address}:#{@port}"

      @socket = new_internet_message_io(tls? ? tlsconnect(s) : s)

      check_response critical { recv_response() }

      do_helo helo_domain

      if starttls_always? or (capable_starttls? and starttls_auto?)

        unless capable_starttls?

          raise SMTPUnsupportedCommand,

              "STARTTLS is not supported on this server"

        end

        starttls

        @socket = new_internet_message_io(tlsconnect(s))

        # helo response may be different after STARTTLS

        do_helo helo_domain

      end

      authenticate user, secret, (authtype || DEFAULT_AUTH_TYPE) if user

      @started = true

    ensure

      unless @started

        # authentication failed, cancel connection.

        s.close if s and not s.closed?

        @socket = nil

      end

    end

    def tlsconnect(s)

      s = OpenSSL::SSL::SSLSocket.new(s, @ssl_context)

      logging "TLS connection started"

      s.sync_close = true

      s.connect

      if @ssl_context.verify_mode != OpenSSL::SSL::VERIFY_NONE

        s.post_connection_check(@address)

      end

      s

    end

    def new_internet_message_io(s)

      io = InternetMessageIO.new(s)

      io.read_timeout = @read_timeout

      io.debug_output = @debug_output

      io

    end

    def do_helo(helo_domain)

      res = @esmtp ? ehlo(helo_domain) : helo(helo_domain)

      @capabilities = res.capabilities

    rescue SMTPError

      if @esmtp

        @esmtp = false

        @error_occured = false

        retry

      end

      raise

    end

    def do_finish

      quit if @socket and not @socket.closed? and not @error_occured

    ensure

      @started = false

      @error_occured = false

      @socket.close if @socket and not @socket.closed?

      @socket = nil

    end

    #

    # Message Sending

    #

    public

    #

    # Sends +msgstr+ as a message.  Single CR ("\r") and LF ("\n") found

    # in the +msgstr+, are converted into the CR LF pair.  You cannot send a

    # binary message with this method. +msgstr+ should include both 

    # the message headers and body.

    #

    # +from_addr+ is a String representing the source mail address.

    #

    # +to_addr+ is a String or Strings or Array of Strings, representing

    # the destination mail address or addresses.

    #

    # === Example

    #

    #     Net::SMTP.start('smtp.example.com') do |smtp|

    #       smtp.send_message msgstr,

    #                         'from@example.com',

    #                         ['dest@example.com', 'dest2@example.com']

    #     end

    #

    # === Errors

    #

    # This method may raise:

    #

    # * Net::SMTPServerBusy

    # * Net::SMTPSyntaxError

    # * Net::SMTPFatalError

    # * Net::SMTPUnknownError

    # * IOError

    # * TimeoutError

    #

    def send_message(msgstr, from_addr, *to_addrs)

      raise IOError, 'closed session' unless @socket

      mailfrom from_addr

      rcptto_list(to_addrs) {data msgstr}

    end

    alias send_mail send_message

    alias sendmail send_message   # obsolete

    #

    # Opens a message writer stream and gives it to the block.

    # The stream is valid only in the block, and has these methods:

    #

    # puts(str = '')::       outputs STR and CR LF.

    # print(str)::           outputs STR.

    # printf(fmt, *args)::   outputs sprintf(fmt,*args).

    # write(str)::           outputs STR and returns the length of written bytes.

    # <<(str)::              outputs STR and returns self.

    #

    # If a single CR ("\r") or LF ("\n") is found in the message,

    # it is converted to the CR LF pair.  You cannot send a binary

    # message with this method.

    #

    # === Parameters

    #

    # +from_addr+ is a String representing the source mail address.

    #

    # +to_addr+ is a String or Strings or Array of Strings, representing

    # the destination mail address or addresses.

    #

    # === Example

    #

    #     Net::SMTP.start('smtp.example.com', 25) do |smtp|

    #       smtp.open_message_stream('from@example.com', ['dest@example.com']) do |f|

    #         f.puts 'From: from@example.com'

    #         f.puts 'To: dest@example.com'

    #         f.puts 'Subject: test message'

    #         f.puts

    #         f.puts 'This is a test message.'

    #       end

    #     end

    #

    # === Errors

    #

    # This method may raise:

    #

    # * Net::SMTPServerBusy

    # * Net::SMTPSyntaxError

    # * Net::SMTPFatalError

    # * Net::SMTPUnknownError

    # * IOError

    # * TimeoutError

    #

    def open_message_stream(from_addr, *to_addrs, &block)   # :yield: stream

      raise IOError, 'closed session' unless @socket

      mailfrom from_addr

      rcptto_list(to_addrs) {data(&block)}

    end

    alias ready open_message_stream   # obsolete

    #

    # Authentication

    #

    public

    DEFAULT_AUTH_TYPE = :plain

    def authenticate(user, secret, authtype = DEFAULT_AUTH_TYPE)

      check_auth_method authtype

      check_auth_args user, secret

      send auth_method(authtype), user, secret

    end

    def auth_plain(user, secret)

      check_auth_args user, secret

      res = critical {

        get_response('AUTH PLAIN ' + base64_encode("\0#{user}\0#{secret}"))

      }

      check_auth_response res

      res

    end

    def auth_ntlm(user, secret)

      check_auth_args user, secret

      res = critical {

        # send type1 message

        t1 = Net::NTLM::Message::Type1.new()

        t1.domain = user[/^[^\\]+/]

        @socket.writeline "AUTH NTLM " + t1.encode64

        # receive type2 message

        line = @socket.readline

	unless /334 (.+)/ =~ line

          raise RuntimeError, "SMTP AUTH don't recognize this: #{line}"

	end

        t2 = Net::NTLM::Message.decode64($1)

        # send Type3 Message

	t3 = t2.response({:user => user[/[^\\]+$/], :password => secret}, {:ntlmv2 => true})

        get_response(t3.encode64)

      }

      check_auth_response res

      res

    end

    def auth_login(user, secret)

      check_auth_args user, secret

      res = critical {

        check_auth_continue get_response('AUTH LOGIN')

        check_auth_continue get_response(base64_encode(user))

        get_response(base64_encode(secret))

      }

      check_auth_response res

      res

    end

    def auth_cram_md5(user, secret)

      check_auth_args user, secret

      res = critical {

        res0 = get_response('AUTH CRAM-MD5')

        check_auth_continue res0

        crammed = cram_md5_response(secret, res0.cram_md5_challenge)

        get_response(base64_encode("#{user} #{crammed}"))

      }

      check_auth_response res

      res

    end

    private

    def check_auth_method(type)

      unless respond_to?(auth_method(type), true)

        raise ArgumentError, "wrong authentication type #{type}"

      end

    end

    def auth_method(type)

      "auth_#{type.to_s.downcase}".intern

    end

    def check_auth_args(user, secret)

      unless user

        raise ArgumentError, 'SMTP-AUTH requested but missing user name'

      end

      unless secret

        raise ArgumentError, 'SMTP-AUTH requested but missing secret phrase'

      end

    end

    def base64_encode(str)

      # expects "str" may not become too long

      [str].pack('m').gsub(/\s+/, '')

    end

    IMASK = 0x36

    OMASK = 0x5c

    # CRAM-MD5: [RFC2195]

    def cram_md5_response(secret, challenge)

      tmp = Digest::MD5.digest(cram_secret(secret, IMASK) + challenge)

      Digest::MD5.hexdigest(cram_secret(secret, OMASK) + tmp)

    end

    CRAM_BUFSIZE = 64

    def cram_secret(secret, mask)

      secret = Digest::MD5.digest(secret) if secret.size > CRAM_BUFSIZE

      buf = secret.ljust(CRAM_BUFSIZE, "\0")

      0.upto(buf.size - 1) do |i|

        buf[i] = (buf[i].ord ^ mask).chr

      end

      buf

    end

    #

    # SMTP command dispatcher

    #

    public

    def starttls

      getok('STARTTLS')

    end

    def helo(domain)

      getok("HELO #{domain}")

    end

    def ehlo(domain)

      getok("EHLO #{domain}")

    end

    def mailfrom(from_addr)

      if $SAFE > 0

        raise SecurityError, 'tainted from_addr' if from_addr.tainted?

      end

      getok("MAIL FROM:<#{from_addr}>")

    end

    def rcptto_list(to_addrs)

      raise ArgumentError, 'mail destination not given' if to_addrs.empty?

      ok_users = []

      unknown_users = []

      to_addrs.flatten.each do |addr|

        begin

          rcptto addr

        rescue SMTPAuthenticationError

          unknown_users << addr.dump

        else

          ok_users << addr

        end

      end

      raise ArgumentError, 'mail destination not given' if ok_users.empty?

      ret = yield

      unless unknown_users.empty?

        raise SMTPAuthenticationError, "failed to deliver for #{unknown_users.join(', ')}"

      end

      ret

    end

    def rcptto(to_addr)

      if $SAFE > 0

        raise SecurityError, 'tainted to_addr' if to_addr.tainted?

      end

      getok("RCPT TO:<#{to_addr}>")

    end

    # This method sends a message.

    # If +msgstr+ is given, sends it as a message.

    # If block is given, yield a message writer stream.

    # You must write message before the block is closed.

    #

    #   # Example 1 (by string)

    #   smtp.data(<<EndMessage)

    #   From: john@example.com

    #   To: betty@example.com

    #   Subject: I found a bug

    #   

    #   Check vm.c:58879.

    #   EndMessage

    #

    #   # Example 2 (by block)

    #   smtp.data {|f|

    #     f.puts "From: john@example.com"

    #     f.puts "To: betty@example.com"

    #     f.puts "Subject: I found a bug"

    #     f.puts ""

    #     f.puts "Check vm.c:58879."

    #   }

    #

    def data(msgstr = nil, &block)   #:yield: stream

      if msgstr and block

        raise ArgumentError, "message and block are exclusive"

      end

      unless msgstr or block

        raise ArgumentError, "message or block is required"

      end

      res = critical {

        check_continue get_response('DATA')

        if msgstr

          @socket.write_message msgstr

        else

          @socket.write_message_by_block(&block)

        end

        recv_response()

      }

      check_response res

      res

    end

    def quit

      getok('QUIT')

    end

    private

    def getok(reqline)

      res = critical {

        @socket.writeline reqline

        recv_response()

      }

      check_response res

      res

    end

    def get_response(reqline)

      @socket.writeline reqline

      recv_response()

    end

    def recv_response

      buf = ''

      while true

        line = @socket.readline

        buf << line << "\n"

        break unless line[3,1] == '-'   # "210-PIPELINING"

      end

      Response.parse(buf)

    end

    def critical(&block)

      return '200 dummy reply code' if @error_occured

      begin

        return yield()

      rescue Exception

        @error_occured = true

        raise

      end

    end

    def check_response(res)

      unless res.success?

        raise res.exception_class, res.message

      end

    end

    def check_continue(res)

      unless res.continue?

        raise SMTPUnknownError, "could not get 3xx (#{res.status})"

      end

    end

    def check_auth_response(res)

      unless res.success?

        raise SMTPAuthenticationError, res.message

      end

    end

    def check_auth_continue(res)

      unless res.continue?

        raise res.exception_class, res.message

      end

    end

    class Response

      def Response.parse(str)

        new(str[0,3], str)

      end

      def initialize(status, string)

        @status = status

        @string = string

      end

      attr_reader :status

      attr_reader :string

      def status_type_char

        @status[0, 1]

      end

      def success?

        status_type_char() == '2'

      end

      def continue?

        status_type_char() == '3'

      end

      def message

        @string.lines.first

      end

      def cram_md5_challenge

        @string.split(/ /)[1].unpack('m')[0]

      end

      def capabilities

        return {} unless @string[3, 1] == '-'

        h = {}

        @string.lines.drop(1).each do |line|

          k, *v = line[4..-1].chomp.split(nil)

          h[k] = v

        end

        h

      end

      def exception_class

        case @status

        when /\A4/  then SMTPServerBusy

        when /\A50/ then SMTPSyntaxError

        when /\A53/ then SMTPAuthenticationError

        when /\A5/  then SMTPFatalError

        else             SMTPUnknownError

        end

      end

    end

    def logging(msg)

      @debug_output << msg + "\n" if @debug_output

    end

  end   # class SMTP

  SMTPSession = SMTP

end