#--
# CyborgHood, a distributed system management software.
# Copyright (c) 2009 Marc Dequènes (Duck) <Duck@DuckCorp.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#++

# add Rails load path for Debian, until rails framework is split properly
DEB_RAILS_PATH = "/usr/share/rails" unless Object.constants.include?("DEB_RAILS_PATH")
Dir.new(DEB_RAILS_PATH).each do |file|
        next if file =~ /^\./
        path = File.join(DEB_RAILS_PATH, file, "lib")
        $: << path if File.directory?(path)
end

require 'cyborghood/base'
require 'delegate'
require 'tmail'
require 'tmail_gpg'
require 'action_mailer/quoting'
require 'action_mailer/utils'
require 'net/smtp'
require 'fileutils'
require 'digest/md5'


# This class handles RFC3156 signed messages, validates them, and extract orders properly.
# Encrypted content are not implemented yet.
module CyborgHood
  class Order
    attr_accessor :ok, :message, :system_message, :user, :commands, :references
    attr_writer = :warn_sender

    def initialize(ok, message = nil, system_message = nil)
      @ok = ok
      @message = message
      @system_message = system_message
    end

    def warn_sender
      # send reply message if user is identified or in selected situations
      # (@warn_sender acts as an override)
      @warn_sender || @user
    end
  end

  class Mail < Delegator
    include ActionMailer::Quoting
    include ActionMailer::Utils
    include GetText

    MAX_DRIFT_TIME = 600

    attr_accessor :user, :signature_timestamp

    def initialize(msg = nil)
      @config = Config.instance

      if msg.nil?
        @mail = TMail::Mail.new
        set_custom_headers
      elsif msg.is_a? TMail::Mail
        @mail = msg
      else
        # unquote headers and transform into TMail object
        @mail = TMail::Mail.parse(TMail::Unquoter.unquote_and_convert_to(msg, "UTF-8"))
      end
    end

    def __getobj__
      @mail
    end

    def parse
      if is_marked?
        return Order.new(false, "Replay detected.")
      end

      return parse_signed() if is_pgp_signed?
      return parse_encrypted() if is_pgp_encrypted?
      # don't parse commands if user is not identified
      return parse_plain if self.user

      Order.new(false, "Mail not RFC3156 compliant.")
    end

    def create_reply
      tmail_reply = @mail.create_reply
      tmail_reply.from_addrs = TMail::Address.parse(@config.mail.from_address || self.to.first)
      reply = self.class.new(tmail_reply.to_s)
      reply.set_custom_headers
      reply.user = self.user
      reply
    end

    def create_simple_reject_reply(msg)
      reply = create_reply()
      reply.set_content_type("text", "plain", {'charset' => "utf-8"})
      reply.set_disposition("inline")
      reply.quoted_printable_body = msg
      reply.sign
      reply.crypt(reply.user.keyFingerPrint) unless reply.user.nil?
      reply
    end

    def set_custom_headers
      @mail['Organization'] = @config.mail.organization
    end

    def check_headers
      @mail.header.keys.each do |h|
        @mail[h] = quote_address_if_necessary(@mail[h].to_s, "utf-8")
      end
    end

    def deliver
      check_headers

      smtp_server = @config.mail.smtp_server || "localhost"
      smtp_port = @config.mail.smtp_port || 25
      smtp_from = @mail.from_addrs.collect{|a| a.address}.join(", ")
      smtp_to = @mail.to_addrs.collect{|a| a.address}
      Net::SMTP.start(smtp_server, smtp_port) do |smtp|
        #p @mail.to_s
        smtp.send_message(@mail.to_s, smtp_from, smtp_to)
      end
    end

    def to_s
      @mail.to_s
    end

    def crypt(fingerprint)
      @mail = @mail.create_encrypted(fingerprint)
    end

    def sign
      # we don't check the uid, as their is only one signer
      @mail = @mail.create_signed(@config.mail.key_id) do |uid_hint, passphrase_info, prev_was_bad|
        @config.mail.key_passphrase
      end
    end

    def sign_and_crypt(fingerprint)
      # not using sign_and_crypt(), to avoid repeating code
      sign()
      crypt(fingerprint)
    end

    def quoted_printable_body=(txt)
      @mail.transfer_encoding = "quoted-printable"
      @mail.body = [normalize_new_lines(txt)].pack("M*")
    end

    private

    def parse_plain
      command_txt = nil
      if multipart?
        if parts[0].content_type == "text/plain"
          command_txt = self.parts[0].body
          refs = self.parts.collect{|p| p.dup }
        end
      else
        command_txt = self.body if self.content_type == "text/plain"
        refs = []
      end
      unless command_txt
        order = Order.new(false, N_("Mail does not contain a proper text part for commands."))
        order.user = self.user
        return order
      end

      commands = []
      command_txt.each_line do |line|
        line.chomp!
        sline = line.strip
        # skip empty lines and comments
        next if sline == "" or sline[0, 1] == "#"
        # stop processing when detecting message signature
        break if line == "-- "

        commands << sline
      end

      logger.debug "Mail OK"
      mark_processed(self.signature_timestamp)

      order = Order.new(true)
      order.user = self.user
      order.commands = commands
      order.refs = refs
    end

    def parse_signed
      sigs_check = verify_pgp_signature()
      return Order.new(false, N_("Mail not formatted correctly (signed part).")) if sigs_check.nil? or sigs_check.size != 1

      sig_check = sigs_check.first
      return Order.new(false, N_("Mail content tampered or badly signed: ") + sig_check.to_s) unless sig_check.status == 0

      logger.info "Mail content was properly signed by key #{sig_check.fingerprint}"
      user = Person.find_by_fingerprint(sig_check.fingerprint)
      if user.nil?
        order = Order.new(false, N_("Mail is from an unknown person."))
        order.warn_sender = true
        return order
      end

      logger.info "Mail is from user #{user.uid} (#{user.cn})"
      self.user = user

      drift = Time.new.to_i - sig_check.timestamp.to_i
      logger.debug "Signature drift time: #{drift}"
      unless drift.abs < MAX_DRIFT_TIME
        if drift > 0
          order = Order.new(false, N_("The signature was made too long ago (check your system clock). Rejected message to avoid replay attacks."))
          order.user = self.user
        else
          # mark message to prevent later replay of the message
          mark_processed(sig_check.timestamp)
          order = Order.new(false, N_("The signature was made in the future (check your system clock). Rejected message to avoid replay attacks."))
          order.user = self.user
        end
        return order
      end

      signed_content = pgp_signed_part()

      # create a fake mail and chain parsing operations
      plain_mail = self.class.new(signed_content)
      plain_mail.user = self.user
      plain_mail.signature_timestamp = sig_check.timestamp
      # propagate message_id to be able to mark messages (replay protection)
      plain_mail.message_id = @mail.message_id
      return plain_mail.parse
    end

    def parse_encrypted
      catch :notforme do
        begin
          # block is not passed to delegate (limitation ?)
          clear_message = @mail.pgp_decrypt do |uid_hint, passphrase_info, prev_was_bad|
            logger.info "Mail crypted for #{uid_hint}"

            # check if requesting passphrase for the expected key
            key_id = passphrase_info.split(" ")[1]
            throw :notforme if key_id != @config.mail.key_id[-(key_id.size)..-1]

            # sending key
            @config.mail.key_passphrase
          end

          # create a fake mail and chain parsing operations
          clear_mail = self.class.new(clear_message)
          clear_mail.user = self.user
          # propagate message_id to be able to mark messages (replay protection)
          clear_mail.message_id = @mail.message_id
          return clear_mail.parse
        rescue GPGME::Error, NotImplementedError => e
          raise CyberError.new(:unrecoverable, "protocol/mail", e.message)
        end
      end

      Order.new(false, N_("Mail not formatted correctly (encrypted part)."))
    end

    def mark_dir
      File.join(@config.work_dir, "marks")
    end

    def mark_filename
      File.join(mark_dir(), Digest::MD5.hexdigest(self.message_id))
    end

    def mark_processed(time)
      FileUtils.mkdir_p(mark_dir())
      File.open(mark_filename(), "w") do |fp|
        fp.write self.message_id
      end
      File.utime(Time.now.to_i, time.to_i, mark_filename())
    end

    def is_marked?
      File.exists?(mark_filename())
    end
  end
end