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root/lib/cyborghood/mail.rb @ 7e9520c0

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#--
# CyborgHood, a distributed system management software.
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# Copyright (c) 2009-2010 Marc Dequènes (Duck) <Duck@DuckCorp.org>
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#
# 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/>.
#++
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require 'delegate'
require 'tmail'
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require 'tmail_gpg'
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require 'tmail_extra'
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require 'net/smtp'
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require 'fileutils'
require 'digest/md5'

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# This class handles RFC3156 signed/encrypted messages, validates them, and extract content properly.
# It also implements a protection against replay attacks.
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module CyborgHood
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class MailReport
attr_reader :error, :warn_sender, :user, :message
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def initialize(params = {})
@error = params[:error]
@warn_sender = params[:warn_sender]
@user = params[:user]
@message = params[:message]
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@warn_sender = false
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end
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def ok?
@error.nil? and @user and @message
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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

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class Mail < Delegator
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include I18nTranslation
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attr_accessor :user, :signature_timestamp
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def initialize(msg = nil)
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@config = Config.instance

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if msg.nil?
@mail = TMail::Mail.new
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set_custom_headers
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elsif msg.is_a? TMail::Mail
@mail = msg
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else
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@mail = TMail::Mail.parse(msg)
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end
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end

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def self.blank
m = self.new
m.clear
m
end

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def __getobj__
@mail
end

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def process
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if is_marked?
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if @config.debug.flags.include?('debug_ignorereplay')
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logger.warn "Debug: ignoring replay"
else
return MailReport.new(:error => _("Replay detected."))
end
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end

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return process_signed() if is_pgp_signed?
return process_encrypted() if is_pgp_encrypted?
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MailReport.new(:error => _("Mail not RFC3156 compliant."))
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end

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def create_reply
tmail_reply = @mail.create_reply
tmail_reply.from_addrs = TMail::Address.parse(@config.mail.from_address || self.to.first)
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tmail_reply.to_addrs = (@mail.reply_to_addrs_pretty || @mail.from_addrs_pretty).collect do |a|
TMail::Address.parse(@mail.class.header_value_smtp(a))
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end
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reply = self.class.new(tmail_reply.to_s)
reply.set_custom_headers
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reply.user = @user
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reply
end

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

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def to_multipart!
self.set_content_type("multipart", "mixed", {'boundary' => TMail.new_boundary})
self.transfer_encoding = "7bit"
self.quoted_body = "This mail is in MIME format.\n"
self.parts.clear
end

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

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

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def default_body_signature
s = "\n" +
"-- \n" +
"#{CyborgHood::PRODUCT} v#{CyborgHood::VERSION}\n"
s += _("Contact eMail:").to_s + " \"#{@config.contact.name}\" <#{@config.contact.email}>\n" if @config.contact.email
s += _("Contact URL:").to_s + " #{@config.contact.url}\n" if @config.contact.url
s
end

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def deliver
check_headers

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smtp_server = @config.mail.smtp_server
smtp_port = @config.mail.smtp_port
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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|
smtp.send_message(@mail.to_s, smtp_from, smtp_to)
end
end

def to_s
@mail.to_s
end

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def crypt(fingerprint = nil)
@mail = @mail.create_encrypted(fingerprint || @user.keyFingerPrint)
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end

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

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def sign_and_crypt(fingerprint = nil)
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# not using sign_and_crypt(), to avoid repeating code
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sign()
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crypt(fingerprint || @user.keyFingerPrint)
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end

private

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def process_signed
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sigs_check = verify_pgp_signature()
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return MailReport.new(:error => _("Mail not formatted correctly (signed part).")) if sigs_check.nil? or sigs_check.size != 1
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sig_check = sigs_check.first
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return MailReport.new(:error => _("Mail content tampered or badly signed: %{sig_err}", :sig_err => sig_check.to_s)) unless sig_check.status == 0
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logger.info "Mail content was properly signed by key #{sig_check.fingerprint}"
user = Person.find_by_fingerprint(sig_check.fingerprint)
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return MailReport.new(:error => _("Mail is from an unknown person."), :warn_sender => true) if user.nil?
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logger.info "Mail is from user #{user.uid} (#{user.cn})"
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@user = user
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drift = Time.new.to_i - sig_check.timestamp.to_i
logger.debug "Signature drift time: #{drift}"
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unless drift.abs < @config.mail.max_drift_time
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if drift > 0
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return MailReport.new(:error => _("The signature was made too long ago (check your system clock). Rejected message to avoid replay attacks."), :user => user)
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else
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# mark message to prevent later replay of the message
mark_processed(sig_check.timestamp)
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return MailReport.new(:error => _("The signature was made in the future (check your system clock). Rejected message to avoid replay attacks."), :user => user)
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end
end

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

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signed_content = pgp_signed_part()

# create a fake mail and chain parsing operations
plain_mail = self.class.new(signed_content)
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plain_mail.user = @user
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plain_mail.signature_timestamp = sig_check.timestamp
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# propagate message_id to be able to mark messages (replay protection)
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plain_mail.message_id = @mail.message_id
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MailReport.new(:user => user, :message => plain_mail)
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end
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def process_encrypted
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catch :notforme do
begin
# block is not passed to delegate (limitation ?)
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clear_message = @mail.pgp_decrypt do |uid_hint, passphrase_info, prev_was_bad|
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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)
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clear_mail.user = @user
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# propagate message_id to be able to mark messages (replay protection)
clear_mail.message_id = @mail.message_id
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return clear_mail.process
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rescue GPGME::Error, NotImplementedError => e
raise CyberError.new(:unrecoverable, "protocol/mail", e.message)
end
end

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MailReport.new(:error => _("Mail not formatted correctly (encrypted part)."))
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end
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def mark_dir
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File.join(Config::VAR_DIR, "marks")
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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
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end
end