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#--
# CyborgHood, a distributed system management software.
# Copyright (c) 2009-2010 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/>.
#++

require 'digest/md5'
require 'tempfile'
require 'fileutils'

# ensure we can find the needed programs (should be handled somewhere else)
ENV['PATH'] = (ENV['PATH'].split(":") + ["/sbin", "/usr/sbin", "/usr/local/sbin"]).uniq.join(":")

module CyborgHood
module Services
module DNS
class System
def initialize
@config = Config.instance

@zone_files_pattern = @config.dns.master_zone_pattern.gsub("#ZONE#", "*")
@zone_files_regex = Regexp.new("^" + @config.dns.master_zone_pattern.gsub("#ZONE#", "(.*)") + "$")
end

def zones
Dir.glob(@zone_files_pattern).collect do |file|
$1 if file =~ @zone_files_regex
end
end

def [](zone)
return unless zones.include?(zone)

Zone.new(zone)
end

def check_config
case @config.dns.software
when 'bind'
output = []
begin
IO.popen("sudo named-checkconf") do |fp|
output << fp.gets.chomp! until fp.eof?
end
rescue
raise CyberError.new(:unrecoverable, "services/dns", "global configuration could not be checked (I/O error)")
end

if $?.success?
return {:ok => true, :warnings => output}.to_ostruct
else
return {:ok => false, :errors => output}.to_ostruct
end
end
end
end

class Zone
def initialize(zone)
@zone = zone

@config = Config.instance
@content = nil
@temp_file = nil

@filename = @config.dns.master_zone_pattern.gsub("#ZONE#", @zone)
end

def content
read_zone(@filename) if @content.nil?
@content
end

def content=(txt)
@content = txt
end

def changed?
return false if @content.nil?

# if original hash is missing, save zone content, reload
# original file, compute hash, and restore previous content
if @content_hash.nil?
content_backup = @content
@content = nil
content
@content = content_backup
end

Digest::MD5.hexdigest(@content) != @content_hash
end

def cancel_changes
@content = nil
cleanup_temp
end

def check(force_real = false)
check_zone_file('full', force_real = false)
end

def serial(force_real = false)
r = check_zone_file('none', force_real = false)
if r.ok
r.serial
else
raise CyberError.new(:unrecoverable, "services/dns", "zone serial for '#{@zone}' could not be found (#{r.errors.first})")
end
end

def import_from_file(new_zone_filename)
read_zone(new_zone_filename)
end

def import_from_backup
read_zone(self.backup_filename)
end

def create_backup
FileUtils.cp(@filename, backup_filename())
end

def save
raise CyberError.new(:unrecoverable, "services/dns", "won't save an empty zone file") if @content.nil?
write_zone(@filename)
update_hash
cleanup_temp
end

def activate
script = @config.dns.update_zone_script
if script.nil?
# TODO: use a factory
case @config.dns.software || :bind
when :bind
script = "rndc reload"
else
# TODO: should be checked at startup time
raise CyberError.new(:unrecoverable, "services/dns", "erroneous configuration: unknown nameserver")
end
end
system "sudo #{script} '#{@zone}' >/dev/null"
raise CyberError.new(:unrecoverable, "services/dns", "zone activation failed") unless $?.success?
end

def __destroy
cleanup_temp
end

protected

def backup_filename
@filename + ".ch-backup"
end

def save_to_temp
return unless @temp_file.nil?

begin
@temp_file = Tempfile.new(@zone)
@temp_file.write(@content)
@temp_file.close
rescue
raise CyberError.new(:unrecoverable, "services/dns", "could not save temporary zone")
end
end

def cleanup_temp
return if @temp_file.nil?

@temp_file.close!
@temp_file = nil
end

def temp_filename
@temp_file.path
end

def current_filename
if changed?
save_to_temp
return temp_filename
end

@filename
end

def update_hash
@content_hash = Digest::MD5.hexdigest(@content)
end

def read_zone(filename)
begin
@content = File.read(filename)
update_hash if filename == @filename
rescue
raise CyberError.new(:unrecoverable, "services/dns", "zone '#{@zone}' cannot be read from '#{filename}' (I/O error, nonexistent or lack of permission)")
end
end

def write_zone(filename)
begin
File.open(filename, "w") do |fp|
fp.print @content
end
rescue
raise CyberError.new(:unrecoverable, "services/dns", "zone '#{@zone}' cannot be written to '#{filename}' (I/O error or lack of permission)")
end
end

def check_zone_file(check_type, force_real = false)
filename = force_real ? @filename : current_filename

# TODO: use a factory
case @config.dns.software
when 'bind'
output = []
begin
IO.popen("named-checkzone -i #{check_type} '#{@zone}' #{filename}") do |fp|
output << fp.gets.chomp! until fp.eof?
end
rescue
raise CyberError.new(:unrecoverable, "services/dns", "zone '#{@zone}' could not be checked (I/O error)")
end

serial = nil
messages = []
output.each do |l|
next if l == "OK"
if l =~ /: loaded serial (\d+)$/
serial = $1
next
end
messages << l
end

if $?.success?
if serial
return {:ok => true, :serial => serial, :warnings => messages}.to_ostruct
else
raise CyberError.new(:unrecoverable, "services/dns", "zone validated but no serial returned")
end
else
return {:ok => false, :errors => messages}.to_ostruct
end
end
end
end
end
end
end
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