RubyDNS

RubyDNS is a tool that allows you to intercept and modify DNS requests. It can provide most typical DNS server functionality, including the ability to pull DNS records from any data source.

• Fully programmatic DNS server: integrate with databases, servers and caches seamlessly.
• Match incoming DNS requests using regular expressions.
• Modify requests in-flight to spoof or manipulate DNS responses.
• Includes several auxiliary commands for DNS migration, verification and testing.

Documentation

1. Installation
2. Basic DNS Server
3. DNS Verification
4. DNS Testing
5. API Documentation

Example

#!/usr/bin/env ruby

# Copyright (c) 2009 Samuel Williams. Released under the GNU GPLv3.
#
# 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 'rubygems'

require 'rexec'
require 'rexec/daemon'

require 'rubygems'
require 'rubydns'

require 'timeout'

# Run as user "daemon"
RUN_AS="daemon"

# Cache DNS entries for 5 minutes
CACHE_TIME=60*5

# We need to be root in order to bind to privileged port
if RExec.current_user != "root"
	$stderr.puts "Sorry, this command needs to be run as root!"
	exit 1
end

# Helper
Name = Resolv::DNS::Name

HARU_A = "10.0.0.80"
SCOOTER_A = "10.0.0.10"

# The Daemon itself
class Server < RExec::Daemon::Base
	@@var_directory = File.dirname(__FILE__)

	def self.run
		# Don't buffer output (for debug purposes)
		$stderr.sync = true

		# Use upstream DNS for name resolution
		# Scooter DNS
		$R = Resolv::DNS.new(:nameserver => SCOOTER_A)

		$CACHE = {}

		# Start the RubyDNS server
		RubyDNS::run_server do
			on(:start) do
				RExec.change_user(RUN_AS)
			end
			
			match(/(gems|git|svn).oriontransfer.org$/, :A) do |match, transaction|
				transaction.respond!(HARU_A)
			end

			match("haru.oriontransfer.org", :A) do |transaction|
				transaction.respond!(HARU_A)
			end

			match("80.0.0.10.in-addr.arpa", :PTR) do |transaction|
				transaction.respond!(Name.create("haru.oriontransfer.org."))
			end

			# Default DNS handler
			otherwise do |transaction|
				key = [transaction.name, transaction.resource_class]
				cache = $CACHE[key]

				if cache and (Time.now - cache[1]) < CACHE_TIME
					logger.info "Cached: #{transaction.name}..."
					transaction.answer.merge!(cache[0])
				else
					logger.info "Lookup: #{transaction.question.to_s}"
					transaction.passthrough!($R) do |reply, reply_name|
						$CACHE[key] = [reply, Time.now]
					end
				end
			end
		end
	end
end

# RExec daemon runner
Server.daemonize