lib/rex/proto/dns/cache.rb
# -*- coding: binary -*-
require 'rex/socket'
module Rex
module Proto
module DNS
class Cache
attr_reader :records, :lock, :monitor_thread
include Rex::Proto::DNS::Constants
# class DNSRecordError < ::Exception
#
# Create DNS cache
#
def initialize
@records = {}
@lock = Mutex.new
end
#
# Find entries in cache, substituting names for '*' in return
#
# @param search [String] Name or address to search for
# @param type [Dnsruby::Types] Record type to search for
#
# @return [Array] Records found
def find(search, type = Dnsruby::Types::A)
self.records.select do |record,expire|
record.type == type and (expire < 1 or expire > ::Time.now.to_i) and
(
record.name == '*' or
record.name.to_s == search.to_s or record.name.to_s[0..-2] == search.to_s or
( record.respond_to?(:address) and record.address.to_s == search.to_s )
)
end.keys.map do |record|
if search.to_s.match(MATCH_HOSTNAME) and record.name == '*'
record = Dnsruby::RR.create(name: name, type: type, address: address)
else
record
end
end
end
#
# Add record to cache, only when "running"
#
# @param record [Dnsruby::RR] Record to cache
def cache_record(record)
return unless @monitor_thread
if record.is_a?(Dnsruby::RR) and
(!record.respond_to?(:address) or Rex::Socket.is_ip_addr?(record.address.to_s)) and
record.name.to_s.match(MATCH_HOSTNAME)
add(record, ::Time.now.to_i + record.ttl)
else
raise "Invalid record for cache entry - #{record.inspect}"
end
end
#
# Delete all cache entries, this is different from pruning because the
# record's expiration is ignored
#
def flush
self.records.each {|rec, _| delete(rec)}
end
#
# Prune cache entries
#
# @param before [Fixnum] Time in seconds before which records are evicted
def prune(before = ::Time.now.to_i)
self.records.select do |rec, expire|
expire > 0 and expire < before
end.each {|rec, exp| delete(rec)}
end
#
# Start the cache monitor
#
def start
@monitor_thread = Rex::ThreadFactory.spawn("DNSServerCacheMonitor", false) {
while true
prune
Rex::ThreadSafe.sleep(0.5)
end
} unless @monitor_thread
end
#
# Stop the cache monitor
#
# @param flush [TrueClass,FalseClass] Remove non-static entries
def stop(flush = false)
self.monitor_thread.kill unless @monitor_thread.nil?
@monitor_thread = nil
if flush
self.records.select do |rec, expire|
rec.ttl > 0
end.each {|rec| delete(rec)}
end
end
protected
#
# Add a record to the cache with thread safety
#
# @param record [Dnsruby::RR] Record to add
# @param expire [Fixnum] Time in seconds when record becomes stale
def add(record, expire = 0)
self.lock.synchronize do
self.records[record] = expire
end
end
#
# Delete a record from the cache with thread safety
#
# @param record [Dnsruby::RR] Record to delete
def delete(record)
self.lock.synchronize do
self.records.delete(record)
end
end
end # Cache
end
end
end