Class: BetterCap::Discovery::Agents::Mdns

Inherits:
Object
  • Object
show all
Defined in:
lib/bettercap/discovery/agents/mdns.rb

Overview

Class responsible for sending mDNS broadcast queries to the network.

Instance Method Summary collapse

Constructor Details

#initialize(ctx, address = nil) ⇒ Mdns

Create a thread which will send an mDNS broadcast query in order to populate the ARP cache with active targets. http://www.multicastdns.org/ http://www.ietf.org/rfc/rfc6762.txt https://en.wikipedia.org/wiki/Multicast_DNS https://en.wikipedia.org/wiki/Zero-configuration_networking#DNS-SD_with_multicast



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# File 'lib/bettercap/discovery/agents/mdns.rb', line 30

def initialize( ctx, address = nil )
  pkt = PacketFu::UDPPacket.new

  pkt.eth_saddr = ctx.iface.mac
  pkt.eth_daddr = '01:00:5e:00:00:fb'
  pkt.ip_saddr  = ctx.iface.ip
  pkt.ip_daddr  = '224.0.0.251'
  pkt.udp_src   = (rand((2 ** 16) - 1024) + 1024).to_i
  pkt.udp_dst   = 5353

  query = "\x09_services\x07_dns-sd\x04_udp\x05local"

  payload =  "\x00\x01" # Transaction ID
  payload << "\x00\x00" # Flags
  payload << "\x00\x01" # Number of questions
  payload << "\x00\x00" # Number of answers
  payload << "\x00\x00" # Number of authority resource records
  payload << "\x00\x00" # Number of additional resource records
  payload << query      # Query
  payload << "\x00"     # Terminator
  payload << "\x00\x0c" # Type (PTR)
  payload << "\x00\x01" # Class

  pkt.payload = payload
  pkt.recalc

  ctx.packets.push(pkt)
end