--- 
-- EAP (Extensible Authentication Protocol) library supporting a
-- limited subset of features.
--
-- The library was designed and tested against hostapd v0.6.10
-- The EAP protocol names are the ones specified in:
-- http://www.iana.org/assignments/eap-numbers/eap-numbers.xml
--
-- Scripts can use the library to start an eap session and then to
-- send identity and nak responses to identity and authentication
-- requests made by AP authenticators to analyze their behaviour.
--
-- The following sample code illustrates how to respond to an identity
-- request:
--
-- <code>
-- pcap:pcap_open(iface.device, 512, true, "ether proto 0x888e")
-- ...
-- local _, _, l2_data, l3_data, _ = pcap:pcap_receive()		
-- local packet = eap.parse(l2_data .. l3_data3) 
-- if packet then
--   if packet.eap.type == eap.eap_t.IDENTITY and  packet.eap.code == eap.code_t.REQUEST then
--	 eap.send_identity_response(iface, packet.eap.id, "anonymous")
--   end
-- end
-- </code>
--
--
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
--
-- @author "Riccardo Cecolin <n@rikiji.de>"
--

module(... or "eap", package.seeall)

-- Created 02/23/2012 - v0.1

require 'nmap'
require 'packet'
require 'bin'


local ETHER_BROADCAST = "01:80:c2:00:00:03"
local ETHER_TYPE_EAPOL_N = 0x888E
local ETHER_TYPE_EAPOL = bin.pack(">S",ETHER_TYPE_EAPOL_N)
local ETHER_HEADER_SIZE = 14
local EAPOL_HEADER_SIZE = 4
local EAP_HEADER_SIZE = 5

eapol_t = {
   PACKET = 0,
   START  = 1,
   LOGOFF = 2,
   KEY    = 3,
   ASF    = 4,
}

eapol_str = {
   [0] = "EAP Packet",
   [1] = "EAPOL Start",
   [2] = "EAPOL Logoff",
   [3] = "EAPOL Key",
   [4] = "EAPOL Encapsulated ASF Alert",
}

code_t = {
   REQUEST   = 1,
   RESPONSE  = 2,
   SUCCESS   = 3,
   FAILURE   = 4,
   INITIATE  = 5,
   FINISH    = 6,
}

code_str = {
   [1] = "Request", 
   [2] = "Response",
   [3] = "Success",
   [4] = "Failure",
   [5] = "Initiate",
   [6] = "Finish",
}

eap_t = {
   IDENTITY     = 1,
   NAK          = 3,
   MD5          = 4,
   TLS          = 13,
   TTLS         = 21,
   PEAP         = 25,
   MSCHAP       = 29,
}

eap_str = {
   [0] = "Reserved",
   [1] = "Identity",
   [2] = "Notification",
   [3] = "Legacy Nak",
   [4] = "MD5-Challenge",
   [5] = "One-Time Password (OTP)",
   [6] = "Generic Token Card (GTC)",
   [7] = "Allocated",
   [8] = "Allocated",
   [9] = "RSA Public Key Authentication",
   [10] = "DSS Unilateral",
   [11] = "KEA",
   [12] = "KEA-VALIDATE",
   [13] = "EAP-TLS",
   [14] = "Defender Token (AXENT)",
   [15] = "RSA Security SecurID EAP",
   [16] = "Arcot Systems EAP",
   [17] = "EAP-Cisco Wireless",
   [18] = "GSM Subscriber Identity Modules (EAP-SIM)",
   [19] = "SRP-SHA1",
   [20] = "Unassigned",
   [21] = "EAP-TTLS",
   [22] = "Remote Access Service",
   [23] = "EAP-AKA Authentication",
   [24] = "EAP-3Com Wireless",
   [25] = "PEAP",
   [26] = "MS-EAP-Authentication",
   [27] = "Mutual Authentication w/Key Exchange (MAKE)",
   [28] = "CRYPTOCard",
   [29] = "EAP-MSCHAP-V2",
   [30] = "DynamID",
   [31] = "Rob EAP",
   [32] = "Protected One-Time Password",
   [33] = "MS-Authentication-TLV",
   [34] = "SentriNET",
   [35] = "EAP-Actiontec Wireless",
   [36] = "Cogent Systems Biometrics Authentication EAP",
   [37] = "AirFortress EAP",
   [38] = "EAP-HTTP Digest",
   [39] = "SecureSuite EAP",
   [40] = "DeviceConnect EAP",
   [41] = "EAP-SPEKE",
   [42] = "EAP-MOBAC",
   [43] = "EAP-FAST",
   [44] = "ZoneLabs EAP (ZLXEAP)",
   [45] = "EAP-Link",
   [46] = "EAP-PAX",
   [47] = "EAP-PSK",
   [48] = "EAP-SAKE",
   [49] = "EAP-IKEv2",
   [50] = "EAP-AKA'",
   [51] = "EAP-GPSK",
   [52] = "EAP-pwd",
   [53] = "EAP-EKE Version 1",
   -- 54-253 Unassigned
   [254] = "Reserved for the Expanded Type",
   [255] = "Experimental",
}

local make_eapol = function (arg)
	if not arg.type then arg.type = eapol_t.PACKET end
	if not arg.version then arg.version = 1 end
	if not arg.payload then arg.payload = "" end		      
	if not arg.src then return nil end

	local p = packet.Frame:new()
	p.mac_src = arg.src
	p.mac_dst = packet.mactobin(ETHER_BROADCAST)
	p.ether_type = ETHER_TYPE_EAPOL	      

	local bin_payload = bin.pack(">A",arg.payload)
	p.buf = bin.pack("C",arg.version) .. bin.pack("C",arg.type) .. bin.pack(">S",bin_payload:len()).. bin_payload
	p:build_ether_frame()
	return p.frame_buf
end

local make_eap = function (arg)

    if not arg.code then arg.code = code_t.REQUEST end
    if not arg.id then arg.id = math.random(0,255) end
    if not arg.type then arg.type = eap_t.IDENTITY end
    if not arg.payload then arg.payload = "" end
    if not arg.header then return nil end

    local bin_payload = bin.pack(">A",arg.payload)
    arg.header.payload = bin.pack("C",arg.code) .. bin.pack("C",arg.id) .. bin.pack(">S",bin_payload:len() + EAP_HEADER_SIZE).. bin.pack("C",arg.type) .. bin_payload
 
    local v = make_eapol(arg.header)
    stdnse.print_debug(2, "make eapol %s", arg.header.src)
		      
    return v
end

parse = function (packet) 
	local tb = {}
	local _

	stdnse.print_debug(2, "packet size: 0x%x", #packet )

	-- parsing ethernet header
	_, tb.mac_src, tb.mac_dst, tb.ether_type = bin.unpack(">A6A6S", packet)
	_, tb.mac_src_str, tb.mac_dst_str = bin.unpack(">H6H6", packet)

	-- parsing eapol header
	_, tb.version, tb.type, tb.length = bin.unpack(">CCS", packet, ETHER_HEADER_SIZE + 1)

	stdnse.print_debug(1, "mac_src: %s, mac_dest: %s, ether_type: 0x%X", 
	tb.mac_src_str, tb.mac_dst_str, tb.ether_type)

	if tb.ether_type ~= ETHER_TYPE_EAPOL_N then return nil, "not an eapol packet" end	   

	stdnse.print_debug(2, "version: %X, type: %s, length: 0x%X", 
	tb.version, eapol_str[tb.type] or "unknown",
	tb.length)	   		   		   

	tb.eap = {}

	if tb.length > 0 then
		-- parsing body

		_, tb.eap.code, tb.eap.id, tb.eap.length, tb.eap.type = bin.unpack(">CCSC", packet,
		ETHER_HEADER_SIZE + EAPOL_HEADER_SIZE + 1) 	      
		stdnse.print_debug(2, "code: %s, id: 0x%X, length: 0x%X, type: %s",
		code_str[tb.eap.code] or "unknown",
		tb.eap.id, tb.eap.length, eap_str[tb.eap.type] or "unknown" )
		if tb.length ~= tb.eap.length then
			stdnse.print_debug(1, "WARNING length mismatch: 0x%X and 0x%X", tb.length, tb.eap.length )
		end
	end

	tb.eap.body = {}

	-- parsing payload
	if tb.length > 5 and tb.eap.type == eap_t.IDENTITY then
		_, tb.eap.body.identity = bin.unpack("z", packet,
		ETHER_HEADER_SIZE + EAPOL_HEADER_SIZE + EAP_HEADER_SIZE + 1)
		stdnse.print_debug(1, "identity: %s", tb.eap.body.identity )
	end

	if tb.length > 5 and tb.eap.type == eap_t.MD5  then
		_, tb.eap.body.challenge = bin.unpack("p", packet, ETHER_HEADER_SIZE + EAPOL_HEADER_SIZE + EAP_HEADER_SIZE + 1) 
	end

	return tb
end

send_identity_response = function (iface, id, identity)

	if not iface then
		stdnse.print_debug(1, "no interface given")
		return
	end	

	local dnet = nmap.new_dnet()		   
	local tb = {src = iface.mac, type = eap.eapol_t.PACKET}
	local response = make_eap{header = tb, code = code_t.RESPONSE, type = eap_t.IDENTITY, id = id, payload = identity}

	dnet:ethernet_open(iface.device)
	dnet:ethernet_send(response)
	dnet:ethernet_close()
end

send_nak_response = function (iface, id, auth)

	if not iface then
		stdnse.print_debug(1, "no interface given")
		return
	end	

	local dnet = nmap.new_dnet()		   
	local tb = {src = iface.mac, type = eap.eapol_t.PACKET}
	local response = make_eap{header = tb, code = code_t.RESPONSE, type = eap_t.NAK, id = id, payload = bin.pack("C",auth)}

	dnet:ethernet_open(iface.device)
	dnet:ethernet_send(response)
	dnet:ethernet_close()
end


send_start = function (iface)
		
	if not iface then
		stdnse.print_debug(1, "no interface given")
		return
	end

	local dnet = nmap.new_dnet()
	local start = make_eapol{type = eap.eapol_t.START, src = iface.mac}   

	dnet:ethernet_open(iface.device)
	dnet:ethernet_send(start)
	dnet:ethernet_close()
		
end
