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Filename : bjnp.lua
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---
-- An implementation of the Canon BJNP protocol used to discover and query
-- Canon network printers and scanner devices.
--
-- The implementation is pretty much based on Wireshark decoded messages
-- the cups-bjnp implementation and the usual guesswork.
--
-- @author "Patrik Karlsson <patrik [at] cqure.net>"
--

local bin = require("bin")
local bit = require("bin")
local nmap = require("nmap")
local os = require("os")
local stdnse = require("stdnse")
local string = require("string")
local table = require("table")

_ENV = stdnse.module("bjnp", stdnse.seeall)

BJNP = {

	-- The common BJNP header
	Header = {
		
		new = function(self, o)
			o = o or {}
			o = {
				id = o.id or "BJNP",
				type = o.type or 1,
				code = o.code,
				seq = o.seq or 1,
				session = o.session or 0,
				length = o.length or 0,
			}
			assert(o.code, "code argument required")
			setmetatable(o, self)
			self.__index = self
			return o
		end,

		parse = function(data)
			local hdr = BJNP.Header:new({ code = -1 })
			local pos
			
			pos, hdr.id, hdr.type, hdr.code,
				hdr.seq, hdr.session, hdr.length = bin.unpack(">A4CCISI", data)
			return hdr
		end,

		__tostring = function(self)
				return bin.pack(">ACCISI", 
					self.id, 
					self.type,
					self.code,
					self.seq,
					self.session,
					self.length
				)
			end
	},
	
	-- Scanner related code
	Scanner = {
		
		Code = {
			DISCOVER = 1,
			IDENTITY = 48,
		},
		
		Request = {

			Discover = {
			
				new = function(self)
					local o = { header = BJNP.Header:new( { type = 2, code = BJNP.Scanner.Code.DISCOVER }) }
					setmetatable(o, self)
					self.__index = self
					return o
				end,

				__tostring = function(self)
					return tostring(self.header)
				end,
			},
			
			
			Identity = {
				
				new = function(self)
					local o = { header = BJNP.Header:new( { type = 2, code = BJNP.Scanner.Code.IDENTITY, length = 4 }), data = 0 }
					setmetatable(o, self)
					self.__index = self
					return o
				end,

				__tostring = function(self)
					return tostring(self.header) .. bin.pack(">I", self.data)
				end,
			}
			
		},
		
		Response = {
			
			Identity = {

				new = function(self)
					local o = {}
					setmetatable(o, self)
					self.__index = self
					return o					
				end,

				parse = function(data)
					local identity = BJNP.Scanner.Response.Identity:new()
					identity.header = BJNP.Header.parse(data)

					local pos = #tostring(identity.header) + 1
					local pos, len = bin.unpack(">S", data, pos)
					if ( len ) then
						pos, identity.data = bin.unpack("A" .. len - 2, data, pos)
						return identity
					end
				end,
				

			}
			
		}

	},

	-- Printer related code
	Printer = {

		Code = {
			DISCOVER = 1,
			IDENTITY = 48,
		},
		
		Request = {

			Discover = {
				new = function(self)
					local o = { header = BJNP.Header:new( { code = BJNP.Printer.Code.DISCOVER }) }
					setmetatable(o, self)
					self.__index = self
					return o
				end,

				__tostring = function(self)
					return tostring(self.header)
				end,
			},
			
			Identity = {
				
				new = function(self)
					local o = { header = BJNP.Header:new( { code = BJNP.Printer.Code.IDENTITY }) }
					setmetatable(o, self)
					self.__index = self
					return o
				end,

				__tostring = function(self)
					return tostring(self.header)
				end,
			}
			
		},

		Response = {
			
			Identity = {

				new = function(self)
					local o = {}
					setmetatable(o, self)
					self.__index = self
					return o
				end,

				parse = function(data)
					local identity = BJNP.Printer.Response.Identity:new()
					identity.header = BJNP.Header.parse(data)
					
					local pos = #tostring(identity.header) + 1
					local pos, len = bin.unpack(">S", data, pos)
					if ( len ) then
						pos, identity.data = bin.unpack("A" .. len - 2, data, pos)
						return identity
					end
				end,
				
				
			}
			
		},
		
	}

}

-- Helper class, the main script writer interface
Helper = {
	
	-- Creates a new Helper instance
	-- @param host table
	-- @param port table
	-- @param options table containing one or more of the following fields;
	--	<code>timeout</code> - the timeout in milliseconds for socket communication
	--	<code>bcast</code> - instructs the library that the host is a broadcast
	--	                     address
	-- @return o new instance of Helper
	new = function(self, host, port, options)
		local o = {
			host = host, port = port, options = options or {}
		}
		o.options.timeout = o.options.timeout or 5000
		setmetatable(o, self)
		self.__index = self
		return o
	end,
	
	-- Connects the socket to the device
	-- This should always be called, regardless if the broadcast option is set
	-- or not.
	--
	-- @return status, true on success, false on failure
	-- @return err string containing the error message if status is false
	connect = function(self)
		self.socket = nmap.new_socket(( self.options.bcast and "udp" ))
		self.socket:set_timeout(self.options.timeout)
		if ( not(self.options.bcast) ) then
			return self.socket:connect(self.host, self.port)
		end
		return true
	end,
	
	-- Discover network devices using either broadcast or unicast
	-- @param packet discovery packet (printer or scanner)
	-- @return status, true on success, false on failure
	-- @return devices table containing discovered devices when status is true
	--         errmsg string containing the error message when status is false
	discoverDevice = function(self, packet)
		if ( not(self.options.bcast) ) then
			if ( not(self.socket:send(tostring(packet))) ) then
				return false, "Failed to send request to server"
			end
		else
			if ( not(self.socket:sendto(self.host, self.port, tostring(packet))) ) then
				return false, "Failed to send request to server"
			end
		end
		-- discover run in loop
		local devices, tmp = {}, {}
		local start = os.time()
		while( true ) do
			local status, data = self.socket:receive()
			if ( not(status) or ( os.time() - start > ( self.options.timeout/1000 - 1 ) )) then
				break
			end
			local status, _, _, rhost = self.socket:get_info()
			tmp[rhost] = true
		end
		for host in pairs(tmp) do table.insert(devices, host) end
		return true, ( self.options.bcast and devices or ( #devices > 0 and devices[1] ))
	end,
	
	-- Discover BJNP supporting scanners
	discoverScanner = function(self)
		return self:discoverDevice(BJNP.Scanner.Request.Discover:new())
	end,
	
	-- Discover BJNP supporting printers
	discoverPrinter = function(self)
		return self:discoverDevice(BJNP.Printer.Request.Discover:new())
	end,
	
	-- Gets a printer identity (additional information)
	-- @param devtype string containing either the string printer or scanner
	-- @return status, true on success, false on failure
	-- @return attribs table containing device attributes when status is true
	--         errmsg string containing the error message when status is false
	getDeviceIdentity = function(self, devtype)
		-- Were currenlty only decoding this as I don't know what the other cruft is
		local attrib_names = { 
			["scanner"] = {
				{ ['MFG'] = "Manufacturer" },
				{ ['MDL'] = "Model" },
				{ ['DES'] = "Description" },
				{ ['CMD'] = "Command" },
			}, 
			["printer"] = {
				{ ['MFG'] = "Manufacturer" },
				{ ['MDL'] = "Model" },
				{ ['DES'] = "Description" },
				{ ['VER'] = "Firmware version" },
				{ ['CMD'] = "Command" },
			}
		}
		local identity
		if ( "printer" == devtype ) then
			identity = BJNP.Printer.Request.Identity:new()
		elseif ( "scanner" == devtype ) then
			identity = BJNP.Scanner.Request.Identity:new()
		end
		assert(not(self.options.bcast), "getIdentity is not supported for broadcast")
		if ( not(self.socket:send(tostring(identity))) ) then
			return false, "Failed to send request to server"
		end
		local status, data = self.socket:receive()
		if ( not(status) ) then
			return false, "Failed to receive response from server"
		end
		
		local identity
		if ( "printer" == devtype ) then
			identity = BJNP.Printer.Response.Identity.parse(data)
		elseif ( "scanner" == devtype ) then
			identity = BJNP.Scanner.Response.Identity.parse(data)
		end
		if ( not(identity) ) then
			return false, "Failed to parse identity"
		end
		local attrs, kvps = {}, {}

		for k, v in ipairs(stdnse.strsplit(";", identity.data)) do
			local nm, val = v:match("^([^:]*):(.*)$")
			if ( nm ) then kvps[nm] = val end
		end

		for _, attrib in ipairs(attrib_names[devtype]) do
			local short, long = next(attrib)
			if ( kvps[short] ) then
				table.insert(attrs, ("%s: %s"):format(long, kvps[short]))
			end
		end
		
		return true, attrs
	end,
	
	-- Retrieves information related to the printer
	getPrinterIdentity = function(self)
		return self:getDeviceIdentity("printer")
	end,
	
	-- Retrieves information related to the scanner
	getScannerIdentity = function(self)
		return self:getDeviceIdentity("scanner")
	end,
	
	-- Closes the connection
	-- @return status, true on success, false on failure
	-- @return errmsg string containing the error message when status is false
	close = function(self)
		return self.socket:close()
	end
	
}

return _ENV;