--- Username/password database library.
-- \n\n
-- The usernames and passwords functions return multiple values for use
-- with exception handling via nmap.new_try().
-- The first value is the boolean success indicator, the second value is
-- the closure.
-- \n\n
-- The closures can take a parameter of "reset" to rewind the list to the
-- beginning.
-- \n\n
-- You can select your own username and/or password database to read from with
-- the script arguments userdb and passdb, respectively.  Comments are allowed
-- in these files, prefixed with "#!comment:".  Comments cannot be on the same
-- line as a username or password because this leaves too much ambiguity, e.g.
-- does the password in "mypass  #!comment: blah" contain a space, two spaces,
-- or do they just separate the password from the comment?
--
-- @author Kris Katterjohn 06/2008

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

local usertable = {}
local passtable = {}

local customdata = false

-- So I don't have to type as much :)
local args = nmap.registry.args

local userfile = function()
	if args.userdb then
		customdata = true
		return args.userdb
	end

	return nmap.fetchfile("nselib/data/usernames.lst")
end

local passfile = function()
	if args.passdb then
		customdata = true
		return args.passdb
	end

	return nmap.fetchfile("nselib/data/passwords.lst")
end

local filltable = function(filename, table)
	if #table ~= 0 then
		return true
	end

	local file = io.open(filename, "r")

	if not file then
		return false
	end

	while true do
		local l = file:read()

		if not l then
			break
		end

		-- Comments takes up a whole line
		if not l:match("#!comment:") then
			table[#table + 1] = l
		end
	end

	file:close()

	return true
end

local closure = function(table)
	local i = 1

	return function(cmd)
		if cmd == "reset" then
			i = 1
			return
		end
		local elem = table[i]
		if elem then i = i + 1 end
		return elem
	end
end

--- Returns the suggested number of seconds to attempt a brute
-- force attack, based on Nmap's timing values (-T4, etc) and whether or not a
-- user-defined list is used.
-- \n\n
-- You can use the script argument "notimelimit" to make this function return
-- nil, which means the brute-force should run until the list is empty. If
-- "notimelimit" is not used, be sure to still check for nil return values on
-- the above two functions in case you finish before the time limit is up.
timelimit = function()
   -- If we're reading from a user-defined username or password list,
   -- we'll give them a timeout 1.5x the default.  If the "notimelimit"
   -- script argument is used, we return nil.
	local t = nmap.timing_level()

	-- Easy enough
	if args.notimelimit then
		return nil
	end

	if t <= 3 then
		return (customdata and 900) or 600
	elseif t == 4 then
		return (customdata and 450) or 300
	elseif t == 5 then
		return (customdata and 270) or 180
	end
end

--- Returns a function closure which returns a new username with every call
-- until the username list is exhausted (in which case it returns nil).
-- @return boolean Status.
-- @return function The usernames iterator.
usernames = function()
	local path = userfile()

	if not path then
		return false, "Cannot find username list"
	end

	if not filltable(path, usertable) then
		return false, "Error parsing username list"
	end

	return true, closure(usertable)
end

--- Returns a function closure which returns a new password with every call
-- until the password list is exhausted (in which case it returns nil).
-- @return boolean Status.
-- @return function The passwords iterator.
passwords = function()
	local path = passfile()

	if not path then
		return false, "Cannot find password list"
	end

	if not filltable(path, passtable) then
		return false, "Error parsing password list"
	end

	return true, closure(passtable)
end