--[[
Iptables file dumper for Alpine Wall
Copyright (C) 2012-2013 Kaarle Ritvanen
See LICENSE file for license details
]]--


module(..., package.seeall)

require 'lpc'

require 'awall.object'
require 'awall.uerror'

local util = require('awall.util')
local sortedkeys = util.sortedkeys

local class = awall.object.class


local families = {inet={cmd='iptables',
			file='rules-save',
			procfile='/proc/net/ip_tables_names'},
		  inet6={cmd='ip6tables',
			 file='rules6-save',
			 procfile='/proc/net/ip6_tables_names'}}

builtin = {filter={'FORWARD', 'INPUT', 'OUTPUT'},
	   mangle={'FORWARD', 'INPUT', 'OUTPUT', 'POSTROUTING', 'PREROUTING'},
	   nat={'INPUT', 'OUTPUT', 'POSTROUTING', 'PREROUTING'},
	   raw={'OUTPUT', 'PREROUTING'},
	   security={'FORWARD', 'INPUT', 'OUTPUT'}}

local backupdir = '/var/run/awall'


local BaseIPTables = class()

function BaseIPTables:print()
   for family, tbls in pairs(families) do
      self:dumpfile(family, io.stdout)
      print()
   end
end

function BaseIPTables:dump(dir)
   for family, tbls in pairs(families) do
      local file = io.output(dir..'/'..families[family].file)
      self:dumpfile(family, file)
      file:close()
   end
end

function BaseIPTables:restore(test)
   local disabled = true

   for family, params in pairs(families) do
      local file = io.open(params.procfile)
      if file then
	 io.close(file)

	 local pid, stdin, stdout = lpc.run(params.cmd..'-restore',
					    unpack({test and '-t' or nil}))
	 stdout:close()
	 self:dumpfile(family, stdin)
	 stdin:close()
	 assert(lpc.wait(pid) == 0)

	 disabled = false

      elseif test then
	 io.stderr:write('Warning: '..family..' rules not tested\n')
      end
   end

   if disabled then awall.uerror.raise('Firewall not enabled in kernel') end
end

function BaseIPTables:activate()
   flush()
   self:restore(false)
end

function BaseIPTables:test() self:restore(true) end


IPTables = class(BaseIPTables)

function IPTables:init()
   self.config = {}
   setmetatable(self.config,
		{__index=function(t, k)
			    t[k] = {}
			    setmetatable(t[k], getmetatable(t))
			    return t[k]
			 end})
end

function IPTables:dumpfile(family, iptfile)
   iptfile:write('# '..families[family].file..' generated by awall\n')
   local tables = self.config[family]
   for i, tbl in sortedkeys(tables) do
      iptfile:write('*'..tbl..'\n')
      local chains = tables[tbl]
      for i, chain in sortedkeys(chains) do
	 local policy = '-'
	 if util.contains(builtin[tbl], chain) then
	    policy = tbl == 'filter' and 'DROP' or 'ACCEPT'
	 end
	 iptfile:write(':'..chain..' '..policy..' [0:0]\n')
      end
      for i, chain in sortedkeys(chains) do
	 for i, rule in ipairs(chains[chain]) do
	    iptfile:write('-A '..chain..' '..rule..'\n')
	 end
      end
      iptfile:write('COMMIT\n')
   end
end


local Current = class(BaseIPTables)

function Current:dumpfile(family, iptfile)
   local pid, stdin, stdout = lpc.run(families[family].cmd..'-save')
   stdin:close()
   for line in stdout:lines() do iptfile:write(line..'\n') end
   stdout:close()
   assert(lpc.wait(pid) == 0)
end


local Backup = class(BaseIPTables)

function Backup:dumpfile(family, iptfile)
   for line in io.lines(backupdir..'/'..families[family].file) do
      iptfile:write(line..'\n')
   end
end


function backup()
   Current.new():dump(backupdir)
end

function revert()
   Backup.new():activate()
end

function flush()
   local empty = IPTables.new()
   for family, params in pairs(families) do
      local success, lines = pcall(io.lines, params.procfile)
      if success then
	 for tbl in lines do
	    for i, chain in ipairs(builtin[tbl]) do
	       empty.config[family][tbl][chain] = {}
	    end
	 end
      end
   end
   empty:restore(false)
end