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--[==========================================================================[
sandbox.lua: Lua sandboxing facilities
--[==========================================================================[
Copyright (C) 2007 the VideoLAN team
Authors: Antoine Cellerier <dionoea at videolan dot org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
--]==========================================================================]
local sandbox = {}
-- See Programming in Lua (second edition) for sandbox examples
-- See http://lua-users.org/wiki/SandBoxes for a list of SAFE/UNSAFE variables
local sandbox_blacklist = {
collectgarbage = true,
dofile = true,
_G = true,
getfenv = true,
getmetatable = true,
load = true, -- Can be protected I guess
loadfile = true, -- Can be protected I guess
rawequal = true,
rawget = true,
rawset = true,
setfenv = true,
setmetatable = true,
module = true,
require = true,
package = true,
debug = true,
}
if _VERSION == "Lua 5.1" then
sandbox_blacklist["loadstring"] = true
end
function sandbox.readonly_table_proxy(name,src,blacklist)
if type(src)=="nil" then return end
if type(src)~="table" then error("2nd argument must be a table (or nil)") end
local name = name
local t = src
local blist = {}
if blacklist then
for _, v in pairs(blacklist) do
blist[v] = true
end
end
local metatable_readonly = {
__index = function(self,key)
if blist[key] then
error("Sandbox: Access to `"..name.."."..key.."' is forbidden.")
end
return t[key]
end,
__newindex = function(self,key,value)
error("It is forbidden to modify elements of this table.")
end,
}
return setmetatable({},metatable_readonly)
end
-- Of course, all of this is useless if the sandbox calling code has
-- another reference to one of these tables in his global environement.
local sandbox_proxy = {
coroutine = sandbox.readonly_table_proxy("coroutine",coroutine),
string = sandbox.readonly_table_proxy("string",string,{"dump"}),
table = sandbox.readonly_table_proxy("table",table),
math = sandbox.readonly_table_proxy("math",math),
io = sandbox.readonly_table_proxy("io",io),
os = sandbox.readonly_table_proxy("os",os,{"exit","getenv","remove",
"rename","setlocale"}),
sandbox = sandbox.readonly_table_proxy("sandbox",sandbox),
}
function sandbox.sandbox(func,override)
local _G = getfenv(2)
local override = override or {}
local sandbox_metatable =
{
__index = function(self,key)
if override[key] then
return override[key]
end
if sandbox_blacklist[key] then
error( "Sandbox: Access to `"..key.."' is forbidden." )
end
--print(key,"not found in env. Looking in sandbox_proxy and _G")
local value = sandbox_proxy[key] or _G[key]
rawset(self,key,value) -- Keep a local copy
return value
end,
__newindex = function(self,key,value)
if override and override[key] then
error( "Sandbox: Variable `"..key.."' is read only." )
end
return rawset(self,key,value)
end,
}
local sandbox_env = setmetatable({},sandbox_metatable)
return function(...)
setfenv(func,sandbox_env)
local ret = {func(...)} -- Not perfect (if func returns nil before
-- another return value) ... but it's better
-- than nothing
setfenv(func,_G)
return unpack(ret)
end
end
_G.sandbox = sandbox
return sandbox
|
