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-- lib/supple/comms.lua
--
-- Sandbox (for) Untrusted Procedure Partitioning (in) Lua Engine
--
-- Management of communications between host and sandbox
--
-- Copyright 2012 Daniel Silverstone <dsilvers@digital-scurf.org>
--
-- For licence terms, see COPYING
--
local luxio = require "luxio"
local capi = require "supple.capi"
local request = require "supple.request"
local objects = require "supple.objects"
local track = require "supple.track"
local unpack = unpack
local tonumber = tonumber
local error = error
local getinfo = debug.getinfo
local concat = table.concat
local xpcall = xpcall
local gc = collectgarbage
local fd = -1
local function set_fd(_fd)
fd = _fd
end
local function send_msg(msg)
if (#msg > 99999) then
error("Message too long")
end
local msglen = ("%05d"):format(#msg)
track.record("XMIT", msg)
luxio.write(fd, msglen .. msg)
end
local function recv_msg()
local len, errno = luxio.read(fd, 5)
if type(len) ~= "string" then
error(luxio.strerror(errno))
end
if #len < 5 then
error("Unable to read 5 byte length")
end
len = tonumber(len)
if len == nil or len < 1 or len > 99999 then
error("Odd, len didn't translate properly")
end
local str = luxio.read(fd, len)
if type(str) ~= "string" or #str ~= len then
error("Unable to read " .. tostring(len) .. " bytes of msg")
end
track.record("RECV", str)
return str
end
local function captcha(msg)
local traceback = {}
local level = 2
local info = getinfo(level, "Snlf")
local function in_supple()
return info.short_src:match("/supple/[^%.]+%.lua$")
end
while info and info.func ~= xpcall do
-- if info.currentline > 0 and not in_supple() then
if true then
local ttype, tag = objects.find_tag(info.func)
if ttype then
info.name = tag
end
local line =
("\t%s:%d in function %s"):format(info.short_src,
info.currentline,
info.name or "<anon>")
traceback[#traceback+1] = line
end
level = level + 1
info = getinfo(level, "Snlf")
end
return {msg, (concat(traceback, "\n") or "") .. "\nComms track:\n" .. track.stop()}
end
local limits = {}
math.randomseed(os.time())
math.randomseed(math.random(luxio.getpid()))
local count_per_hook = 10 + (math.random(5) - 3)
local limiting = false
local function limit_hook()
local inside = getinfo(2, "Snlf")
if inside.short_src == "[C]" or inside.name == "(tail call)" then
return
end
if limiting and not inside.short_src:match("/supple/[^%.]+%.lua$") then
if limits.count then
limits.count = limits.count - count_per_hook
if limits.count < 0 then
limiting = false
error("Used too many instructions", 2)
end
end
if limits.memory then
if limits.memory < gc "count" then
limiting = false
error("Exceeded memory usage limit", 2)
end
end
end
end
local function wait_for_response()
repeat
-- We *MUST* disable GC for the duration of receiving and parsing the
-- message, lest we send a __gc transaction between the first and second
-- read operations. Or indeed if we GC and object between receiving the
-- message and deserialising and thus anchoring the object. If we error
-- out here, we don't really care about restarting gc since we won't
-- survive long anyhow.
gc "stop"
-- Also anchor all the objects just in case
local anchor = objects.get_object_anchor()
-- Now receive and deserialise (thus anchoring relevant objects)
local back = request.deserialise(recv_msg())
-- Now that the request is anchored, release the extra anchor and
-- re-allow GC
anchor = nil
gc "restart"
-- And get on with parsing the message we received..
-- back could be three things
-- an error (raise it)
if back.error then
local msg = back.message
if back.traceback and back.traceback ~= "" then
msg = msg .. "\n" .. back.traceback
end
error(msg, 2)
end
-- A result, return it
if back.error == false then
return unpack(back.results)
end
-- A method call, call it
local function safe_method(fn)
local ok, res = xpcall(fn, captcha)
local resp
if not ok then
resp = request.error(unpack(res))
else
resp = request.response(unpack(res))
end
send_msg(resp)
end
if back.method == "__gc" then
-- __gc is the garbage collect mechanism
objects.forget_mine(back.object)
send_msg(request.response())
elseif back.method == "__call" then
-- __call is the function call mechanism
safe_method(function()
local obj = objects.receive { tag = back.object }
return {obj(unpack(back.args))}
end)
elseif back.method == "__len" then
safe_method(function()
local obj = objects.receive { tag = back.object }
return {#obj}
end)
elseif back.method == "__index" then
safe_method(function()
local obj = objects.receive { tag = back.object }
return {obj[back.args[1]]}
end)
elseif back.method == "__newindex" then
safe_method(function()
local obj = objects.receive { tag = back.object }
obj[back.args[1]] = back.args[2]
return {}
end)
elseif back.method == "__next" then
safe_method(function()
local obj = objects.receive { tag = back.object }
return {next(obj, back.args[1])}
end)
else
safe_method(function()
local obj = objects.receive { tag = back.object }
local meth = capi.raw_getmm(obj, back.method)
if not meth then
error("Unknown or disallowed method: " .. back.method, "")
end
return {meth(obj, unpack(back.args))}
end)
end
until false
end
local function make_call(object, method, ...)
track.enter("make_call", object, method)
local req = request.request(object, method, ...)
send_msg(req)
local ret = {wait_for_response()}
track.leave("make_call", object, method)
return unpack(ret)
end
local function set_limits(newlimits)
limits = newlimits
debug.sethook()
debug.sethook(limit_hook, "c", count_per_hook)
limiting = true
end
return {
call = make_call,
_wait = wait_for_response,
_set_fd = set_fd,
set_limits = set_limits,
}
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