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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 unpack = unpack
local tonumber = tonumber
local error = error
local getinfo = debug.getinfo
local concat = table.concat
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)
luxio.write(fd, msglen .. msg)
end
local function recv_msg()
local len = luxio.read(fd, 5)
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
return str
end
local function captcha(msg)
local traceback = {}
local level = 2
local info = getinfo(level, "Snlf")
while info do
if info.currentline > 0 and
not info.short_src:match("/supple/[^%.]+%.lua$") 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 ""}
end
local function wait_for_response()
repeat
local back = request.deserialise(recv_msg())
-- 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)
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, ...)
local req = request.request(object, method, ...)
send_msg(req)
return wait_for_response()
end
return {
call = make_call,
_wait = wait_for_response,
_set_fd = set_fd,
}
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