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Improving the quota enforcer #12

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24 changes: 19 additions & 5 deletions sandbox.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -153,19 +153,33 @@ function sandbox.protect(code, options)

return function(...)

local queryInvoker = function(...) local tmp = table.pack(pcall(f, ...)); cleanup(); return tmp end;

if quota and quota_supported then
local timeout = function()
cleanup()
error('Quota exceeded: ' .. tostring(quota))
if(type(debug) == 'table' and type(debug.sethook) == 'function') then
-- If the function were to be using pcall, it may capture the error accidentally or intentionally.
-- This allows us to repeatedly invoke the hook on every instruction and only stop if the function
-- which is currently getting executed is our invoker.
-- This will NOT work properly if for whatever reason the sandbox got access to the sandbox.protect
-- as the function sets a new hook and never sets it back to the last one.
sethook( function()
local fn = debug.getinfo(2 , 'f').func;
if( fn ~= queryInvoker and fn ~= cleanup and not (fn == table.pack and debug.getinfo(3 , 'f').func == queryInvoker) ) then
error('Quota exceeded: ' .. tostring(quota))
else
cleanup();
end
end, "", 1)
end
error('Quota exceeded: ' .. tostring(quota));
end
sethook(timeout, "", quota)
end

string.rep = nil -- luacheck: no global

local t = table.pack(pcall(f, ...))

cleanup()
local t = queryInvoker(...);

if not t[1] then error(t[2]) end

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