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copied!<p>Build your sandbox (or multiple sandboxes if they each have different requirements) and move the untrusted code into the sandbox one piece at a time. In my quick cli tests, both 5.1 and 5.2 will run functions that were defined outside of the sandbox without modification. To use Doug's example, assume <code>display</code> is part of your pre-existing code that uses <code>print</code>:</p> <pre class="lang-lua prettyprint-override"><code>-- 5.1 local function display(...) print(...) end local script = loadstring "display(math.log(2, 3))" local env = {display = display, math = math, string = string} setfenv(script, env) print(pcall(script)) -- 5.2 local function display(...) print(...) end local script = loadstring "display(math.log(2, 3))" local e=_ENV _ENV={display = display, math = math, string = string} e.print(e.pcall(script)) _ENV=e </code></pre> <p>Note that in both of the above examples, the <code>display</code> function is using <code>print</code> without modification to that code since you were not in the sandbox when this function was created.</p> <p>In the past, I've stored a local pointer to the un-sandboxed environment, but I can't reproduce the situation where that's needed in my quick cli tests. If you can come up with an example, I can probably come up with a workaround that doesn't require the <code>e</code> variable. Here's an example of that code using 5.2:</p> <pre><code>local e=_ENV for k,v in e.pairs(value) do -- iterate end </code></pre> <p>another example, for my read only table code, I'm again using the <code>e</code>:</p> <pre><code>function ro_table (t) local t = t if t then return e.setmetatable({}, { __index=t, __newindex= function(_,_,_) e.error ("Attempt to modify read-only table") end, }) else return nil end end </code></pre>

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