execute lua string as lua code

Question

I want to share lua modules with coworkers. In order to get the latest version of shared modules I want to store and fetch them with a web server.

My questions is:

Is it possible to load lua code directly from http request or string?

I want to achieve something like that :

module = [[
    local sharedModule = {}
    function sharedModule.greet(name) print("hello " .. name) end  
    return sharedModule
]]
greeter = require (module)
greeter.greet("john")

Maybe this is not the right thing to do. Is there a better approach than this one?

Answer 1

There's a whole section in Programming in Lua devoted to that. Your needs will be directly fulfilled with loadstring.

I would carefully verify the code you're actually executing, though. At the very least, version it (running a wrong version would most probably end up in all sorts of problems, if the code being run depends on the environment being in a certain state). Optimally checksum and sign the code, and verify the signature before doing anything. If your environment isn't protected, this is essentially a huge backdoor opening.

You could also use rings library to isolate the code you're running within the Lua environment itself. It might not be airtight security-wise, but should at least prevent the received code from crashing your application if/when it goes awry.