cavac has asked for the wisdom of the Perl Monks concerning the following question:

Hi!

I need a little help for my Maplat webserver project: To automate some processes i like to give the user the opportunity to write simple embedded script code. This scripts should be able to do math, string matching and change some given data structures - but nothing more. No file access, no access to the host script (written in perl).

This interpreter would be run within a perl script, get the data structures defined by that script and after the interpreter finished (or timed out) the results would be used in the perl script.

Here's a (rather stupid, i admit) example pseudo code how it could be used in a webmail system:
// Forward mail to private account on weekend
if weekday > 5 then
  email.reciever = "private@example.com"
  exit;
end

if email.subject has "TEST" then
  email.mailbox = "testmails"
else if email.sender == "boss@example.com"
  email.mailbox = "bigboss"
else
  email.mailbox = "trash"
end

[download]


I looked into Lua::API, but i'm not sure how to safely sandbox that. I read some Lua documentation, but i'm none the wiser...

Any ideas how to do that?

Rene
UPDATE
Managed to translate http://lua-users.org/wiki/SimpleLuaApiExample into a simple Lua::API script.

test.lua:
x = 0
for i = 1, #foo do
    x = x + foo[i]
end
return x

[download]

test.pl:
use strict;
use warnings;

use Lua::API;

my $L = Lua::API::State->new;

my $status = $L->loadfile("test.lua");
if($status) {
    die "Failed to load file: " . $L->tostring(-1);
}

$L->newtable;
for(my $i = 1; $i <= 5; $i++) {
    $L->pushnumber($i);
    $L->pushnumber($i*2);
    $L->rawset(-3);
}
$L->setglobal("foo");

my $result = $L->pcall(0, Lua::API::MULTRET, 0);
if($result) {
    die "Failed to execute file: " . $L->tostring(-1);
}

my $sum = $L->tonumber(-1);

print "Script returned $sum\n";

$L->pop(1);
$L->close;

[download]
This still needs a lot of work though, but i see a (very dim) light at the end of the (very long) tunnel.
Don't use '#ff0000':
use Acme::AutoColor; my $redcolor = RED();
All colors subject to change without notice.

Replies are listed 'Best First'.
Re: Embedded scripting sandbox? Lua?
by afoken (Chancellor) on Oct 03, 2011 at 18:52 UTC

    Do you know Safe?

    Alexander

    --
    Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
[reply]
      Frankly, i do not trust the concept. Creating a sandbox within the current interpreter seems kind of risky to me.

      But i'll take it into consideration.
      Don't use '#ff0000':
      use Acme::AutoColor; my $redcolor = RED();
      All colors subject to change without notice.
[reply]
Re: Embedded scripting sandbox? Lua?
by perlfan (Parson) on Oct 03, 2011 at 20:04 UTC
    Why not use Perl? Check out the Inline::Foo module example; it'll let you define your own Perl based domain specific "language".
[reply]
      Thanks, but i'm not trying to inlining code, i want to fetch it from a database, execute it in a sandbox and save the results.
      Don't use '#ff0000':
      use Acme::AutoColor; my $redcolor = RED();
      All colors subject to change without notice.
[reply]
        You mention Lua, so I think of Inline::Lua. You can also inline inside of an eval. You're creating a dependency on an whole language ecosystem (as lightweight as it is) just to provide scripting inside of a ... scripting language? Your call. Good luck.
[reply]
[d/l]
Re: Embedded scripting sandbox? Lua?
by Anonymous Monk on Oct 04, 2011 at 06:43 UTC
[reply]
      I would like to use Lua::API. Got any *documented* examples?

      The POD for Lua::API is quite long but doesn't say anything more than "this is more or less similar to the C API". I can work with that but i was really hoping for a more usefull, meaning something i can use without too much trial and error.

      BTW, forgot to mention: I already did a project where i interfaced to LUA from within C.
      Don't use '#ff0000':
      use Acme::AutoColor; my $redcolor = RED();
      All colors subject to change without notice.
[reply]
[reply]

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