Embedded scripting sandbox? Lua?

[cavac]

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 = "[e-mail]"
  exit;
end

if email.subject has "TEST" then
  email.mailbox = "testmails"
else if email.sender == "[e-mail]"
  email.mailbox = "bigboss"
else
  email.mailbox = "trash"
end

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

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;

This still needs a lot of work though, but i see a (very dim) light at the end of the (very long) tunnel.

[afoken]

Do you know Safe?

Alexander

[cavac]

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.

[perlfan]

Why not use Perl? Check out the Inline::Foo module example; it'll let you define your own Perl based domain specific "language".

[cavac]

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.

[perlfan]

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.

[Anonymous Monk]

Inline::Lua? Lua::API?

[cavac]

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.

[Anonymous Monk]

Got any *documented* examples?

I feel http://cpansearch.perl.org/src/DJERIUS/Lua-API-0.04/examples/lua.pl is sufficiently documentary, esp when combined with

• http://www.lua.org/source/5.1/lua.c.html
• http://www.lua.org/source/5.1/lstate.h.html#lua_State
• http://www.lua.org/source/5.1/lua.h.html#lua_Debug
• http://www.lua.org/manual/5.1/manual.html#6
• http://www.lua.org/manual/5.1/manual.html#3
• Lua::API
• Embedding Lua in C: Using Lua from inside C
• How to embed Lua 5.1 in C++ | c/c++ programming by examples
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