I don't think you need to worry about "exit". If you run your server
with SecurityManager, then any 'eval'ed script calling "exit" will get a
SecurityException. Also any sensitive java method call from script (say
Runtime.loadLibrary or file system access) or sensitive java class
access (like accessing sun.misc.Unsafe for eg) will be security checked
as well.
See also:
https://wiki.openjdk.java.net/display/Nashorn/Nashorn+script+security+permissions
Resource contraints (too much memory) is never part of java security.
i.e., you can write a simple java (sandboxed) program that allocates
"too much" memory or creates too many threads and so on. Security checks
don't attempt to limit those anyway! So, script evaluation does not
create any additional issue that didn't exist for Java code!.
Implementing resource constraints is very hard.
You can use ClassFilter (
https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/ClassFilter.html
) to avoid access to java.lang.Thread class to avoid script creating
threads - but then script can call Executor framework to indirectly
create threads! You may have to prevent access to many java classes to
script! You can also create nashorn engine with --no-java option - which
will avoid access to *any* java class /package from script! You've to
use NashornScriptEngineFactory (
https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/NashornScriptEngineFactory.html
) directly to pass options or ClassFilter to engine created.
Last but not least: If you run your server *without* security manager
and try to "manually" contain the script by removing "exit" etc, I'm
afraid that won't work. Because with java calls script can access many
things! It is difficult - if not impossible - to find & cover all cases.
-Sundar
On 01/05/17, 6:25 PM, Jim Laskey (Oracle) wrote:
From: Eliezer
Julian<eliezer.jul...@sapiens.com<mailto:eliezer.jul...@sapiens.com>>
Subject: Running JS code on a server
Date: May 1, 2017 at 6:28:05 AM ADT
To:
"nashorn-dev@openjdk.java.net<mailto:nashorn-dev@openjdk.java.net>"<nashorn-dev@openjdk.java.net<mailto:nashorn-dev@openjdk.java.net>>
Cc: Elior Apelbaum<elior.apelb...@sapiens.com<mailto:elior.apelb...@sapiens.com>>, Moshe
Robinov<moshe.robi...@sapiens.com<mailto:moshe.robi...@sapiens.com>>, Chen
Malka<chen.ma...@sapiens.com<mailto:chen.ma...@sapiens.com>>
Hi,
I am developing a server side application and would like to add a feature that
allows a user to submit JS code to be executed via Nashorn. My concern is that
a user may submit malicious code that may compromise the server. I have already
limited the script’s access to the bare minimum of Java classes, and have
implemented a mechanize to kill the script if execution time runs over a
certain limit. I have also manually removed many of the special methods such as
print, echo, exit and quit from the Bindings object. However, this is extremely
limited in scope compared to the damage a willfully malicious user may be able
to effect via this feature (such as allocating too much memory, try to access
the file system via the script, etc.). I was wondering if the Nashorn
development team had any recommendations as far as security is concerned, and
whether there are any plans to add additional security features in the future.
Thanks,
Eli Julian
Software Developer
Decision Division
Email: eliezer.jul...@sapiens.com<mailto:eliezer.jul...@sapiens.com>
Office: +972-3-7902155
Mobile: +972-50-3697238
Skype handle: eli_julian
Visit us at: www.sapiens.com<http://www.sapiens.com/>
