Scripting and the Java Security Manager

Elasticsearch runs with the Java Security Manager enabled by default. The security policy in Elasticsearch locks down the permissions granted to each class to the bare minimum required to operate. The benefit of doing this is that it severely limits the attack vectors available to a hacker.

Restricting permissions is particularly important with scripting languages like Groovy and Javascript which are designed to do anything that can be done in Java itself, including writing to the file system, opening sockets to remote servers, etc.

Scripting languages are only allowed to load classes which appear in a hardcoded whitelist that can be found in org.elasticsearch.script.ClassPermission.

In a script, attempting to load a class that does not appear in the whitelist may result in a ClassNotFoundException, for instance this script:

GET _search
{
  "script_fields": {
    "the_hour": {
      "script": "use(java.math.BigInteger); new BigInteger(1)"
    }
  }
}

will return the following exception:

{
  "reason": {
    "type": "script_exception",
    "reason": "failed to run inline script [use(java.math.BigInteger); new BigInteger(1)] using lang [groovy]",
    "caused_by": {
      "type": "no_class_def_found_error",
      "reason": "java/math/BigInteger",
      "caused_by": {
        "type": "class_not_found_exception",
        "reason": "java.math.BigInteger"
      }
    }
  }
}

However, classloader issues may also result in more difficult to interpret exceptions. For instance, this script:

use(groovy.time.TimeCategory); new Date(123456789).format('HH')

Returns the following exception:

{
  "reason": {
    "type": "script_exception",
    "reason": "failed to run inline script [use(groovy.time.TimeCategory); new Date(123456789).format('HH')] using lang [groovy]",
    "caused_by": {
      "type": "missing_property_exception",
      "reason": "No such property: groovy for class: 8d45f5c1a07a1ab5dda953234863e283a7586240"
    }
  }
}

If you encounter issues with the Java Security Manager, you have three options for resolving these issues:

The safest and most secure long term solution is to change the code causing the security issue. We recognise that this may take time to do correctly and so we provide the following two alternatives.

You can disable the Java Security Manager entirely with the security.manager.enabled command line flag:

./bin/elasticsearch --security.manager.enabled false

The classloader whitelist can be customised by tweaking the local Java Security Policy either:

Permissions may be granted at the class, package, or global level. For instance:

grant {
    permission org.elasticsearch.script.ClassPermission "java.util.Base64"; // allow class
    permission org.elasticsearch.script.ClassPermission "java.util.*"; // allow package
    permission org.elasticsearch.script.ClassPermission "*"; // allow all (disables filtering basically)
};

Here is an example of how to enable the groovy.time.TimeCategory class:

grant {
    permission org.elasticsearch.script.ClassPermission "java.lang.Class";
    permission org.elasticsearch.script.ClassPermission "groovy.time.TimeCategory";
};

See http://docs.oracle.com/javase/7/docs/technotes/guides/security/PolicyFiles.html for more information.