Site plugins used to be used for things like kibana and marvel, but
there is no longer a need since kibana (and marvel as a kibana plugin)
uses node.js. This change removes site plugins, as well as the flag for
jvm plugins. Now all plugins are jvm plugins.
This fixes the `lenient` parameter to be `missingClasses`. I will remove this boolean and we can handle them via the normal whitelist.
It also adds a check for sheisty classes (jar hell with the jdk).
This is inspired by the lucene "sheisty" classes check, but it has false positives. This check is more evil, it validates every class file against the extension classloader as a resource, to see if it exists there. If so: jar hell.
This jar hell is a problem for several reasons:
1. causes insanely-hard-to-debug problems (like bugs in forbidden-apis)
2. hides problems (like internal api access)
3. the code you think is executing, is not really executing
4. security permissions are not what you think they are
5. brings in unnecessary dependencies
6. its jar hell
The more difficult problems are stuff like jython, where these classes are simply 'uberjared' directly in, so you cant just fix them by removing a bogus dependency. And there is a legit reason for them to do that, they want to support java 1.4.
Since 2.2 we run all scripts with minimal privileges, similar to applets in your browser.
The problem is, they have unrestricted access to other things they can muck with (ES, JDK, whatever).
So they can still easily do tons of bad things
This PR restricts what classes scripts can load via the classloader mechanism, to make life more difficult.
The "standard" list was populated from the old list used for the groovy sandbox: though
a few more were needed for tests to pass (java.lang.String, java.util.Iterator, nothing scary there).
Additionally, each scripting engine typically needs permissions to some runtime stuff.
That is the downside of this "good old classloader" approach, but I like the transparency and simplicity,
and I don't want to waste my time with any feature provided by the engine itself for this, I don't trust them.
This is not perfect and the engines are not perfect but you gotta start somewhere. For expert users that
need to tweak the permissions, we already support that via the standard java security configuration files, the
specification is simple, supports wildcards, etc (though we do not use them ourselves).
Ryan Ernst
Nik Everett
Robert Muir
Adrien Grand
Robert Muir
Jack Conradson