148 lines
4.8 KiB
Plaintext
148 lines
4.8 KiB
Plaintext
[[modules-scripting-security]]
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=== Scripting and the Java Security Manager
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Elasticsearch runs with the https://docs.oracle.com/javase/tutorial/essential/environment/security.html[Java Security Manager]
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enabled by default. The security policy in Elasticsearch locks down the
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permissions granted to each class to the bare minimum required to operate.
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The benefit of doing this is that it severely limits the attack vectors
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available to a hacker.
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Restricting permissions is particularly important with scripting languages
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like Groovy and Javascript which are designed to do anything that can be done
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in Java itself, including writing to the file system, opening sockets to
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remote servers, etc.
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[float]
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=== Script Classloader Whitelist
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Scripting languages are only allowed to load classes which appear in a
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hardcoded whitelist that can be found in
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https://github.com/elastic/elasticsearch/blob/{branch}/core/src/main/java/org/elasticsearch/script/ClassPermission.java[`org.elasticsearch.script.ClassPermission`].
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In a script, attempting to load a class that does not appear in the whitelist
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_may_ result in a `ClassNotFoundException`, for instance this script:
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[source,json]
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------------------------------
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GET _search
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{
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"script_fields": {
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"the_hour": {
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"script": "use(java.math.BigInteger); new BigInteger(1)"
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}
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}
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}
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------------------------------
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will return the following exception:
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[source,json]
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------------------------------
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{
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"reason": {
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"type": "script_exception",
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"reason": "failed to run inline script [use(java.math.BigInteger); new BigInteger(1)] using lang [groovy]",
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"caused_by": {
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"type": "no_class_def_found_error",
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"reason": "java/math/BigInteger",
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"caused_by": {
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"type": "class_not_found_exception",
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"reason": "java.math.BigInteger"
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}
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}
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}
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}
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------------------------------
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However, classloader issues may also result in more difficult to interpret
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exceptions. For instance, this script:
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[source,groovy]
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------------------------------
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use(groovy.time.TimeCategory); new Date(123456789).format('HH')
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------------------------------
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Returns the following exception:
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[source,json]
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------------------------------
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{
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"reason": {
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"type": "script_exception",
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"reason": "failed to run inline script [use(groovy.time.TimeCategory); new Date(123456789).format('HH')] using lang [groovy]",
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"caused_by": {
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"type": "missing_property_exception",
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"reason": "No such property: groovy for class: 8d45f5c1a07a1ab5dda953234863e283a7586240"
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}
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}
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}
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------------------------------
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[float]
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== Dealing with Java Security Manager issues
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If you encounter issues with the Java Security Manager, you have two options
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for resolving these issues:
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[float]
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=== Fix the security problem
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The safest and most secure long term solution is to change the code causing
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the security issue. We recognise that this may take time to do correctly and
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so we provide the following two alternatives.
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[float]
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=== Customising the classloader whitelist
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The classloader whitelist can be customised by tweaking the local Java
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Security Policy either:
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* system wide: `$JAVA_HOME/lib/security/java.policy`,
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* for just the `elasticsearch` user: `/home/elasticsearch/.java.policy`, or
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* from a file specified in the `JAVA_OPTS` environment variable with `-Djava.security.policy=someURL`:
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+
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[source,js]
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---------------------------------
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export JAVA_OPTS="${JAVA_OPTS} -Djava.security.policy=file:///path/to/my.policy`
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./bin/elasticsearch
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---------------------------------
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Permissions may be granted at the class, package, or global level. For instance:
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[source,js]
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----------------------------------
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grant {
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permission org.elasticsearch.script.ClassPermission "java.util.Base64"; // allow class
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permission org.elasticsearch.script.ClassPermission "java.util.*"; // allow package
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permission org.elasticsearch.script.ClassPermission "*"; // allow all (disables filtering basically)
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};
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----------------------------------
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Here is an example of how to enable the `groovy.time.TimeCategory` class:
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[source,js]
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----------------------------------
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grant {
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permission org.elasticsearch.script.ClassPermission "java.lang.Class";
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permission org.elasticsearch.script.ClassPermission "groovy.time.TimeCategory";
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};
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----------------------------------
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[TIP]
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======================================
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Before adding classes to the whitelist, consider the security impact that it
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will have on Elasticsearch. Do you really need an extra class or can your code
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be rewritten in a more secure way?
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It is quite possible that we have not whitelisted a generically useful and
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safe class. If you have a class that you think should be whitelisted by
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default, please open an issue on GitHub and we will consider the impact of
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doing so.
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======================================
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See http://docs.oracle.com/javase/7/docs/technotes/guides/security/PolicyFiles.html for more information.
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