108 lines
4.6 KiB
Plaintext
108 lines
4.6 KiB
Plaintext
[[modules-scripting-security]]
|
|
=== Scripting and security
|
|
|
|
While Elasticsearch contributors make every effort to prevent scripts from
|
|
running amok, security is something best done in
|
|
https://en.wikipedia.org/wiki/Defense_in_depth_(computing)[layers] because
|
|
all software has bugs and it is important to minimize the risk of failure in
|
|
any security layer. Find below rules of thumb for how to keep Elasticsearch
|
|
from being a vulnerability.
|
|
|
|
[float]
|
|
=== Do not run as root
|
|
First and foremost, never run Elasticsearch as the `root` user as this would
|
|
allow any successful effort to circumvent the other security layers to do
|
|
*anything* on your server. Elasticsearch will refuse to start if it detects
|
|
that it is running as `root` but this is so important that it is worth double
|
|
and triple checking.
|
|
|
|
[float]
|
|
=== Do not expose Elasticsearch directly to users
|
|
Do not expose Elasticsearch directly to users, instead have an application
|
|
make requests on behalf of users. If this is not possible, have an application
|
|
to sanitize requests from users. If *that* is not possible then have some
|
|
mechanism to track which users did what. Understand that it is quite possible
|
|
to write a <<search, `_search`>> that overwhelms Elasticsearch and brings down
|
|
the cluster. All such searches should be considered bugs and the Elasticsearch
|
|
contributors make an effort to prevent this but they are still possible.
|
|
|
|
[float]
|
|
=== Do not expose Elasticsearch directly to the Internet
|
|
Do not expose Elasticsearch to the Internet, instead have an application
|
|
make requests on behalf of the Internet. Do not entertain the thought of having
|
|
an application "sanitize" requests to Elasticsearch. Understand that it is
|
|
possible for a sufficiently determined malicious user to write searches that
|
|
overwhelm the Elasticsearch cluster and bring it down. For example:
|
|
|
|
Good:
|
|
|
|
* Users type text into a search box and the text is sent directly to a
|
|
<<query-dsl-match-query>>, <<query-dsl-match-query-phrase>>,
|
|
<<query-dsl-simple-query-string-query>>, or any of the <<search-suggesters>>.
|
|
* Running a script with any of the above queries that was written as part of
|
|
the application development process.
|
|
* Running a script with `params` provided by users.
|
|
* User actions makes documents with a fixed structure.
|
|
|
|
Bad:
|
|
|
|
* Users can write arbitrary scripts, queries, `_search` requests.
|
|
* User actions make documents with structure defined by users.
|
|
|
|
[float]
|
|
[[modules-scripting-other-layers]]
|
|
=== Other security layers
|
|
In addition to user privileges and script sandboxing Elasticsearch uses the
|
|
http://www.oracle.com/technetwork/java/seccodeguide-139067.html[Java Security Manager]
|
|
and native security tools as additional layers of security.
|
|
|
|
As part of its startup sequence Elasticsearch enables the Java Security Manager
|
|
which limits the actions that can be taken by portions of the code. Painless
|
|
uses this to limit the actions that generated Painless scripts can take,
|
|
preventing them from being able to do things like write files and listen to
|
|
sockets.
|
|
|
|
Elasticsearch uses
|
|
https://en.wikipedia.org/wiki/Seccomp[seccomp] in Linux,
|
|
https://www.chromium.org/developers/design-documents/sandbox/osx-sandboxing-design[Seatbelt]
|
|
in macOS, and
|
|
https://msdn.microsoft.com/en-us/library/windows/desktop/ms684147[ActiveProcessLimit]
|
|
on Windows to prevent Elasticsearch from forking or executing other processes.
|
|
|
|
Below this we describe the security settings for scripts and how you can
|
|
change from the defaults described above. You should be very, very careful
|
|
when allowing more than the defaults. Any extra permissions weakens the total
|
|
security of the Elasticsearch deployment.
|
|
|
|
[[allowed-script-types-setting]]
|
|
[float]
|
|
=== Allowed script types setting
|
|
|
|
By default all script types are allowed to be executed. This can be modified using the
|
|
setting `script.allowed_types`. Only the types specified as part of the setting will be
|
|
allowed to be executed. To specify no types are allowed, set `script.allowed_types` to
|
|
be `none`.
|
|
|
|
[source,yaml]
|
|
----
|
|
script.allowed_types: inline <1>
|
|
----
|
|
<1> This will allow only inline scripts to be executed but not stored scripts
|
|
(or any other types).
|
|
|
|
[[allowed-script-contexts-setting]]
|
|
[float]
|
|
=== Allowed script contexts setting
|
|
|
|
By default all script contexts are allowed to be executed. This can be modified using the
|
|
setting `script.allowed_contexts`. Only the contexts specified as part of the setting will
|
|
be allowed to be executed. To specify no contexts are allowed, set `script.allowed_contexts`
|
|
to be `none`.
|
|
|
|
[source,yaml]
|
|
----
|
|
script.allowed_contexts: search, update <1>
|
|
----
|
|
<1> This will allow only search and update scripts to be executed but not
|
|
aggs or plugin scripts (or any other contexts).
|