[role="xpack"]
[[securing-aliases]]
=== Granting privileges for data streams and index aliases

{es} {security-features} allow you to secure operations executed against
<<data-streams,data streams>> and <<indices-aliases,index aliases>>.

[[data-stream-privileges]]
==== Data stream privileges

A data stream consists of one or more backing indices, which store the stream's
data. Most requests sent to a data stream are routed to one or more of these
backing indices.

Similar to an index, you can use <<privileges-list-indices,indices privileges>>
to control access to a data stream. Any role or user granted privileges to a
data stream are automatically granted the same privileges to its backing
indices.

For example, `my-data-stream` consists of two backing indices:
`.ds-my-data-stream-000001` and `.ds-my-data-stream-000002`.

A user is granted the `read` privilege to `my-data-stream`.

[source,js]
--------------------------------------------------
{
  "names" : [ "my-data-stream" ],
  "privileges" : [ "read" ]
}
--------------------------------------------------
// NOTCONSOLE

Because the user is automatically granted the same privileges to the stream's
backing indices, the user can retrieve a document directly from
`.ds-my-data-stream-000002`:

////
[source,console]
----
PUT /_index_template/my-data-stream-template
{
  "index_patterns": [ "my-data-stream*" ],
  "data_stream": { }
}

PUT /_data_stream/my-data-stream

POST /my-data-stream/_rollover/

PUT /my-data-stream/_create/2?refresh=wait_for
{
  "@timestamp": "2020-12-07T11:06:07.000Z"
}
----
////

[source,console]
----
GET /.ds-my-data-stream-000002/_doc/2
----
// TEST[continued]

Later `my-data-stream` <<manually-roll-over-a-data-stream,rolls over>>. This
creates a new backing index: `.ds-my-data-stream-000003`. Because the user still
has the `read` privilege for `my-data-stream`, the user can retrieve
documents directly from `.ds-my-data-stream-000003`:

////
[source,console]
----
POST /my-data-stream/_rollover/

PUT /my-data-stream/_create/2?refresh=wait_for
{
  "@timestamp": "2020-12-07T11:06:07.000Z"
}
----
// TEST[continued]
////

[source,console]
----
GET /.ds-my-data-stream-000003/_doc/2
----
// TEST[continued]

////
[source,console]
----
DELETE /_data_stream/*

DELETE /_index_template/*
----
// TEST[continued]
////

[[index-alias-privileges]]
==== Index alias privileges

An index alias points to one or more indices,
holds metadata and potentially a filter. The {es} {security-features} treat
aliases and indices
the same. Privileges for indices actions are granted on specific indices or
aliases. In order for an indices action to be authorized, the user that executes
it needs to have permissions for that action on all the specific indices or
aliases that the request relates to.

Let's look at an example. Assuming we have an index called `2015`, an alias that
points to it called `current_year`, and a user with the following role:

[source,js]
--------------------------------------------------
{
  "names" : [ "2015" ],
  "privileges" : [ "read" ]
}
--------------------------------------------------
// NOTCONSOLE

The user attempts to retrieve a document from `current_year`:

[source,console]
-------------------------------------------------------------------------------
GET /current_year/event/1
-------------------------------------------------------------------------------
// TEST[s/^/PUT 2015\n{"aliases": {"current_year": {}}}\nPUT 2015\/event\/1\n{}\n/]

The above request gets rejected, although the user has `read` privilege on the
concrete index that the `current_year` alias points to. The correct permission
would be as follows:

[source,js]
--------------------------------------------------
{
  "names" : [ "current_year" ],
  "privileges" : [ "read" ]
}
--------------------------------------------------
// NOTCONSOLE

[discrete]
==== Managing aliases

Unlike creating indices, which requires the `create_index` privilege, adding,
removing and retrieving aliases requires the `manage` permission. Aliases can be
added to an index directly as part of the index creation:

[source,console]
-------------------------------------------------------------------------------
PUT /2015
{
  "aliases": {
    "current_year": {}
  }
}
-------------------------------------------------------------------------------

or via the dedicated aliases api if the index already exists:

[source,console]
-------------------------------------------------------------------------------
POST /_aliases
{
  "actions" : [
    { "add" : { "index" : "2015", "alias" : "current_year" } }
  ]
}
-------------------------------------------------------------------------------
// TEST[s/^/PUT 2015\n/]

The above requests both require the `manage` privilege on the alias name as well
as the targeted index, as follows:

[source,js]
--------------------------------------------------
{
  "names" : [ "20*", "current_year" ],
  "privileges" : [ "manage" ]
}
--------------------------------------------------
// NOTCONSOLE

The index aliases api also allows also to delete aliases from existing indices.
The privileges required for such a request are the same as above. Both index and
alias need the `manage` permission.


[discrete]
==== Filtered aliases

Aliases can hold a filter, which allows to select a subset of documents that can
be accessed out of all the documents that the physical index contains. These
filters are not always applied and should not be used in place of
<<document-level-security, document level security>>.
