Elasticsearch allows to execute operations against index aliases, which are effectively virtual indices. An alias points to one or more indices, holds metadata and potentially a filter. The Elasticsearch 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:

{
  "names" : [ "2015" ],
  "privileges" : [ "read" ]
}

The user attempts to retrieve a document from current_year:

GET /current_year/event/1

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:

{
  "names" : [ "current_year" ],
  "privileges" : [ "read" ]
}

Managing aliasesedit

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:

PUT /2015
{
    "aliases" : {
        "current_year" : {}
    }
}

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

POST /_aliases
{
    "actions" : [
        { "add" : { "index" : "2015", "alias" : "current_year" } }
    ]
}

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

{
  "names" : [ "20*", "current_year" ],
  "privileges" : [ "manage" ]
}

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.

Filtered aliasesedit

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.