Appendix 4. Securing Indices & Aliases

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. Shield treats 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 by Shield, 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:

current_year_read:
  indices:
    '2015': read

The user attempts to retrieve a document from current_year:

curl -XGET 'localhost:9200/current_year/logs/1'

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

current_year_read:
  indices:
    'current_year': read

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

curl -XPUT localhost:9200/2015 -d '{
    "aliases" : {
        "current_year" : {}
    }
}'

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

curl -XPOST 'http://localhost:9200/_aliases' -d '
{
    "actions" : [
        { "add" : { "index" : "2015", "alias" : "current_year" } }
    ]
}'

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

admin:
  indices:
    '20*,current_year': create_index,manage_aliases

Note also that the manage privilege includes both create_index and manage_aliases in addition to all of the other management related privileges:

admin:
  indices:
    '20*,current_year': manage

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

curl -XPOST 'http://localhost:9200/_aliases' -d '
{
    "actions" : [
        { "delete" : { "index" : "2015", "alias" : "current_year" } }
    ]
}'

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. Filtered aliases allow to mimic document level security, but have limitations. Please read the limitations section to know more.