Overview: The ReadonlyREST Suite

ReadonlyREST is a light weight Elasticsearch plugin that adds encryption, authentication, authorization and access control capabilities to Elasticsearch embedded REST API. The core of this plugin is an ACL engine that checks each incoming request through a sequence of rules a bit like a firewall. There are a dozen rules that can be grouped in sequences of blocks and form a powerful representation of a logic chain.

The Elasticsearch plugin known as ReadonlyREST Free is released under the GPLv3 license, or alternatively, a commercial license (see ReadonlyREST Embedded) and lays the technological foundations for the companion Kibana plugin which is released in two versions: ReadonlyREST PRO and ReadonlyREST Enterprise.

Unlike the Elasticsearch plugin, the Kibana plugins are commercial only. But rely on the Elasticsearch plugin in order to work.

For a description of the Kibana plugins, skip to the dedicated documentation page instead.

ReadonlyREST Free plugin for Elasticsearch

In this document we are going to describe how to operate the Elasticsearch plugin in all its features. Once installed, this plugin will greatly extend the Elasticsearch HTTP API (port 9200), adding numerous extra capabilities:

• Encryption: transform the Elasticsearch API from HTTP to HTTPS

• Authentication: require credentials

• Authorization: declare groups of users, permissions and partial access to indices.

• Access control: complex logic can be modeled using an ACL (access control list) written in YAML.

• Audit logs: a trace of the access requests can be logged to file or index (or both).

Flow of a Search Request

The following diagram models an instance of Elasticsearch with the ReadonlyREST plugin installed, and configured with SSL encryption and an ACL with at least one "allow" type ACL block.

1. The User Agent (i.e. cURL, Kibana) sends a search request to Elasticsearch using the port 9200 and the HTTPS URL schema.

2. The HTTPS filter in ReadonlyREST plugin unwraps the SSL layer and hands over the request to Elasticsearch HTTP stack

3. The HTTP stack in Elasticsearch parses the HTTP request

4. The HTTP handler in Elasticsearch extracts the indices, action, request type and creates a SearchRequest (internal Elasticsearch format).

5. The SearchRequest goes through the ACL (access control list), external systems like LDAP can be asynchronously queried, and an exit result is eventually produced.

6. The exit result is used by the audit log serializer, to write a record to index and/or Elasticsearch log file

7. If no ACL block was matched, or if a type: forbid block was matched, ReadonlyREST does not forward the search request to the search engine, and creates an "unauthorized" HTTP response.

8. In case the ACL matched an type: allow block, the request is forwarded to the search engine

9. The Elasticsearch code creates a search response containing the results of the query

   10.The search response is converted to an HTTP response by the Elasticsearch code

10. The HTTP response flows back to ReadonlyREST's HTTPS filter and to the User agent

Installing the plugin

To install ReadonlyREST plugin for Elasticsearch:

1. Obtain the build

From the official download page. Select your Elasticsearch version and send yourself a link to the compatible ReadonlyREST zip file.

2. Install the build

bin/elasticsearch-plugin install file:///tmp/readonlyrest-X.Y.Z_esW.Q.U.zip

Notice how we need to type in the format file:// + absolute path (yes, with three slashes).

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@     WARNING: plugin requires additional permissions     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

When prompted about additional permissions, answer y.

3.Create settings file

Create and edit the readonlyrest.yml settings file in the same directory where elasticsearch.yml is found:

 vim $ES_PATH_CONF/conf/readonlyrest.yml

Now write some basic settings, just to get started. In this example we are going to tell ReadonlyREST to require HTTP Basic Authentication for all the HTTP requests, and return 401 Unauthorized otherwise.

readonlyrest:
    access_control_rules:
​
    - name: "Require HTTP Basic Auth"
      type: allow
      auth_key: user:password

4. Disable X-Pack security module

(applies to ES 6.4.0 or greater)

ReadonlyREST and X-Pack security module can't run together, so the latter needs to be disabled.

Edit elasticsearch.yml and append xpack.security.enabled: false.

 vim $ES_PATH_CONF/conf/elasticsearch.yml

5. Start Elasticsearch

bin/elasticsearch

or:

service start elasticsearch

Depending on your environment.

Now you should be able to see the logs and ReadonlyREST related lines like the one below:

[2018-09-18T13:56:25,275][INFO ][o.e.p.PluginsService     ] [c3RKGFJ] loaded plugin [readonlyrest]

6. Test everything is working

The following command should succeed, and the response should show a status code 200.

curl -vvv -u user:password "http://localhost:9200/_cat/indices"

The following command should not succeed, and the response should show a status code 401

curl -vvv "http://localhost:9200/_cat/indices"

Upgrading the plugin

To upgrade ReadonlyREST for Elasticsearch:

1. Stop Elasticsearch.

Either kill the process manually, or use:

service stop elasticsearch

depending on your environment.

2. Uninstall ReadonlyREST

bin/elasticsearch-plugin remove readonlyrest

3. Install the new version of ReadonlyREST into Elasticsearch.

bin/elasticsearch-plugin install file://<download_dir>/readonlyrest-<ROR_VERSION>_es<ES_VERSION>.zip

e.g.

bin/elasticsearch-plugin install file:///tmp/readonlyrest-1.16.15_es6.1.1.zip

4. Restart Elasticsearch.

bin/elasticsearch

or:

service start elasticsearch

Depending on your environment.

Now you should be able to see the logs and ReadonlyREST related lines like the one below:

[2018-09-18T13:56:25,275][INFO ][o.e.p.PluginsService     ] [c3RKGFJ] loaded plugin [readonlyrest]

Removing the plugin

1. Stop Elasticsearch.

Either kill the process manually, or use:

service stop elasticsearch

depending on your environment.

2. Uninstall ReadonlyREST from Elasticsearch:

bin/elasticsearch-plugin remove readonlyrest

3. Start Elasticsearch.

bin/elasticsearch

or:

service start elasticsearch

Depending on your environment.

Deploying ReadonlyREST in a stable production cluster

Unless some advanced features are being used (see below),this Elasticsearch plugin operates like a lightweight, stateless filter glued in front of Elasticsearch HTTP API. Therefore it's sufficient to install the plugin only in the nodes that expose the HTTP interface (port 9200).

Installing ReadonlyREST in a dedicated node has numerous advantages:

• No need to restart all nodes, only the one you have installed the plugin into.

• No need to restart all nodes for updating the security settings

• No need to restart all nodes when a security update is out

• Less complexity on the actual cluster nodes.

For example, if we want to move to HTTPS all the traffic coming from Logstash into a 9 nodes Elasticsearch cluster which has been running stable in production for a while, it's not necessary to install ReadonlyREST plugin in all the nodes.

Creating a dedicated, lightweight ES node where to install ReadonlyREST:

1. (Optional) disable the HTTP interface from all the existing nodes

2. Create a new, lightweight, dedicated node without shards, nor master eligibility.

3. Configure ReadonlyREST with SSL encryption in the new node

4. Configure Logstash to connect to the new node directly in HTTPS.

An exception

⚠️IMPORTANT By default when fields rule is used, it's required to install ReadonlyREST plugin in all the data nodes.

ACL basics

The core of this plugin is an ACL (access control list). A logic structure very similar to the one found in firewalls. The ACL is part of the plugin configuration, and it's written in YAML.

• The ACL is composed of an ordered sequence of named blocks

• Each block contains some rules, and a policy (forbid or allow)

• HTTP requests run through the blocks, starting from the first,

• The first block that satisfies all the rules decides if to forbid or allow the request (according to its policy).

• If none of the block match, the request is rejected

⚠️IMPORTANT: The ACL blocks are evaluated sequentially, therefore the ordering of the ACL blocks is crucial. The order of the rules inside an ACL block instead, is irrelevant.

readonlyrest:
    access_control_rules:
​
    - name: "Block 1 - only Logstash indices are accessible"
      type: allow # <-- default policy type is "allow", so this line could be omitted
      indices: ["logstash-*"] # <-- This is a rule
​
    - name: "Block 2 - Blocking everything from a network"
      type: forbid
      hosts: ["10.0.0.0/24"] # <-- this is a rule

An Example of Access Control List (ACL) made of 2 blocks.

The YAML snippet above, like all of this plugin's settings should be saved inside the readonlyrest.yml file. Create this file on the same path where elasticsearch.yml is found.

TIP: If you are a subscriber of the PRO or Enterprise Kibana plugin, you can edit and refresh the settings through a GUI. For more on this, see the documentation for ReadonlyREST plugin for Kibana.

Encryption

An SSL encrypted connection is a prerequisite for secure exchange of credentials and data over the network. Letsencrypt certificates work just fine, once they are inside a JKS keystore. ReadonlyREST can be configured to encrypt network traffic on two independent levels:

External REST API

It wraps connection between client and exposed REST API in SSL context, hence making it encrypted and secure. ⚠️IMPORTANT: To enable SSL for REST API, open elasticsearch.yml and append this one line:

http.type: ssl_netty4

Now in readonlyrest.yml add the following settings:

readonlyrest:
    ssl:
      keystore_file: "keystore.jks"
      keystore_pass: readonlyrest
      key_pass: readonlyrest

The keystore should be stored in the same directory with elasticsearch.yml and readonlyrest.yml.

Internode communication - transport module

This option encrypts communication between nodes forming Elasticsearch cluster.

⚠️IMPORTANT: To enable SSL for internode communication open elasticsearch.yml and append this one line:

transport.type: ror_ssl_internode

In readonlyrest.yml following settings must be added (it's just example configuration presenting most important properties):

readonlyrest:
    ssl_internode:
      keystore_file: "keystore.jks"
      keystore_pass: readonlyrest
      key_pass: readonlyrest

Similar to ssl for HTTP, the keystore should be stored in the same directory with elasticsearch.yml and readonlyrest.yml. This config must be added to all nodes taking part in encrypted communication within cluster.

Certificate verification

By default certificate verification is disabled. It means that certificate is not validated in any way, so all certificates are accepted. It is useful on local/test environment, where security is not the most important concern. On production environment it is adviced to enable this option. It can be done by means of:

certificate_verification: true

under ssl_internode section. This option is applicable only for internode ssl.

Client authentication

By default the client authentication is disabled. When enabled, the server asks the client about its certificate, so ES is able to verify the client's identity. It can be enabled by means of:

client_authentication: true

under ssl section. This option is applicable only for REST API external ssl.

Both certificate_verification and client_authentication can be enabled with single property verification. Using this property is deprecated and allowed because of backward compatibility support. Specialized properties make configuration more readable and explicit.

Restrict SSL protocols and ciphers

Optionally, it's possible to specify a list allowed SSL protocols and SSL ciphers. Connections from clients that don't support the listed protocols or ciphers will be dropped.

readonlyrest:
    ssl:
      # put the keystore in the same dir with elasticsearch.yml
      keystore_file: "keystore.jks"
      keystore_pass: readonlyrest
      key_pass: readonlyrest
      allowed_protocols: [TLSv1.2]
      allowed_ciphers: [TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256]

ReadonlyREST will log a list of available ciphers and protocols supported by the current JVM at startup.

[2018-01-03T10:09:38,683][INFO ][t.b.r.e.SSLTransportNetty4] ROR SSL: Available ciphers: TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,TLS_RSA_WITH_AES_128_GCM_SHA256,TLS_RSA_WITH_AES_128_CBC_SHA
[2018-01-03T10:09:38,684][INFO ][t.b.r.e.SSLTransportNetty4] ROR SSL: Restricting to ciphers: TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
[2018-01-03T10:09:38,684][INFO ][t.b.r.e.SSLTransportNetty4] ROR SSL: Available SSL protocols: TLSv1,TLSv1.1,TLSv1.2
[2018-01-03T10:09:38,685][INFO ][t.b.r.e.SSLTransportNetty4] ROR SSL: Restricting to SSL protocols: TLSv1.2
[2018-0

Custom truststore

ReadonlyREST allows using custom truststore, replacing (provided by JRE) default one. Custom truststore can be set with:

truststore_file: "truststore.jks"
truststore_pass: truststorepass

under ssl or ssl_internode section. This option is applicable for both ssl modes - external ssl and internode ssl. The truststore should be stored in the same directory with elasticsearch.yml and readonlyrest.yml (like keystore). When not specifed, ReadonlyREST uses default truststore.

Blocks of rules

Every block must have at least the name field, and optionally a type field valued either "allow" or "forbid". If you omit the type, your block will be treated as type: allow by default.

Keep in mind that ReadonlyREST ACL is a white list, so by default all request are blocked, unless you specify a block of rules that allowes all or some requests.

• name will appear in logs, so keep it short and distinctive.

• type can be either allow or forbid. Can be omitted, default is allow.

    - name: "Block 1 - Allowing anything from localhost"
      type: allow
      # In real life now you should increase the specificity by adding rules here (otherwise this block will allow all requests!)

Example: the simplest example of an allow block.

⚠️IMPORTANT: if no blocks are configured, ReadonlyREST rejects all requests.

Rules

ReadonlyREST access control rules allow to take decisions on three levels:

• Network level

• HTTP level

• Elasticsearch level

Please refrain from using HTTP level rules to protect certain indices or limit what people can do to an index. The level of control at this level is really coarse, especially because Elasticsearch REST API does not always respect RESTful principles. This makes of HTTP a bad abstraction level to write ACLs in Elasticsearch all together.

The only clean and exhaustive way to implement access control is to reason about requests AFTER ElasticSearch has parsed them. Only then, the list of affected indices and the action will be known for sure. See Elasticsearch level rules.

Transport level rules

These are the most basic rules. It is possible to allow/forbid requests originating from a list of IP addresses, host names or IP networks (in slash notation).

hosts

hosts: ["10.0.0.0/24"] Match a request whose origin IP address (also called origin address, or OA in logs) matches one of the specified IP addresses or subnets.

hosts_local

hosts_local: ["127.0.0.1", "127.0.0.2"] Match a request whose destination IP address (called DA in logs) matches one of the specified IP addresses or subnets. This finds application when Elasticsearch HTTP API is bound to multiple IP addresses.

HTTP Level rules

accept_x-forwarded-for_header

accept_x-forwarded-for_header: false

⚠️DEPRECATED (use x_forwarded_for instead) A modifier for hosts rule: if the origin IP won't match, fallback to check the X-Forwarded-For header

x_forwarded_for

x_forwarded_for: ["192.168.1.0/24"]

Behaves exactly like hosts, but gets the source IP address (a.k.a. origin address, OA in logs) inside the X-Forwarded-For header only (useful replacement to hostsrule when requests come through a load balancer like AWS ELB)

Load balancers

This is a nice tip if your Elasticsearch is behind a load balancer. If you want to match all the requests that come through the load balancer, use x_forwarded_for: ["0.0.0.0/0"]. This will match the requests with a valid IP address as a value of the X-Forwarded-For header.

DNS lookup caching

It's worth to note that resolutions of DNS are going to be cached by JVM. By default successfully resolved IPs will be cached forever (until Elasticsearch is restarted) for security reasons. However, this may not always be the desired behaviour, and it can be changed by adding the following JVM options either in the jvm.options file or declaring the ES_JAVA_OPTS environment variable: sun.net.inetaddr.ttl=TTL_VALUE (or/and sun.net.inetaddr.negative.ttl=TTL_VALUE). More details about the problem can be found here.

methods

methods: [GET, DELETE]

Match requests with HTTP methods specified in the list. N.B. Elasticsearch HTTP stack does not make any difference between HEAD and GET, so all the HEAD request will appear as GET.

headers

headers: ["h1:x*y","~h2:*xy"]

Match if all the HTTP headers in the request match the defined patterns in headers rule. This is useful in conjunction with proxy_auth, to carry authorization information (i.e. headers: x-usr-group: admins).

The ~ sign is a pattern negation, so eg. ~h2:*xy means: match if h2 header's value does not match the pattern *xy, or h2 is not present at all.

headers_and

headers_and: ["hdr1:val_*xyz","~hdr2:xyz_*"]

Alias for headers rule

headers_or

headers_or: ["x-myheader:val*","~header2:*xy"]

Match if at least one the specified HTTP headers key:value pairs is matched.

uri_re

uri_re: ["^/secret-index/.*", "^/some-index/.*"]

☠️HACKY (try to use indices/actions rule instead)

Match if at least one specifed regular expression matches requested URI.

maxBodyLength

maxBodyLength: 0

Match requests having a request body length less or equal to an integer. Use 0 to match only requests without body.

NB: Elasticsearch HTTP API breaks the specifications, nad GET requests might have a body length greater than zero.

api_keys

api_keys: [123456, abcdefg]

A list of api keys expected in the header X-Api-Key

Elasticsearch level rules

indices

indices: ["sales", "logstash-*"]

Matches if the request involves a set of indices whose name is "sales", or starts with the string "logstash-", or a combination of both.

If a request involves a wildcard (i.e. "logstash-*", "*"), this is first expanded to the list of available indices, and then treated normally as follows:

• Requests that do not involve any indices (cluster admin, etc) result in a "match".

• Requests that involve only allowed indices result in a "match".

• Requests that involve a mix of allowed and prohibited indices, are rewritten to only involve allowed indices, and result in a "match".

• Requests that involve only prohibited indices result in a "no match". And the ACL evaluation moves on to the next block.

The rejection message and HTTP status code returned to the requester are chosen carefully with the main intent to make ES behave like the prohibited indices do not exist at all.

The rule has also an extended version:

indices:
  patterns: ["sales", "logstash-*"]`
  must_involve_indices: false

The definition above has the same meaning as the shortest version shown at the beginning of this section. By default the rule will be matched when a request doesn't involve indices (eg. /_cat/nodes request). But we can change the behaviour by configuring must_involve_indices: true - in this case the request above will be rejected by the rule.

In detail, with examples

In ReadonlyREST we roughly classify requests as:

• "read": the request will not change the data or the configuration of the cluster

• "write": when allowed, the request changes the internal state of the cluster or the data.

If a read request asks for a some indices they have permissions for and some indices that they do NOT have permission for, the request is rewritten to involve only the subset of indices they have permission for. This is behaviour is very useful in Kibana: different users can see the same dashboards with data from only their own indices.

When the subset of indices is empty, it means that user are not allowed to access requested indices. In multitenancy environment we should consider two options:

• requested indices don't exist

• requested indices exist but logged user is not authorized to access them

For both of these cases ROR is going to return HTTP 404 or HTTP 200 with an empty response. The same behaviour will be observed for ES with ROR disabled (for nonexistent index). If an index does exist, but a user is not authorized to access it, ROR is going to pretend that the index doesn't exist and a response will be the same like the index actually did not exist. See detailed example.

It's also worth mentioning, that when prompt_for_basic_auth is set to true (that is, the default value), ROR is going to return 401 instead of 404 HTTP status code. It is relevant for users who don't use ROR Kibana's plugin and who would like to take advantage of default Kibana's behaviour which shows the native browser basic auth dialog, when it receives HTTP 401 response.

If a write request wants to write to indices they don't have permission for, the write request is rejected.

Requests related to templates

Templates are also connected with indices, but rather indirectly. An index template has index patterns and could also have aliases. During an index template creation or modification, ROR checks if index patterns and aliases, defined in a request body, are allowed. When a user tries to remove or get template by name, ROR checks if the template can be considered as allowed for the user, and based on that information, it allows/forbids to remove or see it. See details.

actions

actions: ["indices:data/read/*"]

Match if the request action starts with "indices:data/read/".

In Elasticsearch, each request carries only one action. We extracted from Elasticsearch source code the full list of valid action strings as of all Elasticsearch versions. Please see the dedicated section to find the actions list of your specific Elasticsearch version.

Example actions (see above for the full list):

 "cluster:admin/data_frame/delete"
 "cluster:admin/data_frame/preview"
 ...
 "cluster:monitor/data_frame/stats/get"
 "cluster:monitor/health"
 "cluster:monitor/main"
 "cluster:monitor/nodes/hot_threads"
 "cluster:monitor/nodes/info"
...
 "indices:admin/aliases"
 "indices:admin/aliases/get"
 "indices:admin/analyze"
...
 "indices:data/read/get"
 "indices:data/read/mget"
 "indices:data/read/msearch"
 "indices:data/read/msearch/template"
 ...
 "indices:data/write/bulk"
 "indices:data/write/bulk_shard_operations[s]"
 "indices:data/write/delete"
 "indices:data/write/delete/byquery"
 "indices:data/write/index"
 "indices:data/write/reindex"
 ...
 many more...

kibana_access

kibana_access: ro

Enables the minimum set of actions necessary for browsers to use Kibana.

This "macro" rule allows the minimum set of actions necessary for a browser to use Kibana. This rule allows a set of actions towards the designated kibana index (see kibana_index rule - defaults to ".kibana"), plus a stricter subset of read-only actions towards other indices, which are considered "data indices".

The idea is that with one single rule we allow the bare minimum set of index+action combinations necessary to support a Kibana browsing session.

Possible access levels:

• ro_strict: the browser has a read-only view on Kibana dashboards and settings and all other indices.

• ro: some write requests can go through to the .kibana index so that UI state in discover can be saved and short urls can be created.

• rw: some more actions will be allowed towards the .kibana index only, so Kibana dashboards and settings can be modified.

• admin: like above, but has additional permissions to use the ReadonlyREST PRO/Enterprise Kibana app.

NB: The "admin" access level does not mean the user will be allowed to access all indices/actions. It's just like "rw" with settings changes privileges. If you want really unrestricted access for your Kibana user, including ReadonlyREST PRO/Enterprise app, set kibana_access: unrestricted. You can use this rule with the users rule to restrict access to selected admins.

This rule is often used with the indices rule, to limit the data a user is able to see represented on the dashboards. In that case do not forget to allow the custom kibana index in the indices rule!

kibana_index

kibana_index: .kibana-user1

Default value is .kibana

Specify to what index we expect Kibana to attempt to read/write its settings (use this together with kibana.index setting in kibana.yml.)

This value directly affects how kibana_access works because at all the access levels (yes, even admin), kibana_access rule will not maatch any write request in indices that are not the designated kibana index.

If used in conjunction with ReadonlyREST Enterprise, this rule enables multi tenancy, because in ReadonlyREST, a tenancy is identified with a set of Kibana configurations, which are by design collected inside a kibana index (default: .kibana).

snapshots

snapshots: ["[email protected]{user}_*"]

Restrict what snapshots names can be saved or restored

repositories

repositories: ["[email protected]{user}_*"]

Restrict what repositories can snapshots be saved into

filter

filter: '{"query_string":{"query":"user:@{user}"}}'

This rule enables Document Level Security (DLS). That is: return only the documents that satisfy the boolean query provided as an argument.

This rule lets you filter the results of a read request using a boolean query. You can use dynamic variables i.e. @{user} (see dedicated paragraph) to inject a user name or some header values in the query, or even environmental variables.

Example: per-user index segmentation

In the index "test-dls", each user can only search documents whose field "user" matches their user name. I.e. A user with username "paul" requesting all documents in "test-dls" index, won't see returned a document containing a field "user": "jeff" .

- name: "::PER-USER INDEX SEGMENTATION::"
  proxy_auth: "*"
  indices: ["test-dls"]
  filter: '{"bool": { "must": { "match": { "user": "@{user}" }}}}'

Example 2: Prevent search of "classified" documents.

In this example, we want to avoid that users belonging to group "press" can see any document that has a field "access_level" with the value "CLASSIFIED". And this policy is applied to all indices (no indices rule is specified).

- name: "::Press::"
  groups: ["press"]
  filter: '{"bool": { "must_not": { "match": { "access_level": "CLASSIFIED" }}}}'

⚠️IMPORTANT The filterand fields rules will only affect "read" requests, therefore "write" requests will not match because otherwise it would implicitly allow clients to "write" without the filtering restriction. For reference, this behaviour is identical to x-pack and search guard.

⚠️IMPORTANT Beginning with version 1.27.0 all ROR internal requests from kibana will not match blocks containing filter and/or fields rules. There requests are used to perform kibana login and dynamic config reload.

If you want to allow write requests (i.e. for Kibana sessions), just duplicate the ACL block, have the first one with filter and/or fields rule, and the second one without.

fields

This rule enables Field Level Security (FLS). That is:

• for responses where fields with values are returned (e.g. Search/Get API) - filter and show only allowed fields

• make not allowed fields unsearchable - used in QueryDSL requests (e.g. Search/MSearch API) do not have impact on search result.

In other words: FLS protects from usage some not allowed fields for a certain user. From user's perspective it seems like such fields are nonexistent.

Definition

Field rule definition consists of two parts:

• A non empty list of fields (blacklisted or whitelisted) names. Supports wildcards and user runtime variables.

• The FLS engine definition (global setting, optional). See: engine details.

⚠️IMPORTANT With default FLS engine it's required to install ReadonlyREST plugin in all the data nodes. Different configurations allowing to avoid such requirement are described in engine details.

Field names

Fields can be defined using two access modes: blacklist and whitelist.

Blacklist mode (recommended)

Specifies which fields should not be allowed prefixed with ~ (other fields from mapping become allowed implicitly). Example:

fields: ["~excluded_fields_prefix_*", "~excluded_field", "~another_excluded_field.nested_field"]

Return documents but deprived of the fields that:

• start with excluded_fields_prefix_

• are equal to excluded_field

• are equal to another_excluded_field.nested_field

Whitelist mode

Specifies which fields should be allowed explicitly (other fields from mapping become not allowed implicitly). Example:

fields: ["allowed_fields_prefix_*", "_*", "allowed_field.nested_field.text"]

Return documents deprived of all the fields, except the ones that:

• start with allowed_fields_prefix_

• start with underscore

• are equal to allowed_field.nested_field.text

NB: You can only provide a full black list or white list. Grey lists (i.e. ["~a", "b"]) are invalid settings and ROR will refuse to boot up if this condition is detected.

Example: hide prices from catalogue indices

- name: "External users - hide prices"
  fields: ["~price"]
  indices: ["catalogue_*"]

⚠️IMPORTANT Any metadata fields e.g. _id or _index can not be used in fields rule.

⚠️IMPORTANT The filterand fields rules will only affect "read" requests, therefore "write" requests will not match because otherwise it would implicitly allow clients to "write" without the filtering restriction. For reference, this behaviour is identical to x-pack and search guard.

⚠️IMPORTANT Beginning with version 1.27.0 all ROR internal requests from kibana will not match blocks containing filter and/or fields rules. There requests are used to perform kibana login and dynamic config reload.

If you want to allow write requests (i.e. for Kibana sessions), just duplicate the ACL block, have the first one with filter and/or fields rule, and the second one without.

Configuring an ACL with filter/fields rules when using Kibana

A normal Kibana session interacts with Elasticsearch using a mix of actions which we can roughly group in two macro categories of "read" and "write" actions. However the fields and filter rules will only match read requests. They will also block ROR internal request used to log in to kibana and reload config. This means that a complete Kibana session cannot anymore be entirely matched by a single ACL block like it normally would.

For example, this ACL block would perfectly support a complete Kibana session. That is, 100% of the actions (browser HTTP requests) would be allowed by this ACL block.

    - name: "::RW_USER::"
      auth_key: rw_user:pwd
      kibana_access: rw
      indices: ["r*", ".kibana"]

However, when we introduce a filter (or fields) rule, this block will be able to match only some of the actions (only the "read" ones).

    - name: "::RW_USER::"
      auth_key: rw_user:pwd
      kibana_access: rw  # <-- won't work because of filter present in block
      indices: ["r*", ".kibana"]
      filter: '{"query_string":{"query":"DestCountry:FR"}}'  # <-- will reject all write requests! :(

The solution is to duplicate the block. The first one will intercept (and filter!) the read requests. The second one will intercept the remaining actions. Both ACL blocks together will entirely support a whole Kibana session.

    - name: "::RW_USER (filter read requests)::"  
      auth_key: rw_user:pwd
      indices: ["r*"]  # <-- DO NOT FILTER THE .kibana INDEX!
      filter: '{"query_string":{"query":"DestCountry:FR"}}'
​
    - name: "::RW_USER (allow remaining requests)::"
      auth_key: rw_user:pwd
      kibana_access: rw
      indices: ["r*", ".kibana"]

NB: Look at how we make sure that the requests to ".kibana" won't get filtered by specifying an indices rule in the first block.

Here is another example, a bit more complex. Look at how we can duplicate the "PERSONAL_GRP" ACL block so that the read requests to the "r*" indices can be filtered, and all the other requests can be intercepted by the second rule (which is identical to the one we had before the duplication).

Before adding the filter rule:

  - name: "::PERSONAL_GRP::"
    groups: ["Personal"]
    kibana_access: rw
    indices: ["r*", "[email protected]{user}"]
    kibana_hide_apps: ["readonlyrest_kbn", "timelion"]
    kibana_index: "[email protected]{user}"

After adding the filter rule (using the block duplication strategy).

    - name: "::PERSONAL_GRP (FILTERED SEARCH)::"
      groups: ["Personal"]
      indices: [ "r*" ]
      filter: '{"query_string":{"query":"DestCountry:FR"}}'
​
    - name: "::PERSONAL_GRP::"
      groups: ["Personal"]
      kibana_access: rw
      indices: ["r*", "[email protected]{user}"]
      kibana_hide_apps: ["readonlyrest_kbn", "timelion"]
      kibana_index: "[email protected]{user}"

response_fields

This rule allows filtering Elasticsearch responses using a list of fields. It works in very similar way to fields rule. In contrast to fields rule, which filters out document fields, this rule filters out response fields. It doesn't make use of Field Level Security (FLS) and can be applied to every response returned by Elasticsearch.

It can be configured in two modes:

• whitelist allowing only the defined fields from the response object

• blacklist filtering out (removing) only the defined fields from the response object

Blacklist mode

Specifies which fields should be filtered out by adding the ~ prefix to the field name. Other fields in the response will be implicitly allowed. For example:

response_fields: ["~excluded_fields_prefix_*", "~excluded_field", "~another_excluded_field.nested_field"]

The above will return the usual response object, but deprived (if found) of the fields that:

• start with excluded_fields_prefix_

• are equal to excluded_field

• are equal to another_excluded_field.nested_field

Whitelist mode

In this mode rule is configured to filter out each field that isn't defined in the rule.

response_fields: ["allowed_fields_prefix_*", "_*", "allowed_field.nested_field.text"]

Return response deprived of all the fields, except the ones that:

• start with allowed_fields_prefix_

• start with underscore

• are equal to allowed_field.nested_field.text

NB: You can only provide a full black list or white list. Grey lists (i.e. ["~a", "b"]) are invalid settings and ROR will refuse to boot up if this condition is detected.

Example: allow only cluster_name and status field in cluster health response:

Without any filtering response from /_cluster/health looks more or less like:

{
    "cluster_name": "ROR_SINGLE",
    "status": "yellow",
    "timed_out": false,
    "number_of_nodes": 1,
    "number_of_data_nodes": 1,
    "active_primary_shards": 2,
    "active_shards": 2,
    "relocating_shards": 0,
    "initializing_shards": 0,
    "unassigned_shards": 2,
    "delayed_unassigned_shards": 0,
    "number_of_pending_tasks": 0,
    "number_of_in_flight_fetch": 0,
    "task_max_waiting_in_queue_millis": 0,
    "active_shards_percent_as_number": 50.0
}

but after configuring such rule:

- name: "Filter cluster health response"
  uri_re: "^/_cluster/health"
  response_fields: ["cluster_name", "status"]

response from above will look like:

{
    "cluster_name": "ROR_SINGLE",
    "status": "yellow"
}

NB: Any response field can be filtered using this rule.

Authentication

Local ReadonlyREST users are authenticated via HTTP Basic Auth. This authentication method is secure only if SSL is enabled.

auth_key

auth_key: sales:p455wd

Accepts HTTP Basic Auth. Configure this value in clear text. Clients will need to provide the header e.g. Authorization: Basic c2FsZXM6cDQ1NXdk where "c2FsZXM6cDQ1NXdk" is Base64 for "sales:p455wd".

⚠️IMPORTANT: this rule is handy just for tests, replace it with another rule that hashes credentials, like: auth_key_sha512, or auth_key_unix.

auth_key_sha512

auth_key_sha512: 280ac6f...94bf9

Accepts HTTP Basic Auth. The value is a string like username:password hashed in SHA512. Clients will need to provide the usual Authorization header.

There are also available other rules with less secure SHA algorithms auth_key_sha256 and auth_key_sha1.

The rules support also alternative syntax, where only password is hashed, eg:

auth_key_sha512: "admin:280ac6f...94bf9"

In the example below admin is the username and 280ac6f...94bf9 is the hashed secret.

auth_key_pbkdf2

auth_key_pbkdf2: "KhIxF5EEYkH5GPX51zTRIR4cHqhpRVALSmTaWE18mZEL2KqCkRMeMU4GR848mGq4SDtNvsybtJ/sZBuX6oFaSg==" # logstash:logstash

auth_key_pbkdf2: "logstash:JltDNAoXNtc7MIBs2FYlW0o1f815ucj+bel3drdAk2yOufg2PNfQ51qr0EQ6RSkojw/DzrDLFDeXONumzwKjOA==" # logstash:logstash

Accepts HTTP Basic Auth. The value is hashed in the same way as it's done in auth_key_sha512 rule, but it uses PBKDF2 key derivation function. At the moment there is no way to configure it, so during the hash generation, the user has to take into consideration the following PBKDF2 input parameters values:

The hash can be calculated using this calculator (notice that the salt has to base Base64 encoded).

auth_key_unix

auth_key_unix: test:$6$rounds=65535$d07dnv4N$QeErsDT9Mz.ZoEPXW3dwQGL7tzwRz.eOrTBepIwfGEwdUAYSy/NirGoOaNyPx8lqiR6DYRSsDzVvVbhP4Y9wf0 # Hashed for "test:test"

⚠️IMPORTANT this hashing algorithm is very CPU intensive, so we implemented a caching mechanism around it. However, this will not protect Elasticsearch from a DoS attack with a high number of requests with random credentials.

This method is based on /etc/shadow file syntax.

If you configured sha512 encryption with 65535 rounds on your system the hash in /etc/shadow for the account test:test will be test:$6$rounds=65535$d07dnv4N$QeErsDT9Mz.ZoEPXW3dwQGL7tzwRz.eOrTBepIwfGEwdUAYSy/NirGoOaNyPx8lqiR6DYRSsDzVvVbhP4Y9wf0

readonlyrest:
    access_control_rules:
    - name: Accept requests from users in group team1 on index1
      groups: ["team1"]
      indices: ["index1"]
​
    users:
    - username: test
      auth_key_unix: test:$6$rounds=65535$d07dnv4N$QeErsDT9Mz.ZoEPXW3dwQGL7tzwRz.eOrTBepIwfGEwdUAYSy/NirGoOaNyPx8lqiR6DYRSsDzVvVbhP4Y9wf0 #test:test
      groups: ["team1"]

You can generate the hash with mkpasswd Linux command, you need whois package apt-get install whois (or equivalent)

mkpasswd -m sha-512 -R 65534

Also you can generate the hash with a python script (works on Linux):

#!/usr/bin/python
import crypt
import random
import sys
import string
​
def sha512_crypt(password, salt=None, rounds=None):
    if salt is None:
        rand = random.SystemRandom()
        salt = ''.join([rand.choice(string.ascii_letters + string.digits)
                        for _ in range(8)])
​
    prefix = '$6$'
    if rounds is not None:
        rounds = max(1000, min(999999999, rounds or 5000))
        prefix += 'rounds={0}$'.format(rounds)
    return crypt.crypt(password, prefix + salt)
​
​
if __name__ == '__main__':
    if len(sys.argv) > 1:
        print sha512_crypt(sys.argv[1], rounds=65635)
    else:
        print "Argument is missing, <password>"

Finally you have to put your username at the begining of the hash with ":" separator test:$6$rounds=65535$d07dnv4N$QeErsDT9Mz.ZoEPXW3dwQGL7tzwRz.eOrTBepIwfGEwdUAYSy/NirGoOaNyPx8lqiR6DYRSsDzVvVbhP4Y9wf0

For example, test is the username and $6$rounds=65535$d07dnv4N$QeErsDT9Mz.ZoEPXW3dwQGL7tzwRz.eOrTBepIwfGEwdUAYSy/NirGoOaNyPx8lqiR6DYRSsDzVvVbhP4Y9wf0 is the hash for test (the password is identical to the username in this example).

proxy_auth: "*"

proxy_auth: "*"

Delegated authentication. Trust that a reverse proxy has taken care of authenticating the request and has written the resolved user name into the X-Forwarded-User header. The value "*" in the example, will let this rule match any username value contained in the X-Forwarded-User header.

If you are using this technique for authentication using our Kibana plugins, don't forget to add this snippet to conf/kibana.yml:

readonlyrest_kbn.proxy_auth_passthrough: true

So that Kibana will forward the necessary headers to Elasticsearch.

users

users: ["root", "*@mydomain.com"]

Limit access to of specific users whose username is contained or matches the patterns in the array. This rule is independent from the authentication mathod chosen, so it will work well in conjunction LDAP, JWT, proxy_auth, and all others.

For example:

readonlyrest:
  access_control_rules:
    - name: "JWT auth for viewer role, limited to certain usernames"
      kibana_access: ro
      users: ["root", "*@mydomain.com"]
      jwt_auth:
        name: "jwt_provider_1"
        roles: ["viewer"]

groups

groups: ["group1", "group2"]

Limit access to members of specific user groups. The members and groups are defined in users section.

The single entry inside the users section tells us that:

• a given member with a username matching one of patterns in the username array ...

• belongs to groups listed in the groups array ...

• when he can be authenticated or/and authorized by auth rule(s)

In general it looks like this:

  users:
  - username: ["pattern1", "pattern2", ...]
    groups: ["group1", "group2", ...]
    authentication_rule: ...
​
  - username: ["pattern1", "pattern2", ...]
    groups: ["group1", "group2", ...]
    authentication_rule: ...
    authorization_rule: ...
​
  - username: ["pattern1", "pattern2", ...]
    groups: ["group1", "group2", ...]
    authentication_with_authorization_rule: ... # `ldap_auth` or `jwt_auth` or `ror_kbn_auth`

For details see User management .

session_max_idle

session_max_idle: 1h

⚠️DEPRECATED Browser session timeout (via cookie). Example values 1w (one week), 10s (10 seconds), 7d (7 days), etc. NB: not available for Elasticsearch 2.x.

ldap_auth

See below, the dedicated LDAP section​

jwt_auth

See below, the dedicated JSON Web Tokens section​

external-basic-auth

Used to delegate authentication to another server that supports HTTP Basic Auth. See below, the dedicated External BASIC Auth section​

groups_provider_authorization

Used to delegate groups resolution for a user to a JSON microservice. See below, the dedicated Groups Provider Authorization section​

ror_kbn_auth

For Enterprise customers only, required for SAML authentication.

readonlyrest:
  access_control_rules:
​
    - name: "ReadonlyREST Enterprise instance #1"
      ror_kbn_auth:
        name: "kbn1"
        roles: ["SAML_GRP_1"]
​
    - name: "ReadonlyREST Enterprise instance #2"
      ror_kbn_auth:
        name: "kbn2"
​
  ror_kbn:
    - name: kbn1
      signature_key: "shared_secret_kibana1" # <- use environmental variables for better security!
​
    - name: kbn2
      signature_key: "shared_secret_kibana2" # <- use environmental variables for better security!

This authentication and authorization connector represents the secure channel (based on JWT tokens) of signed messages necessary for our Enterprise Kibana plugin to securely pass back to ES the username and groups information coming from browser-driven authentication protocols like SAML

Continue reading about this in the kibana plugin documentation, in the dedicated SAML section​

Ancillary rules

verbosity

verbosity: error

Don't spam elasticsearch log file printing log lines for requests that match this block. Defaults to info.

Audit & Troubleshooting

The main issues seen in support cases:

• Bad ordering or ACL blocks. Remember that the ACL is evaluated sequentially, block by block. And the first block whose rules all match is accepted.

• Users don't know how to read the HIS field in the logs, which instead is crucial because it contains a trace of the evaluation of rules and blocks.

• LDAP configuration: LDAP is tricky to configure in any system. Configure ES root logger to DEBUG editing $ES_PATH_CONF/config/log4j2.properties to see a trace of the LDAP messages.

Interpreting logs

ReadonlyREST prints a log line for each incoming request (this can be selectively avoided on ACL block level using the verbosity rule).

Allowed requests

This is an example of a request that matched an ACL block (allowed) and has been let through to Elasticsearch.

ALLOWED by { name: '::PERSONAL_GRP::', policy: ALLOW} req={ ID:1667655475--1038482600#1312339, TYP:SearchRequest, CGR:N/A, USR:simone, BRS:true, ACT:indices:data/read/search, OA:127.0.0.1, IDX:, MET:GET, PTH:/_search, CNT:<N/A>, HDR:Accept,Authorization,content-length,Content-Type,Host,User-Agent,X-Forwarded-For, HIS:[::PERSONAL_GRP::->[kibana_access->true, kibana_hide_apps->true, auth_key->true, kibana_index->true]], [::Kafka::->[auth_key->false]], [::KIBANA-SRV::->[auth_key->false]], [guest lol->[auth_key->false]], [::LOGSTASH::->[auth_key->false]] }

Explanation

The log line immediately states that this request has been allowed by an ACL block called "::PERSONAL_GRP::". Immediately follows a summary of the requests' anatomy. The format is semi-structured, and it's intended for humans to read quickly, it's not JSON, or anything else.

Similar information gets logged in JSON format into Elasticsearch documents enabling the audit logs feature described later.

Here is a glossary:

• ID: ReadonlyREST-level request id

• TYP: String, the name of the Java class that internally represent the request type (very useful for debug)

• CGR: String, the request carries a "current group" header (used for multi-tenancy).

• USR: String, the user name ReadonlyREST was able to extract from Basic Auth, JWT, LDAP, or other methods as specified in the ACL.

• BRS: Boolean, an heuristic attempt to tell if the request comes from a browser.

• ACT: String, the elasticsearch level action associated with the request. For a list of actions, see our actions rule docs.

• OA: IP Address, originating address (source address) of the TCP connection underlying the http session.

• IDX: Strings array: the list of indices affected by this request.

• MET: String, HTTP Method

• CNT: String, HTTP body content. Comes as a summary of its lenght, full body of the request is available in debug mode.

• HDR: String array, list of HTTP headers, headers' content is available in debug mode.

• HIS: Chronologically ordered history of the ACL blocks and their rules being evaluated, This is super useful for knowing what ACL block/rule is forbidding/allowing this request.

In the example, the block ::PERSONAL_GRP:: is allowing the request because all the rules in this block evaluate to true.

Forbidden requests

This is an example of a request that gets forbidden by ReadonlyREST ACL.

FORBIDDEN by default req={ ID:747832602--1038482600#1312150, TYP:SearchRequest, CGR:N/A, USR:[no basic auth header], BRS:true, ACT:indices:data/read/search, OA:127.0.0.1, IDX:, MET:GET, PTH:/_search, CNT:<N/A>, HDR:Accept,content-length,Content-Type,Host,User-Agent,X-Forwarded-For, HIS:[::Infosec::->[groups->false]], [::KIBANA-SRV::->[auth_key->false]], [guest lol->[auth_key->false]], [::LOGSTASH::->[auth_key->false]], [::Infosec::->[groups->false]], [::ADMIN_GRP::->[groups->false]], [::Kafka::->[auth_key->false]], [::PERSONAL_GRP::->[groups->false]] }

The above rule gets forbidden "by default". This means that no ACL block has matched the request, so ReadonlyREST's default policy of rejection takes effect.

Requests finished with INDEX NOT FOUND

This is an example of such request:

INDEX NOT FOUND req={  ID:501806845-1996085406#74,  TYP:GetIndexRequest,  CGR:N/A,  USR:dev1 (attempted),  BRS:true,  KDX:null,  ACT:indices:admin/get,  OA:172.20.0.1/32,  XFF:null,  DA:172.20.0.2/32,  IDX:nonexistent*,  MET:GET,  PTH:/nonexistent*/_alias/,  CNT:<N/A>,  HDR:Accept-Encoding=gzip,deflate, Authorization=<OMITTED>, Connection=Keep-Alive, Host=localhost:32773, User-Agent=Apache-HttpClient/4.5.2 (Java/1.8.0_162), content-length=0,  HIS:[CONTAINER ADMIN-> RULES:[auth_key->false]], [dev1 indexes-> RULES:[auth_key->true, indices->false], RESOLVED:[user=dev1]], [dev2 aliases-> RULES:[auth_key->false]], [dev3 - no indices rule-> RULES:[auth_key->false]]  }

The state above is only possible for read-only ES requests (ES requests which don't change ES cluster state) for a block containing an indices rule. If all other rules within the block are matched, but only the indices rule is mismatched, the final state of the block is forbidden due to an index not found.

Audit logs

ReadonlyREST can write events very similarly to Logstash into to a series of indices named by default readonlyrest_audit-YYYY-MM-DD. Every event contains information about a request and how the system has handled it. Here is an example of the data points contained in each audit event. We can leverage all this information to build interesting Kibana dashboards, or any other visualization.

{
    "error_message": null,
    "headers": [
      "Accept",
      "Authorization",
      "content-length",
      "Host",
      "User-Agent"
    ],
    "acl_history": "[[::LOGSTASH::->[auth_key->false]], [::RW::->[kibana_access->true, indices->true, kibana_hide_apps->true, auth_key->true]], [kibana->[auth_key->false]], [::RO::->[auth_key->false]]]",
    "origin": "127.0.0.1",
    "final_state": "ALLOWED",
    "task_id": 1158,
    "type": "SearchRequest",
    "req_method": "GET",
    "path": "/readonlyrest_audit-2017-06-29/_search?pretty",
    "indices": [
      "readonlyrest_audit-2017-06-29"
    ],
    "@timestamp": "2017-06-30T09:41:58Z",
    "content_len_kb": 0,
    "error_type": null,
    "processingMillis": 0,
    "action": "indices:data/read/search",
    "matched_block": "::RW::",
    "id": "933409190-292622897#1158",
    "content_len": 0,
    "user": "simone"
  }

Here is a configuration example, you can see the audit_collector: true setting, which nomally defaults to false. Note how the successful requests matched by the first rule (Kibana) will not be written to the audit log, because the verbosity is set to error. Audit log in facts, obey the verbosity setting the same way regular text logs do.

readonlyrest:
​
    audit_collector: true
​
    access_control_rules:
​
    - name: Kibana
      type: allow
      auth_key: kibana:kibana
      verbosity: error
​
    - name: "::RO::"
      auth_key: simone:ro
      kibana_access: ro

Extended audit

If you want to log the request content then an additional serializer is provided. This will log the entire user request within the content field of the audit event. To enable, configure the audit_serializer parameter as below.

readonlyrest:
  audit_collector: true
  audit_serializer: tech.beshu.ror.requestcontext.QueryAuditLogSerializer
  ...

Custom audit indices name and time granularity

It is possible to change the name of the produced audit log indices by specifying a template value as audit_index_template.

Example: tell ROR to write on monthly index.

readonlyrest:
  audit_collector: true
  audit_index_template: "'custom-prefix'-yyyy-MM"  # <--monthly pattern
  ...

⚠️IMPORTANT: notice the single quotes inside the double quoted expression. This is the same syntax used for Java's SimpleDateFormat.

Custom audit log serializer

You can write your own custom audit log serializer class, add it to the ROR plugin class path and configure it through the YAML settings.

We provided 2 project examples with custom serializers (in Scala and Java). You can use them as an example to write yours in one of those languages.

Create custom audit log serializer in Scala

1. Checkout https://github.com/sscarduzio/elasticsearch-readonlyrest-plugin​

   git clone [email protected]:sscarduzio/elasticsearch-readonlyrest-plugin.git

2. Install SBT

   https://www.scala-sbt.org/download.html

3. Find and go to: elasticsearch-readonlyrest-plugin/custom-audit-examples/ror-custom-scala-serializer/

4. Create own serializer:

   • from scratch (example can be found in class ScalaCustomAuditLogSerializer)

   • extending default one (example can be found in class ScalaCustomAuditLogSerializer)

5. Build serializer JAR:

   sbt assembly

6. Jar can be find in:

   elasticsearch-readonlyrest-plugin/custom-audit-examples/ror-custom-scala-serializer/target/scala-2.13/ror-custom-scala-serializer-1.0.0.jar

Create custom audit log serializer in Java

1. Checkout https://github.com/sscarduzio/elasticsearch-readonlyrest-plugin​

   git clone [email protected]:sscarduzio/elasticsearch-readonlyrest-plugin.git

2. Install Maven

   https://maven.apache.org/install.html

3. Find and go to: elasticsearch-readonlyrest-plugin/custom-audit-examples/ror-custom-java-serializer/

4. Create own serializer:

   • from scratch (example can be found in class JavaCustomAuditLogSerializer)

   • extending default one (example can be found in class JavaCustomAuditLogSerializer)

5. Build serializer JAR:

   mvn package

6. Jar can be find in:

   elasticsearch-readonlyrest-plugin/custom-audit-examples/ror-custom-java-serializer/target/ror-custom-java-serializer-1.0.0.jar

Configuration

1. mv ror-custom-java-serializer-1.0.0.jar plugins/readonlyrest/

2. Your config/readonlyrest.yml should start like this

    readonlyrest:
        audit_collector: true
        audit_serializer: "JavaCustomAuditLogSerializer" # when your serializer class is not in default package, you should use full class name here (eg. "tech.beshu.ror.audit.instances.QueryAuditLogSerializer")

3. Start elasticsearch (with ROR installed) and grep for:

    [2017-11-09T09:42:51,260][INFO ][t.b.r.r.SerializationTool] Using custom serializer: JavaCustomAuditLogSerializer

Troubleshooting

Follow these approaches until you find the solution to your problem

Scenario: you can't understand why your requests are being forbidden by ReadonlyREST (or viceversa)

Step 1: see what block/rule is matching Take the Elasticsearch log file, and grep the logs for ACT:. This will show you the whole request context (including the action and indices fields) of the blocked requests. You can now tweak your ACL blocks to include that action.

Step 2: enable debug logs

Logs are good for auditing the activity on the REST API. You can configure them by editing $ES_PATH_CONF/config/logging.yml (Elasticsearch 2.x) or $ES_PATH_CONF/config/log4j2.properties file (Elasticsearch 5.x)

For example, you can enable the debug log globally by setting the rootLoggerto debug.

rootLogger.level = debug

This is really useful especially to debug the activity of LDAP and other external connectors.

Trick: log requests to different files

Here is a log4j2.properties snippet for ES 5.x that logs all the received requests as a new line in a separate file:

#Plugin readonly rest separate access logging file definition
appender.access_log_rolling.type = RollingFile
appender.access_log_rolling.name = access_log_rolling
appender.access_log_rolling.fileName = ${sys:es.logs}_access.log
appender.access_log_rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c] %marker%.-10000m%n
appender.access_log_rolling.layout.type = PatternLayout
appender.access_log_rolling.filePattern = ${sys:es.logs}_access-%d{yyyy-MM-dd}.log
appender.access_log_rolling.policies.type = Policies
appender.access_log_rolling.policies.time.type = TimeBasedTriggeringPolicy
appender.access_log_rolling.policies.time.interval = 1
appender.access_log_rolling.policies.time.modulate = true
​
logger.access_log_rolling.name = tech.beshu.ror
logger.access_log_rolling.level = info
logger.access_log_rolling.appenderRef.access_log_rolling.ref = access_log_rolling
logger.access_log_rolling.additivity = false
​
# exclude kibana, beat and logstash users as they generate too much noise
logger.access_log_rolling.filter.regex.type = RegexFilter
logger.access_log_rolling.filter.regex.regex = .*USR:(kibana|beat|logstash),.*
logger.access_log_rolling.filter.regex.onMatch = DENY
logger.access_log_rolling.filter.regex.onMismatch = ACCEPT

Users and Groups

Sometimes we want to make allow/forbid decisions according to the username associated to a HTTP request. The extraction of the user identity (username) can be done via HTTP Basic Auth (Authorization header) or delegated to a reverse proxy (see proxy_auth rule).

The validation of the said credentials can be carried on locally with hard coded credential hashes (see auth_key_sha256 rule), via one or more LDAP server, or we can forward the Authorization header to an external web server and examine the HTTP status code (see external_authentication).

Optionally we can introduce the notion of groups (see them as bags of users). The aim of having groups is to write a very specific block once, and being able to allow multiple usernames that satisfy the block.

Groups can be declared and associated to users statically in the readonlyrest.yml file. Alternatively, groups for a given username can be retrieved from an LDAP server or from a LDAP server, or a custom JSON/XML service.

You can mix and match the techniques to satisfy your requirements. For example, you can configure ReadonlyREST to:

• Extract the username from X-Forwarded-User

• Resolve groups associated to said user through a JSON microservice

Another example:

• Extract the username from Authorization header (HTTP Basic Auth)

• Validate said username's password via LDAP server

• resolve groups associated to the user from groups defined in readonlyrest.yml

More examples are shown below together with a sample configuration.

Local users and groups

The groups rule accepts a list of group names. This rule will match if the resolved username (i.e. via auth_key) is associated to the given groups. In this example, the usernames are statically associated to group names.

 access_control_rules:
​
    - name: Accept requests from users in group team1 on index1
      type: allow  # Optional, defaults to "allow" will omit now on.
      groups: ["team1"]
      indices: ["index1"]
​
    - name: Accept requests from users in group team2 on index2
      groups: ["team2"]
      indices: ["index2"]
​
    - name: Accept requests from users in groups team1 or team2 on index3
      groups: ["team1", "team2"]
      indices: ["index3"]
​
    users:
​
    - username: "alice"
      groups: ["team1"]
      auth_key: alice:p455phrase
​
    - username: "bob"
      groups: ["team2", "team4"]
      auth_key: bob:s3cr37
​
    - username: "claire"
      groups: ["team1", "team5"]
      auth_key_sha256: e0bba5fda92dbb0570fd2e729a3c8ed6b1d52b380581f32427a38e396ba28ec6 #claire:p455key

Example: rules are associated to groups (instead of users) and users-group association is declared separately later under users:

Group mapping

Sometimes we'd like to take advantage of roles existing in external systems (like LDAP). We can do that in users section too. It's possible to map external groups to local ones. For details see External to local groups mapping .

Username case sensitivity

ReadonlyREST can cooperate with services, that operates in case-insensitive way. For this case ROR has toggleable username case sensitivity option username_case_sensitivity.

readonlyrest:
  username_case_sensitivity: case_sensitive

By default, usernames are case-sensitive username_case_sensitivity: case_sensitive. By setting username_case_sensitivity: case_sensitive username comparison will be case-insensitive in any rule.

Environmental variables

Anywhere in readonlyrest.yml you can use the espression ${MY_ENV_VAR} to replace in place the environmental variables. This is very useful for injecting credentials like LDAP bind passwords, especially in Docker.

For example, here we declare an environment variable, and we write ${LDAP_PASSWORD} in our settings:

$ export LDAP_PASSWORD=S3cr3tP4ss
$ cat readonlyrest.yml

....
ldaps:
​
    - name: ldap1
      host: "ldap1.example.com"
      port: 389                                                     
      ssl_enabled: false                                            
      ssl_trust_all_certs: true                                     
      bind_dn: "cn=admin,dc=example,dc=com"                         
      bind_password: "${LDAP_PASSWORD}"                                     
      search_user_base_DN: "ou=People,dc=example,dc=com"
....

And ReadonlyREST ES will load "S3cr3tP4ss" as bind_password.

Dynamic variables

One of the neatest feature in ReadonlyREST is that you can use dynamic variables inside most rules values. The variables you can currently replace into rules values are these:

• @{acl:user} gets replaced with the username of the successfully authenticated user. Using this variable is allowed only in blocks where one of the rules is authentication rule (of course it must be rule different from the one containing given variable).

• @{user} old style user variable definition. Preferred approach is to use @{acl:user}.

• @{acl:current_group} gets replaced with user's current group. Usually resolved by authorization rule defined in block, but value can be also retrieved by means of kibana plugin. This variable doesn't specify usage requirements.

• @{xyz} gets replaced with any xyz HTTP header included in the incoming request (useful when reverse proxies handle authentication)

Indices from user name

You can let users authenticate externally, i.e. via LDAP, and use their user name string inside the indices rule.

readonlyrest:
    access_control_rules:
​
    - name: "Users can see only their logstash indices i.e. alice can see alice_logstash-20170922"
      ldap_authentication:
        name: "myLDAP"
      indices: ["@{acl:user}_logstash-*"]
​
    # LDAP connector settings omitted, see LDAP section below..

Uri regex matching user's current group

You can let users authorize externally, i.e. via LDAP, and use their group inside the uri_re rule.

readonlyrest:
    access_control_rules:
​
    - name: "Users can access uri with value containing user's current group, i.e. user with group 'g1' can access: '/path/g1/some_thing'"
      ldap_authorization:
        name: "ldap1"
        groups: ["g1", "g2", "g3"]
      uri_re: ["^/path/@{acl:current_group}/.*"]
​
    # LDAP connector settings omitted, see LDAP section below..

Kibana index from headers

Imagine that we delegate authentication to a reverse proxy, so we know that only authenticated users will ever reach Elasticsearch. We can tell the reverse proxy (i.e. Nginx) to inject a header called x-nginx-user containing the username.

readonlyrest:
    access_control_rules:
​
    - name: "Identify a personal kibana index where each user is supposed to save their dashboards"
      kibana_access: rw
      kibana_index: "[email protected]{x-nginx-user}"

Dynamic variables from JWT claims

The JWT token is an authentication string passed generally as a header or a query parameter to the web browser. If you squint, you can see it's a concatenation of three base64 encoded strings. If you base64 decode the middle string, you can see the "claims object". That is, the object containing the current user's metadata.

Here is an example of JWT claims object.

{
  "user": "jdoe",
  "display_name": "John Doe",
  "department": "infosec",
  "allowedIndices": ["x", "y"]
}

Here follow some examples of how to use JWT claims as dynamic variables in ReadonlyREST ACL blocks, notice the "jwt:" prefix:

# Using JWT claims as dynamic variables
indices: [ "[email protected]{jwt:department}", "otherIdx" ]
# claims = { "user": "u1", "department": "infosec"}
# -> indices: [".kibana_infosec", "otherIdx"]
​
# Using nested values in JWT using JSONPATH as dynamic variables
indices: [ "[email protected]{jwt:jsonpath.to.department}", "otherIdx"]  
# claims = { "jsonpath": {"to": { "department": "infosec" }}}
# -> indices: [".kibana_infosec", "otherIdx"]
​
# Referencing array-typed values from JWT claims will expand in a list of strings
indices: [ "[email protected]{jwt:allowedIndices}", "otherIdx"]  
# claims = {"username": "u1", "allowedIndices":  ["x", "y"] }
# -> indices: [".kibana_x", ".kibana_y", "otherIdx"]
​
# Explode operator will generate an array of strings from a comma-separated string
indices: ["[email protected]{x-indices_csv_string}*", "otherIdx"]  
# HTTP Headers: [{ "x-indices_csv_string": "a,b"}]
# -> indices: ["logstash_a*", "logstash_b*", "otherIdx"]

LDAP connector

In this example, users credentials are validated via LDAP. The groups associated to each validated users are resolved using the same LDAP server.

Simpler: authentication and authorization in one rule

readonlyrest:
​
    access_control_rules:
​
    - name: Accept requests from users in group team1 on index1
      type: allow                                           # Optional, defaults to "allow", will omit from now on.
      ldap_auth:
        name: "ldap1"                                       # ldap name from below 'ldaps' section
        groups: ["g1", "g2"]                                # group within 'ou=Groups,dc=example,dc=com'
      indices: ["index1"]
​
    - name: Accept requests from users in group team2 on index2
      ldap_auth:
        name: "ldap2"
        groups: ["g3"]
        cache_ttl_in_sec: 60
      indices: ["index2"]
​
    ldaps:
​
    - name: ldap1
      host: "ldap1.example.com"
      port: 389                                                     # optional, default 389
      ssl_enabled: false                                            # optional, default true
      ssl_trust_all_certs: true                                     # optional, default false
      ignore_ldap_connectivity_problems: true                       # optional, default false
      bind_dn: "cn=admin,dc=example,dc=com"                         # optional, skip for anonymous bind
      bind_password: "password"                                     # optional, skip for anonymous bind
      search_user_base_DN: "ou=People,dc=example,dc=com"
      user_id_attribute: "uid"                                      # optional, default "uid"
      search_groups_base_DN: "ou=Groups,dc=example,dc=com"
      unique_member_attribute: "uniqueMember"                       # optional, default "uniqueMember"
      connection_pool_size: 10                                      # optional, default 30
      connection_timeout_in_sec: 10                                 # optional, default 1
      request_timeout_in_sec: 10                                    # optional, default 1
      cache_ttl_in_sec: 60                                          # optional, default 0 - cache disabled
      group_search_filter: "(objectClass=group)(cn=application*)"   # optional, default (cn=*)
      group_name_attribute: "cn"                                    # optional, default "cn"
      circuit_breaker:                                              # optional section, default configuration used when not declared
        max_retries: 2                                              # required, default 10 when circuit_breaker is not declared
        reset_duration: 5s                                          # required, default 10s when circuit_breaker is not declared
​
    # High availability LDAP settings (using "hosts", rather than "host")
    - name: ldap2
      hosts:                                                        # HA style, alternative to "host"
      - "ldaps://ssl-ldap2.foo.com:636"                             # can use ldap:// or ldaps:// (for ssl)
      - "ldaps://ssl-ldap3.foo.com:636"                             # the port is declared in line
      ha: "ROUND_ROBIN"                                             # optional, default "FAILOVER"
      search_user_base_DN: "ou=People,dc=example2,dc=com"
      search_groups_base_DN: "ou=Groups,dc=example2,dc=com"
​
    # Server discovery variant
    - name: ldap3
      server_discovery: true                                        # Using _ldaps._tcp SRV DNS record for getting LDAP addresses
      search_user_base_DN: "ou=People,dc=example2,dc=com"
      search_groups_base_DN: "ou=Groups,dc=example2,dc=com"

Advanced: authentication and authorization in separate rules

readonlyrest:
    enable: true
    response_if_req_forbidden: Forbidden by ReadonlyREST ES plugin
​
    access_control_rules:
​
    - name: Accept requests to index1 from users with valid LDAP credentials, belonging to LDAP group 'team1'
      ldap_authentication: "ldap1"  
      ldap_authorization:
        name: "ldap1"                                       # ldap name from 'ldaps' section
        groups: ["g1", "g2"]                                # group within 'ou=Groups,dc=example,dc=com'
      indices: ["index1"]
​
    - name: Accept requests to index2 from users with valid LDAP credentials, belonging to LDAP group 'team2'
      ldap_authentication:
        name: "ldap2"  
        cache_ttl_in_sec: 60
      ldap_authorization:
        name: "ldap2"
        groups: ["g3"]
        cache_ttl_in_sec: 60
      indices: ["index2"]
​
    ldaps:
​
    - name: ldap1
      host: "ldap1.example.com"
      port: 389                                                 # default 389
      ssl_enabled: false                                        # default true
      ssl_trust_all_certs: true                                 # default false
      ignore_ldap_connectivity_problems: true                   # optional, default false
      bind_dn: "cn=admin,dc=example,dc=com"                     # skip for anonymous bind
      bind_password: "password"                                 # skip for anonymous bind
      search_user_base_DN: "ou=People,dc=example,dc=com"
      user_id_attribute: "uid"                                  # default "uid"
      search_groups_base_DN: "ou=Groups,dc=example,dc=com"
      unique_member_attribute: "uniqueMember"                   # default "uniqueMember"
      connection_pool_size: 10                                  # default 30
      connection_timeout_in_sec: 10                             # default 1
      request_timeout_in_sec: 10                                # default 1
      cache_ttl_in_sec: 60                                      # default 0 - cache disabled
​
    # High availability LDAP settings (using "hosts", rather than "host")
    - name: ldap2
      hosts:                                                        # HA style, alternative to "host"
      - "ldaps://ssl-ldap2.foo.com:636"                             # can use ldap:// or ldaps:// (for ssl)
      - "ldaps://ssl-ldap3.foo.com:636"                             # the port is declared in line
      ha: "ROUND_ROBIN"                                             # optional, default "FAILOVER"
      search_user_base_DN: "ou=People,dc=example2,dc=com"
      search_groups_base_DN: "ou=Groups,dc=example2,dc=com"