Kong Session plugin

A Kong plugin to support implementing sessions for Kong authentication plugins.

Description

Kong Session plugin can be used to manage browser sessions for APIs proxied through the Kong API Gateway. It provides configuration and management for session data storage, encyption, renewal, expiry, and sending browser cookies 🍪.

For more information on security, configs, and underlying session mechanism, check out lua-resty-session docs.

Usage

Kong Session plugin can be configured globally or per entity (service, route, etc) and is always used in conjunction with another Kong authentication plugin. This plugin is intended to work similarly to the multiple authentication setup.

Once Kong Session plugin is enabled in conjunction with an authentication plugin, it will run prior to credential verification. If no session is found, then the authentication plugin will run and credentials will be checked as normal. If the credential verification is successful, then the session plugin will create a new session for usage with subsequent requests. When a new request comes in, and a session is present, then Kong Session plugin will attach the ngx.ctx variables to let the authentication plugin know that authentication has already occured via session validation. Since this configuration is a logical OR scenario, it is desired that anonymous access be forbidden, then the request termination plugin should be configured on an anonymous consumer. Failure to do so will allow unauthorized requests. For more information please see section on multiple authentication.

For usage with key-auth plugin

1. Create an example Service and a Route

   Issue the following cURL request to create example-service pointing to mockbin.org, which will echo the request:

   $ curl -i -X POST \
     --url http://localhost:8001/services/ \
     --data 'name=example-service' \
     --data 'url=http://mockbin.org/request'

   Add a route to the Service:

   $ curl -i -X POST \
     --url http://localhost:8001/services/example-service/routes \
     --data 'paths[]=/sessions-test'

   The url http://localhost:8000/sessions-test will now echo whatever is being requested.

2. Configure the key-auth Plugin for the Service

   Issue the following cURL request to add the key-auth plugin to the Service:

   $ curl -i -X POST \
     --url http://localhost:8001/services/example-service/plugins/ \
     --data 'name=key-auth'

   Be sure to note the created Plugin id - it will be needed later.

3. Verify that the key-auth plugin is properly configured

   Issue the following cURL request to verify that the key-auth plugin was properly configured on the Service:

   $ curl -i -X GET \
     --url http://localhost:8000/sessions-test

   Since the required header or parameter apikey was not specified, and anonymous access was not yet enabled, the response should be 401 Unauthorized:

4. Create a Consumer and an anonymous Consumer

   Every request proxied and authenticated by Kong must be associated with a Consumer. You'll now create a Consumer named anonymous_users by issuing the following request:

   $ curl -i -X POST \
     --url http://localhost:8001/consumers/ \
     --data "username=anonymous_users"

   Be sure to note the Consumer id - you'll need it in a later step.

   Now create a consumer that will authenticate via sessions

   $ curl -i -X POST \
     --url http://localhost:8001/consumers/ \
     --data "username=fiona"

5. Provision key-auth credentials for your Consumer

   $ curl -i -X POST \
     --url http://localhost:8001/consumers/fiona/key-auth/ \
     --data 'key=open_sesame'

6. Enable anonymous access

   You'll now re-configure the key-auth plugin to permit anonymous access by issuing the following request (replace the uuids below by the id value from previous steps):

   $ curl -i -X PATCH \
     --url http://localhost:8001/plugins/<your-key-auth-plugin-id> \
     --data "config.anonymous=<anonymous_consumer_id>"

7. Add the Kong Session plugin to the service

   $ curl -X POST http://localhost:8001/services/example-service/plugins \
       --data "name=session"  \
       --data "config.storage=kong" \
       --data "config.cookie_secure=false"

   Note: cookie_secure is true by default, and should always be true, but is set to false for the sake of this demo in order to avoid using HTTPS.

8. Add the Request Termination plugin

   To disable anonymous access to only allow users access via sessions or via authentication credentials, enable the Request Termination plugin.

   $ curl -X POST http://localhost:8001/services/example-service/plugins \
       --data "name=request-termination"  \
       --data "config.status_code=403" \
       --data "config.message=So long and thanks for all the fish!" \
       --data "consumer.id=<anonymous_consumer_id>"

   Anonymous requests now will return status 403.

     $ curl -i -X GET \
       --url http://localhost:8000/sessions-test

   Should return 403.

9. Verify that the session plugin is properly configured

   $ curl -i -X GET \
     --url http://localhost:8000/sessions-test?apikey=open_sesame

   The response should now have the Set-Cookie header. Make sure that this cookie works.

   If cookie looks like this:

   Set-Cookie: session=emjbJ3MdyDsoDUkqmemFqw..|1544654411|4QMKAE3I-jFSgmvjWApDRmZHMB8.; Path=/; SameSite=Strict; HttpOnly
   

   Use it like this:

     $ curl -i -X GET \
       --url http://localhost:8000/sessions-test \
       -H "cookie:session=emjbJ3MdyDsoDUkqmemFqw..|1544654411|4QMKAE3I-jFSgmvjWApDRmZHMB8."

   This request should succeed, and Set-Cookie response header will not appear until renewal period.

Defaults

By default, Kong Session plugin favors security using a Secure, HTTPOnly, Samesite=Strict cookie. cookie_domain is automatically set using Nginx variable host, but can be overridden.

Session Data Storage

The session data can be stored in the cookie itself (encrypted) storage=cookie , or inside Kong. The session data these context variables:

ngx.ctx.authenticated_consumer.id
ngx.ctx.authenticated_credential.id
ngx.ctx.authenticated_groups

The plugin also sets a ngx.ctx.authenticated_session for communication between the access and header_filter phases in the plugin.

Groups

Authenticated groups are stored on ngx.ctx.authenticated_groups from other authentication plugins and the session plugin will store them in the data of the current session. Since the session plugin runs before authentication plugins, it will also set authenticated_groups associated headers.

🦍 Kong Storage Adapter

Kong Session plugin extends the functionality of lua-resty-session with its own session data storage adapter when storage=kong. This will store encrypted session data into the current database strategy (e.g. postgres, cassandra etc.) and the cookie will not contain any session data. Data stored in the database is encrypted and the cookie will contain only the session id, expiration time and HMAC signature. Sessions will use built-in Kong DAO ttl mechanism which destroys sessions after specified cookie_lifetime unless renewal occurs during normal browser activity. It is recommended that the application logout via XHR request or similar to manually handle redirects.

👋🏻 Logging Out

It is typical to provide users the ability to log out, or manually destroy, their current session. Logging out is done via either query params or POST params in the request url. The configs logout_methods allows the plugin to limit logging out based on HTTP verb. When logout_query_arg is set, it will check the presence of the url query param specified, and likewise when logout_post_arg is set it will check the presence of the specified variable in the request body. Allowed HTTP verbs are GET, DELETE, and POST. When there is a session present and the incoming request is a logout request, Kong Session plugin will return a 200 before continuing in the plugin run loop, and the request will not continue to the upstream.

Dependencies

Kong Session Plugin depends on lua-resty-session.

Known Limitations

Due to limitations of OpenResty, the header_filter phase cannot connect to the database, which poses a problem for initial retrieval of cookie (fresh session). There is a small window of time where cookie is sent to client, but database insert has not yet been committed, as database call is in ngx.timer thread. Current workaround is to wait some interval of time (~100-500ms) after Set-Cookie header is sent to client before making subsequent requests. This is not a problem during session renewal period as renew happens in access phase.