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Introspection authentication flow
As with JWT Access Token Authentication, the introspection authentication relies on a bearer token that the client has already gotten from somewhere. The difference to stateless JWT authentication is that the plugin needs to call the introspection endpoint of the identity provider to find out whether the token is valid and active. This makes it possible to issue opaque tokens to the clients.
sequenceDiagram autonumber participant client as Client
(e.g. mobile app) participant kong as API Gateway
(Kong) participant idp as IDP
(e.g. Keycloak) participant httpbin as Upstream
(backend service,
e.g. httpbin) activate client activate kong client->>kong: service with access token deactivate client kong->>kong: load access token activate idp kong->>idp: keycloak/introspect with
client credentials and access token deactivate kong idp->>idp: authenticate client
and introspect access token activate kong idp->>kong: return introspection response deactivate idp kong->>kong: verify introspection response activate httpbin kong->>httpbin: request with
access token httpbin->>kong: response deactivate httpbin activate client kong->>client: response deactivate kong deactivate client
Prerequisites
In most cases, the OpenID Connect plugin relies on a third party identity provider (IdP). The examples in this guide use Keycloak as a sample IdP.
Expand the following sections to configure Keycloak and Kong Gateway.
Configure Keycloak
All the *.test
domains in the following examples point to the localhost
(127.0.0.1
and/or ::1
).
We use Keycloak as the identity provider in the following examples, but the steps will be similar in other standard identity providers. If you encounter difficulties during this phase, refer to the Keycloak documentation.
- Create a confidential client
kong
withprivate_key_jwt
authentication and configure Keycloak to download the public keys from [the OpenID Connect Plugin JWKS endpoint][json-web-key-set]:
-
Create another confidential client
service
withclient_secret_basic
authentication. For this client, Keycloak will auto-generate a secret similar to the following:cf4c655a-0622-4ce6-a0de-d3353ef0b714
. Enable the client credentials grant for the client:
-
(Optional) Create another confidential client
cert-bound
with settings similar to theservice
client created previously. From the Advanced tab, enable the OAuth 2.0 Mutual TLS Certificate Bound Access Tokens Enabled toggle. -
(Optional, to test mTLS Client Authentication) Create another confidential client
client-tls-auth
with settings similar to theservice
client created above. From the Credentials tab, select the X509 Certificate Client Authenticator and fill the Subject DN field so that it matches the Kong client certificate’s, e.g.:CN=JohnDoe, OU=IT
. -
(Optional, to test Demonstrating Proof-of-Possession Client Authentication) Create another confidential client
client-dpop-auth
with settings similar to theservice
client created above. From the Advanced tab, enable theOAuth 2.0 DPoP Bound Access Tokens Enabled toggle. - Create a verified user with the name:
john
and the non-temporary password:doe
that can be used with the password grant:
Alternatively you can download the exported Keycloak configuration, and use it to configure the Keycloak. Please refer to Keycloak import documentation for more information.
You need to modify Keycloak standalone.xml
configuration file, and change the socket binding from:
<socket-binding name="https" port="${jboss.https.port:8443}"/>
to
<socket-binding name="https" port="${jboss.https.port:8440}"/>
The Keycloak default https
port conflicts with the default Kong TLS proxy port,
and that can be a problem if both are started on the same host.
Note: The mTLS Client Authentication, along with the proof of possession feature that validates OAuth 2.0 Mutual TLS Certificate Bound Access Tokens, both require configuring Keycloak to validate client certificates with mTLS using the
--https-client-auth=request
option, and to configure TLS appropriately, including adding the trusted client certificates to the truststore. For more information, refer to the Keycloak documentation.
Configure Kong Gateway
-
Create a service:
curl -i -X POST http://localhost:8001/services \ --data "name=openid-connect" \ --data "url=https://httpbin.konghq.com/anything"
-
Create a route:
curl -i -X POST http://localhost:8001/services/openid-connect/routes \ --data "name=openid-connect" \ --data "paths[]=/"
Set up introspection authentication
The following examples are built with simplicity in mind, and are not meant for a production environment. Because
httpbin.konghq.com
is the upstream service in these examples, we highly recommended that you do not run these examples with a production identity provider as there is a high chance of leaking information. The examples also use the plain HTTP protocol, which you should never use in production.
Using the Keycloak and Kong Gateway configuration from the prerequisites, set up an instance of the OpenID Connect plugin with introspection authentication.
For the demo, we’re going to set up the following:
- Issuer, client ID, and client auth: settings that connect the plugin to your IdP (in this case, the sample Keycloak app).
- Auth method: you only need introspection authentication for this flow. For the purposes of the demo, the example also enables the password grant.
- We want to only search headers for the bearer token for introspection.
With all of the above in mind, let’s test out the introspection auth flow with Keycloak.
Enable the OpenID Connect plugin on the openid-connect
service:
Test the introspection authentication
At this point you have created a service, routed traffic to the service, and enabled the OpenID Connect plugin on the service. You can now test the introspection auth flow.
-
Check the discovery cache:
curl -i -X GET http://localhost:8001/openid-connect/issuers
It should contain Keycloak OpenID Connect discovery document and the keys.
-
Request the service with a bearer token:
curl -I http://localhost:8000/openid-connect \ -H "Authorization: \ \"$(curl --user john:doe http://localhost:8000/openid-connect \ | jq -r .headers.Authorization)\""
or:
curl -I http://localhost:8000/openid-connect -H "Authorization: Bearer <access-token>"