Configure OpenID Connect with client credentials

Uses: Kong Gateway deck

Deployment Platform

konnect

on-prem

Prerequisites

Kong Konnect

This is a Konnect tutorial and requires a Konnect personal access token.

Create a new personal access token by opening the Konnect PAT page and selecting Generate Token.
Export your token to an environment variable:
```
 export KONNECT_TOKEN='YOUR_KONNECT_PAT'
```
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Run the quickstart script to automatically provision a Control Plane and Data Plane, and configure your environment:
```
 curl -Ls https://get.konghq.com/quickstart | bash -s -- -k $KONNECT_TOKEN --deck-output
```
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This sets up a Konnect Control Plane named quickstart, provisions a local Data Plane, and prints out the following environment variable exports:
```
 export DECK_KONNECT_TOKEN=$KONNECT_TOKEN
 export DECK_KONNECT_CONTROL_PLANE_NAME=quickstart
 export KONNECT_CONTROL_PLANE_URL=https://us.api.konghq.com
 export KONNECT_PROXY_URL='http://localhost:8000'
```
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Copy and paste these into your terminal to configure your session.

Kong Gateway running

This tutorial requires Kong Gateway Enterprise. If you don’t have Kong Gateway set up yet, you can use the quickstart script with an enterprise license to get an instance of Kong Gateway running almost instantly.

Export your license to an environment variable:

 export KONG_LICENSE_DATA='LICENSE-CONTENTS-GO-HERE'

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Run the quickstart script:

curl -Ls https://get.konghq.com/quickstart | bash -s -- -e KONG_LICENSE_DATA

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Once Kong Gateway is ready, you will see the following message:

 Kong Gateway Ready

decK v1.43+

decK is a CLI tool for managing Kong Gateway declaratively with state files. To complete this tutorial, install decK version 1.43 or later.

This guide uses deck gateway apply, which directly applies entity configuration to your Gateway instance. We recommend upgrading your decK installation to take advantage of this tool.

You can check your current decK version with deck version.

Required entities

For this tutorial, you’ll need Kong Gateway entities, like Gateway Services and Routes, pre-configured. These entities are essential for Kong Gateway to function but installing them isn’t the focus of this guide. Follow these steps to pre-configure them:

Run the following command:

echo '
_format_version: "3.0"
services:
  - name: example-service
    url: http://httpbin.konghq.com/anything
routes:
  - name: example-route
    paths:
    - "/anything"
    service:
      name: example-service
' | deck gateway apply -

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To learn more about entities, you can read our entities documentation.

Set up Keycloak

This tutorial requires an identity provider (IdP). If you don’t have one, you can use Keycloak. The steps will be similar in other standard identity providers.

Create a client

Install Keycloak (version 26 or later) on your platform.

For example, you can use the Keycloak Docker image:

 docker run -p 127.0.0.1:8080:8080 \
   -e KC_BOOTSTRAP_ADMIN_USERNAME=admin \
   -e KC_BOOTSTRAP_ADMIN_PASSWORD=admin \
   quay.io/keycloak/keycloak start-dev

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Open the admin console.

The default URL of the console is http://$YOUR_KEYCLOAK_HOST:8080/admin/master/console/.
In the sidebar, open Clients, then click Create client.
Configure the client:

Section	Settings
General settings	Client type: OpenID Connect Client ID: any unique name, for example `kong`
Capability config	Toggle Client authentication to on Make sure that Standard flow, Direct access grants, and Service accounts roles are checked.
Login settings	Valid redirect URIs: `http://localhost:8000/*`

Set up keys and credentials

In your client, open the Credentials tab.
Set Client Authenticator to Client ID and Secret.
Copy the Client Secret.
Switch to the Users menu and add a user.
Open the user’s Credentials tab and add a password. Be sure to disable Temporary Password.

In this guide, we’re going to use an example user named alex with the password doe.

Export to environment variables

Export your client secret, client ID, and issuer URL to environment variables so that you can pass them more securely. For example:

```bash export DECK_ISSUER="http://host.docker.internal:8080/realms/master" export DECK_CLIENT_ID="kong" export DECK_CLIENT_SECRET="UNT3GPzCKI7zUbhAmFSUGbj4wmiBDGiW" ```

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export DECK_ISSUER="http://host.docker.internal:8080/realms/master"
export DECK_CLIENT_ID="kong"
export DECK_CLIENT_SECRET="UNT3GPzCKI7zUbhAmFSUGbj4wmiBDGiW"

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Enable the OpenID Connect plugin with the client credentials grant

Using the Keycloak and Kong Gateway configuration from the prerequisites, set up an instance of the OpenID Connect plugin with the client credentials grant.

Enable the OpenID Connect plugin on the example-service Service:

echo '
_format_version: "3.0"
plugins:
  - name: openid-connect
    service: example-service
    config:
      issuer: "${{ env "DECK_ISSUER" }}"
      client_id:
      - "${{ env "DECK_CLIENT_ID" }}"
      client_secret:
      - "${{ env "DECK_CLIENT_SECRET" }}"
      client_auth:
      - client_secret_post
      auth_methods:
      - client_credentials
      client_credentials_param_type:
      - header
' | deck gateway apply -

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In this example:

issuer, client ID, client secret, and client auth: Settings that connect the plugin to your IdP (in this case, the sample Keycloak app).
auth_methods: Specifies that the plugin should use client credentials (client ID and secret) for authentication.
client_credentials_param_type: Restricts client credential lookup to request headers only.

Note: Setting config.client_auth to client_secret_post lets you easily test the connection to your IdP, but we recommend using a more secure auth method in production. You can use any of the supported client auth methods.

Validate the client credentials grant

Now, validate the setup by accessing the example-route Route using the credentials in client-id:client-secret format:

 curl  -i -X GET "$KONNECT_PROXY_URL/anything" \
     --no-progress-meter --fail-with-body  \
     -u $DECK_CLIENT_ID:$DECK_CLIENT_SECRET

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 curl  -i -X GET "http://localhost:8000/anything" \
     --no-progress-meter --fail-with-body  \
     -u $DECK_CLIENT_ID:$DECK_CLIENT_SECRET

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If Kong Gateway successfully authenticates with Keycloak, you’ll see a 200 response with your bearer token in the Authorization header.

If you make another request using the same credentials, you’ll see that Kong Gateway adds less latency to the request because it has cached the token endpoint call to Keycloak:

X-Kong-Proxy-Latency: 25

Cleanup

Clean up Konnect environment

If you created a new control plane and want to conserve your free trial credits or avoid unnecessary charges, delete the new control plane used in this tutorial.

Destroy the Kong Gateway container

curl -Ls https://get.konghq.com/quickstart | bash -s -- -d

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FAQs

Why does the OIDC plugin not use cached tokens with the client credentials grant, and instead connects to the IdP on every request?

Token caching doesn’t work if both client_credentials and password are set as auth methods in the config.auth_methods parameter, and credentials are sent using the Authorization: Basic header.

In this scenario, either authentication method could match, but the plugin prioritises the password grant. To resolve this caching issue, make sure you only have the client_credentials method enabled.

Configure OpenID Connect with client credentials

Prerequisites

Kong Konnect

Kong Gateway running

decK v1.43+

Required entities

Set up Keycloak

Create a client

Set up keys and credentials

Export to environment variables

Enable the OpenID Connect plugin with the client credentials grant

Validate the client credentials grant

Cleanup

Clean up Konnect environment

Destroy the Kong Gateway container

FAQs

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