Configure OpenID Connect with client credentials

Uses: Kong Gateway decK
TL;DR

Using the OpenID Connect plugin, set up the client credentials grant flow to connect to an identity provider (IdP) by passing a client ID and client secret in a header.

Prerequisites

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

  1. Create a new personal access token by opening the Konnect PAT page and selecting Generate Token.

  2. Export your token to an environment variable:

     export KONNECT_TOKEN='YOUR_KONNECT_PAT'
    
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  3. 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.

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" \
     -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

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.

FAQs

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