Filter requests based on header names

Uses: Kong Gateway decK

Deployment Platform:

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

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.

Enable the Pre-Function plugin

The Pre-Function plugin lets you execute Lua code that runs before other plugins in a particular phase. In this case, we’re using the plugin to look for a specific header, x-custom-auth.

The following example applies the Pre-Function plugin globally, in the access phase:

echo '
_format_version: "3.0"
plugins:
  - name: pre-function
    config:
      access:
      - |
        -- Get list of request headers
        local custom_auth = kong.request.get_header("x-custom-auth")
           -- Terminate request early if the custom authentication header
        -- does not exist
        if not custom_auth then
          return kong.response.exit(401, "Invalid Credentials")
        end
' | deck gateway apply -

      
        
      
    
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Validate

Let’s test that the code will terminate the request when no header is passed:

curl -i "$KONNECT_PROXY_URL/anything"

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You should get a 401 status code with the message Invalid Credentials.

Now, test the code by making a valid request with the x-custom-auth header:

curl -i "$KONNECT_PROXY_URL/anything" \
     -H "x-custom-auth: example"

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This time, the request will pass through and you’ll see a 200 response.

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.