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TLS Metadata Headers

The TLS Metadata Header plugin detects client certificates in requests, retrieves the TLS metadata, such as the URL encoded client certificate, and proxies this metadata via HTTP headers. This is useful when an upstream service performs some validation for the proxied TLS client certificate.

The plugin itself does not perform any validation on the client certificate.

Used in conjunction with any plugin which requests a client certificate, such as the mTLS Authentication or TLS Handshake Modifier plugins.

Configuration Reference

This plugin is compatible with DB-less mode.

In DB-less mode, you configure Kong Gateway declaratively. Therefore, the Admin API is mostly read-only. The only tasks it can perform are all related to handling the declarative config, including:

  • Setting a target's health status in the load balancer
  • Validating configurations against schemas
  • Uploading the declarative configuration using the /config endpoint

Example plugin configuration

The following examples provide some typical configurations for enabling the tls-metadata-headers plugin on a service.

Make the following request:

curl -X POST http://localhost:8001/services/SERVICE_NAME|SERVICE_ID/plugins \
    --data "name=tls-metadata-headers"  \
    --data "config.inject_client_cert_details=true" \
    --data "config.client_cert_header_name=X-Forwarded-Client-Cert"

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: tls-metadata-headers-example
config: 
  inject_client_cert_details: true
  client_cert_header_name: X-Forwarded-Client-Cert
plugin: tls-metadata-headers

Next, apply the KongPlugin resource to a service by annotating the service as follows:

apiVersion: v1
kind: Service
metadata:
  name: SERVICE_NAME|SERVICE_ID
  labels:
    app: SERVICE_NAME|SERVICE_ID
  annotations:
    konghq.com/plugins: tls-metadata-headers-example
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: SERVICE_NAME|SERVICE_ID
  selector:
    app: SERVICE_NAME|SERVICE_ID

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

Add this section to your declarative configuration file:

plugins:
- name: tls-metadata-headers
  service: SERVICE_NAME|SERVICE_ID
  config: 
    inject_client_cert_details: true
    client_cert_header_name: X-Forwarded-Client-Cert

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. From the Services section, click View for the service row.
  3. From the plugin section, click Add Plugin.
  4. Find and select the TLS Metadata Headers plugin.
    Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
  5. If the option is available, select Scoped.
  6. Add the service name and ID to the Service field if it is not already pre-filled.

  7. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Inject Client Cert Details: select checkbox
    • Config.Client Cert Header Name: X-Forwarded-Client-Cert
  8. Click Create.

The following examples provide some typical configurations for enabling the tls-metadata-headers plugin on a route.

Make the following request:

curl -X POST http://localhost:8001/routes/ROUTE_NAME|ROUTE_ID/plugins \
  --data "name=tls-metadata-headers"  \
    --data "config.inject_client_cert_details=true" \
    --data "config.client_cert_header_name=X-Forwarded-Client-Cert"

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: tls-metadata-headers-example
config: 
  inject_client_cert_details: true
  client_cert_header_name: X-Forwarded-Client-Cert
plugin: tls-metadata-headers

Then, apply it to an ingress (route or routes) by annotating the ingress as follows:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ROUTE_NAME|ROUTE_ID
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: tls-metadata-headers-example
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          service:
            name: echo
            port:
              number: 80

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

Add this section to your declarative configuration file:

plugins:
- name: tls-metadata-headers
  route: ROUTE_NAME
  config: 
    inject_client_cert_details: true
    client_cert_header_name: X-Forwarded-Client-Cert

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. Open Routes from the menu, then click View for the route row.
  3. From the plugin section, click Add Plugin.
  4. Find and select the TLS Metadata Headers plugin.
    Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
  5. If the option is available, select Scoped.
  6. Add the route ID if it is not already prefilled.

  7. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Inject Client Cert Details: select checkbox
    • Config.Client Cert Header Name: X-Forwarded-Client-Cert
  8. Click Create.

A plugin which is not associated to any service, route, or consumer is considered global, and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

The following examples provide some typical configurations for enabling the tls-metadata-headers plugin globally.

Make the following request:

curl -X POST http://localhost:8001/plugins/ \
  --data "name=tls-metadata-headers"  \
    --data "config.inject_client_cert_details=true" \
    --data "config.client_cert_header_name=X-Forwarded-Client-Cert"

Create a KongClusterPlugin resource and label it as global:

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: <global-tls-metadata-headers>
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: \"true\"
config: 
  inject_client_cert_details: true
  client_cert_header_name: X-Forwarded-Client-Cert
plugin: tls-metadata-headers

Add a plugins entry in the declarative configuration file:

plugins:
- name: tls-metadata-headers
  config: 
    inject_client_cert_details: true
    client_cert_header_name: X-Forwarded-Client-Cert

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. Open Plugins from the menu, then click New Plugin.
  3. Find and select the TLS Metadata Headers plugin.
    Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
  4. If the option is available, set the plugin scope to Global.

  5. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Inject Client Cert Details: select checkbox
    • Config.Client Cert Header Name: X-Forwarded-Client-Cert
  6. Click Create.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Form Parameter Description
name
required

Type: string		 The name of the plugin, in this case tls-metadata-headers.
service.name or service.id

Type: string		 The name or ID of the service the plugin targets.

Set one of these parameters if adding the plugin to a service through the top-level /plugins endpoint.

Not required if using /services/SERVICE_NAME|SERVICE_ID/plugins.
route.name or route.id

Type: string		 The name or ID of the route the plugin targets.

Set one of these parameters if adding the plugin to a route through the top-level /plugins endpoint.

Not required if using /routes/ROUTE_NAME|ROUTE_ID/plugins.
enabled

Type: boolean

Default value: true		 Whether this plugin will be applied.
config.inject_client_cert_details
required

Type: boolean

Default value: false

Enables TLS client certificate metadata values to be injected into HTTP headers.
config.client_cert_header_name
required

Type: string

Default value: X-Client-Cert

Define the HTTP header name used for the PEM format URL encoded client certificate.
config.client_serial_header_name
required

Type: string

Default value: X-Client-Cert-Serial

Define the HTTP header name used for the serial number of the client certificate.
config.client_cert_issuer_dn_header_name
required

Type: string

Default value: X-Client-Cert-Issuer-DN

Define the HTTP header name used for the issuer DN of the client certificate.
config.client_cert_subject_dn_header_name
required

Type: string

Default value: X-Client-Cert-Subject-DN

Define the HTTP header name used for the subject DN of the client certificate.
config.client_cert_fingerprint_header_name
required

Type: string

Default value: X-Client-Cert-Fingerprint

Define the HTTP header name used for the SHA1 fingerprint of the client certificate.

The plugin must be used in conjunction with any plugin which requests a client certificate, such as the mTLS Authentication or TLS Handshake Modifier plugins.