# JWT Verification

This example demonstrates how to verify the Pomerium JWT assertion header (opens new window) using Envoy (opens new window). This is useful for legacy or 3rd party applications which can't be modified to perform verification themselves.

This guide is a practical demonstration of some of the topics discussed in Mutual Authentication: A Component of Zero Trust.

# Requirements

This guide assumes you already have a working IdP connection to provide user data. See our Identity Provider docs for more information.

# Overview

Three services are configured in a docker-compose.yaml file:

pomerium running an all-in-one deployment of Pomerium on *.localhost.pomerium.io
envoy-jwt-checker running envoy with a JWT Authn filter
httpbin as our example legacy application without JWT verifivation.

In our Docker Compose configuration we'll define two networks. pomerium and envoy-jwt-checker will be on the frontend network, simulating your local area network (LAN). envoy-jwt-checker will also be on the backend network, along with httpbin. This means that envoy-jwt-checker is the only other service that can communicate with httpbin.

For a detailed explanation of this security model, see Mutual Authentication With a Sidecar

Once running, the user visits verify.localhost.pomerium.io (opens new window), is authenticated through authenticate.localhost.pomerium.io (opens new window), and then the HTTP request is sent to envoy which proxies it to the httpbin app.

Before allowing the request Envoy will verify the signed JWT assertion header using the public key defined by authenticate.localhost.pomerium.io/.well-known/pomerium/jwks.json.

# Setup

The configuration presented here assumes a working route to the domain space *.localhost.pomerium.io. You can make entries in your hosts file for the domains used, or change this value to match your local environment.

TIP

Mac and Linux users can use DNSMasq to map the *.localhost.pomerium.io domain (including all subdomains) to a specified test address:

Create a docker-compose.yaml file containing:

version: "3.9"
networks:
  frontend:
    driver: "bridge"
  backend:
    driver: "bridge"
services:
  pomerium:
    image: pomerium/pomerium:latest
    ports:
      - "443:443"
    volumes:
      - type: bind
        source: ./cfg/pomerium.yaml
        target: /pomerium/config.yaml
      - type: bind
        source: ./certs/_wildcard.localhost.pomerium.io.pem
        target: /pomerium/_wildcard.localhost.pomerium.io.pem
      - type: bind
        source: ./certs/_wildcard.localhost.pomerium.io-key.pem
        target: /pomerium/_wildcard.localhost.pomerium.io-key.pem
    networks:
      - frontend

  envoy-jwt-checker:
    image: envoyproxy/envoy:v1.17.1
    ports:
      - "10000:10000"
    volumes:
      - type: bind
        source: ./cfg/envoy.yaml
        target: /etc/envoy/envoy.yaml
    networks:
      frontend:
        aliases:
          - "httpbin-sidecar"
      backend:

  httpbin:
    image: kennethreitz/httpbin
    ports:
      - "80:80"
    networks:
      - backend

Using mkcert (opens new window), generate a certificate for *.localhost.pomerium.io in a certs directory:
```
mkdir certs
cd certs
mkcert '*.localhost.pomerium.io'
```

Create a cfg directory containing the following envoy.yaml file. Envoy configuration can be quite verbose, but the crucial bit is the HTTP filter (highlighted below):

admin:
  access_log_path: /dev/null
  address:
    socket_address: { address: 127.0.0.1, port_value: 9901 }

static_resources:
  listeners:
    - name: ingress-http
      address:
        socket_address: { address: 0.0.0.0, port_value: 10000 }
      filter_chains:
        - filters:
            - name: envoy.filters.network.http_connection_manager
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
                stat_prefix: ingress_http
                codec_type: AUTO
                route_config:
                  name: verify
                  virtual_hosts:
                    - name: httpbin
                      domains: ["httpbin-sidecar"]
                      routes:
                        - match:
                            prefix: "/"
                          route:
                            cluster: egress-httpbin
                            auto_host_rewrite: true
                http_filters:
                  - name: envoy.filters.http.jwt_authn
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.filters.http.jwt_authn.v3.JwtAuthentication
                      providers:
                        pomerium:
                          issuer: authenticate.localhost.pomerium.io
                          audiences:
                            - httpbin.localhost.pomerium.io
                          from_headers:
                            - name: X-Pomerium-Jwt-Assertion
                          remote_jwks:
                            http_uri:
                              uri: https://authenticate.localhost.pomerium.io/.well-known/pomerium/jwks.json
                              cluster: egress-authenticate
                              timeout: 1s
                      rules:
                        - match:
                            prefix: /
                          requires:
                            provider_name: pomerium
                  - name: envoy.filters.http.router
  clusters:
    - name: egress-httpbin
      connect_timeout: 0.25s
      type: STRICT_DNS
      lb_policy: ROUND_ROBIN
      load_assignment:
        cluster_name: httpbin
        endpoints:
          - lb_endpoints:
              - endpoint:
                  address:
                    socket_address:
                      address: httpbin
                      port_value: 80
    - name: egress-authenticate
      connect_timeout: '0.25s'
      type: STRICT_DNS
      lb_policy: ROUND_ROBIN
      load_assignment:
        cluster_name: authenticate
        endpoints:
          - lb_endpoints:
              - endpoint:
                  address:
                    socket_address:
                      address: pomerium
                      port_value: 443
      transport_socket:
        name: tls
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext
          sni: authenticate.localhost.pomerium.io

This configuration pulls the JWT out of the X-Pomerium-Jwt-Assertion header, verifies the iss and aud claims and checks the signature via the public key defined at the jwks.json endpoint. Documentation for additional configuration options is available here: Envoy JWT Authentication (opens new window).

Create a pomerium.yaml file in the cfg directory containing:

authenticate_service_url: https://authenticate.localhost.pomerium.io

certificate_file: "/pomerium/_wildcard.localhost.pomerium.io.pem"
certificate_key_file: "/pomerium/_wildcard.localhost.pomerium.io-key.pem"

idp_provider: google
idp_client_id: REPLACE_ME
idp_client_secret: REPLACE_ME

cookie_secret: REPLACE_ME
shared_secret: REPLACE_ME
signing_key: REPLACE_ME

routes:
  - from: https://httpbin.localhost.pomerium.io
    to: http://httpbin-sidecar:10000
    pass_identity_headers: true
    policy:
      - allow:
          or:
            - domain:
                is: example.com

Replace the identity provider credentials, secrets, and signing key. Adjust the policy to match your configuration.

# Run

You should now be able to run the example with:

Turn on the example configuration in Docker:
```
docker-compose up
```
Visit httpbin.localhost.pomerium.io (opens new window). Login and you will be redirected to the httpbin page.
In this network configuration you cannot access httpbin directly. However, visiting Envoy directly via localhost.pomerium.io:10000/ (opens new window) will return a Jwt is missing error, confirming that you must authenticate with Pomerium to access Envoy, and any services accessible through it.

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