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JWT Verification

This example demonstrates how to verify the Pomerium JWT assertion header using Envoy. 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 verification.

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, is authenticated through authenticate.localhost.pomerium.io, 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 httpbin.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:

  1. Create a docker-compose.yaml file containing:

    docker-compose.yaml
    networks:
    frontend:
    driver: 'bridge'
    backend:
    driver: 'bridge'
    services:
    pomerium:
    image: cr.pomerium.com/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
  2. Using mkcert, generate a certificate for *.localhost.pomerium.io in a certs directory:

    mkdir certs
    cd certs
    mkcert '*.localhost.pomerium.io'
  3. 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):

    envoy.yaml
    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: httpbin.localhost.pomerium.io
    audiences:
    - httpbin.localhost.pomerium.io
    from_headers:
    - name: X-Pomerium-Jwt-Assertion
    remote_jwks:
    http_uri:
    uri: https://httpbin.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.

Audience and issuer claims

Pomerium uses the claims provided by the identity provider's JWT to populate the audience and issuer claims in the attestation JWT.

Audience is the URL of the target upstream application. The aud claim defines what application the JWT is intended for.

Issuer is the URL of the domain that issued the JWT. The iss claim tells the target upstream application who the issuing authority is and provides context about the subject.

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

    pomerium.yaml
    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:

  1. Turn on the example configuration in Docker:

    docker-compose up
  2. Visit httpbin.localhost.pomerium.io. Login and you will be redirected to the httpbin page.

  3. In this network configuration you cannot access httpbin directly. However, visiting Envoy directly via localhost.pomerium.io:10000/ will return a Jwt is missing error, confirming that you must authenticate with Pomerium to access Envoy, and any services accessible through it.