GCP Authentication filter client (https://blog.salrashid.dev/articles/2022/envoy_gcp_authn/ )

client_tmpl.yaml

admin:
  access_log_path: /dev/null
  address:
    socket_address:
      address: 127.0.0.1
      port_value: 19000
node:
  cluster: service_greeter
  id: test-id
static_resources:
  listeners:
  - name: listener_0
    address:
      socket_address: { address: 0.0.0.0, port_value: 8080 }
    filter_chains:
    - filters:
      - name: envoy.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: local_route
            virtual_hosts:
              - name: backend
                domains:
                  - "server.c.$PROJECT_ID.internal"
                routes:
                  - match:
                      prefix: "/get"
                    route:
                      cluster: service_b                            
          http_filters:
          - name: envoy.filters.http.gcp_authn
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.http.gcp_authn.v3.GcpAuthnFilterConfig          
              http_uri: 
                uri: "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/identity?audience=[AUDIENCE]"
                cluster: metadata_server
                timeout: 1s
          - name: envoy.filters.http.router
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
                      
  clusters:
  - name: metadata_server
    type: STRICT_DNS
    dns_lookup_family: V4_ONLY
    connect_timeout: 2s
    lb_policy: ROUND_ROBIN   
    load_assignment:
      cluster_name: metadata_server
      endpoints:
      - lb_endpoints:
        - endpoint:     
            address:
              socket_address:
                address:  metadata.google.internal
                port_value: 80  
  - name: service_b
    type: LOGICAL_DNS
    dns_lookup_family: V4_ONLY
    connect_timeout: 2s
    lb_policy: ROUND_ROBIN
    metadata:
      typed_filter_metadata:
        envoy.filters.http.gcp_authn:
          "@type": type.googleapis.com/envoy.extensions.filters.http.gcp_authn.v3.Audience
          url: "server.c.$PROJECT_ID.internal"       
    load_assignment:
      cluster_name: service_b
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address:
                address: server.c.$PROJECT_ID.internal
                port_value: 10000
    transport_socket:
      name: envoy.transport_sockets.alts
      typed_config:
        "@type": type.googleapis.com/envoy.extensions.transport_sockets.alts.v3.Alts
        handshaker_service: "169.254.169.254:8080"
        peer_service_accounts:
        - "$SERVER_SERVICE_ACCOUNT"