Configuring Envoy as an edge proxy

Envoy is a production-ready edge proxy, however, the default settings are tailored for the service mesh use case, and some values need to be adjusted when using Envoy as an edge proxy.

TCP proxies should configure:

HTTP proxies should additionally configure:

If Envoy is configured with RBAC filter or makes route selection based on URL path it is recommended to enable the following path normalization options to minimize probability of path confusion vulnerabilities. Path confusion vulnerabilities occur when parties participating in request use different path representations.

Additionally the path_with_escaped_slashes_action setting should be set according to following recommendations:

  • REJECT_REQUEST if dowstream clients are expected to use RFC 3986 compliant normalized paths (i.e. gRPC clients).

  • UNESCAPE_AND_REDIRECT if downstream client supports HTTP redirect (i.e. a browser). This option minimizes possibility of path confusion by forcing request to be re-issued with the same path across all parties: downstream client, Envoy and upstream server. Note that gRPC requests will still be rejected with the INTERNAL (13) error code, as gRPC clients do not support redirect.

  • KEEP_UNCHANGED for servers that are not RFC 3986 compliant and require encoded slashes.

  • UNESCAPE_AND_FORWARD for servers that are known to treat escaped and unescaped slashes equivalently. Choosing this option may increase probablity of path confusion vulnerabilities if intermediaries perform path based access control.

The following is a YAML example of the above recommendation (taken from the Google VRP edge server configuration):

  1. overload_manager:
  2.   refresh_interval: 0.25s
  3.   resource_monitors:
  4.   - name: "envoy.resource_monitors.fixed_heap"
  5.     typed_config:
  6.       "@type": type.googleapis.com/envoy.extensions.resource_monitors.fixed_heap.v3.FixedHeapConfig
  7.       # TODO: Tune for your system.
  8.       max_heap_size_bytes: 2147483648  # 2 GiB
  9.   actions:
  10.   - name: "envoy.overload_actions.shrink_heap"
  11.     triggers:
  12.     - name: "envoy.resource_monitors.fixed_heap"
  13.       threshold:
  14.         value: 0.95
  15.   - name: "envoy.overload_actions.stop_accepting_requests"
  16.     triggers:
  17.     - name: "envoy.resource_monitors.fixed_heap"
  18.       threshold:
  19.         value: 0.98
  21. admin:
  22.   address:
  23.     socket_address:
  24.       address: 127.0.0.1
  25.       port_value: 9090
  27. static_resources:
  28.   listeners:
  29.   - address:
  30.       socket_address:
  31.         address: 0.0.0.0
  32.         port_value: 443
  33.     listener_filters:
  34.     - name: "envoy.filters.listener.tls_inspector"
  35.       typed_config:
  36.         "@type": type.googleapis.com/envoy.extensions.filters.listener.tls_inspector.v3.TlsInspector
  37.     # Uncomment if Envoy is behind a load balancer that exposes client IP address using the PROXY protocol.
  38.     # - name: envoy.filters.listener.proxy_protocol
  39.     #   typed_config:
  40.     #     "@type": type.googleapis.com/envoy.extensions.filters.listener.proxy_protocol.v3.ProxyProtocol
  41.     per_connection_buffer_limit_bytes: 32768  # 32 KiB
  42.     filter_chains:
  43.     - filter_chain_match:
  44.         server_names: ["example.com", "www.example.com"]
  45.       transport_socket:
  46.         name: envoy.transport_sockets.tls
  47.         typed_config:
  48.           "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext
  49.           common_tls_context:
  50.             tls_certificates:
  51.             - certificate_chain: {filename: "certs/servercert.pem"}
  52.               private_key: {filename: "certs/serverkey.pem"}
  53.             alpn_protocols: ["h2,http/1.1"]
  54.       filters:
  55.       - name: envoy.filters.network.http_connection_manager
  56.         typed_config:
  57.           "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
  58.           stat_prefix: ingress_http
  59.           use_remote_address: true
  60.           normalize_path: true
  61.           merge_slashes: true
  62.           path_with_escaped_slashes_action: UNESCAPE_AND_REDIRECT
  63.           common_http_protocol_options:
  64.             idle_timeout: 3600s  # 1 hour
  65.             headers_with_underscores_action: REJECT_REQUEST
  66.           http2_protocol_options:
  67.             max_concurrent_streams: 100
  68.             initial_stream_window_size: 65536  # 64 KiB
  69.             initial_connection_window_size: 1048576  # 1 MiB
  70.           stream_idle_timeout: 300s  # 5 mins, must be disabled for long-lived and streaming requests
  71.           request_timeout: 300s  # 5 mins, must be disabled for long-lived and streaming requests
  72.           http_filters:
  73.           - name: envoy.filters.http.router
  74.             typed_config:
  75.               "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
  76.           route_config:
  77.             virtual_hosts:
  78.             - name: default
  79.               domains: ["*"]
  80.               routes:
  81.               - match: {prefix: "/"}
  82.                 route:
  83.                   cluster: service_foo
  84.                   idle_timeout: 15s  # must be disabled for long-lived and streaming requests
  85.   clusters:
  86.   - name: service_foo
  87.     per_connection_buffer_limit_bytes: 32768  # 32 KiB
  88.     load_assignment:
  89.       cluster_name: some_service
  90.       endpoints:
  91.       - lb_endpoints:
  92.         - endpoint:
  93.             address:
  94.               socket_address:
  95.                 address: 127.0.0.1
  96.                 port_value: 8080
  97.     typed_extension_protocol_options:
  98.       envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
  99.         "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
  100.         explicit_http_config:
  101.           http2_protocol_options:
  102.             initial_stream_window_size: 65536  # 64 KiB
  103.             initial_connection_window_size: 1048576  # 1 MiB
  105. layered_runtime:
  106.   layers:
  107.   - name: static_layer_0
  108.     static_layer:
  109.       envoy:
  110.         resource_limits:
  111.           listener:
  112.             example_listener_name:
  113.               connection_limit: 10000
  114.       overload:
  115.         global_downstream_max_connections: 50000