External Authorization

• External authorization architecture overview

• This filter should be configured with the type URL type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthz.

• HTTP filter v3 API reference

The external authorization filter calls an external gRPC or HTTP service to check whether an incoming HTTP request is authorized or not. If the request is deemed unauthorized, then the request will be denied normally with 403 (Forbidden) response. Note that sending additional custom metadata from the authorization service to the upstream, to the downstream or to the authorization service is also possible. This is explained in more details at HTTP filter.

The content of the requests that are passed to an authorization service is specified by CheckRequest.

The HTTP filter, using a gRPC/HTTP service, can be configured as follows. You can see all the configuration options at HTTP filter.

Configuration Examples

A sample filter configuration for a gRPC authorization server:

http_filters:
  - name: envoy.filters.http.ext_authz
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthz
      grpc_service:
        envoy_grpc:
          cluster_name: ext-authz

        # Default is 200ms; override if your server needs e.g. warmup time.
        timeout: 0.5s
      include_peer_certificate: true

clusters:
  - name: ext-authz
    type: static
    typed_extension_protocol_options:
      envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
        "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
        explicit_http_config:
          http2_protocol_options: {}
    load_assignment:
      cluster_name: ext-authz
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address:
                address: 127.0.0.1
                port_value: 10003

    # This timeout controls the initial TCP handshake timeout - not the timeout for the
    # entire request.
    connect_timeout: 0.25s

Note

One of the features of this filter is to send HTTP request body to the configured gRPC authorization server as part of the check request.

A sample configuration is as follows:

http_filters:
  - name: envoy.filters.http.ext_authz
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthz
      grpc_service:
        envoy_grpc:
          cluster_name: ext-authz
      with_request_body:
        max_request_bytes: 1024
        allow_partial_message: true
        pack_as_bytes: true

Please note that by default check request carries the HTTP request body as UTF-8 string and it fills the body field. To pack the request body as raw bytes, it is needed to set pack_as_bytes field to true. In effect to that, the raw_body field will be set and body field will be empty.

A sample filter configuration for a raw HTTP authorization server:

http_filters:
  - name: envoy.filters.http.ext_authz
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthz
      http_service:
          server_uri:
            uri: 127.0.0.1:10003
            cluster: ext-authz
            timeout: 0.25s
            failure_mode_allow: false
      include_peer_certificate: true

clusters:
  - name: ext-authz
    connect_timeout: 0.25s
    type: logical_dns
    lb_policy: round_robin
    load_assignment:
      cluster_name: ext-authz
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address:
                address: 127.0.0.1
                port_value: 10003

Per-Route Configuration

A sample virtual host and route filter configuration. In this example we add additional context on the virtual host, and disabled the filter for /static prefixed routes.

route_config:
  name: local_route
  virtual_hosts:
  - name: local_service
    domains: ["*"]
    typed_per_filter_config:
      envoy.filters.http.ext_authz:
        "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthzPerRoute
        check_settings:
          context_extensions:
            virtual_host: local_service
    routes:
    - match: { prefix: "/static" }
      route: { cluster: some_service }
      typed_per_filter_config:
        envoy.filters.http.ext_authz:
          "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthzPerRoute
          disabled: true
    - match: { prefix: "/" }
      route: { cluster: some_service }

Statistics

The HTTP filter outputs statistics in the cluster.<route target cluster>.ext_authz. namespace.

Name	Type	Description
ok	Counter	Total responses from the filter.
error	Counter	Total errors contacting the external service.
denied	Counter	Total responses from the authorizations service that were to deny the traffic.
disabled	Counter	Total requests that are allowed without calling external services due to the filter is disabled.
failure_mode_allowed	Counter	Total requests that were error(s) but were allowed through because of failure_mode_allow set to true.

Dynamic Metadata

The External Authorization filter supports emitting dynamic metadata as an opaque google.protobuf.Struct.

When using a gRPC authorization server, dynamic metadata will be emitted only when the CheckResponse contains a filled dynamic_metadata field.

When using an HTTP authorization server, dynamic metadata will be emitted only when there are response headers from the authorization server that match the configured dynamic_metadata_from_headers, if set. For every response header that matches, the filter will emit dynamic metadata whose key is the name of the matched header and whose value is the value of the matched header.

Both the HTTP and gRPC external authorization filters support a dynamic metadata field called ext_authz_duration which records the time it takes to complete an authorization request in milliseconds. This field will not be populated if the request does not complete.

Runtime

The fraction of requests for which the filter is enabled can be configured via the runtime_key value of the filter_enabled field.

Tracing

The ext_authz span keeps the sampling status of the parent span, i.e. in the tracing backend we will either see both the parent span and the child ext_authz span, or none of them.