Module: LittleGhost::Network::EnvoyConfig

Defined in:
lib/little_ghost/network/envoy_config.rb

Overview

Builds Envoy v3 configuration for exact-destination CONNECT filtering and optional TLS-intercepted external authorization.

Constant Summary collapse

TYPE_URL =

:nodoc:

"type.googleapis.com/"
DOMAIN = 
/\A(?:[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\z/
BLOCKED_DESTINATIONS = 
[
  ["0.0.0.0", 8], ["10.0.0.0", 8], ["100.64.0.0", 10], ["127.0.0.0", 8],
  ["169.254.0.0", 16], ["172.16.0.0", 12], ["192.0.0.0", 24], ["192.0.2.0", 24],
  ["192.168.0.0", 16], ["198.18.0.0", 15], ["198.51.100.0", 24],
  ["203.0.113.0", 24], ["224.0.0.0", 4], ["240.0.0.0", 4],
  ["::", 128], ["::1", 128], ["::ffff:0:0", 96], ["64:ff9b::", 96],
  ["64:ff9b:1::", 48], ["100::", 64], ["2001::", 23], ["2002::", 16],
  ["fc00::", 7], ["fec0::", 10], ["fe80::", 10], ["ff00::", 8]
].freeze

Class Method Summary collapse

Class Method Details

.authorizer_filter(forward_headers, mutation_headers) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 273

def authorizer_filter(forward_headers, mutation_headers)
  patterns = Array(forward_headers).map { |name| {"exact" => name} }
  authorization_request = patterns.empty? ? {} : {"allowed_headers" => {"patterns" => patterns}}
  authorization_response = {
    "allowed_client_headers" => {"patterns" => [{"exact" => "content-type"}]}
  }
  unless mutation_headers.empty?
    authorization_response["allowed_upstream_headers"] = {
      "patterns" => mutation_headers.map { |name| {"exact" => name} }
    }
  end
  {
    "name" => "envoy.filters.http.ext_authz",
    "typed_config" => typed(
      "envoy.extensions.filters.http.ext_authz.v3.ExtAuthz",
      failure_mode_allow: false,
      status_on_error: {code: "ServiceUnavailable"},
      validate_mutations: true,
      disallowed_headers: {
        "patterns" => %w[authorization proxy-authorization cookie].map { |name| {"exact" => name} }
      },
      http_service: {
        "server_uri" => {
          "uri" => "http://little-ghost-authorizer",
          "cluster" => "little_ghost_authorizer",
          "timeout" => "5s"
        },
        "authorization_request" => authorization_request,
        "authorization_response" => authorization_response
      }
    )
  }
end

.build(policy:, listener:, paths: {}) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 24

def build(policy:, listener:, paths: {})
  endpoints = endpoints(policy.allow)
  if policy.inspection == :http
    build_http(policy:, endpoints:, listener:, paths:)
  else
    build_connect(endpoints:, listener:, access_log: paths[:access_log])
  end
end

.build_connect(endpoints:, listener:, access_log: nil) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 54

def build_connect(endpoints:, listener:, access_log: nil)
  routes = endpoints.map do |host, port|
    {
      "match" => {
        "connect_matcher" => {},
        "headers" => [{"name" => ":authority", "string_match" => {"exact" => "#{host}:#{port}"}}]
      },
      "route" => {
        "cluster" => "little_ghost_egress",
        "timeout" => "0s",
        "upgrade_configs" => [{"upgrade_type" => "CONNECT", "connect_config" => {}}]
      }
    }
  end
  routes << {"match" => {"connect_matcher" => {}}, "direct_response" => {"status" => 403}}
  routes << {"match" => {"prefix" => "/"}, "direct_response" => {"status" => 403}}
  filters = [dynamic_forward_proxy_filter, router_filter]
  {
    "static_resources" => {
      "listeners" => [http_listener(
        name: "little_ghost_explicit_proxy",
        address: listener,
        route_config: route_config("little_ghost_connect", routes),
        filters:,
        connect: true,
        access_log:
      )],
      "clusters" => [dynamic_forward_proxy_cluster(tls: false)]
    }
  }
end

.build_http(policy:, endpoints:, listener:, paths:) ⇒ Object

Raises:



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# File 'lib/little_ghost/network/envoy_config.rb', line 86

def build_http(policy:, endpoints:, listener:, paths:)
  unless endpoints.all? { |_host, port| port == 443 }
    raise PolicyError, "HTTP inspection supports only TLS destinations on port 443"
  end
  required = %i[interceptor_socket authorizer_socket certificate_chain private_key trusted_ca]
  missing = required.reject { |name| paths[name] }
  raise PolicyError, "HTTP inspection is missing #{missing.join(", ")}" unless missing.empty?
  raise PolicyError, "HTTP inspection requires an authorizer" unless policy.authorizer

  outer_routes = endpoints.map do |host, port|
    {
      "match" => {
        "connect_matcher" => {},
        "headers" => [{"name" => ":authority", "string_match" => {"exact" => "#{host}:#{port}"}}]
      },
      "route" => {
        "cluster" => "little_ghost_tls_interceptor",
        "timeout" => "0s",
        "upgrade_configs" => [{"upgrade_type" => "CONNECT", "connect_config" => {}}]
      }
    }
  end
  outer_routes << {"match" => {"connect_matcher" => {}}, "direct_response" => {"status" => 403}}
  outer_routes << {"match" => {"prefix" => "/"}, "direct_response" => {"status" => 403}}
  inner_virtual_hosts = endpoints.map do |host, port|
    {
      "name" => "host_#{host.tr(".-", "__")}",
      "domains" => [host, "#{host}:#{port}"],
      "routes" => [{
        "match" => {"prefix" => "/"},
        "route" => {"cluster" => "little_ghost_egress", "timeout" => "0s"},
        "typed_per_filter_config" => {
          "envoy.filters.http.dynamic_forward_proxy" => typed(
            "envoy.extensions.filters.http.dynamic_forward_proxy.v3.PerRouteConfig",
            host_rewrite_literal: host
          )
        },
        "response_headers_to_remove" => ["set-cookie", "set-cookie2"]
      }]
    }
  end
  interceptor_listener = {
    "name" => "little_ghost_tls_interceptor",
    "address" => pipe_address(paths.fetch(:interceptor_socket), 0o600),
    "filter_chains" => [{
      "transport_socket" => {
        "name" => "envoy.transport_sockets.tls",
        "typed_config" => typed(
          "envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext",
          common_tls_context: {
            "tls_params" => {"tls_minimum_protocol_version" => "TLSv1_2"},
            "tls_certificates" => [{
              "certificate_chain" => {"filename" => paths.fetch(:certificate_chain)},
              "private_key" => {"filename" => paths.fetch(:private_key)}
            }]
          }
        )
      },
      "filters" => [{
        "name" => "envoy.filters.network.http_connection_manager",
        "typed_config" => hcm(
          route_config: {
            "name" => "little_ghost_upstream_routes",
            "virtual_hosts" => inner_virtual_hosts
          },
          filters: [authorizer_filter(policy.forward_headers, policy.mutation_headers), dynamic_forward_proxy_filter, router_filter],
          access_log: paths[:access_log]
        )
      }]
    }]
  }
  {
    "static_resources" => {
      "listeners" => [
        http_listener(
          name: "little_ghost_explicit_proxy",
          address: listener,
          route_config: route_config("little_ghost_connect", outer_routes),
          filters: [router_filter],
          connect: true
        ),
        interceptor_listener
      ],
      "clusters" => [
        unix_cluster("little_ghost_tls_interceptor", paths.fetch(:interceptor_socket)),
        unix_cluster("little_ghost_authorizer", paths.fetch(:authorizer_socket)),
        dynamic_forward_proxy_cluster(tls: true, trusted_ca: paths.fetch(:trusted_ca))
      ]
    }
  }
end

.dns_cache_config ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 178

def dns_cache_config
  {
    "name" => "little_ghost_egress_dns",
    "dns_lookup_family" => "ALL",
    "max_hosts" => 256,
    "dns_query_timeout" => "5s",
    "dns_cache_circuit_breaker" => {"max_pending_requests" => 64},
    "resolved_address_filter" => {
      "ranges" => BLOCKED_DESTINATIONS.map do |address, prefix|
        {"address_prefix" => address, "prefix_len" => prefix}
      end
    }
  }
end

.dynamic_forward_proxy_cluster(tls:, trusted_ca: nil) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 193

def dynamic_forward_proxy_cluster(tls:, trusted_ca: nil)
  cluster = {
    "name" => "little_ghost_egress",
    "connect_timeout" => "15s",
    "lb_policy" => "CLUSTER_PROVIDED",
    "circuit_breakers" => {
      "thresholds" => [{
        "priority" => "DEFAULT",
        "max_connections" => 128,
        "max_pending_requests" => 128,
        "max_requests" => 256,
        "max_retries" => 0
      }]
    },
    "cluster_type" => {
      "name" => "envoy.clusters.dynamic_forward_proxy",
      "typed_config" => typed(
        "envoy.extensions.clusters.dynamic_forward_proxy.v3.ClusterConfig",
        dns_cache_config: dns_cache_config
      )
    }
  }
  if tls
    cluster["transport_socket"] = {
      "name" => "envoy.transport_sockets.tls",
      "typed_config" => typed(
        "envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext",
        common_tls_context: {
          "tls_params" => {"tls_minimum_protocol_version" => "TLSv1_2"},
          "validation_context" => {"trusted_ca" => {"filename" => trusted_ca}}
        }
      )
    }
  end
  cluster
end

.dynamic_forward_proxy_filter ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 307

def dynamic_forward_proxy_filter
  {
    "name" => "envoy.filters.http.dynamic_forward_proxy",
    "typed_config" => typed(
      "envoy.extensions.filters.http.dynamic_forward_proxy.v3.FilterConfig",
      dns_cache_config: dns_cache_config
    )
  }
end

.endpoints(values) ⇒ Object

Raises:



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# File 'lib/little_ghost/network/envoy_config.rb', line 33

def endpoints(values)
  parsed = Array(values).map { |value| parse_endpoint(value) }
  raise PolicyError, "network allowlist must contain at least one destination" if parsed.empty?
  raise PolicyError, "network allowlist destinations must be unique" if parsed.uniq.length != parsed.length

  parsed.freeze
end

.hcm(route_config:, filters:, connect: false, access_log: nil) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 245

def hcm(route_config:, filters:, connect: false, access_log: nil)
  config = typed(
    "envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager",
    stat_prefix: "little_ghost_egress",
    codec_type: "AUTO",
    max_request_headers_kb: 8,
    stream_error_on_invalid_http_message: true,
    route_config:,
    http_filters: filters
  )
  config["upgrade_configs"] = [{"upgrade_type" => "CONNECT"}] if connect
  if access_log
    config["access_log"] = [{
      "name" => "envoy.access_loggers.file",
      "typed_config" => typed(
        "envoy.extensions.access_loggers.file.v3.FileAccessLog",
        path: access_log,
        log_format: {
          "text_format_source" => {
            "inline_string" => "%START_TIME% %REQ(:METHOD)% %REQ(:AUTHORITY)% %RESPONSE_CODE% %RESPONSE_FLAGS% %UPSTREAM_HOST% %BYTES_RECEIVED% %BYTES_SENT% %DURATION%\n"
          }
        }
      )
    }]
  end
  config
end

.http_listener(name:, address:, route_config:, filters:, connect: false, access_log: nil) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 230

def http_listener(name:, address:, route_config:, filters:, connect: false, access_log: nil)
  {
    "name" => name,
    "address" => address,
    "listener_filters" => [{
      "name" => "envoy.filters.listener.http_inspector",
      "typed_config" => typed("envoy.extensions.filters.listener.http_inspector.v3.HttpInspector")
    }],
    "filter_chains" => [{"filters" => [{
      "name" => "envoy.filters.network.http_connection_manager",
      "typed_config" => hcm(route_config:, filters:, connect:, access_log:)
    }]}]
  }
end

.ip_address?(value) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/little_ghost/network/envoy_config.rb', line 354

def ip_address?(value)
  IPAddr.new(value)
  true
rescue IPAddr::InvalidAddressError
  false
end

.parse_endpoint(value) ⇒ Object

Raises:



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# File 'lib/little_ghost/network/envoy_config.rb', line 41

def parse_endpoint(value)
  supplied = String(value)
  match = supplied.match(/\A(.+):(\d+)\z/)
  raise PolicyError, "network allowlist entries must use exact host:port syntax" unless match

  host = match[1]
  port = Integer(match[2], 10)
  unless DOMAIN.match?(host) && host == host.downcase && !ip_address?(host) && port.between?(1, 65_535)
    raise PolicyError, "network allowlist entries must use exact lowercase DNS names and valid ports"
  end
  [host.freeze, port].freeze
end

.pipe_address(path, mode = 0o600) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 342

def pipe_address(path, mode = 0o600)
  {"pipe" => {"path" => path, "mode" => mode}}
end

.route_config(name, routes) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 324

def route_config(name, routes)
  {"name" => name, "virtual_hosts" => [{"name" => name, "domains" => ["*"], "routes" => routes}]}
end

.router_filter ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 317

def router_filter
  {
    "name" => "envoy.filters.http.router",
    "typed_config" => typed("envoy.extensions.filters.http.router.v3.Router")
  }
end

.socket_address(host, port) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 346

def socket_address(host, port)
  {"socket_address" => {"address" => host, "port_value" => port}}
end

.typed(name, **values) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 350

def typed(name, **values)
  {"@type" => "#{TYPE_URL}#{name}", **values.transform_keys(&:to_s)}
end

.unix_cluster(name, path) ⇒ Object 



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# File 'lib/little_ghost/network/envoy_config.rb', line 328

def unix_cluster(name, path)
  {
    "name" => name,
    "type" => "STATIC",
    "connect_timeout" => "5s",
    "load_assignment" => {
      "cluster_name" => name,
      "endpoints" => [{
        "lb_endpoints" => [{"endpoint" => {"address" => {"pipe" => {"path" => path}}}}]
      }]
    }
  }
end