If you are reporting any crash or any potential security issue, do not
open an issue in this repo. Please report the issue via emailing
envoy-security@googlegroups.com where the issue will be triaged appropriately.

Title: Oauth2 extention not work

Description:
Hi All:
When I try to follow the instruction (https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/oauth2_filter), to test Oauth2 functionality, but I met the challenge about below when I start envoy, any idea about this? and would like to know what kind of hmac_secret i need to provide. Thx

[2020-09-09 12:02:32.681][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:98] #20: [0x563ac830b885]
[2020-09-09 12:02:32.681][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:98] #21: [0x563ac76a1dab]
[2020-09-09 12:02:32.681][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:98] #22: [0x563ac76a14cd]
[2020-09-09 12:02:32.682][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:98] #23: [0x563ac76a23c2]
[2020-09-09 12:02:32.682][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:98] #24: [0x563ac76a2783]
[2020-09-09 12:02:32.682][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:98] #25: [0x563ac76a0f9c]
[2020-09-09 12:02:32.682][14][critical][backtrace] [bazel-out/k8-opt/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:96] #26: __libc_start_main [0x7f7a631e1b97]
Segmentation fault

[optional Relevant Links:]

Any extra documentation required to understand the issue.

This is my yaml file setting:

admin:
access_log_path: /tmp/admin_access.log
address:
socket_address: { address: 127.0.0.1, port_value: 9901 }

static_resources:
listeners:

• name: listener_0
  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: local_route
      virtual_hosts:
      - name: local_service
      domains: ["*"]
      routes:
      - match: { prefix: "/" }
      route: { cluster: auth }
      http_filters:
      - name: auth
      typed_config:
      "@type": type.googleapis.com/envoy.extensions.filters.http.oauth2.v3alpha.OAuth2
      config:
      token_endpoint:
      cluster: auth
      uri: authorization-server.com/token
      timeout: 3s
      authorization_endpoint: https://authorization-server.com/authorize
      redirect_uri: "https://www.oauth.com/playground/oidc.html"
      redirect_path_matcher:
      path:
      exact: /callback
      signout_path:
      path:
      exact: /signout
      credentials:
      client_id: <client_id from Oauth website>
      token_secret:
      name:
      hmac_secret:
      name: hmac
      # timeout: 3s
      - name: envoy.filters.http.router

clusters:

• name: some_service
  connect_timeout: 0.25s
  type: STATIC
  lb_policy: ROUND_ROBIN
  load_assignment:
  cluster_name: some_service
  endpoints:
  • lb_endpoints:
    • endpoint:
      address:
      socket_address:
      address: 0.0.0.0
      port_value: 1234
• name: auth
  connect_timeout: 5s
  type: LOGICAL_DNS
  lb_policy: ROUND_ROBIN
  load_assignment:
  cluster_name: auth
  endpoints:
  • lb_endpoints:
    • endpoint:
      address: { socket_address: { address: www.oauth.com, port_value: 443 }}
      tls_context: { sni: www.oauth.com }