OAuth2

  • v3 API reference

  • This filter should be configured with the name envoy.filters.http.oauth2.

The OAuth filter’s flow involves:

  • An unauthenticated user arrives at myapp.com, and the oauth filter redirects them to the authorization_endpoint for login. The client_id and the redirect_uri are sent as query string parameters in this first redirect.

  • After a successful login, the authn server should be configured to redirect the user back to the redirect_uri provided in the query string in the first step. In the below code example, we choose /callback as the configured match path. An “authorization grant” is included in the query string for this second redirect.

  • Using this new grant and the token_secret, the filter then attempts to retrieve an access token from the token_endpoint. The filter knows it has to do this instead of reinitiating another login because the incoming request has a path that matches the redirect_path_matcher criteria.

  • Upon receiving an access token, the filter sets cookies so that subseqeuent requests can skip the full flow. These cookies are calculated using the hmac_secret to assist in encoding.

  • The filter calls continueDecoding() to unblock the filter chain.

When the authn server validates the client and returns an authorization token back to the OAuth filter, no matter what format that token is, if forward_bearer_token is set to true the filter will send over a cookie named BearerToken to the upstream. Additionally, the Authorization header will be populated with the same value.

Attention

The OAuth2 filter is currently under active development.

Example configuration

The following is an example configuring the filter.

config:
  token_endpoint:
    cluster: oauth
    uri: oauth.com/token
    timeout: 3s
  authorization_endpoint: https://oauth.com/oauth/authorize/
  redirect_uri: "%REQ(:x-forwarded-proto)%://%REQ(:authority)%/callback"
  redirect_path_matcher:
    path:
      exact: /callback
  signout_path:
    path:
      exact: /signout
  credentials:
    client_id: foo
    token_secret:
      name: token
      sds_config:
        path: "/etc/envoy/token-secret.yaml"
    hmac_secret:
      name: hmac
      sds_config:
        path: "/etc/envoy/hmac.yaml"

Below is a complete code example of how we employ the filter as one of HttpConnectionManager HTTP filters

static_resources:
  listeners:
  - name:
    address:
  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
        http_filters:
        - name: envoy.filters.http.oauth2
          typed_config:
            "@type": type.googleapis.com/envoy.extensions.filters.http.oauth2.v3alpha.OAuth2
            config:
              token_endpoint:
                cluster: oauth
                uri: oauth.com/token
                timeout: 3s
              authorization_endpoint: https://oauth.com/oauth/authorize/
              redirect_uri: "%REQ(:x-forwarded-proto)%://%REQ(:authority)%/callback"
              redirect_path_matcher:
                path:
                  exact: /callback
              signout_path:
                path:
                  exact: /signout
              credentials:
                client_id: foo
                token_secret:
                  name: token
                  sds_config:
                    path: "/etc/envoy/token-secret.yaml"
                hmac_secret:
                  name: hmac
                  sds_config:
                    path: "/etc/envoy/hmac.yaml"
        - name: envoy.router
        tracing: {}
        codec_type: "AUTO"
        stat_prefix: ingress_http
        route_config:
          virtual_hosts:
          - name: service
            domains: ["*"]
            routes:
            - match:
                prefix: "/"
              route:
                cluster: service
                timeout: 5s

clusters:
- name: service
  connect_timeout: 5s
  type: STATIC
  lb_policy: ROUND_ROBIN
  load_assignment:
    cluster_name: service
    endpoints:
    - lb_endpoints:
      - endpoint:
          address:
            socket_address:
              address: 127.0.0.1
              port_value: 8080
- 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: auth.example.com
              port_value: 443
  tls_context:
    sni: auth.example.com

Finally, the following code block illustrates sample contents inside a yaml file containing both credential secrets. Both the token_secret and the hmac_secret can be defined in one shared file.

static_resources:
  secrets:
  - name: token
    generic_secret:
      secret: <Your token secret here>
  - name: hmac
    generic_secret:
      secret: <Your hmac secret here>

Notes

When enabled, the OAuth filter does not protect against Cross-Site-Request-Forgery attacks on domains with cached authentication (in the form of cookies). It is recommended to pair this filter with the CSRF Filter to prevent malicious social engineering.

The service must be served over HTTPS for this filter to work properly, as the cookies use ;secure. Without https, your authorization_endpoint provider will likely reject the incoming request, and your access cookies will not be cached to bypass future logins.

The signout path will redirect the current user to ‘/’, and clear all authentication cookies related to the HMAC validation. Consequently, the OAuth filter will then restart the full OAuth flow at the root path, sending the user to the configured auth endpoint.

pass_through_matcher provides an interface for users to provide specific header matching criteria such that, when applicable, the OAuth flow is entirely skipped. When this occurs, the oauth_success metric is still incremented.

Generally, allowlisting is inadvisable from a security standpoint.

Statistics

The OAuth2 filter outputs statistics in the <stat_prefix>. namespace.

Name

Type

Description

oauth_failure

Counter

Total requests that were denied.

oauth_success

Counter

Total requests that were allowed.

oauth_unauthorization_rq

Counter

Total unauthorized requests.