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Edge Stack2.2External Filter
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External Filter
The External Filter calls out to an external service speaking the
ext_authz protocol, providing
a highly flexible interface to plug in your own authentication,
authorization, and filtering logic.
Example
The External spec is identical to the AuthService
spec, with the following
exceptions:
- In an
AuthService, thetlsfield must be a string referring to aTLSContext. In anExternalFilter, it may only be a Boolean; referring to aTLSContextis not supported. - In an
AuthService, the default value of theadd_linkerd_headersfield is based on theambassadorModule. In anExternalFilter, the default value is alwaysfalse. ExternalFilterslack thestats_name,protocol_version, andadd_auth_headersfields thatAuthServiceshave.
Fields
auth_service is the only required field, all others are optional.
| Attribute | Default value | Description |
|---|---|---|
auth_service | (none; a value is required) | Identifies the external auth service to talk to. The format of this field is scheme://host:port where scheme:// and :port are optional. The scheme-part, if present, must be either http:// or https://; if the scheme-part is not present, it behaves as if http:// is given. The scheme-part influences the default value of the tls field and the default value of the port-part. The host-part must be the namespace-qualified DNS name of the service you want to use for authentication. |
tls | true if auth_service starts with "https://" | Controls whether to use TLS or cleartext when speaking to the external auth service. The default is based on the scheme-part of the auth_service. |
proto | http | Specifies which variant of the ext_authz protocol to use when communicating with the external auth service. Valid options are http or grpc. |
timeout_ms | 5000 | The total maximum duration in milliseconds for the request to the external auth service, before triggering status_on_error or failure_mode_allow. |
include_body | null | Controls how much to buffer the request body to pass to the external auth service, for use cases such as computing an HMAC or request signature. If include_body is null or unset, then the request body is not buffered at all, and an empty body is passed to the external auth service. If include_body is not null, the max_bytes and allow_partial subfields are required. Unfortunately, in order for include_body to function properly, the AuthService in aes.yaml must be edited to have include_body set with max_bytes greater than the largest max_bytes used by any External Filter (so if an External Filter has max_bytes: 4096, then the AuthService will need max_bytes: 4097), and allow_partial: true. |
include_body.max_bytes | (none; a value is required if include_body is not null) | Controls the amount of body data that is passed to the external auth service. |
include_body.allow_partial | (none; a value is required if include_body is not null) | Controls what happens to requests with bodies larger than max_bytes. If allow_partial is true, the first max_bytes of the body are sent to the external auth service. If false, the message is rejected with HTTP 413 ("Payload Too Large"). |
status_on_error.code | 403 | Controls the status code returned when unable to communicate with external auth service. This is ignored if failure_mode_allow: true. |
failure_mode_allow | false | Controls whether to allow or reject requests when there is an error communicating with the external auth service; a value of true allows the request through to the upstream backend service, a value of false returns a status_on_error.code response to the client. |
The following fields are only used if proto is set to http. They
are ignored if proto is grpc.
| Attribute | Default value | Description |
|---|---|---|
path_prefix | "" | Prepends a string to the request path of the request when sending it to the external auth service. By default this is empty, and nothing is prepended. For example, if the client makes a request to /foo, and path_prefix: /bar, then the path in the request made to the external auth service will be /foo/bar. |
allowed_request_headers | [] | Lists the headers (case-insensitive) that are copied from the incoming request to the request made to the external auth service. In addition to the headers listed in this field, the following headers are always included: Authorization, Cookie, From, Proxy-Authorization, User-Agent, X-Forwarded-For, X-Forwarded-Host, and X-Forwarded-Proto. |
allowed_authorization_headers | [] | Lists the headers (case-insensitive) that are copied from the response from the external auth service to the request sent to the upstream backend service (if the external auth service indicates that the request to the upstream backend service should be allowed). In addition to the headers listed in this field, the following headers are always included: Authorization, Location, Proxy-Authenticate, Set-cookie, WWW-Authenticate |
add_linkerd_headers | false | When true, in the request to the external auth service, adds an l5d-dst-override HTTP header that is set to the hostname and port number of the external auth service. |