// file included in the following:
//
// assembly-built-in-filters.adoc

[id='con-oauthbearer-{context}']
= OAUTHBEARER validation

[role="_abstract"]
OauthBearerValidation filter enables a validation on the JWT token received from client before forwarding it to cluster.

If the token is not validated, then the request is short-circuited.
It reduces resource consumption on the cluster when a client sends too many invalid SASL requests.

[a2s, format="svg"]
....
.----------------------------------------------------------------------------------------.
|                                                                                        |
|    '---------'                  '---------------'                  '----------'        |
|    |         |                  |               |                  |          |        |
|    | Client  |                  | Kroxylicious  |                  | Cluster  |        |
|    |         |                  |               |                  |          |        |
|    '---------'                  '---------------'                  '----------'        |
|         |                               |                                |             |
|         |      Handshake request        |                                |             |
|         |==============================>|   Forward handshake request    |             |
|         |                               |===============================>|             |
|         |                               |       Handshake response       |             |
|         |      Handshake response       |<===============================|             |
|         |<==============================|                                |             |
|         |                               |                                |             |
|         |                               |                                |             |
|         |   Authenticate request        |                                |             |
|         |==============================>|                                |             |
|         |                               |==+                             |             |
|         |                               |  : Validate Token              |             |
|         |                               |<=+                             |             |
|         |                               |                                |             |
| '=======|===============================|=='                             |             |
| :if     | [Validation fails]            |  :                             |             |
| :       |                               |  :                             |             |
| :       |       Invalid token           |  :                             |             |
| :       |<==============================|  :                             |             |
| :       |                               |  :                             |             |
| '=======|===============================|=='                             |             |
|         |                               |                                |             |
| '=======|===============================|================================|=='          |
| :if     | [Validation succeeds]         |                                |  :          |
| :       |                               |  Forward authenticate request  |  :          |
| :       |                               |===============================>|  :          |
| :       |                               |     Authenticate response      |  :          |
| :       |                               |<===============================|  :          |
| :       |   Authenticate response       |                                |  :          |
| :       |<==============================|                                |  :          |
| :       |                               |                                |  :          |
| '=======|===============================|================================|=='          |
|         |                               |                                |             |
|         |                               |                                |             |
|    '---------'                  '---------------'                  '----------'        |
|    |         |                  |               |                  |          |        |
|    | Client  |                  | Kroxylicious  |                  | Cluster  |        |
|    |         |                  |               |                  |          |        |
|    '---------'                  '---------------'                  '----------'        |
|                                                                                        |
.----------------------------------------------------------------------------------------.
[0,0]: {"fill":"#99d","a2s:delref":1}
....

== How to use the filter

There are two steps to using the filter.

1. <<Configuring virtual clusters>>
2. Configuring the filter within Kroxylicious.

=== Configuring the filter within Kroxylicious.

[source, yaml]
----
filters:
  - type: OauthBearerValidation
    config:
      jwksEndpointUrl: https://oauth/JWKS   #<1>
      jwksEndpointRefreshMs: 3600000        #<2>
      jwksEndpointRetryBackoffMs: 100       #<3>
      jwksEndpointRetryBackoffMaxMs: 10000  #<4>
      scopeClaimName: scope                 #<5>
      subClaimName: sub                     #<6>
      authenticateBackOffMaxMs: 60000       #<7>
      authenticateCacheMaxSize: 1000        #<8>
      expectedAudience: https://first.audience, https//second.audience #<9>
      expectedIssuer: https://your-domain.auth/ #<10>
----

<1> The OAuth/OIDC provider URL from which the provider's JWKS (JSON Web Key Set) can be retrieved.
<2> The (optional) value in milliseconds for the broker to wait between refreshing its JWKS (JSON Web Key Set) cache that contains the keys to verify the signature of the JWT.
<3> The (optional) value in milliseconds for the initial wait between JWKS (JSON Web Key Set) retrieval attempts from the external authentication provider.
<4> The (optional) value in milliseconds for the maximum wait between attempts to retrieve the JWKS (JSON Web Key Set) from the external authentication provider.
<5> This (optional) setting can provide a different name to use for the scope included in the JWT payload's claims.
<6> This (optional) setting can provide a different name to use for the subject included in the JWT payload's claims.
<7> The (optional) maximum value in milliseconds to limit the client sending authenticate request. Setting 0 will never limit the client. Otherwise, an exponential delay is added to each authenticate request until the authenticateBackOffMaxMs has been reached.
<8> The (optional) maximum number of failed tokens kept in cache.
<9> The (optional) comma-delimited setting for the broker to use to verify that the JWT was issued for one of the expected audiences.
<10> The (optional) setting for the broker to use to verify that the JWT was created by the expected issuer.

Note: OauthBearer config follows https://kafka.apache.org/documentation/#security_ssl[kafka's properties]