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Esta é uma documentação não divulgada para Admission Controller 1.34-dev.

Validando políticas

O servidor de política SUSE Security Admission Controller recebe:

  • Kubernetes AdmissionReview objetos do servidor da API Kubernetes. Em seguida, ele encaminha o valor de seu atributo request, do tipo AdmissionRequest, para a política para avaliação.

Ou:

  • Um atributo JSON request contendo o documento de solicitação em formato livre, no caso de uma política bruta. Verifique a seção Políticas brutas para mais detalhes.

A política avalia o request e declara se deve aceitá-lo ou não. Quando a rejeição da solicitação ocorre, a política pode fornecer a mensagem de explicação e um código de erro para exibir ao usuário final.

Por convenção, do projeto policy-server, o convidado deve expor uma função chamada validate, através do SDK waPC guest, para que o policy-server (host waPC) possa invocá-la.

A função validate recebe um objeto JSON ValidationRequest e retorna um objeto JSON ValidationResponse.

O objeto ValidationRequest

O ValidationRequest é um objeto JSON recebido pela função validate. Ele se parece com:

{
  "request": <AdmissionReview.request data> | <RawReviewRequest.request data>,
  "settings": {
    # your policy configuration
  }
}

A chave settings aponta para um documento JSON em formato livre que contém as configurações específicas da política. O capítulo anterior focou em políticas e configurações.

Um exemplo

Dado o seguinte Kubernetes AdmissionReview:

Expanda para ver AdmissionReview 
{
  "apiVersion": "admission.k8s.io/v1",
  "kind": "AdmissionReview",
  "request": {
    # Random uid uniquely identifying this admission call
    "uid": "705ab4f5-6393-11e8-b7cc-42010a800002",

    # Fully-qualified group/version/kind of the incoming object
    "kind": {"group":"autoscaling","version":"v1","kind":"Scale"},
    # Fully-qualified group/version/kind of the resource being modified
    "resource": {"group":"apps","version":"v1","resource":"deployments"},
    # subresource, if the request is to a subresource
    "subResource": "scale",

    # Fully-qualified group/version/kind of the incoming object in the original request to the API server.
    # This only differs from `+kind+` if the webhook specified `+matchPolicy: Equivalent+` and the
    # original request to the API server was converted to a version the webhook registered for.
    "requestKind": {"group":"autoscaling","version":"v1","kind":"Scale"},
    # Fully-qualified group/version/kind of the resource being modified in the original request to the API server.
    # This only differs from `+resource+` if the webhook specified `+matchPolicy: Equivalent+` and the
    # original request to the API server was converted to a version the webhook registered for.
    "requestResource": {"group":"apps","version":"v1","resource":"deployments"},
    # subresource, if the request is to a subresource
    # This only differs from `+subResource+` if the webhook specified `+matchPolicy: Equivalent+` and the
    # original request to the API server was converted to a version the webhook registered for.
    "requestSubResource": "scale",

    # Name of the resource being modified
    "name": "my-deployment",
    # Namespace of the resource being modified, if the resource is namespaced (or is a Namespace object)
    "namespace": "my-namespace",

    # operation can be CREATE, UPDATE, DELETE, or CONNECT
    "operation": "UPDATE",

    "userInfo": {
      # Username of the authenticated user making the request to the API server
      "username": "admin",
      # UID of the authenticated user making the request to the API server
      "uid": "014fbff9a07c",
      # Group memberships of the authenticated user making the request to the API server
      "groups": ["system:authenticated","my-admin-group"],
      # Arbitrary extra info associated with the user making the request to the API server.
      # This is populated by the API server authentication layer and should be included
      # if any SubjectAccessReview checks are performed by the webhook.
      "extra": {
        "some-key":["some-value1", "some-value2"]
      }
    },

    # object is the new object being admitted.
    # It is null for DELETE operations.
    "object": {"apiVersion":"autoscaling/v1","kind":"Scale",...},
    # oldObject is the existing object.
    # It is null for CREATE and CONNECT operations.
    "oldObject": {"apiVersion":"autoscaling/v1","kind":"Scale",...},
    # options contains the options for the operation being admitted, like meta.k8s.io/v1 CreateOptions, UpdateOptions, or DeleteOptions.
    # It is null for CONNECT operations.
    "options": {"apiVersion":"meta.k8s.io/v1","kind":"UpdateOptions",...},

    # dryRun indicates the API request is running in dry run mode and will not be persisted.
    # Webhooks with side effects should avoid actuating those side effects when dryRun is true.
    # See http://k8s.io/docs/reference/using-api/api-concepts/#make-a-dry-run-request for more details.
    "dryRun": false
  }
}

O objeto ValidationRequest teria a seguinte aparência:

Expanda para ver o ValidationRequest 
{
  "request": {
    # Random uid uniquely identifying this admission call
    "uid": "705ab4f5-6393-11e8-b7cc-42010a800002",

    # Fully-qualified group/version/kind of the incoming object
    "kind": {"group":"autoscaling","version":"v1","kind":"Scale"},
    # Fully-qualified group/version/kind of the resource being modified
    "resource": {"group":"apps","version":"v1","resource":"deployments"},
    # subresource, if the request is to a subresource
    "subResource": "scale",

    # Fully-qualified group/version/kind of the incoming object in the original request to the API server.
    # This only differs from `+kind+` if the webhook specified `+matchPolicy: Equivalent+` and the
    # original request to the API server was converted to a version the webhook registered for.
    "requestKind": {"group":"autoscaling","version":"v1","kind":"Scale"},
    # Fully-qualified group/version/kind of the resource being modified in the original request to the API server.
    # This only differs from `+resource+` if the webhook specified `+matchPolicy: Equivalent+` and the
    # original request to the API server was converted to a version the webhook registered for.
    "requestResource": {"group":"apps","version":"v1","resource":"deployments"},
    # subresource, if the request is to a subresource
    # This only differs from `+subResource+` if the webhook specified `+matchPolicy: Equivalent+` and the
    # original request to the API server was converted to a version the webhook registered for.
    "requestSubResource": "scale",

    # Name of the resource being modified
    "name": "my-deployment",
    # Namespace of the resource being modified, if the resource is namespaced (or is a Namespace object)
    "namespace": "my-namespace",

    # operation can be CREATE, UPDATE, DELETE, or CONNECT
    "operation": "UPDATE",

    "userInfo": {
      # Username of the authenticated user making the request to the API server
      "username": "admin",
      # UID of the authenticated user making the request to the API server
      "uid": "014fbff9a07c",
      # Group memberships of the authenticated user making the request to the API server
      "groups": ["system:authenticated","my-admin-group"],
      # Arbitrary extra info associated with the user making the request to the API server.
      # This is populated by the API server authentication layer and should be included
      # if any SubjectAccessReview checks are performed by the webhook.
      "extra": {
        "some-key":["some-value1", "some-value2"]
      }
    },

    # object is the new object being admitted.
    # It is null for DELETE operations.
    "object": {"apiVersion":"autoscaling/v1","kind":"Scale",...},
    # oldObject is the existing object.
    # It is null for CREATE and CONNECT operations.
    "oldObject": {"apiVersion":"autoscaling/v1","kind":"Scale",...},
    # options contains the options for the operation being admitted, like meta.k8s.io/v1 CreateOptions, UpdateOptions, or DeleteOptions.
    # It is null for CONNECT operations.
    "options": {"apiVersion":"meta.k8s.io/v1","kind":"UpdateOptions",...},

    # dryRun indicates the API request is running in dry run mode and will not be persisted.
    # Webhooks with side effects should avoid actuating those side effects when dryRun is true.
    # See http://k8s.io/docs/reference/using-api/api-concepts/#make-a-dry-run-request for more details.
    "dryRun": false
  },
  "settings": {
    # policy settings
  }
}

O objeto ValidationResponse

A função validate retorna o resultado de sua validação usando um objeto ValidationResponse.

O ValidationResponse tem esta estrutura:

{
  # mandatory
  "accepted": <boolean>,

  # optional, ignored if accepted - recommended for rejections
  "message": <string>,

  # optional, ignored if accepted
  "code": <integer>,

  # optional, used by mutation policies
  "mutated_object": <string>
}

Você pode especificar esses atributos message e code quando a solicitação não for aceita. O message é um erro textual livre e code representa um código de erro HTTP.

O servidor da API do Kubernetes ignora os valores message e code na aceitação da solicitação.

Na negação da solicitação e se message ou code estiverem presentes, o servidor da API do Kubernetes retorna essas informações. As informações fazem parte do corpo do erro, e o servidor as retorna ao cliente da API do Kubernetes que fez a solicitação rejeitada.

O mutated_object é um campo opcional usado apenas por políticas de mutação. Este é o tópico do próximo capítulo.