WIP: admission webhooks

Signed-off-by: Sergey Vasilyev <nolar@nolar.info>

README.md

@@ -47,6 +47,8 @@ the same packages, the same developer(s).
   * Dynamically generated or conditional sub-handlers (an advanced feature).
   * Timers that tick as long as the resource exists, optionally with a delay since the last change.
   * Daemons that run as long as the resource exists (in threads or asyncio-tasks).
+  * Validating and mutating admission webhook (with dev-mode tunneling).
+  * Live in-memory indexing of resources or their excerpts.
   * Filtering with stealth mode (no logging): by arbitrary filtering functions,
     by labels/annotations with values, presence/absence, or dynamic callbacks.
   * In-memory all-purpose containers to store non-serializable objects for individual resources.

docs/deployment-rbac.yaml

@@ -24,6 +24,11 @@ rules:
     resources: [namespaces]
     verbs: [list, watch]
 
+  # Framework: admission webhook configuration management.
+  - apiGroups: [admissionregistration.k8s.io/v1, admissionregistration.k8s.io/v1beta1]
+    resources: [validatingwebhookconfigurations, mutatingwebhookconfigurations]
+    verbs: [create, patch]
+
   # Application: read-only access for watching cluster-wide.
   - apiGroups: [kopf.dev]
     resources: [kopfexamples]

docs/index.rst

@@ -39,6 +39,7 @@ Kopf: Kubernetes Operators Framework
    scopes
    memos
    indexing
+   admission
 
 .. toctree::
    :maxdepth: 2

docs/kwargs.rst

@@ -261,3 +261,75 @@ Its ``.wait()`` method can be used to replace ``time.sleep()``
 or ``asyncio.sleep()`` for faster (instant) termination on resource deletion.
 
 See more: :doc:`daemons`.
+
+
+Resource admission kwargs
+=========================
+
+.. kwarg:: dryrun
+
+Dry run
+-------
+
+Admission handlers, both validating and mutating, must skip any side effects
+if ``dryrun`` is ``True``. It is ``True`` when a dry-run API request is made,
+e.g. with ``kubectl --dry-run=server ...``.
+
+Regardless of ``dryrun`, the handlers must not make any side effects
+unless they declare themselves as ``side_effects=True``.
+
+See more: :doc:`admission`.
+
+
+.. kwarg:: warnings
+
+Admission warnings
+------------------
+
+``warnings`` (``list[str]``) is a **mutable** list of string used as warnings.
+The admission webhook handlers can populate the list with warnings (strings),
+and the webhook servers/tunnels return them to Kubernetes, which shows them
+to ``kubectl``.
+
+See more: :doc:`admission`.
+
+
+.. kwarg:: userinfo
+
+User information
+----------------
+
+``userinfo`` (``Mapping[str, Any]``) is an information about a user that
+sends the API request to Kubernetes.
+
+It usually contains the keys ``'username'``, ``'uid'``, ``'groups'``,
+but this might change in the future. The information is provided exactly
+as Kubernetes sends it in the admission request.
+
+See more: :doc:`admission`.
+
+
+.. kwarg:: headers
+.. kwarg:: sslpeer
+
+Request credentials
+-------------------
+
+For rudimentary authentication and authorization, Kopf passes the information
+from the admission requests to the admission handlers as is,
+without additional interpretation of it.
+
+``headers`` (``Mapping[str, str]``) contains all HTTPS request headers,
+including ``Authorization: Basic ...``, ``Authorization: Bearer ...``.
+
+``sslpeer`` (``Mapping[str, Any]``) contains the SSL peer information
+as returned by `ssl.SSLSocket.getpeercert`. It is ``None`` if no proper
+SSL client certificate was provided (i.e. by apiservers talking to webhooks),
+or if the SSL protocol could not verify the provided certificate with its CA.
+
+.. note::
+    This is an identity of the apiservers that send the admission request,
+    not of the user or an app that sends the API request to Kubernetes.
+    For the user's identity, use :kwarg:`userinfo`.
+
+See more: :doc:`admission`.

examples/17-admission/example.py

@@ -0,0 +1,53 @@
+import pathlib
+
+import kopf
+
+
+@kopf.on.startup()
+def config(settings: kopf.OperatorSettings, **_):
+    ROOT = (pathlib.Path.cwd() / pathlib.Path(__file__)).parent.parent.parent
+    settings.admission.managed = 'auto.kopf.dev'
+    # settings.admission.server = kopf.WebhookServer()
+    # settings.admission.server = kopf.WebhookServer(certfile=ROOT/'cert.pem', pkeyfile=ROOT/'key.pem', port=1234)
+    # settings.admission.server = kopf.WebhookK3dServer(certfile=ROOT/'k3d-cert.pem', pkeyfile=ROOT/'k3d-key.pem', port=1234)
+    # settings.admission.server = kopf.WebhookK3dServer(port=1234, cadump=ROOT/'ca.pem', verify_cafile=ROOT/'client-cert.pem')
+    settings.admission.server = kopf.WebhookK3dServer(cadump=ROOT/'ca.pem')
+    # settings.admission.server = kopf.WebhookNgrokTunnel()
+    # settings.admission.server = kopf.WebhookNgrokTunnel(binary="/usr/local/bin/ngrok", token='...', port=1234)
+    # settings.admission.server = kopf.WebhookNgrokTunnel(binary="/usr/local/bin/ngrok", port=1234, path='/xyz', region='eu')
+    # settings.admission.server = kopf.WebhookInletsTunnel(...)
+
+
+@kopf.on.validation('kex', persisted=True, field='spec.field2', value='value')
+def validate1(spec, dryrun, **_):
+    print(f'{dryrun=}')
+    if spec.get('field') == 'value':
+        raise kopf.AdmissionError("Meh! I don't like it. Change the field.")
+
+
+@kopf.on.validation('kex')
+def authhook(headers, sslpeer, warnings, **_):
+    print(f'{headers=}')
+    print(f'{sslpeer=}')
+    if not sslpeer:
+        warnings.append("SSL peer is not identified.")
+    else:
+        common_name = None
+        for key, val in sslpeer['subject'][0]:
+            if key == 'commonName':
+                common_name = val
+                break
+        else:
+            warnings.append("SSL peer's common name is absent.")
+        if common_name is not None:
+            warnings.append(f"SSL peer is {common_name}.")
+
+
+@kopf.on.validation('kex')
+def validate2(**_):
+    raise kopf.AdmissionError("I'm too lazy anyway. Go away!", status=555)
+
+
+@kopf.on.mutation('kex')
+def mutate1(patch: kopf.Patch, **_):
+    patch.spec['injected'] = 123

kopf/__init__.py

@@ -32,6 +32,9 @@
 from kopf.reactor import (
     lifecycles,  # as a separate name on the public namespace
 )
+from kopf.reactor.admission import (
+    AdmissionError,
+)
 from kopf.reactor.handling import (
     TemporaryError,
     PermanentError,
@@ -130,6 +133,14 @@
     Resource,
     EVERYTHING,
 )
+from kopf.structs.reviews import (
+    WebhookClientConfigService,
+    WebhookClientConfig,
+    Operation,
+    UserInfo,
+    WebhookFn,
+    WebhookServerProtocol,
+)
 from kopf.toolkits.hierarchies import (
     adopt,
     label,
@@ -138,6 +149,13 @@
     append_owner_reference,
     remove_owner_reference,
 )
+from kopf.toolkits.webhooks import (
+    WebhookServer,
+    WebhookK3dServer,
+    WebhookMinikubeServer,
+    WebhookNgrokTunnel,
+    WebhookInletsTunnel,
+)
 from kopf.utilities.piggybacking import (
     login_via_pykube,
     login_via_client,
@@ -158,6 +176,18 @@
     'build_object_reference', 'build_owner_reference',
     'append_owner_reference', 'remove_owner_reference',
     'ErrorsMode',
+    'AdmissionError',
+    'WebhookClientConfigService',
+    'WebhookClientConfig',
+    'Operation',
+    'UserInfo',
+    'WebhookFn',
+    'WebhookServerProtocol',
+    'WebhookServer',
+    'WebhookK3dServer',
+    'WebhookMinikubeServer',
+    'WebhookNgrokTunnel',
+    'WebhookInletsTunnel',
     'PermanentError',
     'TemporaryError',
     'HandlerTimeoutError',

kopf/clients/creating.py

@@ -0,0 +1,33 @@
+from typing import Optional
+
+from kopf.clients import auth, errors
+from kopf.structs import bodies, references
+
+
+@auth.reauthenticated_request
+async def create_obj(
+        *,
+        resource: references.Resource,
+        namespace: references.Namespace = None,
+        name: Optional[str] = None,
+        body: Optional[bodies.RawBody] = None,
+        context: Optional[auth.APIContext] = None,  # injected by the decorator
+) -> Optional[bodies.RawBody]:
+    """
+    TODO
+    """
+    if context is None:
+        raise RuntimeError("API instance is not injected by the decorator.")
+
+    body = body if body is not None else {}
+    if namespace is not None:
+        body.setdefault('metadata', {}).setdefault('namespace', namespace)
+    if name is not None:
+        body.setdefault('metadata', {}).setdefault('name', name)
+
+    response = await context.session.post(
+        url=resource.get_url(server=context.server, namespace=namespace),
+        json=body,
+    )
+    created_body: bodies.RawBody = await errors.parse_response(response)
+    return created_body

kopf/clients/errors.py

@@ -101,6 +101,10 @@ class APINotFoundError(APIError):
     pass
 
 
+class APIConflictError(APIError):
+    pass
+
+
 async def check_response(
         response: aiohttp.ClientResponse,
 ) -> None:
@@ -124,6 +128,7 @@ async def check_response(
             APIUnauthorizedError if response.status == 401 else
             APIForbiddenError if response.status == 403 else
             APINotFoundError if response.status == 404 else
+            APIConflictError if response.status == 409 else
             APIError
         )