ValidatingAdmissionPolicy: support namespace access (#118267)

* Support namespace access from cel expression in validatingadmissionpolicy.

* Whitelist the exposed fields in namespace object and add test

* better handling of cluster-scoped resources.

* [API REVIEW] namespaceObject in Expression doc.

* compatibility with composition.

* generated: ./hack/update-codegen.sh && ./hack/update-openapi-spec.sh

* workaround namespace of namespace is unexpectedly set.

* basic test coverage for namespaceObject.

---------

Co-authored-by: Jiahui Feng <jhf@google.com>

api/openapi-spec/v3/apis__admissionregistration.k8s.io__v1alpha1_openapi.json

@@ -552,7 +552,7 @@
         "properties": {
           "expression": {
             "default": "",
-            "description": "Expression represents the expression which will be evaluated by CEL. ref: https://github.com/google/cel-spec CEL expressions have access to the contents of the API request/response, organized into CEL variables as well as some other useful variables:\n\n- 'object' - The object from the incoming request. The value is null for DELETE requests. - 'oldObject' - The existing object. The value is null for CREATE requests. - 'request' - Attributes of the API request([ref](/pkg/apis/admission/types.go#AdmissionRequest)). - 'params' - Parameter resource referred to by the policy binding being evaluated. Only populated if the policy has a ParamKind. - 'variables' - Map of composited variables, from its name to its lazily evaluated value.\n  For example, a variable named 'foo' can be accessed as 'variables.foo'.\n- 'authorizer' - A CEL Authorizer. May be used to perform authorization checks for the principal (user or service account) of the request.\n  See https://pkg.go.dev/k8s.io/apiserver/pkg/cel/library#Authz\n- 'authorizer.requestResource' - A CEL ResourceCheck constructed from the 'authorizer' and configured with the\n  request resource.\n\nThe `apiVersion`, `kind`, `metadata.name` and `metadata.generateName` are always accessible from the root of the object. No other metadata properties are accessible.\n\nOnly property names of the form `[a-zA-Z_.-/][a-zA-Z0-9_.-/]*` are accessible. Accessible property names are escaped according to the following rules when accessed in the expression: - '__' escapes to '__underscores__' - '.' escapes to '__dot__' - '-' escapes to '__dash__' - '/' escapes to '__slash__' - Property names that exactly match a CEL RESERVED keyword escape to '__{keyword}__'. The keywords are:\n\t  \"true\", \"false\", \"null\", \"in\", \"as\", \"break\", \"const\", \"continue\", \"else\", \"for\", \"function\", \"if\",\n\t  \"import\", \"let\", \"loop\", \"package\", \"namespace\", \"return\".\nExamples:\n  - Expression accessing a property named \"namespace\": {\"Expression\": \"object.__namespace__ > 0\"}\n  - Expression accessing a property named \"x-prop\": {\"Expression\": \"object.x__dash__prop > 0\"}\n  - Expression accessing a property named \"redact__d\": {\"Expression\": \"object.redact__underscores__d > 0\"}\n\nEquality on arrays with list type of 'set' or 'map' ignores element order, i.e. [1, 2] == [2, 1]. Concatenation on arrays with x-kubernetes-list-type use the semantics of the list type:\n  - 'set': `X + Y` performs a union where the array positions of all elements in `X` are preserved and\n    non-intersecting elements in `Y` are appended, retaining their partial order.\n  - 'map': `X + Y` performs a merge where the array positions of all keys in `X` are preserved but the values\n    are overwritten by values in `Y` when the key sets of `X` and `Y` intersect. Elements in `Y` with\n    non-intersecting keys are appended, retaining their partial order.\nRequired.",
+            "description": "Expression represents the expression which will be evaluated by CEL. ref: https://github.com/google/cel-spec CEL expressions have access to the contents of the API request/response, organized into CEL variables as well as some other useful variables:\n\n- 'object' - The object from the incoming request. The value is null for DELETE requests. - 'oldObject' - The existing object. The value is null for CREATE requests. - 'request' - Attributes of the API request([ref](/pkg/apis/admission/types.go#AdmissionRequest)). - 'params' - Parameter resource referred to by the policy binding being evaluated. Only populated if the policy has a ParamKind. - 'namespaceObject' - The namespace object that the incoming object belongs to. The value is null for cluster-scoped resources. - 'variables' - Map of composited variables, from its name to its lazily evaluated value.\n  For example, a variable named 'foo' can be accessed as 'variables.foo'.\n- 'authorizer' - A CEL Authorizer. May be used to perform authorization checks for the principal (user or service account) of the request.\n  See https://pkg.go.dev/k8s.io/apiserver/pkg/cel/library#Authz\n- 'authorizer.requestResource' - A CEL ResourceCheck constructed from the 'authorizer' and configured with the\n  request resource.\n\nThe `apiVersion`, `kind`, `metadata.name` and `metadata.generateName` are always accessible from the root of the object. No other metadata properties are accessible.\n\nOnly property names of the form `[a-zA-Z_.-/][a-zA-Z0-9_.-/]*` are accessible. Accessible property names are escaped according to the following rules when accessed in the expression: - '__' escapes to '__underscores__' - '.' escapes to '__dot__' - '-' escapes to '__dash__' - '/' escapes to '__slash__' - Property names that exactly match a CEL RESERVED keyword escape to '__{keyword}__'. The keywords are:\n\t  \"true\", \"false\", \"null\", \"in\", \"as\", \"break\", \"const\", \"continue\", \"else\", \"for\", \"function\", \"if\",\n\t  \"import\", \"let\", \"loop\", \"package\", \"namespace\", \"return\".\nExamples:\n  - Expression accessing a property named \"namespace\": {\"Expression\": \"object.__namespace__ > 0\"}\n  - Expression accessing a property named \"x-prop\": {\"Expression\": \"object.x__dash__prop > 0\"}\n  - Expression accessing a property named \"redact__d\": {\"Expression\": \"object.redact__underscores__d > 0\"}\n\nEquality on arrays with list type of 'set' or 'map' ignores element order, i.e. [1, 2] == [2, 1]. Concatenation on arrays with x-kubernetes-list-type use the semantics of the list type:\n  - 'set': `X + Y` performs a union where the array positions of all elements in `X` are preserved and\n    non-intersecting elements in `Y` are appended, retaining their partial order.\n  - 'map': `X + Y` performs a merge where the array positions of all keys in `X` are preserved but the values\n    are overwritten by values in `Y` when the key sets of `X` and `Y` intersect. Elements in `Y` with\n    non-intersecting keys are appended, retaining their partial order.\nRequired.",
             "type": "string"
           },
           "message": {

pkg/apis/admissionregistration/types.go

@@ -281,6 +281,7 @@ type Validation struct {
 	//'oldObject' - The existing object. The value is null for CREATE requests.
 	//'request' - Attributes of the API request([ref](/pkg/apis/admission/types.go#AdmissionRequest)).
 	//'params' - Parameter resource referred to by the policy binding being evaluated. Only populated if the policy has a ParamKind.
+	//'namespaceObject' - The namespace object that the incoming object belongs to. The value is null for cluster-scoped resources.
 	//'variables' - Map of composited variables, from its name to its lazily evaluated value.
 	//  For example, a variable named 'foo' can be accessed as 'variables.foo'
 	// - 'authorizer' - A CEL Authorizer. May be used to perform authorization checks for the principal (user or service account) of the request.