implement OpenAPI-based schema resolver.

staging/src/k8s.io/apiserver/pkg/cel/openapi/resolver/definitions.go

@@ -0,0 +1,141 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package resolver
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/endpoints/openapi"
+	"k8s.io/kube-openapi/pkg/common"
+	"k8s.io/kube-openapi/pkg/validation/spec"
+)
+
+// DefinitionsSchemaResolver resolves the schema of a built-in type
+// by looking up the OpenAPI definitions.
+type DefinitionsSchemaResolver struct {
+	defs        map[string]common.OpenAPIDefinition
+	gvkToSchema map[schema.GroupVersionKind]*spec.Schema
+}
+
+// NewDefinitionsSchemaResolver creates a new DefinitionsSchemaResolver.
+// An example working setup:
+// scheme         = "k8s.io/client-go/kubernetes/scheme".Scheme
+// getDefinitions = "k8s.io/kubernetes/pkg/generated/openapi".GetOpenAPIDefinitions
+func NewDefinitionsSchemaResolver(scheme *runtime.Scheme, getDefinitions common.GetOpenAPIDefinitions) *DefinitionsSchemaResolver {
+	gvkToSchema := make(map[schema.GroupVersionKind]*spec.Schema)
+	namer := openapi.NewDefinitionNamer(scheme)
+	defs := getDefinitions(func(path string) spec.Ref {
+		return spec.MustCreateRef(path)
+	})
+	for name, def := range defs {
+		_, e := namer.GetDefinitionName(name)
+		gvks := extensionsToGVKs(e)
+		for _, gvk := range gvks {
+			gvkToSchema[gvk] = &def.Schema
+		}
+	}
+	return &DefinitionsSchemaResolver{
+		gvkToSchema: gvkToSchema,
+		defs:        defs,
+	}
+}
+
+func (d *DefinitionsSchemaResolver) ResolveSchema(gvk schema.GroupVersionKind) (*spec.Schema, error) {
+	s, ok := d.gvkToSchema[gvk]
+	if !ok {
+		return nil, fmt.Errorf("cannot resolve %v: %w", gvk, ErrSchemaNotFound)
+	}
+	result, err := deepCopy(s)
+	if err != nil {
+		return nil, fmt.Errorf("cannot deep copy schema for %v: %v", gvk, err)
+	}
+	err = populateRefs(func(ref string) (*spec.Schema, bool) {
+		// find the schema by the ref string, and return a deep copy
+		def, ok := d.defs[ref]
+		if !ok {
+			return nil, false
+		}
+		s, err := deepCopy(&def.Schema)
+		if err != nil {
+			return nil, false
+		}
+		return s, true
+	}, result)
+	if err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+// deepCopy generates a deep copy of the given schema with JSON marshalling and
+// unmarshalling.
+// The schema is expected to be "shallow", with all its field being Refs instead
+// of nested schemas.
+// If the schema contains cyclic reference, for example, a properties is itself
+// it will return an error. This resolver does not support such condition.
+func deepCopy(s *spec.Schema) (*spec.Schema, error) {
+	b, err := json.Marshal(s)
+	if err != nil {
+		return nil, err
+	}
+	result := new(spec.Schema)
+	err = json.Unmarshal(b, result)
+	if err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func extensionsToGVKs(extensions spec.Extensions) []schema.GroupVersionKind {
+	gvksAny, ok := extensions[extGVK]
+	if !ok {
+		return nil
+	}
+	gvks, ok := gvksAny.([]any)
+	if !ok {
+		return nil
+	}
+	result := make([]schema.GroupVersionKind, 0, len(gvks))
+	for _, gvkAny := range gvks {
+		// type check the map and all fields
+		gvkMap, ok := gvkAny.(map[string]any)
+		if !ok {
+			return nil
+		}
+		g, ok := gvkMap["group"].(string)
+		if !ok {
+			return nil
+		}
+		v, ok := gvkMap["version"].(string)
+		if !ok {
+			return nil
+		}
+		k, ok := gvkMap["kind"].(string)
+		if !ok {
+			return nil
+		}
+		result = append(result, schema.GroupVersionKind{
+			Group:   g,
+			Version: v,
+			Kind:    k,
+		})
+	}
+	return result
+}

staging/src/k8s.io/apiserver/pkg/cel/openapi/resolver/discovery.go

@@ -0,0 +1,153 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package resolver
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/discovery"
+	"k8s.io/kube-openapi/pkg/validation/spec"
+)
+
+// ClientDiscoveryResolver uses client-go discovery to resolve schemas at run time.
+type ClientDiscoveryResolver struct {
+	Discovery discovery.DiscoveryInterface
+}
+
+var _ SchemaResolver = (*ClientDiscoveryResolver)(nil)
+
+func (r *ClientDiscoveryResolver) ResolveSchema(gvk schema.GroupVersionKind) (*spec.Schema, error) {
+	p, err := r.Discovery.OpenAPIV3().Paths()
+	if err != nil {
+		return nil, err
+	}
+	resourcePath := resourcePathFromGV(gvk.GroupVersion())
+	c, ok := p[resourcePath]
+	if !ok {
+		return nil, fmt.Errorf("cannot resolve group version %q: %w", gvk.GroupVersion(), ErrSchemaNotFound)
+	}
+	b, err := c.Schema(runtime.ContentTypeJSON)
+	if err != nil {
+		return nil, err
+	}
+	resp := new(schemaResponse)
+	err = json.Unmarshal(b, resp)
+	if err != nil {
+		return nil, err
+	}
+	s, err := resolveType(resp, gvk)
+	if err != nil {
+		return nil, err
+	}
+	err = populateRefs(func(ref string) (*spec.Schema, bool) {
+		s, ok := resp.Components.Schemas[strings.TrimPrefix(ref, refPrefix)]
+		return s, ok
+	}, s)
+	if err != nil {
+		return nil, err
+	}
+	return s, nil
+}
+
+func populateRefs(schemaOf func(ref string) (*spec.Schema, bool), schema *spec.Schema) error {
+	ref, isRef := refOf(schema)
+	if isRef {
+		// replace the whole schema with the referred one.
+		resolved, ok := schemaOf(ref)
+		if !ok {
+			return fmt.Errorf("internal error: cannot resolve Ref %q: %w", ref, ErrSchemaNotFound)
+		}
+		*schema = *resolved
+	}
+	// schema is an object, populate its properties and additionalProperties
+	for name, prop := range schema.Properties {
+		err := populateRefs(schemaOf, &prop)
+		if err != nil {
+			return err
+		}
+		schema.Properties[name] = prop
+	}
+	if schema.AdditionalProperties != nil && schema.AdditionalProperties.Schema != nil {
+		err := populateRefs(schemaOf, schema.AdditionalProperties.Schema)
+		if err != nil {
+			return err
+		}
+	}
+	// schema is a list, populate its items
+	if schema.Items != nil && schema.Items.Schema != nil {
+		err := populateRefs(schemaOf, schema.Items.Schema)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func refOf(schema *spec.Schema) (string, bool) {
+	if schema.Ref.GetURL() != nil {
+		return schema.Ref.String(), true
+	}
+	// A Ref may be wrapped in allOf to preserve its description
+	// see https://github.com/kubernetes/kubernetes/issues/106387
+	// For kube-openapi, allOf is only used for wrapping a Ref.
+	for _, allOf := range schema.AllOf {
+		if ref, isRef := refOf(&allOf); isRef {
+			return ref, isRef
+		}
+	}
+	return "", false
+}
+
+func resolveType(resp *schemaResponse, gvk schema.GroupVersionKind) (*spec.Schema, error) {
+	for _, s := range resp.Components.Schemas {
+		var gvks []schema.GroupVersionKind
+		err := s.Extensions.GetObject(extGVK, &gvks)
+		if err != nil {
+			return nil, err
+		}
+		for _, g := range gvks {
+			if g == gvk {
+				return s, nil
+			}
+		}
+	}
+	return nil, fmt.Errorf("cannot resolve group version kind %q: %w", gvk, ErrSchemaNotFound)
+}
+
+func resourcePathFromGV(gv schema.GroupVersion) string {
+	var resourcePath string
+	if len(gv.Group) == 0 {
+		resourcePath = fmt.Sprintf("api/%s", gv.Version)
+	} else {
+		resourcePath = fmt.Sprintf("apis/%s/%s", gv.Group, gv.Version)
+	}
+	return resourcePath
+}
+
+type schemaResponse struct {
+	Components struct {
+		Schemas map[string]*spec.Schema `json:"schemas"`
+	} `json:"components"`
+}
+
+const refPrefix = "#/components/schemas/"
+
+const extGVK = "x-kubernetes-group-version-kind"

staging/src/k8s.io/apiserver/pkg/cel/openapi/resolver/resolver.go

@@ -0,0 +1,39 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package resolver
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/kube-openapi/pkg/validation/spec"
+)
+
+// SchemaResolver finds the OpenAPI schema for the given GroupVersionKind.
+// This interface uses the type defined by k8s.io/kube-openapi
+type SchemaResolver interface {
+	// ResolveSchema takes a GroupVersionKind (GVK) and returns the OpenAPI schema
+	// identified by the GVK.
+	// The function returns a non-nil error if the schema cannot be found or fail
+	// to resolve. The returned error wraps ErrSchemaNotFound if the resolution is
+	// attempted but the corresponding schema cannot be found.
+	ResolveSchema(gvk schema.GroupVersionKind) (*spec.Schema, error)
+}
+
+// ErrSchemaNotFound is wrapped and returned if the schema cannot be located
+// by the resolver.
+var ErrSchemaNotFound = fmt.Errorf("schema not found")