Merge pull request #121651 from jiahuif-forks/fix/cel/type-resolver-safe-guard

CEL type resolvers: avoid infinite recursion for type resolvers.

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

@@ -38,7 +38,7 @@ type combinedSchemaResolver struct {
 // If the DefinitionsSchemaResolver knows the gvk, the DefinitionsSchemaResolver handles the resolution,
 // otherwise, the secondary does.
 func (r *combinedSchemaResolver) ResolveSchema(gvk schema.GroupVersionKind) (*spec.Schema, error) {
-	if _, ok := r.definitions.gvkToSchema[gvk]; ok {
+	if _, ok := r.definitions.gvkToRef[gvk]; ok {
 		return r.definitions.ResolveSchema(gvk)
 	}
 	return r.secondary.ResolveSchema(gvk)

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

@@ -29,8 +29,8 @@ import (
 // DefinitionsSchemaResolver resolves the schema of a built-in type
 // by looking up the OpenAPI definitions.
 type DefinitionsSchemaResolver struct {
-	defs        map[string]common.OpenAPIDefinition
+	defs     map[string]common.OpenAPIDefinition
-	gvkToSchema map[schema.GroupVersionKind]*spec.Schema
+	gvkToRef map[schema.GroupVersionKind]string
 }
 
 // NewDefinitionsSchemaResolver creates a new DefinitionsSchemaResolver.
@@ -38,31 +38,30 @@ type DefinitionsSchemaResolver struct {
 // getDefinitions = "k8s.io/kubernetes/pkg/generated/openapi".GetOpenAPIDefinitions
 // scheme         = "k8s.io/client-go/kubernetes/scheme".Scheme
 func NewDefinitionsSchemaResolver(getDefinitions common.GetOpenAPIDefinitions, schemes ...*runtime.Scheme) *DefinitionsSchemaResolver {
-	gvkToSchema := make(map[schema.GroupVersionKind]*spec.Schema)
+	gvkToRef := make(map[schema.GroupVersionKind]string)
 	namer := openapi.NewDefinitionNamer(schemes...)
 	defs := getDefinitions(func(path string) spec.Ref {
 		return spec.MustCreateRef(path)
 	})
-	for name, def := range defs {
+	for name := range defs {
 		_, e := namer.GetDefinitionName(name)
 		gvks := extensionsToGVKs(e)
-		s := def.Schema // map value not addressable, make copy
 		for _, gvk := range gvks {
-			gvkToSchema[gvk] = &s
+			gvkToRef[gvk] = name
 		}
 	}
 	return &DefinitionsSchemaResolver{
-		gvkToSchema: gvkToSchema,
+		gvkToRef: gvkToRef,
-		defs:        defs,
+		defs:     defs,
 	}
 }
 
 func (d *DefinitionsSchemaResolver) ResolveSchema(gvk schema.GroupVersionKind) (*spec.Schema, error) {
-	s, ok := d.gvkToSchema[gvk]
+	ref, ok := d.gvkToRef[gvk]
 	if !ok {
 		return nil, fmt.Errorf("cannot resolve %v: %w", gvk, ErrSchemaNotFound)
 	}
-	s, err := populateRefs(func(ref string) (*spec.Schema, bool) {
+	s, 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 {
@@ -70,7 +69,7 @@ func (d *DefinitionsSchemaResolver) ResolveSchema(gvk schema.GroupVersionKind) (
 		}
 		s := def.Schema
 		return &s, true
-	}, s)
+	}, ref)
 	if err != nil {
 		return nil, err
 	}

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

@@ -53,34 +53,34 @@ func (r *ClientDiscoveryResolver) ResolveSchema(gvk schema.GroupVersionKind) (*s
 	if err != nil {
 		return nil, err
 	}
-	s, err := resolveType(resp, gvk)
+	ref, err := resolveRef(resp, gvk)
 	if err != nil {
 		return nil, err
 	}
-	s, err = populateRefs(func(ref string) (*spec.Schema, bool) {
+	s, err := PopulateRefs(func(ref string) (*spec.Schema, bool) {
 		s, ok := resp.Components.Schemas[strings.TrimPrefix(ref, refPrefix)]
 		return s, ok
-	}, s)
+	}, ref)
 	if err != nil {
 		return nil, err
 	}
 	return s, nil
 }
 
-func resolveType(resp *schemaResponse, gvk schema.GroupVersionKind) (*spec.Schema, error) {
+func resolveRef(resp *schemaResponse, gvk schema.GroupVersionKind) (string, error) {
-	for _, s := range resp.Components.Schemas {
+	for ref, s := range resp.Components.Schemas {
 		var gvks []schema.GroupVersionKind
 		err := s.Extensions.GetObject(extGVK, &gvks)
 		if err != nil {
-			return nil, err
+			return "", err
 		}
 		for _, g := range gvks {
 			if g == gvk {
-				return s, nil
+				return ref, nil
 			}
 		}
 	}
-	return nil, fmt.Errorf("cannot resolve group version kind %q: %w", gvk, ErrSchemaNotFound)
+	return "", fmt.Errorf("cannot resolve group version kind %q: %w", gvk, ErrSchemaNotFound)
 }
 
 func resourcePathFromGV(gv schema.GroupVersion) string {

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

@@ -19,19 +19,41 @@ package resolver
 import (
 	"fmt"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/kube-openapi/pkg/validation/spec"
 )
 
-// populateRefs recursively replaces Refs in the schema with the referred one.
+// PopulateRefs recursively replaces Refs in the schema with the referred one.
 // schemaOf is the callback to find the corresponding schema by the ref.
 // This function will not mutate the original schema. If the schema needs to be
 // mutated, a copy will be returned, otherwise it returns the original schema.
-func populateRefs(schemaOf func(ref string) (*spec.Schema, bool), schema *spec.Schema) (*spec.Schema, error) {
+func PopulateRefs(schemaOf func(ref string) (*spec.Schema, bool), rootRef string) (*spec.Schema, error) {
+	visitedRefs := sets.New[string]()
+	rootSchema, ok := schemaOf(rootRef)
+	visitedRefs.Insert(rootRef)
+	if !ok {
+		return nil, fmt.Errorf("internal error: cannot resolve Ref for root schema %q: %w", rootRef, ErrSchemaNotFound)
+	}
+	return populateRefs(schemaOf, visitedRefs, rootSchema)
+}
+
+func populateRefs(schemaOf func(ref string) (*spec.Schema, bool), visited sets.Set[string], schema *spec.Schema) (*spec.Schema, error) {
 	result := *schema
 	changed := false
 
 	ref, isRef := refOf(schema)
 	if isRef {
+		if visited.Has(ref) {
+			return &spec.Schema{
+				// for circular ref, return an empty object as placeholder
+				SchemaProps: spec.SchemaProps{Type: []string{"object"}},
+			}, nil
+		}
+		visited.Insert(ref)
+		// restore visited state at the end of the recursion.
+		defer func() {
+			visited.Delete(ref)
+		}()
 		// replace the whole schema with the referred one.
 		resolved, ok := schemaOf(ref)
 		if !ok {
@@ -44,7 +66,7 @@ func populateRefs(schemaOf func(ref string) (*spec.Schema, bool), schema *spec.S
 	props := make(map[string]spec.Schema, len(schema.Properties))
 	propsChanged := false
 	for name, prop := range result.Properties {
-		populated, err := populateRefs(schemaOf, &prop)
+		populated, err := populateRefs(schemaOf, visited, &prop)
 		if err != nil {
 			return nil, err
 		}
@@ -58,7 +80,7 @@ func populateRefs(schemaOf func(ref string) (*spec.Schema, bool), schema *spec.S
 		result.Properties = props
 	}
 	if result.AdditionalProperties != nil && result.AdditionalProperties.Schema != nil {
-		populated, err := populateRefs(schemaOf, result.AdditionalProperties.Schema)
+		populated, err := populateRefs(schemaOf, visited, result.AdditionalProperties.Schema)
 		if err != nil {
 			return nil, err
 		}
@@ -69,7 +91,7 @@ func populateRefs(schemaOf func(ref string) (*spec.Schema, bool), schema *spec.S
 	}
 	// schema is a list, populate its items
 	if result.Items != nil && result.Items.Schema != nil {
-		populated, err := populateRefs(schemaOf, result.Items.Schema)
+		populated, err := populateRefs(schemaOf, visited, result.Items.Schema)
 		if err != nil {
 			return nil, err
 		}

test/integration/apiserver/cel/typeresolution_test.go

@@ -36,6 +36,7 @@ import (
 	storagev1 "k8s.io/api/storage/v1"
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 	extclientset "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset"
+	apiextensionsscheme "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset/scheme"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -79,7 +80,7 @@ func TestTypeResolver(t *testing.T) {
 		}
 	}(crd)
 	discoveryResolver := &resolver.ClientDiscoveryResolver{Discovery: client.Discovery()}
-	definitionsResolver := resolver.NewDefinitionsSchemaResolver(openapi.GetOpenAPIDefinitions, k8sscheme.Scheme)
+	definitionsResolver := resolver.NewDefinitionsSchemaResolver(openapi.GetOpenAPIDefinitions, k8sscheme.Scheme, apiextensionsscheme.Scheme)
 	// wait until the CRD schema is published at the OpenAPI v3 endpoint
 	err = wait.PollImmediate(time.Second, time.Minute, func() (done bool, err error) {
 		p, err := client.OpenAPIV3().Paths()
@@ -330,7 +331,7 @@ func TestBuiltinResolution(t *testing.T) {
 	}{
 		{
 			name:     "definitions",
-			resolver: resolver.NewDefinitionsSchemaResolver(openapi.GetOpenAPIDefinitions, k8sscheme.Scheme),
+			resolver: resolver.NewDefinitionsSchemaResolver(openapi.GetOpenAPIDefinitions, k8sscheme.Scheme, apiextensionsscheme.Scheme),
 			scheme:   buildTestScheme(),
 		},
 		{
@@ -354,6 +355,14 @@ func TestBuiltinResolution(t *testing.T) {
 				if gvk.Version == "__internal" {
 					continue
 				}
+				// apiextensions.k8s.io/v1beta1 not published
+				if tc.name == "discovery" && gvk.Group == "apiextensions.k8s.io" && gvk.Version == "v1beta1" {
+					continue
+				}
+				// apiextensions.k8s.io ConversionReview not published
+				if tc.name == "discovery" && gvk.Group == "apiextensions.k8s.io" && gvk.Kind == "ConversionReview" {
+					continue
+				}
 				_, err = tc.resolver.ResolveSchema(gvk)
 				if err != nil {
 					t.Errorf("resolver %q cannot resolve %v", tc.name, gvk)
@@ -506,5 +515,6 @@ func buildTestScheme() *runtime.Scheme {
 	_ = networkingv1.AddToScheme(scheme)
 	_ = nodev1.AddToScheme(scheme)
 	_ = storagev1.AddToScheme(scheme)
+	_ = apiextensionsscheme.AddToScheme(scheme)
 	return scheme
 }