kyverno/pkg/cel/policy/policy.go

package policy

import (
	"context"

	"github.com/google/cel-go/cel"
	"github.com/google/cel-go/common/types"
	"github.com/google/cel-go/common/types/ref"
	"github.com/kyverno/kyverno/pkg/cel/utils"
	"go.uber.org/multierr"
	admissionregistrationv1 "k8s.io/api/admissionregistration/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apiserver/pkg/cel/lazy"
)

type (
	resource  = *unstructured.Unstructured
	namespace = *unstructured.Unstructured
)

type CompiledPolicy interface {
	Evaluate(context.Context, resource, namespace) (bool, error)
}

type compiledPolicy struct {
	failurePolicy    admissionregistrationv1.FailurePolicyType
	matchConditions  []cel.Program
	variables        map[string]cel.Program
	validations      []cel.Program
	auditAnnotations map[string]cel.Program
}

func (p *compiledPolicy) Evaluate(ctx context.Context, resource resource, namespace namespace) (bool, error) {
	match, err := p.match(ctx, resource, namespace)
	if err != nil {
		return false, err
	}
	if !match {
		return true, nil
	}
	var nsData map[string]any
	if namespace != nil {
		nsData = namespace.UnstructuredContent()
	}
	variables := func() map[string]any {
		vars := lazy.NewMapValue(VariablesType)
		data := map[string]any{
			NamespaceObjectKey: nsData,
			ObjectKey:          resource.UnstructuredContent(),
			VariablesKey:       vars,
		}
		for name, variable := range p.variables {
			vars.Append(name, func(*lazy.MapValue) ref.Val {
				out, _, err := variable.Eval(data)
				if out != nil {
					return out
				}
				if err != nil {
					return types.WrapErr(err)
				}
				return nil
			})
		}
		return data
	}
	data := variables()
	for _, rule := range p.validations {
		out, _, err := rule.Eval(data)
		// check error
		if err != nil {
			return false, err
		}
		response, err := utils.ConvertToNative[bool](out)
		// check error
		if err != nil {
			return false, err
		}
		// if response is false, return
		if !response {
			return false, nil
		}
	}
	return true, nil
}

func (p *compiledPolicy) match(ctx context.Context, resource resource, namespace namespace) (bool, error) {
	var nsData map[string]any
	if namespace != nil {
		nsData = namespace.UnstructuredContent()
	}
	data := map[string]any{
		NamespaceObjectKey: nsData,
		ObjectKey:          resource.UnstructuredContent(),
	}
	var errs []error
	for _, matchCondition := range p.matchConditions {
		// evaluate the condition
		out, _, err := matchCondition.ContextEval(ctx, data)
		// check error
		if err != nil {
			errs = append(errs, err)
			continue
		}
		// try to convert to a bool
		result, err := utils.ConvertToNative[bool](out)
		// check error
		if err != nil {
			errs = append(errs, err)
			continue
		}
		// if condition is false, skip
		if !result {
			return false, nil
		}
	}
	return true, multierr.Combine(errs...)
}