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restrictusers.go
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restrictusers.go
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package restrictusers
import (
"errors"
"fmt"
"io"
kclientset "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
"github.com/golang/glog"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
kerrors "k8s.io/apimachinery/pkg/util/errors"
"k8s.io/apiserver/pkg/admission"
kapi "k8s.io/kubernetes/pkg/api"
kadmission "k8s.io/kubernetes/pkg/kubeapiserver/admission"
authorizationapi "github.com/openshift/origin/pkg/authorization/apis/authorization"
oclient "github.com/openshift/origin/pkg/client"
oadmission "github.com/openshift/origin/pkg/cmd/server/admission"
usercache "github.com/openshift/origin/pkg/user/cache"
)
func init() {
admission.RegisterPlugin("openshift.io/RestrictSubjectBindings",
func(config io.Reader) (admission.Interface, error) {
return NewRestrictUsersAdmission()
})
}
// restrictUsersAdmission implements admission.Interface and enforces
// restrictions on adding rolebindings in a project to permit only designated
// subjects.
type restrictUsersAdmission struct {
*admission.Handler
oclient oclient.Interface
kclient kclientset.Interface
groupCache *usercache.GroupCache
}
var _ = oadmission.WantsOpenshiftClient(&restrictUsersAdmission{})
var _ = oadmission.WantsGroupCache(&restrictUsersAdmission{})
var _ = kadmission.WantsInternalKubeClientSet(&restrictUsersAdmission{})
// NewRestrictUsersAdmission configures an admission plugin that enforces
// restrictions on adding role bindings in a project.
func NewRestrictUsersAdmission() (admission.Interface, error) {
return &restrictUsersAdmission{
Handler: admission.NewHandler(admission.Create, admission.Update),
}, nil
}
func (q *restrictUsersAdmission) SetInternalKubeClientSet(c kclientset.Interface) {
q.kclient = c
}
func (q *restrictUsersAdmission) SetOpenshiftClient(c oclient.Interface) {
q.oclient = c
}
func (q *restrictUsersAdmission) SetGroupCache(c *usercache.GroupCache) {
q.groupCache = c
}
// objectReferenceDelta returns the relative complement of
// []ObjectReference elementsToIgnore in []ObjectReference elements
// (i.e., elements∖elementsToIgnore).
func objectReferenceDelta(elementsToIgnore, elements []kapi.ObjectReference) []kapi.ObjectReference {
result := []kapi.ObjectReference{}
for _, el := range elements {
keep := true
for _, skipEl := range elementsToIgnore {
if el == skipEl {
keep = false
break
}
}
if keep {
result = append(result, el)
}
}
return result
}
// Admit makes admission decisions that enforce restrictions on adding
// project-scoped role-bindings. In order for a role binding to be permitted,
// each subject in the binding must be matched by some rolebinding restriction
// in the namespace.
func (q *restrictUsersAdmission) Admit(a admission.Attributes) (err error) {
// We only care about rolebindings and policybindings; ignore anything else.
gr := a.GetResource().GroupResource()
switch {
case authorizationapi.IsResourceOrLegacy("policybindings", gr), authorizationapi.IsResourceOrLegacy("rolebindings", gr):
default:
return nil
}
// Ignore all operations that correspond to subresource actions.
if len(a.GetSubresource()) != 0 {
return nil
}
ns := a.GetNamespace()
// Ignore cluster-level resources.
if len(ns) == 0 {
return nil
}
var subjects, oldSubjects []kapi.ObjectReference
obj, oldObj := a.GetObject(), a.GetOldObject()
switch {
case authorizationapi.IsResourceOrLegacy("rolebindings", gr):
rolebinding, ok := obj.(*authorizationapi.RoleBinding)
if !ok {
return admission.NewForbidden(a,
fmt.Errorf("wrong object type for new rolebinding: %T", obj))
}
subjects = rolebinding.Subjects
if len(subjects) == 0 {
return nil
}
if oldObj != nil {
oldrolebinding, ok := oldObj.(*authorizationapi.RoleBinding)
if !ok {
return admission.NewForbidden(a,
fmt.Errorf("wrong object type for old rolebinding: %T", oldObj))
}
oldSubjects = oldrolebinding.Subjects
}
glog.V(4).Infof("Handling rolebinding %s/%s",
rolebinding.Namespace, rolebinding.Name)
case authorizationapi.IsResourceOrLegacy("policybindings", gr):
policybinding, ok := obj.(*authorizationapi.PolicyBinding)
if !ok {
return admission.NewForbidden(a,
fmt.Errorf("wrong object type for new policybinding: %T", obj))
}
for _, rolebinding := range policybinding.RoleBindings {
subjects = append(subjects, rolebinding.Subjects...)
}
if len(subjects) == 0 {
return nil
}
if oldObj != nil {
oldpolicybinding, ok := oldObj.(*authorizationapi.PolicyBinding)
if !ok {
return admission.NewForbidden(a,
fmt.Errorf("wrong object type for old policybinding: %T", oldObj))
}
for _, rolebinding := range oldpolicybinding.RoleBindings {
oldSubjects = append(oldSubjects, rolebinding.Subjects...)
}
}
glog.V(4).Infof("Handling policybinding %s/%s",
policybinding.Namespace, policybinding.Name)
}
newSubjects := objectReferenceDelta(oldSubjects, subjects)
if len(newSubjects) == 0 {
glog.V(4).Infof("No new subjects; admitting")
return nil
}
// TODO: Cache rolebinding restrictions.
roleBindingRestrictionList, err := q.oclient.RoleBindingRestrictions(ns).
List(metav1.ListOptions{})
if err != nil {
return admission.NewForbidden(a, err)
}
if len(roleBindingRestrictionList.Items) == 0 {
glog.V(4).Infof("No rolebinding restrictions specified; admitting")
return nil
}
if !q.groupCache.Running() {
return admission.NewForbidden(a, errors.New("groupCache not running"))
}
checkers := []SubjectChecker{}
for _, rbr := range roleBindingRestrictionList.Items {
checker, err := NewSubjectChecker(&rbr.Spec)
if err != nil {
return admission.NewForbidden(a, err)
}
checkers = append(checkers, checker)
}
roleBindingRestrictionContext, err := NewRoleBindingRestrictionContext(ns,
q.kclient, q.oclient, q.groupCache)
if err != nil {
return admission.NewForbidden(a, err)
}
checker := NewUnionSubjectChecker(checkers)
errs := []error{}
for _, subject := range newSubjects {
allowed, err := checker.Allowed(subject, roleBindingRestrictionContext)
if err != nil {
errs = append(errs, err)
}
if !allowed {
errs = append(errs,
fmt.Errorf("rolebindings to %s %q are not allowed in project %q",
subject.Kind, subject.Name, ns))
}
}
if len(errs) != 0 {
return admission.NewForbidden(a, kerrors.NewAggregate(errs))
}
glog.V(4).Infof("All new subjects are allowed; admitting")
return nil
}
func (q *restrictUsersAdmission) Validate() error {
if q.kclient == nil {
return errors.New("RestrictUsersAdmission plugin requires a Kubernetes client")
}
if q.oclient == nil {
return errors.New("RestrictUsersAdmission plugin requires an OpenShift client")
}
if q.groupCache == nil {
return errors.New("RestrictUsersAdmission plugin requires a group cache")
}
return nil
}