// Admit determines if the pod should be admitted based on the requested security context
// and the available SCCs.
//
// 1. Find SCCs for the user.
// 2. Find SCCs for the SA. If there is an error retrieving SA SCCs it is not fatal.
// 3. Remove duplicates between the user/SA SCCs.
// 4. Create the providers, includes setting pre-allocated values if necessary.
// 5. Try to generate and validate an SCC with providers. If we find one then admit the pod
// with the validated SCC. If we don't find any reject the pod and give all errors from the
// failed attempts.
func (c *constraint) Admit(a kadmission.Attributes) error {
if a.GetResource() != string(kapi.ResourcePods) {
return nil
}
pod, ok := a.GetObject().(*kapi.Pod)
// if we can't convert then we don't handle this object so just return
if !ok {
return nil
}
// get all constraints that are usable by the user
glog.V(4).Infof("getting security context constraints for pod %s (generate: %s) in namespace %s with user info %v", pod.Name, pod.GenerateName, a.GetNamespace(), a.GetUserInfo())
matchedConstraints, err := getMatchingSecurityContextConstraints(c.store, a.GetUserInfo())
if err != nil {
return kadmission.NewForbidden(a, err)
}
// get all constraints that are usable by the SA
if len(pod.Spec.ServiceAccountName) > 0 {
userInfo := serviceaccount.UserInfo(a.GetNamespace(), pod.Spec.ServiceAccountName, "")
glog.V(4).Infof("getting security context constraints for pod %s (generate: %s) with service account info %v", pod.Name, pod.GenerateName, userInfo)
saConstraints, err := getMatchingSecurityContextConstraints(c.store, userInfo)
if err != nil {
return kadmission.NewForbidden(a, err)
}
matchedConstraints = append(matchedConstraints, saConstraints...)
}
// remove duplicate constraints and sort
matchedConstraints = deduplicateSecurityContextConstraints(matchedConstraints)
sort.Sort(ByRestrictions(matchedConstraints))
providers, errs := c.createProvidersFromConstraints(a.GetNamespace(), matchedConstraints)
logProviders(pod, providers, errs)
if len(providers) == 0 {
return kadmission.NewForbidden(a, fmt.Errorf("no providers available to validated pod request"))
}
// all containers in a single pod must validate under a single provider or we will reject the request
validationErrs := fielderrors.ValidationErrorList{}
for _, provider := range providers {
if errs := assignSecurityContext(provider, pod); len(errs) > 0 {
validationErrs = append(validationErrs, errs.Prefix(fmt.Sprintf("provider %s: ", provider.GetSCCName()))...)
continue
}
// the entire pod validated, annotate and accept the pod
glog.V(4).Infof("pod %s (generate: %s) validated against provider %s", pod.Name, pod.GenerateName, provider.GetSCCName())
if pod.ObjectMeta.Annotations == nil {
pod.ObjectMeta.Annotations = map[string]string{}
}
pod.ObjectMeta.Annotations[allocator.ValidatedSCCAnnotation] = provider.GetSCCName()
return nil
}
// we didn't validate against any security context constraint provider, reject the pod and give the errors for each attempt
glog.V(4).Infof("unable to validate pod %s (generate: %s) against any security context constraint: %v", pod.Name, pod.GenerateName, validationErrs)
return kadmission.NewForbidden(a, fmt.Errorf("unable to validate against any security context constraint: %v", validationErrs))
}
func validateServiceAccount(kClient *kclient.Client, ns string, sa string) error {
// get cluster sccs
sccList, err := kClient.SecurityContextConstraints().List(labels.Everything(), fields.Everything())
if err != nil {
return fmt.Errorf("unable to validate service account %v", err)
}
// get set of sccs applicable to the service account
userInfo := serviceaccount.UserInfo(ns, sa, "")
for _, scc := range sccList.Items {
if admission.ConstraintAppliesTo(&scc, userInfo) {
if scc.AllowHostPorts {
return nil
}
}
}
return fmt.Errorf("unable to validate service account, host ports are forbidden")
}