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webhook.go
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webhook.go
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package main
import (
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
"strings"
"github.com/golang/glog"
"k8s.io/api/admission/v1beta1"
admissionregistrationv1beta1 "k8s.io/api/admissionregistration/v1beta1"
corev1 "k8s.io/api/core/v1"
networkingv1beta1 "k8s.io/api/networking/v1beta1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/runtime/serializer"
"k8s.io/kubernetes/pkg/apis/core/v1"
)
var (
runtimeScheme = runtime.NewScheme()
codecs = serializer.NewCodecFactory(runtimeScheme)
deserializer = codecs.UniversalDeserializer()
)
var (
ignoredNamespaces = []string{
metav1.NamespaceSystem,
metav1.NamespacePublic,
}
)
const (
admissionWebhookAnnotationValidateKey = "admission-webhook-example.citrix.com/validate"
admissionWebhookAnnotationMutateKey = "admission-webhook-example.citrix.com/mutate"
admissionWebhookAnnotationStatusKey = "admission-webhook-example.citrix.com/status"
)
type WebhookServer struct {
server *http.Server
defaultAnnotations []map[string]interface{}
}
// Webhook Server parameters
type WhSvrParameters struct {
port int // webhook server port
certFile string // path to the x509 certificate for https
keyFile string // path to the x509 private key matching `CertFile`
annotationCfg string // path to annotation configuration file
}
type patchOperation struct {
Op string `json:"op"`
Path string `json:"path"`
Value interface{} `json:"value,omitempty"`
}
func init() {
_ = corev1.AddToScheme(runtimeScheme)
_ = admissionregistrationv1beta1.AddToScheme(runtimeScheme)
// defaulting with webhooks:
// https://github.com/kubernetes/kubernetes/issues/57982
_ = v1.AddToScheme(runtimeScheme)
}
func admissionRequired(ignoredList []string, admissionAnnotationKey string, metadata *metav1.ObjectMeta) bool {
// skip special kubernetes system namespaces
for _, namespace := range ignoredList {
if metadata.Namespace == namespace {
glog.Infof("Skip validation for %v for it's in special namespace:%v", metadata.Name, metadata.Namespace)
return false
}
}
return true
}
func mutationRequired(ignoredList []string, defaultAnnotations []map[string]interface{}, metadata *metav1.ObjectMeta) bool {
required := admissionRequired(ignoredList, admissionWebhookAnnotationMutateKey, metadata)
annotations := metadata.GetAnnotations()
if annotations == nil {
annotations = map[string]string{}
}
name := metadata.GetName()
ingressFound := false
for _, dflt := range defaultAnnotations {
ingressName, ok := dflt["ingressName"]
if !ok {
continue
}
glog.Infof("Checking default for %v/%v", ingressName.(string), metadata.Name)
if strings.Compare(strings.ToLower(ingressName.(string)), strings.ToLower(name)) == 0 {
ingressFound = true
break
}
}
required = required && ingressFound
glog.Infof("Mutation policy for %v/%v: required:%v", metadata.Namespace, metadata.Name, required)
status := annotations[admissionWebhookAnnotationStatusKey]
if strings.ToLower(status) == "mutated" {
required = false
}
glog.Infof("Mutation policy for %v/%v: required:%v", metadata.Namespace, metadata.Name, required)
return required
}
func validationRequired(ignoredList []string, metadata *metav1.ObjectMeta) bool {
required := admissionRequired(ignoredList, admissionWebhookAnnotationValidateKey, metadata)
glog.Infof("Validation policy for %v/%v: required:%v", metadata.Namespace, metadata.Name, required)
return required
}
func updateAnnotation(annotations map[string]string, defaultAnnotations map[string]interface{}) (patch []patchOperation) {
for ann, val := range defaultAnnotations {
annotations[ann] = val.(string)
}
patch = append(patch, patchOperation{
Op: "add",
Path: "/metadata/annotations",
Value: annotations,
})
return patch
}
func createPatch(ingressName string, availableAnnotations map[string]string, allDefaultAnnotations []map[string]interface{}) ([]byte, error) {
var patch []patchOperation
defaultAnnotationsForIngressName := map[string]interface{}{}
for _, dflt := range allDefaultAnnotations {
name, ok := dflt["ingressName"]
if !ok {
continue
}
ingressName := name.(string)
if strings.Compare(strings.ToLower(dflt["ingressName"].(string)), strings.ToLower(ingressName)) == 0 {
defaultAnnotationsForIngressName = dflt["defaultAnnotations"].(map[string]interface{})
break
}
}
patch = append(patch, updateAnnotation(availableAnnotations, defaultAnnotationsForIngressName)...)
return json.Marshal(patch)
}
// main mutation process
func (whsvr *WebhookServer) mutate(ar *v1beta1.AdmissionReview) *v1beta1.AdmissionResponse {
req := ar.Request
var (
objectMeta *metav1.ObjectMeta
resourceNamespace, resourceName string
)
glog.Infof("Mutating AdmissionReview for Kind=%v, Namespace=%v Name=%v (%v) UID=%v patchOperation=%v UserInfo=%v",
req.Kind, req.Namespace, req.Name, resourceName, req.UID, req.Operation, req.UserInfo)
switch req.Kind.Kind {
case "Ingress":
var ingress networkingv1beta1.Ingress
if err := json.Unmarshal(req.Object.Raw, &ingress); err != nil {
glog.Errorf("Could not unmarshal raw object: %v", err)
return &v1beta1.AdmissionResponse{
Result: &metav1.Status{
Message: err.Error(),
},
}
}
resourceName, resourceNamespace, objectMeta = ingress.Name, ingress.Namespace, &ingress.ObjectMeta
}
if !mutationRequired(ignoredNamespaces, whsvr.defaultAnnotations, objectMeta) {
glog.Infof("Skipping validation for %s/%s due to policy check", resourceNamespace, resourceName)
return &v1beta1.AdmissionResponse{
Allowed: true,
}
}
patchBytes, err := createPatch(resourceName, objectMeta.GetAnnotations(), whsvr.defaultAnnotations)
if err != nil {
return &v1beta1.AdmissionResponse{
Result: &metav1.Status{
Message: err.Error(),
},
}
}
glog.Infof("AdmissionResponse: patch=%v\n", string(patchBytes))
return &v1beta1.AdmissionResponse{
Allowed: true,
Patch: patchBytes,
PatchType: func() *v1beta1.PatchType {
pt := v1beta1.PatchTypeJSONPatch
return &pt
}(),
}
}
// Serve method for webhook server
func (whsvr *WebhookServer) serve(w http.ResponseWriter, r *http.Request) {
var body []byte
if r.Body != nil {
if data, err := ioutil.ReadAll(r.Body); err == nil {
body = data
}
}
if len(body) == 0 {
glog.Error("empty body")
http.Error(w, "empty body", http.StatusBadRequest)
return
}
// verify the content type is accurate
contentType := r.Header.Get("Content-Type")
if contentType != "application/json" {
glog.Errorf("Content-Type=%s, expect application/json", contentType)
http.Error(w, "invalid Content-Type, expect `application/json`", http.StatusUnsupportedMediaType)
return
}
var admissionResponse *v1beta1.AdmissionResponse
ar := v1beta1.AdmissionReview{}
if _, _, err := deserializer.Decode(body, nil, &ar); err != nil {
glog.Errorf("Can't decode body: %v", err)
admissionResponse = &v1beta1.AdmissionResponse{
Result: &metav1.Status{
Message: err.Error(),
},
}
} else {
fmt.Println(r.URL.Path)
if r.URL.Path == "/mutate" {
admissionResponse = whsvr.mutate(&ar)
} else if r.URL.Path == "/validate" {
//admissionResponse = whsvr.validate(&ar)
glog.Errorf("Not set up to do validation")
}
}
admissionReview := v1beta1.AdmissionReview{}
if admissionResponse != nil {
admissionReview.Response = admissionResponse
if ar.Request != nil {
admissionReview.Response.UID = ar.Request.UID
}
}
resp, err := json.Marshal(admissionReview)
if err != nil {
glog.Errorf("Can't encode response: %v", err)
http.Error(w, fmt.Sprintf("could not encode response: %v", err), http.StatusInternalServerError)
}
glog.Infof("Ready to write reponse ...")
if _, err := w.Write(resp); err != nil {
glog.Errorf("Can't write response: %v", err)
http.Error(w, fmt.Sprintf("could not write response: %v", err), http.StatusInternalServerError)
}
}