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csr: add expirationSeconds field to control cert lifetime

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This change updates the CSR API to add a new, optional field called
expirationSeconds.  This field is a request to the signer for the
maximum duration the client wishes the cert to have.  The signer is
free to ignore this request based on its own internal policy.  The
signers built-in to KCM will honor this field if it is not set to a
value greater than --cluster-signing-duration.  The minimum allowed
value for this field is 600 seconds (ten minutes).

This change will help enforce safer durations for certificates in
the Kube ecosystem and will help related projects such as
cert-manager with their migration to the Kube CSR API.

Future enhancements may update the Kubelet to take advantage of this
field when it is configured in a way that can tolerate shorter
certificate lifespans with regular rotation.

Signed-off-by: Monis Khan <mok@vmware.com>

Kubernetes-commit: cd91e59f7c351fce47c064a5162c2cb79075159c
This commit is contained in:
Monis Khan 2021-06-25 22:08:10 -04:00 committed by Kubernetes Publisher
parent 843bb800b1
commit 30cd4e9a49
2 changed files with 41 additions and 21 deletions
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41
util/certificate/certificate_manager.go
View File

@ -88,6 +88,11 @@ type Config struct {
// SignerName is the name of the certificate signer that should sign certificates
// generated by the manager.
SignerName string
// RequestedCertificateLifetime is the requested lifetime length for certificates generated by the manager.
// Optional.
// This will set the spec.expirationSeconds field on the CSR. Controlling the lifetime of
// the issued certificate is not guaranteed as the signer may choose to ignore the request.
RequestedCertificateLifetime *time.Duration
// Usages is the types of usages that certificates generated by the manager
// can be used for.
Usages []certificates.KeyUsage
@ -184,10 +189,11 @@ type manager struct {
lastRequestCancel context.CancelFunc
lastRequest *x509.CertificateRequest
dynamicTemplate bool
signerName string
usages []certificates.KeyUsage
forceRotation bool
dynamicTemplate bool
signerName string
requestedCertificateLifetime *time.Duration
usages []certificates.KeyUsage
forceRotation bool
certStore Store
@ -230,18 +236,19 @@ func NewManager(config *Config) (Manager, error) {
}
m := manager{
stopCh: make(chan struct{}),
clientsetFn: config.ClientsetFn,
getTemplate: getTemplate,
dynamicTemplate: config.GetTemplate != nil,
signerName: config.SignerName,
usages: config.Usages,
certStore: config.CertificateStore,
cert: cert,
forceRotation: forceRotation,
certificateRotation: config.CertificateRotation,
certificateRenewFailure: config.CertificateRenewFailure,
now: time.Now,
stopCh: make(chan struct{}),
clientsetFn: config.ClientsetFn,
getTemplate: getTemplate,
dynamicTemplate: config.GetTemplate != nil,
signerName: config.SignerName,
requestedCertificateLifetime: config.RequestedCertificateLifetime,
usages: config.Usages,
certStore: config.CertificateStore,
cert: cert,
forceRotation: forceRotation,
certificateRotation: config.CertificateRotation,
certificateRenewFailure: config.CertificateRenewFailure,
now: time.Now,
}
name := config.Name
@ -459,7 +466,7 @@ func (m *manager) rotateCerts() (bool, error) {
// Call the Certificate Signing Request API to get a certificate for the
// new private key.
reqName, reqUID, err := csr.RequestCertificate(clientSet, csrPEM, "", m.signerName, m.usages, privateKey)
reqName, reqUID, err := csr.RequestCertificate(clientSet, csrPEM, "", m.signerName, m.requestedCertificateLifetime, m.usages, privateKey)
if err != nil {
utilruntime.HandleError(fmt.Errorf("%s: Failed while requesting a signed certificate from the control plane: %v", m.name, err))
if m.certificateRenewFailure != nil {

21
util/certificate/csr/csr.go
View File

@ -25,8 +25,6 @@ import (
"reflect"
"time"
"k8s.io/klog/v2"
certificatesv1 "k8s.io/api/certificates/v1"
certificatesv1beta1 "k8s.io/api/certificates/v1beta1"
"k8s.io/apimachinery/pkg/api/errors"
@ -41,12 +39,16 @@ import (
"k8s.io/client-go/tools/cache"
watchtools "k8s.io/client-go/tools/watch"
certutil "k8s.io/client-go/util/cert"
"k8s.io/klog/v2"
"k8s.io/utils/pointer"
)
// RequestCertificate will either use an existing (if this process has run
// before but not to completion) or create a certificate signing request using the
// PEM encoded CSR and send it to API server.
func RequestCertificate(client clientset.Interface, csrData []byte, name string, signerName string, usages []certificatesv1.KeyUsage, privateKey interface{}) (reqName string, reqUID types.UID, err error) {
// PEM encoded CSR and send it to API server. An optional requestedDuration may be passed
// to set the spec.expirationSeconds field on the CSR to control the lifetime of the issued
// certificate. This is not guaranteed as the signer may choose to ignore the request.
func RequestCertificate(client clientset.Interface, csrData []byte, name, signerName string, requestedDuration *time.Duration, usages []certificatesv1.KeyUsage, privateKey interface{}) (reqName string, reqUID types.UID, err error) {
csr := &certificatesv1.CertificateSigningRequest{
// Username, UID, Groups will be injected by API server.
TypeMeta: metav1.TypeMeta{Kind: "CertificateSigningRequest"},
@ -62,6 +64,9 @@ func RequestCertificate(client clientset.Interface, csrData []byte, name string,
if len(csr.Name) == 0 {
csr.GenerateName = "csr-"
}
if requestedDuration != nil {
csr.Spec.ExpirationSeconds = DurationToExpirationSeconds(*requestedDuration)
}
reqName, reqUID, err = create(client, csr)
switch {
@ -85,6 +90,14 @@ func RequestCertificate(client clientset.Interface, csrData []byte, name string,
}
}
func DurationToExpirationSeconds(duration time.Duration) *int32 {
return pointer.Int32(int32(duration / time.Second))
}
func ExpirationSecondsToDuration(expirationSeconds int32) time.Duration {
return time.Duration(expirationSeconds) * time.Second
}
func get(client clientset.Interface, name string) (*certificatesv1.CertificateSigningRequest, error) {
v1req, v1err := client.CertificatesV1().CertificateSigningRequests().Get(context.TODO(), name, metav1.GetOptions{})
if v1err == nil || !apierrors.IsNotFound(v1err) {