#### TLS Bootstrapping
* [alpha] Rotation of the server TLS certificate on the kubelet. See [TLS bootstrapping - approval controller](https://kubernetes.io/docs/admin/kubelet-tls-bootstrapping/#approval-controller).

* [alpha] Rotation of the client TLS certificate on the kubelet. See [TLS bootstrapping - kubelet configuration](https://kubernetes.io/docs/admin/kubelet-tls-bootstrapping/#kubelet-configuration).

    * --boot_id_file
    * --container_hints
    * --containerd
    * --docker
    * --docker_env_metadata_whitelist
    * --docker_only
    * --docker-tls
    * --docker-tls-ca
    * --docker-tls-cert
    * --docker-tls-key
    * --enable_load_reader
    * --event_storage_age_limit
    * --event_storage_event_limit
    * --global_housekeeping_interval
    * --google-json-key

* `kubeadm join` is now blocking on the kubelet performing the TLS Bootstrap properly. Earlier, `kubeadm join` only did the discovery part and exited successfully without checking that the kubelet actually started properly and performed the TLS bootstrap correctly. Now, as kubeadm runs some post-join steps (for example, annotating the Node API object with the CRISocket), `kubeadm join` is now waiting for the kubelet to perform the TLS Bootstrap, and then uses that credential to perform further actions....

        * requests for a TLS client certificate for any node are approved if the CSR creator has `create` permission on the `certificatesigningrequests` resource and `nodeclient` subresource in the `certificates.k8s.io` API group

- TLS Server Name overrides can now be specified in a kubeconfig file and via --tls-server-name in kubectl ([#88769](https://github.com/kubernetes/kubernetes/pull/88769), [@deads2k](https://github.com/deads2k)) [SIG API Machinery, Auth and CLI]

#### Metrics:

- Kubeadm increased to 5 minutes its timeout for the TLS bootstrapping process to complete upon join ([#89735](https://github.com/kubernetes/kubernetes/pull/89735), [@rosti](https://github.com/rosti)) [SIG Cluster Lifecycle]
- hyperkube: Use debian-hyperkube-base@v1.1.0 image
  

### kubeadm
* **[beta]** Introduces an API for clients to request TLS certificates from the API server. See the [tutorial](https://kubernetes.io/docs/tasks/tls/managing-tls-in-a-cluster).

- kube-controller-manager currently needs a writable `--cert-dir` (default is `/var/run/kubernetes`) for generating self-signed certificates, when no `--tls-cert-file` or `--tls-private-key-file` are provided.

- github.com/lucas-clemente/quic-go: [v0.10.2](https://github.com/lucas-clemente/quic-go/tree/v0.10.2)
- github.com/marten-seemann/qtls: [v0.2.3](https://github.com/marten-seemann/qtls/tree/v0.2.3)
- github.com/mattn/go-colorable: [v0.0.9](https://github.com/mattn/go-colorable/tree/v0.0.9)
- github.com/mattn/go-isatty: [v0.0.3](https://github.com/mattn/go-isatty/tree/v0.0.3)

- Added support for max attach limit for Cinder ([#72980](https://github.com/kubernetes/kubernetes/pull/72980), [@gnufied](https://github.com/gnufied))
- Enabled mTLS encryption between etcd and kube-apiserver in GCE ([#70144](https://github.com/kubernetes/kubernetes/pull/70144), [@wenjiaswe](https://github.com/wenjiaswe))