Update localization guidelines (#10485)
* Update localization guidelines for language labels
Continuing work
Continuing work
Continuing work
More work in progress
Add local OWNERS folders
Add an OWNERS file to Chinese
Remove shortcode for repos
Add Japanese
Alphabetize languages, change weights accordingly
More updates
Add Korean in Korean
Add English to languageName
Feedback from gochist
Move Chinese content from cn/ to zh/
Move OWNERS from cn/ to zh/
Resolve merge conflicts by updating from master
Add files back in to prep for resolution
After rebase on upstream/master, remove files
Review and update localization guidelines
Feedback from gochist, tnir, cstoku
Add a trailing newline to content/ja/OWNERS
Add a trailing newline to content/zh/OWNERS
Drop requirement for GH repo project
Clarify language about forks/branches
Edits and typos
Remove a shortcode specific to a multi-repo language setup
Update aliases and owners
Add explicit OWNERS for content/en
Migrate content from Chinese repo, update regex in config.toml
Remove untranslated strings
Add trailing newline to content/en/OWNERS
Add trailing newlines to OWNERS files
add Jaguar project description (#10433)
* add Jaguar project description
[Jaguar](https://gitlab.com/sdnlab/jaguar) is an open source solution for Kubernetes's network based on OpenDaylight.
Jaguar provides overlay network using vxlan and Jaguar CNIPlugin provides one IP address per pod.
* Minor newline tweak
blog post for azure vmss (#10538)
Add microk8s to pick-right-solution.md (#10542)
* Add microk8s to pick-right-solution.md
Microk8s is a single-command installation of upstream Kubernetes on any Linux and should be included in the list of local-machine solutions.
* capitalized Istio
Add microk8s to foundational.md (#10543)
* Add microk8s to foundational.md
Adding microk8s as credible and stable alternative to get started with Kubernetes on a local machine. This is especially attractive for those not wanting to incur the overhead of running a VM for a local cluster.
* Update foundational.md
Thank you for your suggestions! LMK if this works now?
* Rewrote first paragraph
And included a bullet list of features of microk8s
* Copyedit
fix typo (#10545)
Fix the kubectl subcommands links. (#10550)
Signed-off-by: William Zhang <warmchang@outlook.com>
Fix command issue (#10515)
Signed-off-by: mooncake <xcoder@tenxcloud.com>
remove imported community files per issue 10184 (#10501)
networking.md: Markdown fix (#10498)
Fix front matter, federation command-line tools (#10500)
Clean up glossary entry (#10399)
update slack link (#10536)
typo in StatefulSet docs (#10558)
fix discription about horizontal pod autoscale (#10557)
Remove redundant symbols (#10556)
Fix issue #10520 (#10554)
Signed-off-by: William Zhang <warmchang@outlook.com>
Update api-concepts.md (#10534)
Revert "Fix command issue (#10515)"
This reverts commit c02a7fb9f9.
Update memory-constraint-namespace.md (#10530)
update memory request to 100MiB corresponding the yaml content
Blog: Introducing Volume Snapshot Alpha for Kubernetes (#10562)
* blog post for azure vmss
* snapshot blog post
Resolve merge conflicts in OWNERS*
Minor typo fix (#10567)
Not sure what's supposed to be here, proposing removing it.
* Feedback from gochist
Tweaks to feedback
* Feedback from ClaudiaJKang
This commit is contained in:
Zach Corleissen
committed by
k8s-ci-robot
k8s-ci-robot
parent
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commit
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---
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approvers:
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- ericchiang
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- mikedanese
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- jcbsmpsn
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title: TLS bootstrapping
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---
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{{< toc >}}
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## Overview
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This document describes how to set up TLS client certificate bootstrapping for kubelets.
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Kubernetes 1.4 introduced an API for requesting certificates from a cluster-level Certificate Authority (CA). The original intent of this API is to enable provisioning of TLS client certificates for kubelets. The proposal can be found [here](https://github.com/kubernetes/kubernetes/pull/20439)
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and progress on the feature is being tracked as [feature #43](https://github.com/kubernetes/features/issues/43).
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## kube-apiserver configuration
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The API server should be configured with an [authenticator](/docs/admin/authentication/) that can authenticate tokens as a user in the `system:bootstrappers` group.
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This group will later be used in the controller-manager configuration to scope approvals in the default approval
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controller. As this feature matures, you should ensure tokens are bound to a Role-Based Access Control (RBAC) policy which limits requests
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(using the bootstrap token) strictly to client requests related to certificate provisioning. With RBAC in place, scoping the tokens to a group allows for great flexibility (e.g. you could disable a particular bootstrap group's access when you are done provisioning the nodes).
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While any authentication strategy can be used for the kubelet's initial bootstrap credentials, the following two authenticators are recommended for ease of provisioning.
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1. [Bootstrap Tokens](/docs/admin/bootstrap-tokens/) - __alpha__
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2. [Token authentication file](###token-authentication-file)
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Using bootstrap tokens is currently __alpha__ and will simplify the management of bootstrap token management especially in a HA scenario.
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### Token authentication file
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Tokens are arbitrary but should represent at least 128 bits of entropy derived from a secure random number
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generator (such as /dev/urandom on most modern systems). There are multiple ways you can generate a token. For example:
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`head -c 16 /dev/urandom | od -An -t x | tr -d ' '`
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will generate tokens that look like `02b50b05283e98dd0fd71db496ef01e8`
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The token file should look like the following example, where the first three values can be anything and the quoted group
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name should be as depicted:
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```
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02b50b05283e98dd0fd71db496ef01e8,kubelet-bootstrap,10001,"system:bootstrappers"
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```
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Add the `--token-auth-file=FILENAME` flag to the kube-apiserver command (in your systemd unit file perhaps) to enable the token file.
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See docs [here](/docs/admin/authentication/#static-token-file) for further details.
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### Client certificate CA bundle
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Add the `--client-ca-file=FILENAME` flag to the kube-apiserver command to enable client certificate authentication,
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referencing a certificate authority bundle containing the signing certificate (e.g. `--client-ca-file=/var/lib/kubernetes/ca.pem`).
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## kube-controller-manager configuration
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The API for requesting certificates adds a certificate-issuing control loop to the Kubernetes Controller Manager. This takes the form of a
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[cfssl](https://blog.cloudflare.com/introducing-cfssl/) local signer using assets on disk. Currently, all certificates issued have one year validity and a default set of key usages.
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### Signing assets
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You must provide a Certificate Authority in order to provide the cryptographic materials necessary to issue certificates.
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This CA should be trusted by kube-apiserver for authentication with the `--client-ca-file=FILENAME` flag. The management
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of the CA is beyond the scope of this document but it is recommended that you generate a dedicated CA for Kubernetes.
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Both certificate and key are assumed to be PEM-encoded.
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The kube-controller-manager flags are:
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```
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--cluster-signing-cert-file="/etc/path/to/kubernetes/ca/ca.crt" --cluster-signing-key-file="/etc/path/to/kubernetes/ca/ca.key"
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```
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### Approval controller
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In 1.7 the experimental "group auto approver" controller is dropped in favor of the new `csrapproving` controller
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that ships as part of [kube-controller-manager](/docs/admin/kube-controller-manager/) and is enabled by default.
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The controller uses the [`SubjectAccessReview` API](/docs/admin/authorization/#checking-api-access) to determine
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if a given user is authorized to request a CSR, then approves based on the authorization outcome. To prevent
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conflicts with other approvers, the builtin approver doesn't explicitly deny CSRs, only ignoring unauthorized requests.
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The controller categorizes CSRs into three subresources:
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1. `nodeclient` - a request by a user for a client certificate with `O=system:nodes` and `CN=system:node:(node name)`.
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2. `selfnodeclient` - a node renewing a client certificate with the same `O` and `CN`.
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3. `selfnodeserver` - a node renewing a serving certificate. (ALPHA, requires feature gate)
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The checks to determine if a CSR is a `selfnodeserver` request is currently tied to the kubelet's credential rotation
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implementation, an __alpha__ feature. As such, the definition of `selfnodeserver` will likely change in a future and
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requires the `RotateKubeletServerCertificate` feature gate on the controller manager. The feature progress can be
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tracked at [kubernetes/features#267](https://github.com/kubernetes/features/issues/267).
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```
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--feature-gates=RotateKubeletServerCertificate=true
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```
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The following RBAC `ClusterRoles` represent the `nodeclient`, `selfnodeclient`, and `selfnodeserver` capabilities. Similar roles
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may be automatically created in future releases.
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```yml
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# A ClusterRole which instructs the CSR approver to approve a user requesting
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# node client credentials.
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: approve-node-client-csr
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rules:
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- apiGroups: ["certificates.k8s.io"]
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resources: ["certificatesigningrequests/nodeclient"]
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verbs: ["create"]
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---
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# A ClusterRole which instructs the CSR approver to approve a node renewing its
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# own client credentials.
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: approve-node-client-renewal-csr
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rules:
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- apiGroups: ["certificates.k8s.io"]
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resources: ["certificatesigningrequests/selfnodeclient"]
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verbs: ["create"]
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---
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# A ClusterRole which instructs the CSR approver to approve a node requesting a
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# serving cert matching its client cert.
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: approve-node-server-renewal-csr
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rules:
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- apiGroups: ["certificates.k8s.io"]
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resources: ["certificatesigningrequests/selfnodeserver"]
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verbs: ["create"]
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```
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These powers can be granted to credentials, such as bootstrapping tokens. For example, to replicate the behavior
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provided by the removed auto-approval flag, of approving all CSRs by a single group:
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```
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# REMOVED: This flag no longer works as of 1.7.
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--insecure-experimental-approve-all-kubelet-csrs-for-group="system:bootstrappers"
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```
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An admin would create a `ClusterRoleBinding` targeting that group.
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```yml
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# Approve all CSRs for the group "system:bootstrappers"
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kind: ClusterRoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: auto-approve-csrs-for-group
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subjects:
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- kind: Group
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name: system:bootstrappers
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apiGroup: rbac.authorization.k8s.io
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roleRef:
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kind: ClusterRole
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name: approve-node-client-csr
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apiGroup: rbac.authorization.k8s.io
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```
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To let a node renew its own credentials, an admin can construct a `ClusterRoleBinding` targeting
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that node's credentials:
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```yml
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kind: ClusterRoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: node1-client-cert-renewal
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subjects:
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- kind: User
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name: system:node:node-1 # Let "node-1" renew its client certificate.
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apiGroup: rbac.authorization.k8s.io
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roleRef:
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kind: ClusterRole
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name: approve-node-client-renewal-csr
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apiGroup: rbac.authorization.k8s.io
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```
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Deleting the binding will prevent the node from renewing its client credentials, effectively
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removing it from the cluster once its certificate expires.
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## kubelet configuration
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To request a client certificate from kube-apiserver, the kubelet first needs a path to a kubeconfig file that contains the
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bootstrap authentication token. You can use `kubectl config set-cluster`, `set-credentials`, and `set-context` to build this kubeconfig. Provide the name `kubelet-bootstrap` to `kubectl config set-credentials` and include `--token=<token-value>` as follows:
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```
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kubectl config set-credentials kubelet-bootstrap --token=${BOOTSTRAP_TOKEN} --kubeconfig=bootstrap.kubeconfig
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```
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When starting the kubelet, if the file specified by `--kubeconfig` does not exist, the bootstrap kubeconfig is used to request a client certificate from the API server. On approval of the certificate request and receipt back by the kubelet, a kubeconfig file referencing the generated key and obtained certificate is written to the path specified by `--kubeconfig`. The certificate and key file will be placed in the directory specified by `--cert-dir`.
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**Note:** The following flags are required to enable this bootstrapping when starting the kubelet:
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```
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--bootstrap-kubeconfig="/path/to/bootstrap/kubeconfig"
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```
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Additionally, in 1.7 the kubelet implements __alpha__ features for enabling rotation of both its client and/or serving certs.
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These can be enabled through the respective `RotateKubeletClientCertificate` and `RotateKubeletServerCertificate` feature
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flags on the kubelet, but may change in backward incompatible ways in future releases.
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```
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--feature-gates=RotateKubeletClientCertificate=true,RotateKubeletServerCertificate=true
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```
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`RotateKubeletClientCertificate` causes the kubelet to rotate its client certificates by creating new CSRs as its existing
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credentials expire. `RotateKubeletServerCertificate` causes the kubelet to both request a serving certificate after
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bootstrapping its client credentials and rotate the certificate. The serving cert currently does not request DNS or IP
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SANs.
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## kubectl approval
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The signing controller does not immediately sign all certificate requests. Instead, it waits until they have been flagged with an
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"Approved" status by an appropriately-privileged user. This is intended to eventually be an automated process handled by an external
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approval controller, but for the alpha version of the API it can be done manually by a cluster administrator using kubectl.
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An administrator can list CSRs with `kubectl get csr` and describe one in detail with `kubectl describe csr <name>`. Before the 1.6 release there were
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[no direct approve/deny commands](https://github.com/kubernetes/kubernetes/issues/30163) so an approver had to update
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the Status field directly ([rough how-to](https://github.com/gtank/csrctl)). Later versions of Kubernetes offer `kubectl certificate approve <name>` and `kubectl certificate deny <name>` commands.
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