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Merge pull request kubernetes#29154 from cslauritsen/patch-1
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k8s-ci-robot authored Jul 29, 2021
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28 changes: 15 additions & 13 deletions content/en/docs/tasks/administer-cluster/securing-a-cluster.md
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Expand Up @@ -26,7 +26,7 @@ and provides recommendations on overall security.

## Controlling access to the Kubernetes API

As Kubernetes is entirely API driven, controlling and limiting who can access the cluster and what actions
As Kubernetes is entirely API-driven, controlling and limiting who can access the cluster and what actions
they are allowed to perform is the first line of defense.

### Use Transport Layer Security (TLS) for all API traffic
Expand All @@ -40,7 +40,7 @@ potentially unsecured traffic.
### API Authentication

Choose an authentication mechanism for the API servers to use that matches the common access patterns
when you install a cluster. For instance, small single user clusters may wish to use a simple certificate
when you install a cluster. For instance, small, single-user clusters may wish to use a simple certificate
or static Bearer token approach. Larger clusters may wish to integrate an existing OIDC or LDAP server that
allow users to be subdivided into groups.

Expand All @@ -54,7 +54,7 @@ Consult the [authentication reference document](/docs/reference/access-authn-aut
Once authenticated, every API call is also expected to pass an authorization check. Kubernetes ships
an integrated [Role-Based Access Control (RBAC)](/docs/reference/access-authn-authz/rbac/) component that matches an incoming user or group to a
set of permissions bundled into roles. These permissions combine verbs (get, create, delete) with
resources (pods, services, nodes) and can be namespace or cluster scoped. A set of out of the box
resources (pods, services, nodes) and can be namespace-scoped or cluster-scoped. A set of out-of-the-box
roles are provided that offer reasonable default separation of responsibility depending on what
actions a client might want to perform. It is recommended that you use the
[Node](/docs/reference/access-authn-authz/node/) and
Expand All @@ -69,8 +69,8 @@ With authorization, it is important to understand how updates on one object may
other places. For instance, a user may not be able to create pods directly, but allowing them to
create a deployment, which creates pods on their behalf, will let them create those pods
indirectly. Likewise, deleting a node from the API will result in the pods scheduled to that node
being terminated and recreated on other nodes. The out of the box roles represent a balance
between flexibility and the common use cases, but more limited roles should be carefully reviewed
being terminated and recreated on other nodes. The out-of-the box roles represent a balance
between flexibility and common use cases, but more limited roles should be carefully reviewed
to prevent accidental escalation. You can make roles specific to your use case if the out-of-box ones don't meet your needs.

Consult the [authorization reference section](/docs/reference/access-authn-authz/authorization/) for more information.
Expand Down Expand Up @@ -104,7 +104,7 @@ reserved resources like memory, or to provide default limits when none are speci
### Controlling what privileges containers run with

A pod definition contains a [security context](/docs/tasks/configure-pod-container/security-context/)
that allows it to request access to running as a specific Linux user on a node (like root),
that allows it to request access to run as a specific Linux user on a node (like root),
access to run privileged or access the host network, and other controls that would otherwise
allow it to run unfettered on a hosting node. [Pod security policies](/docs/concepts/policy/pod-security-policy/)
can limit which users or service accounts can provide dangerous security context settings. For example, pod security policies can limit volume mounts, especially `hostPath`, which are aspects of a pod that should be controlled.
Expand Down Expand Up @@ -155,10 +155,10 @@ within their namespaces. Many of the supported [Kubernetes networking providers]
now respect network policy.

Quota and limit ranges can also be used to control whether users may request node ports or
load balanced services, which on many clusters can control whether those users applications
load-balanced services, which on many clusters can control whether those users applications
are visible outside of the cluster.

Additional protections may be available that control network rules on a per plugin or per
Additional protections may be available that control network rules on a per-plugin or per-
environment basis, such as per-node firewalls, physically separating cluster nodes to
prevent cross talk, or advanced networking policy.

Expand All @@ -169,15 +169,15 @@ By default these APIs are accessible by pods running on an instance and can cont
credentials for that node, or provisioning data such as kubelet credentials. These credentials
can be used to escalate within the cluster or to other cloud services under the same account.

When running Kubernetes on a cloud platform limit permissions given to instance credentials, use
When running Kubernetes on a cloud platform, limit permissions given to instance credentials, use
[network policies](/docs/tasks/administer-cluster/declare-network-policy/) to restrict pod access
to the metadata API, and avoid using provisioning data to deliver secrets.

### Controlling which nodes pods may access

By default, there are no restrictions on which nodes may run a pod. Kubernetes offers a
[rich set of policies for controlling placement of pods onto nodes](/docs/concepts/scheduling-eviction/assign-pod-node/)
and the [taint based pod placement and eviction](/docs/concepts/scheduling-eviction/taint-and-toleration/)
and the [taint-based pod placement and eviction](/docs/concepts/scheduling-eviction/taint-and-toleration/)
that are available to end users. For many clusters use of these policies to separate workloads
can be a convention that authors adopt or enforce via tooling.

Expand Down Expand Up @@ -223,8 +223,9 @@ do not use.
The shorter the lifetime of a secret or credential the harder it is for an attacker to make
use of that credential. Set short lifetimes on certificates and automate their rotation. Use
an authentication provider that can control how long issued tokens are available and use short
lifetimes where possible. If you use service account tokens in external integrations, plan to
rotate those tokens frequently. For example, once the bootstrap phase is complete, a bootstrap token used for setting up nodes should be revoked or its authorization removed.
lifetimes where possible. If you use service-account tokens in external integrations, plan to
rotate those tokens frequently. For example, once the bootstrap phase is complete, a bootstrap
token used for setting up nodes should be revoked or its authorization removed.

### Review third party integrations before enabling them

Expand All @@ -246,7 +247,8 @@ and may grant an attacker significant visibility into the state of your cluster.
your backups using a well reviewed backup and encryption solution, and consider using full disk
encryption where possible.

Kubernetes supports [encryption at rest](/docs/tasks/administer-cluster/encrypt-data/), a feature introduced in 1.7, and beta since 1.13. This will encrypt `Secret` resources in etcd, preventing
Kubernetes supports [encryption at rest](/docs/tasks/administer-cluster/encrypt-data/), a feature
introduced in 1.7, and beta since 1.13. This will encrypt `Secret` resources in etcd, preventing
parties that gain access to your etcd backups from viewing the content of those secrets. While
this feature is currently beta, it offers an additional level of defense when backups
are not encrypted or an attacker gains read access to etcd.
Expand Down

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