CIS Kubernetes Benchmark v1.9.0

2.1 Ensure that the --cert-file and --key-file arguments are set as appropriate (Automated)
Profile Applicability:
Level 1 - Master Node
Description:
Configure TLS encryption for the etcd service.
Rationale:
etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should be encrypted in transit.
Impact:
Client connections only over TLS would be served.
Audit:
Run the following command on the etcd server node 

ps -ef | grep etcd 

Verify that the --cert-file and the --key-file arguments are set as appropriate.
Remediation:
Follow the etcd service documentation and configure TLS encryption. Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and set the below parameters. 

--cert-file= 
--key-file= 

Default Value:
By default, TLS encryption is not set. 

2.2 Ensure that the --client-cert-auth argument is set to true (Automated)
Profile Applicability:
Level 1 - Master Node
Description:
Enable client authentication on etcd service.
Rationale:
etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should not be available to unauthenticated clients. You should enable the client authentication via valid certificates to secure the access to the etcd service.
Impact:
All clients attempting to access the etcd server will require a valid client certificate.
Audit:
Run the following command on the etcd server node: 

ps -ef | grep etcd 

Verify that the --client-cert-auth argument is set to true.
Remediation:
Edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and set the below parameter. 

--client-cert-auth="true" 

Default Value:
By default, the etcd service can be queried by unauthenticated clients. 

2.3 Ensure that the --auto-tls argument is not set to true (Automated)
Profile Applicability:
Level 1 - Master Node
Description:
Do not use self-signed certificates for TLS.
Rationale:
etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should not be available to unauthenticated clients. You should enable the client authentication via valid certificates to secure the access to the etcd service.
Impact:
Clients will not be able to use self-signed certificates for TLS.
Audit:
Run the following command on the etcd server node: 

ps -ef | grep etcd 

Verify that if the --auto-tls argument exists, it is not set to true.
Remediation:
Edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and either remove the --auto-tls parameter or set it to false. 

--auto-tls=false 

Default Value:
By default, --auto-tls is set to false.

2.4 Ensure that the --peer-cert-file and --peer-key-file arguments are set as appropriate (Automated)
Profile Applicability:
Level 1 - Master Node
Description:
etcd should be configured to make use of TLS encryption for peer connections.
Rationale:
etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should be encrypted in transit and also amongst peers in the etcd clusters.
Impact:
etcd cluster peers would need to set up TLS for their communication.
Audit:
Run the following command on the etcd server node: 

ps -ef | grep etcd 

Verify that the --peer-cert-file and --peer-key-file arguments are set as appropriate.
Note: This recommendation is applicable only for etcd clusters. If you are using only one etcd server in your environment then this recommendation is not applicable.
Remediation:
Follow the etcd service documentation and configure peer TLS encryption as appropriate for your etcd cluster. Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and set the below parameters.

--peer-client-file=
--peer-key-file= 

Default Value:
Note: This recommendation is applicable only for etcd clusters. If you are using only one etcd server in your environment then this recommendation is not applicable. 
By default, peer communication over TLS is not configured.

2.5 Ensure that the --peer-client-cert-auth argument is set to true (Automated)
Profile Applicability:
Level 1 - Master Node
Description:
etcd should be configured for peer authentication.
Rationale:
etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should be accessible only by authenticated etcd peers in the etcd cluster.
Impact:
All peers attempting to communicate with the etcd server will require a valid client certificate for authentication.
Audit:
Run the following command on the etcd server node: 

ps -ef | grep etcd 

Verify that the --peer-client-cert-auth argument is set to true.
Note: This recommendation is applicable only for etcd clusters. If you are using only one etcd server in your environment then this recommendation is not applicable.
Remediation:
Edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and set the below parameter.

--peer-client-cert-auth=true 

Default Value:
Note: This recommendation is applicable only for etcd clusters. If you are using only one etcd server in your environment then this recommendation is not applicable. 
By default, --peer-client-cert-auth argument is set to false. 

2.6 Ensure that the --peer-auto-tls argument is not set to true (Automated)
Profile Applicability:
Level 1 - Master Node
Description:
Do not use automatically generated self-signed certificates for TLS connections between peers.
Rationale:
etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should be accessible only by authenticated etcd peers in the etcd cluster. Hence, do not use self-signed certificates for authentication.
Impact:
All peers attempting to communicate with the etcd server will require a valid client certificate for authentication.
Audit:
Run the following command on the etcd server node: 

ps -ef | grep etcd 

Verify that if the --peer-auto-tls argument exists, it is not set to true.
Note: This recommendation is applicable only for etcd clusters. If you are using only one etcd server in your environment then this recommendation is not applicable.
Remediation:
Edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and either remove the --peer-auto-tls parameter or set it to false. 

--peer-auto-tls=false 

Default Value:
Note: This recommendation is applicable only for etcd clusters. If you are using only one etcd server in your environment then this recommendation is not applicable. 
By default, --peer-auto-tls argument is set to false. 

2.7 Ensure that a unique Certificate Authority is used for etcd (Manual)
Profile Applicability:
Level 2 - Master Node
Description:
Use a different certificate authority for etcd from the one used for Kubernetes.
Rationale:
etcd is a highly available key-value store used by Kubernetes deployments for persistent storage of all of its REST API objects. Its access should be restricted to specifically designated clients and peers only.
Authentication to etcd is based on whether the certificate presented was issued by a trusted certificate authority. There is no checking of certificate attributes such as common name or subject alternative name. As such, if any attackers were able to gain access to any certificate issued by the trusted certificate authority, they would be able to gain full access to the etcd database.
Impact:
Additional management of the certificates and keys for the dedicated certificate authority will be required.
Audit:
Review the CA used by the etcd environment and ensure that it does not match the CA certificate file used for the management of the overall Kubernetes cluster. Run the following command on the master node: 

ps -ef | grep etcd 

Note the file referenced by the --trusted-ca-file argument. 
Run the following command on the master node: 

ps -ef | grep apiserver 

Verify that the file referenced by the --client-ca-file for apiserver is different from the --trusted-ca-file used by etcd.
Remediation:
Follow the etcd documentation and create a dedicated certificate authority setup for the etcd service. 
Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and set the below parameter.

--trusted-ca-file=</path/to/ca-file> 

Default Value:
By default, no etcd certificate is created and used.