* **Pod**: Wrapper around a container or multiple containers with. A pod should only contain one application \(so usually, a pod run just 1 container\). The pod is the way kubernetes abstracts the container technology running.
* **Service**: Each pod has 1 service attached, which is 1 **IP address**. It's goal is to maintain the communication between pods even if one dies and a new copy is run. It can be configured as internal or external. The service also actuates as a **load balancer when 2 pods are connected** to the same service.
* **Kubelet**: Primary node agent. The component that establishes communication between node and kubectl, and only can run pods \(through API server\). The kubelet doesn’t manage containers that were not created by Kubernetes.
* **Kube-proxy**: is the service in charge of the communications \(services\) between the apiserver and the node. The base is an IPtables for nodes. Most experienced users could install other kube-proxies from other vendors.
* **Sidecar container**: Sidecar containers are the containers that should run along with the main container in the pod. This sidecar pattern extends and enhances the functionality of current containers without changing them. Nowadays, We know that we use container technology to wrap all the dependencies for the application to run anywhere. A container does only one thing and does that thing very well.
* **Api Server:** Is the way the users and the pods use to communicate with the master process. Only authenticated request should be allowed.
* **Scheduler**: Scheduling refers to making sure that Pods are matched to Nodes so that Kubelet can run them. It has enough intelligence to decide which node has more available resources the assign the new pod to it. Note that the scheduler doesn't start new pods, it just communicate with the Kubelet process running inside the node, which will launch the new pod.
* **Kube Controller manager**: It checks resources like replica sets or deployments to check if, for example, the correct number of pods or nodes are running. In case a pod is missing, it will communicate with the scheduler to start a new one. It controls replication, tokens, and account services to the API.
* **etcd**: Data storage, persistent, consistent, and distributed. Is Kubernetes’s database and the key-value storage where it keeps the complete state of the clusters \(each change is logged here\). Components like the Scheduler or the Controller manager depends on this date to know which changes have occurred \(available resourced of the nodes, number of pods running...\)
Note that as the might be several nodes \(running several pods\), there might also be several master processes which their access to the Api server load balanced and their etcd synchronized.
#### Volumes:
When a pod creates data that shouldn't be lost when the pod disappear it should be stored in a physical volume. **Kubernetes allow to attach a volume to a pod to persist the data**. The volume can be in the local machine or in a remote storage.
#### Other configurations:
* **ConfigMap**: You can configure **URLs** to access services. The pod will obtain data from here to learn how to communicate with the rest of the services \(pods\). Not that this is not the recommended place to save credentials!
* **Secret**: This is the place to **store secret data** like passwords, API keys... encoded in B64. The pod will be able to access this data to use the required credentials.
* **Deployments**: This is where the components to be run by kubernetes are indicated. A user usually won't work directly with pods, pods are abstracted in **ReplicaSets** \(number of same pods replicated\), which are run via deployments. Note that deployments are for **stateless** applications. The minimum configuration for a deployment is the name and the image to run.
**Minikube** can be used to perform some **quick tests** on kubernetes without needing to deploy a whole kubernetes environment. It will run the **master and node processes in one machine**. Minikube will use virtualbox to run the node. See [**here how to install it**](https://minikube.sigs.k8s.io/docs/start/).
```text
$ minikube start
😄 minikube v1.19.0 on Ubuntu 20.04
✨ Automatically selected the virtualbox driver. Other choices: none, ssh
💿 Downloading VM boot image ...
> minikube-v1.19.0.iso.sha256: 65 B / 65 B [-------------] 100.00% ? p/s 0s
**`Kubectl`** is the command line tool fro kubernetes clusters. It communicates with the Api server of the master process to perform actions in kubernetes or to ask for data.
Each configuration file has 3 parts: **metadata**, **specification** \(what need to be launch\), **status** \(desired state\).
Inside the specification of the deployment configuration file you can find the template defined with a new configuration structure defining the image to run:
Note how in the metadata element key-value pairs are created. In the following case: "app": "nginx". Then, this key-value pair can be used on other parts of the configuration file:
A Secret is an object that contains a small amount of sensitive data such as a password, a token or a key. Such information might otherwise be put in a Pod specification or in an image. Users can create Secrets and the system also creates some Secrets. The name of a Secret object must be a valid **DNS subdomain name**.
Secrets can be things like:
* API, SSH Keys.
* OAuth tokens.
* Credentials, Passwords \(plain text or b64 + encryption\).
kubectl run pod --image=nginx -oyaml --dry-run=client
kubectl run pod --image=nginx -oyaml --dry-run=client > <podName.yaml>
```
This is the generated file:
```text
apiVersion: v1
kind: Pod
metadata:
name: mypod
spec:
containers:
- name: mypod
image: redis
volumeMounts:
- name: <secret_01>
mountPath: "/etc/<secret_01>"
readOnly: true
volumes:
- name: <secret_01>
secret:
secretName: <secret_01>
items:
- key: username
path: my-group/my-username
```
### Using Secrets as environment variables
If you want to use a secret in an environment variable to allow the rest of the pods to reference the same secret, you could use:
In the you could add the uncomment lines:
```text
#apiVersion: v1
#kind: Pod
#metadata:
# name: secret-env-pod
#spec:
# containers:
# - name: mycontainer
# image: redis
env:
- name: SECRET_USERNAME
valueFrom:
secretKeyRef:
name: mysecret
key: username
# - name: SECRET_PASSWORD
# valueFrom:
# secretKeyRef:
# name: mysecret
# key: password
# restartPolicy: Never
```
The result is:
```text
apiVersion: v1
kind: Pod
metadata:
name: mypod
spec:
containers:
- name: mypod
image: redis
env:
- name: PASSWORD
valueFrom:
secretKeyRef:
name: <secret_02>
key: <password>
volumeMounts:
- name: <secret_01>
mountPath: "/etc/<secret_01>"
readOnly: true
volumes:
- name: <secret_01>
secret:
secretName: <secret_01>
items:
- key: username
path: my-group/my-username
```
Save and:
```text
kubectl -f <podName.yaml> delete --force
kubectl -f <podName.yaml> create
```
or:
```text
kubectl -f <podName.yaml> replace --force
```
More info: [https://kubernetes.io/docs/concepts/configuration/secret/\#using-secrets-as-environment-variables](https://kubernetes.io/docs/concepts/configuration/secret/#using-secrets-as-environment-variables)
### Discover secrets in docker:
To get the id of the container.
```text
docker ps | grep <service>
```
Inspect:
```text
docker inspect <docker_id>
```
Check env \(environment variable section\) for secrets and you will see:
* Passwords.
* Ip’s.
* Ports.
* Paths.
* Others… .
If you want to copy:
```text
docker cp <docket_id>:/etc/<secret_01><secret_01>
```
### Discover secrets in etcd: <a id="discover-secrets-in-etcd"></a>
Remember that etcd is a consistent and highly-available key-value store used as Kubernetes backing store for all cluster data. Let’s access to the secret in etcd:
### Adding encryption to the ETCD <a id="adding-encryption-to-the-etcd"></a>
So, by default all the secrets are in plain text unless you apply an encryption layer: If the identity provider is empty with the default value = {} so the secrets are in plain text. [https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/](https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/)
**Encryption types**
\| Name \| Encryption \| Strength \| Speed \| Key Length \| Other Considerations \| \|-\|-\|-\|-\|-\|-\| \| identity \| None \| N/A \| N/A \| N/A \| Resources written as-is without encryption. When set as the first provider, the resource will be decrypted as new values are written. \| \| aescbc \| AES-CBC with PKCS\#7 padding \| Strongest \| Fast \| 32-byte \| The recommended choice for encryption at rest but may be slightly slower than secretbox. \| \| secretbox \| XSalsa20 and Poly1305 \| Strong \| Faster \| 32-byte \| A newer standard and may not be considered acceptable in environments that require high levels of review. \| \| aesgcm \| AES-GCM with random nonce \| Must be rotated every 200k writes \| Fastest \| 16, 24, or 32-byte \| Is not recommended for use except when an automated key rotation scheme is implemented. \| \| kms \| Uses envelope encryption scheme: Data is encrypted by data encryption keys \(DEKs\) using AES-CBC with PKCS\#7 padding, DEKs are encrypted by key encryption keys \(KEKs\) according to configuration in Key Management Service \(KMS\) \| Strongest \| Fast \| 32-bytes \| The recommended choice for using a third party tool for key management. Simplifies key rotation, with a new DEK generated for each encryption, and KEK rotation controlled by the user. \|
The secrets will be encrypted with the above algorithms and encoded by base64.
Create a directory in /etc/kubernetes ; in this case you will name it as etcd, so you have:
```text
/etc/kubernetes/etcd
```
You create a yaml file with the configuration.
```text
vi <configFile.yaml>
```
You can copy the content of [https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/](https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/)
```text
apiVersion: apiserver.config.k8s.io/v1
kind: EncryptionConfiguration
resources:
- resources:
- secrets
providers:
- aescbc:
keys:
- name: key1
secret: <yourpassinb64>
- identity: {}
```
Generate pass in b64 \(remember to use a pass character with lenght = 16 or = 24 or = 32\) :
```text
echo -n <password> | base64
```
You can see how the encryption provider is not setting.
After that, you have to edit the file /etc/kubernetes/manifest/kube-apiserver.yaml and add the following lines into the sections: And add the following line: spec:
### Vulnerabilities - OS <a id="vulnerabilities---os"></a>
Is mandatory to keep in mind to define privilege and access control for container / pod:
* userID’s and groupID’s.
* Privileged or unprivileged escalation runs.
* Linux.
More info at: [https://kubernetes.io/docs/tasks/configure-pod-container/security-context/](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/)
#### userID and groupID <a id="userid-and-groupid"></a>
```text
# kubectl run pod --image=busybox --command -oyaml --dry-run=client > <podName.yaml> -- sh -c 'sleep 1h'
# vi <podName>.yaml
```
Add the uncomment lines:
```text
#apiVersion: v1
#kind: Pod
#metadata:
# name: security-context-demo
spec:
securityContext:
runAsUser: 1000
runAsGroup: 3000
fsGroup: 2000
# volumes:
# - name: sec-ctx-vol
# emptyDir: {}
# containers:
# - name: sec-ctx-demo
# image: busybox
# command: [ "sh", "-c", "sleep 1h" ]
securityContext:
runAsNonRoot: true
# volumeMounts:
# - name: sec-ctx-vol
# mountPath: /data/demo
# securityContext:
# allowPrivilegeEscalation: true
```
Save and:
```text
# kubectl -f <podName>.yaml delete --force
# kubectl -f <podName>.yaml create
```
Check permissions:
```text
# kubectl exec -it <podName> -- sh
```
#### How to disable privilege escalation: <a id="how-to-disable-privilege-escalation"></a>
Pod security policies control the security policies about how a pod has to run. More info at: [https://kubernetes.io/docs/concepts/policy/pod-security-policy/](https://kubernetes.io/docs/concepts/policy/pod-security-policy/)
More info at: [https://kubernetes.io/docs/tasks/configure-pod-container/security-context/](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/)
#### Create a sidecar proxy app <a id="create-a-sidecar-proxy-app"></a>
More info at: [https://kubernetes.io/docs/tasks/configure-pod-container/security-context/](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/)
## PART 3 - HARDENING.
### CLUSTER HARDENING - RBAC
[https://kubernetes.io/docs/reference/access-authn-authz/rbac/](https://kubernetes.io/docs/reference/access-authn-authz/rbac/) **RBAC** = Role-based access control \(RBAC\) is a method of regulating access to a computer or network resources based on the roles of individual users within your organization. RBAC authorization uses the rbac.authorization.k8s.io API group to drive authorization decisions, allowing you to dynamically configure policies through the Kubernetes API
To enable RBAC, start the API server with the –authorization-mode flag set to a comma-separated list that includes RBAC; for example:
Kubernetes supports multiple virtual clusters backed by the same physical cluster. These virtual clusters are called **namespaces**. These are intended for use in environments with many users spread across multiple teams, or projects. For clusters with a few to tens of users, you should not need to create or think about namespaces at all. Start using namespaces when you need the features they provide.
Namespaces provide a scope for names. Names of resources need to be unique within a namespace, but not across namespaces. Namespaces cannot be nested inside one another and each Kubernetes resource can only be in one namespace.
**VIEWING NAMESPACES:**
You can list the current namespaces in a cluster using:
```text
kubectl get namespace
NAME STATUS AGE
default Active 1d
kube-node-lease Active 1d
kube-public Active 1d
kube-system Active 1d
```
#### **SETTING THE NAMESPACE PREFERENCE**
You can permanently save the namespace for all subsequent kubectl commands in that context.
Not All Objects are in a Namespace. Most Kubernetes resources \(e.g. pods, services, replication controllers, and others\) are in some namespaces. However, namespace resources are not themselves in a namespace. And low-level resources, such as nodes and persistentVolumes, are not in any namespace.
To see which Kubernetes resources are and aren’t in a namespace:
**IN A NAMESPACE**
```text
kubectl api-resources --namespaced=true
```
**NOT IN A NAMESPACE**
```text
kubectl api-resources --namespaced=false
```
#### Difference between Role and ClusterRole: <a id="difference-between-role-and-clusterrole"></a>
**ROLE:**
RBAC allows setting different permissions for the same role with the independence of the namespace. Roles example:
```text
/api/v1/namespaces/{namespace}/pods/{name}/log
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
namespace: defaultGreen
name: pod-and-pod-logs-reader
rules:
- apiGroups: [""]
resources: ["pods", "pods/log"]
verbs: ["get", "list", "watch"]
```
Other example, same Role different nameSpace and permissions:
```text
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
namespace: defaultYellow
name: pod-and-pod-logs-reader
rules:
- apiGroups: [""]
resources: ["pods", "pods/log"]
verbs: ["watch"]
```
**CLUSTERROLE:**
A ClusterRole can be used to grant the same permissions as a Role. Because ClusterRoles are cluster-scoped, you can also use them to grant access to:
* cluster-scoped resources \(like nodes\).
* non-resource endpoints \(like /healthz\).
* namespaced resources \(like Pods\), across all namespaces.
For example you can use a ClusterRole to allow a particular user to run:
```text
kubectl get pods --all-namespaces
```
**CLUSTERROLE EXAMPLE:**
```text
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
# "namespace" omitted since ClusterRoles are not namespaced
name: secret-reader
rules:
- apiGroups: [""]
#
# at the HTTP level, the name of the resource for accessing Secret
# objects is "secrets"
resources: ["secrets"]
verbs: ["get", "watch", "list"]
```
**Role and ClusterRole Binding concept:**
A role binding grants the permissions defined in a role to a user or set of users. It holds a list of subjects \(users, groups, or service accounts\), and a reference to the role being granted. A RoleBinding grants permissions within a specific namespace whereas a ClusterRoleBinding grants that access cluster-wide.
A RoleBinding may reference any Role in the same namespace. Alternatively, a RoleBinding can reference a ClusterRole and bind that ClusterRole to the namespace of the RoleBinding. If you want to bind a ClusterRole to all the namespaces in your cluster, you use a ClusterRoleBinding.
RoleBinding example:
```text
apiVersion: rbac.authorization.k8s.io/v1
# This role binding allows "jane" to read pods in the "default" namespace.
# You need to already have a Role named "pod-reader" in that namespace.
kind: RoleBinding
metadata:
name: read-pods
namespace: default
subjects:
# You can specify more than one "subject"
- kind: User
name: jane # "name" is case sensitive
apiGroup: rbac.authorization.k8s.io
roleRef:
# "roleRef" specifies the binding to a Role / ClusterRole
kind: Role #this must be Role or ClusterRole
name: pod-reader # this must match the name of the Role or ClusterRole you wish to bind to
apiGroup: rbac.authorization.k8s.io
```
ClusterRoleBinding example:
```text
apiVersion: rbac.authorization.k8s.io/v1
# This cluster role binding allows anyone in the "manager" group to read secrets in any namespace.
kind: ClusterRoleBinding
metadata:
name: read-secrets-global
subjects:
- kind: Group
name: manager # Name is case sensitive
apiGroup: rbac.authorization.k8s.io
roleRef:
kind: ClusterRole
name: secret-reader
apiGroup: rbac.authorization.k8s.io
```
Permissions are additive so if you have a clusterRole with “list” and “delete” secrets you can add it with a Role with “get”. So be aware and test always your roles and permissions and specify what is ALLOWED, because everything is DENIED.
* Accounts for “persons” who hold a certificate integrated with the Kubernetes Identity Management of cloud providers.
* There is no Kubernetes user resource.
* A user has a Key and a Cert.
**HOW IT WORKS:**
Openssl –> CSR \(CertificateSigningRequest\) –> CertificateSignedRequest –> Kubernetes API <– CA
Be aware of the certificates because there is no way to invalidate them, you have to wait until the expiration date reaches. So what could you do in case you have to restrict the access?
* Create a new CA and reissue all certificates.
* Remove all RBAC access
**ServiceAccounts:**
* Accounts for “machines”. Is managed by the kubernetes API.
* Namespaced.
* Can interact with the Kubernetes API.
* The “Default” SA is in every namespaced used by the PODS.
### KUBERNETES API HARDENING
API requests are always assigned to a User, ServiceAccount or Anonymous request. After the request must be authenticated. [https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-authentication-authorization/](https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-authentication-authorization/)
**REQUEST PROCESS:**
User or K8s ServiceAccount –> Authentication –> Authorization –> Admission Control.
TIPS:
* Close ports.
* Avoid Anonymous access.
* NodeRestriction; No access from specific nodes to the API.
* Basically prevents kubelets from adding/removing/updating labels with a node-restriction.kubernetes.io/ prefix. This label prefix is reserved for administrators to label their Node objects for workload isolation purposes, and kubelets will not be allowed to modify labels with that prefix.
* And also, allows kubelets to add/remove/update these labels and label prefixes.
* Ensure with labels the secure workload isolation.
* Avoid specific pods from API access.
* Avoid ApiServer exposure to the internet.
* Avoid unauthorized access RBAC.
* ApiServer port with firewall and IP whitelisting.
### KUBERNETES CLUSTER HARDENING
Upgrade it frecuently, you will receive:
* Dependencies up to date.
* Bug and security patches.
Release cycles: Each 3 months there is a new minor release [https://kubernetes.io/docs/setup/release/version-skew-policy/](https://kubernetes.io/docs/setup/release/version-skew-policy/) 1.20.3 = 1\(Major\).20\(Minor\).3\(patch\)
**BEST WAY TO UPDATE OR UPGRADE A KUBERNETES CLUSTER:**
