# Pentesting Kubernetes **The main author of this page is** [**Jorge**](https://www.linkedin.com/in/jorge-belmonte-a924b616b/) **\(read his original post** [**here**](https://sickrov.github.io/)**\)** ## Architecture & Basics ### What does Kubernetes do? * Allows running container/s in a container engine. * Schedule allows containers mission efficient. * Keep containers alive. * Allows container communications. * Allows deployment techniques. * Handle volumes of information. ### Architecture ![](https://sickrov.github.io/media/Screenshot-68.jpg) * **Node**: operating system with pod or pods. * **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 internal **IP address** from the internal range of the node. However, it can be also exposed via a service. The **service has also an IP address** and its goal is to maintain the communication between pods so if one dies the **new replacement** \(with a different internal IP\) **will be accessible** exposed in the **same IP of the service**. 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. When a **service** is **created** you can find the endpoints of each service running `kubectl get endpoints` ![](../../.gitbook/assets/image%20%28466%29.png) * **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. * **Master process:** * **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 \(available resourced of the nodes, number of pods running...\) * **Cloud controller manager**: Is the specific controller for flow controls and applications, i.e: if you have clusters in AWS or OpenStack. 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**. If you are running pods in different physical nodes you should use a remote storage so all the pods can access it. #### Other configurations: * **ConfigMap**: You can configure **URLs** to access services. The pod will obtain data from here to know how to communicate with the rest of the services \(pods\). Note 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. * **StatefulSet**: This component is meant specifically for applications like **databases** which needs to **access the same storage**. * **Ingress**: This is the configuration that is use to **expose the application publicly with an URL**. Note that this can also be done using external services, but this is the correct way to expose the application. * If you implement an Ingress you will need to create **Ingress Controllers**. The Ingress Controller is a **pod** that will be the endpoint that will receive the requests and check and will load balance them to the services. the ingress controller will **send the request based on the ingress rules configured**. Note that the ingress rules can point to different paths or even subdomains to different internal kubernetes services. * A better security practice would be to use a cloud load balancer or a proxy server as entrypoint to don't have any part of the Kubernetes cluster exposed. * When request that doesn't match any ingress rule is received, the ingress controller will direct it to the "**Default backend**". You can `describe` the ingress controller to get the address of this parameter. * `minikube addons enable ingress` ### PKI infrastructure - Certificate Authority CA: ![](https://sickrov.github.io/media/Screenshot-66.jpg) * CA is the trusted root for all certificates inside the cluster. * Allows components to validate to each other. * All cluster certificates are signed by the CA. * ETCd has its own certificate. * types: * apiserver cert. * kubelet cert. * scheduler cert. ### Minikube **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 > minikube-v1.19.0.iso: 244.49 MiB / 244.49 MiB 100.00% 1.78 MiB p/s 2m17. 👍 Starting control plane node minikube in cluster minikube 💾 Downloading Kubernetes v1.20.2 preload ... > preloaded-images-k8s-v10-v1...: 491.71 MiB / 491.71 MiB 100.00% 2.59 MiB 🔥 Creating virtualbox VM (CPUs=2, Memory=3900MB, Disk=20000MB) ... 🐳 Preparing Kubernetes v1.20.2 on Docker 20.10.4 ... ▪ Generating certificates and keys ... ▪ Booting up control plane ... ▪ Configuring RBAC rules ... 🔎 Verifying Kubernetes components... ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5 🌟 Enabled addons: storage-provisioner, default-storageclass 🏄 Done! kubectl is now configured to use "minikube" cluster and "default" namespace by defaul $ minikube status host: Running kubelet: Running apiserver: Running kubeconfig: Configured ---- ONCE YOU HAVE A K8 SERVICE RUNNING WITH AN EXTERNAL SERVICE ----- $ minikube service mongo-express-service (This will open your browser to access the service exposed port) $ minikube delete 🔥 Deleting "minikube" in virtualbox ... 💀 Removed all traces of the "minikube" cluster ``` ### Kubectl Basics **`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. ```bash kubectl version #Get client and server version kubectl get pod kubectl get services kubectl get deployment kubectl get replicaset kubectl get secret kubectl get all kubectl get ingress kubectl get endpoints #kubectl create deployment --image= kubectl create deployment nginx-deployment --image=nginx #Access the configuration of the deployment and modify it #kubectl edit deployment kubectl edit deployment nginx-deployment #Get the logs of the pod for debbugging (the output of the docker container running) #kubectl logs kubectl logs nginx-deployment-84cd76b964 #kubectl describe pod kubectl describe pod mongo-depl-5fd6b7d4b4-kkt9q #kubectl exec -it -- bash kubectl exec -it mongo-depl-5fd6b7d4b4-kkt9q -- bash #kubectl describe service kubectl describe service mongodb-service #kubectl delete deployment kubectl delete deployment mongo-depl #Deploy from config file kubectl apply -f deployment.yml ``` ### YAML configuration files examples 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: ![](../../.gitbook/assets/image%20%28458%29.png) #### Example of Deployment + Service declared in the same configuration file \(from [here](https://gitlab.com/nanuchi/youtube-tutorial-series/-/blob/master/demo-kubernetes-components/mongo.yaml)\) As a service usually is related to one deployment it's possible to declare both in the same configuration file \(the service declared in this config is only accessible internally\): ```yaml apiVersion: apps/v1 kind: Deployment metadata: name: mongodb-deployment labels: app: mongodb spec: replicas: 1 selector: matchLabels: app: mongodb template: metadata: labels: app: mongodb spec: containers: - name: mongodb image: mongo ports: - containerPort: 27017 env: - name: MONGO_INITDB_ROOT_USERNAME valueFrom: secretKeyRef: name: mongodb-secret key: mongo-root-username - name: MONGO_INITDB_ROOT_PASSWORD valueFrom: secretKeyRef: name: mongodb-secret key: mongo-root-password --- apiVersion: v1 kind: Service metadata: name: mongodb-service spec: selector: app: mongodb ports: - protocol: TCP port: 27017 targetPort: 27017 ``` #### Example of external service config This service will be accessible externally \(check the `nodePort` and `type: LoadBlancer` attributes\): ```yaml --- apiVersion: v1 kind: Service metadata: name: mongo-express-service spec: selector: app: mongo-express type: LoadBalancer ports: - protocol: TCP port: 8081 targetPort: 8081 nodePort: 30000 ``` {% hint style="info" %} This is useful for testing but for production you should have only internal services and an Ingress to expose the application. {% endhint %} #### Example of Ingress config file This will expose the application in `http://dashboard.com`. ```yaml apiVersion: networking.k8s.io/v1 kind: Ingress metadata: name: dashboard-ingress namespace: kubernetes-dashboard spec: rules: - host: dashboard.com http: paths: - backend: serviceName: kubernetes-dashboard servicePort: 80 ``` #### Example of secrets config file Note how the password are encoded in B64 \(which isn't secure!\) ```yaml apiVersion: v1 kind: Secret metadata: name: mongodb-secret type: Opaque data: mongo-root-username: dXNlcm5hbWU= mongo-root-password: cGFzc3dvcmQ= ``` #### Example of ConfigMap A **ConfigMap** is the configuration that is given to the pods so they know how to locate and access other services. In this case, each pod will know that the name `mongodb-service` is the address of a pod that they can communicate with \(this pod will be executing a mongodb\): ```yaml apiVersion: v1 kind: ConfigMap metadata: name: mongodb-configmap data: database_url: mongodb-service ``` Then, inside a **deployment config** this address can be specified in the following way so it's loaded inside the env of the pod: ```yaml [...] spec: [...] template: [...] spec: containers: - name: mongo-express image: mongo-express ports: - containerPort: 8081 env: - name: ME_CONFIG_MONGODB_SERVER valueFrom: configMapKeyRef: name: mongodb-configmap key: database_url [...] ``` #### Example of volume config You can find different example of storage configuration yaml files in [https://gitlab.com/nanuchi/youtube-tutorial-series/-/tree/master/kubernetes-volumes](https://gitlab.com/nanuchi/youtube-tutorial-series/-/tree/master/kubernetes-volumes). **Note that volumes aren't inside namespaces** ### Namespaces 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. You only should start using namespaces to have a better control and organization of each part of the application deployed in kubernetes. 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**. There are 4 namespaces by default if you are using minikube: ```text kubectl get namespace NAME STATUS AGE default Active 1d kube-node-lease Active 1d kube-public Active 1d kube-system Active 1d ``` * **kube-system**: It's not meant or the users use and you shouldn't touch it. It's for master and kubectl processes. * **kube-public**: Publicly accessible date. Contains a configmap which contains cluster information * **kube-node-lease**: Determines the availability of a node * **default**: The namespace the user will use to create resources ```bash #Create namespace kubectl create namespace my-namespace ``` {% hint style="info" %} Note that most Kubernetes resources \(e.g. pods, services, replication controllers, and others\) are in some namespaces. However, other resources like namespace resources and low-level resources, such as nodes and persistenVolumes are not in a namespace. To see which Kubernetes resources are and aren’t in a namespace: ```bash kubectl api-resources --namespaced=true #In a namespace kubectl api-resources --namespaced=false #Not in a namespace ``` {% endhint %} You can save the namespace for all subsequent kubectl commands in that context. ```bash kubectl config set-context --current --namespace= ``` ### Helm Helm is the **package manager** for Kubernetes. It allows to package YAML files and distribute them in public and private repositories. These packages are called **Helm Charts**. ```text helm search ``` Helm is also a template engine that allows to generate config files with variables: ![](../../.gitbook/assets/image%20%28465%29.png) ## Pentesting Kubernetes from the outside ## VULNERABILITIES and some fixes ### Enumeration inside a Pod {% page-ref page="enumeration-from-a-pod.md" %} ### Vulnerabilities - kubernetes secrets A Secret is an object that contains 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 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 \(plain text or b64 + encryption\). * Information or comments. * Database connection code, strings… . Secret types: | Builtin Type | Usage | | :--- | :--- | | Opaque | arbitrary user-defined data | | kubernetes.io/service-account-token | service account token | | kubernetes.io/dockercfg | serialized ~/.dockercfg file | | kubernetes.io/dockerconfigjson | serialized ~/.docker/config.json file | | kubernetes.io/basic-auth | credentials for basic authentication | | kubernetes.io/ssh-auth | credentials for SSH authentication | | kubernetes.io/tls | data for a TLS client or server | | bootstrap.kubernetes.io/token | bootstrap token data | **How secrets works:** [https://kubernetes.io/docs/concepts/configuration/secret/\#using-secrets-as-files-from-a-pod](https://kubernetes.io/docs/concepts/configuration/secret/#using-secrets-as-files-from-a-pod) ![](https://sickrov.github.io/media/Screenshot-164.jpg) Create a secret, commands: ```bash kubectl create secret generic secret_01 --from-literal user= kubectl create secret generic secret_01 --from-literal password= kubectl run pod --image=nginx -oyaml --dry-run=client kubectl run pod --image=nginx -oyaml --dry-run=client > ``` This is the generated file: ```yaml apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: mypod image: redis volumeMounts: - name: mountPath: "/etc/" readOnly: true volumes: - name: secret: secretName: 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: ```yaml #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: ```yaml apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: mypod image: redis env: - name: PASSWORD valueFrom: secretKeyRef: name: key: volumeMounts: - name: mountPath: "/etc/" readOnly: true volumes: - name: secret: secretName: items: - key: username path: my-group/my-username ``` Save and: ```bash kubectl -f delete --force kubectl -f create ``` or: ```bash kubectl -f 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. ```bash docker ps | grep ``` Inspect: ```bash docker inspect ``` Check env \(environment variable section\) for secrets and you will see: * Passwords. * Ip’s. * Ports. * Paths. * Others… . If you want to copy: ```bash docker cp :/etc/ ``` ### Discover secrets in etcd: 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: ```bash cat /etc/kubernetes/manifests/kube-apiserver.yaml | grep etcd ``` You will see certs, keys and url’s were are located in the FS. Once you get it, you would be able to connect to etcd. ```bash #ETCDCTL_API=3 etcdctl --cert --key --cacert endpoint=[] health ETCDCTL_API=3 etcdctl --cert /etc/kubernetes/pki/apiserver-etcd-client.crt --key /etc/kubernetes/pki/apiserver-etcd-client.key --cacert /etc/kubernetes/pki/etcd/etcd/ca.cert endpoint=[127.0.0.1:1234] health ``` Once you achieve establish communication you would be able to get the secrets: ```bash #ETCDCTL_API=3 etcdctl --cert --key --cacert endpoint=[] get ETCDCTL_API=3 etcdctl --cert /etc/kubernetes/pki/apiserver-etcd-client.crt --key /etc/kubernetes/pki/apiserver-etcd-client.key --cacert /etc/kubernetes/pki/etcd/etcd/ca.cert endpoint=[127.0.0.1:1234] get /registry/secrets/default/secret_02 ``` ### Adding encryption to the ETCD 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. ```bash kubectl get secrets --all-namespaces -o json | kubectl replace -f - ``` ### **How to encrypt the ETCD** Create a directory in /etc/kubernetes ; in this case you will name it as etcd, so you have `/etc/kubernetes/etcd` You create a yaml file with the configuration. ```text vi ``` You can copy the content of [https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/](https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/) ```yaml apiVersion: apiserver.config.k8s.io/v1 kind: EncryptionConfiguration resources: - resources: - secrets providers: - aescbc: keys: - name: key1 secret: - identity: {} ``` Generate pass in b64 \(remember to use a pass character with lenght = 16 or = 24 or = 32\) : ```bash echo -n | 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: ```yaml containers: - command: - kube-apiserver - --encriyption-provider-config=/etc/kubernetes/etcd/ ``` Scroll down in the volumeMounts: ```yaml - mountPath: /etc/kubernetes/etcd name: etcd readOnly: true ``` Scroll down in the volumeMounts to hostPath: ```yaml - hostPath: path: /etc/kubernetes/etcd type: DirectoryOrCreate name: etcd ``` ### Get information about the secrets. ```bash kubectl get secret kubectl get secret -oyaml ETCDCTL_API=3 etcdctl get /registry/secrets/default/secret1 [...] | hexdump -C kubectl create secret generic test-secret --from-literal='username=my-app' --from-literal='password=45tRf$we34rR' ``` With root access: ```bash # kubectl get secret kubectl get secret test-secret -oyaml ``` Do not forget to delete de secrets and re-create them again in order to apply the encryption layer. #### Final tips: * Try not to keep secrets in the FS, get them from other places. * Check out [https://www.vaultproject.io/](https://www.vaultproject.io/) for add more protection to your secrets. * [https://kubernetes.io/docs/concepts/configuration/secret/\#risks](https://kubernetes.io/docs/concepts/configuration/secret/#risks) * [https://docs.cyberark.com/Product-Doc/OnlineHelp/AAM-DAP/11.2/en/Content/Integrations/Kubernetes\_deployApplicationsConjur-k8s-Secrets.htm](https://docs.cyberark.com/Product-Doc/OnlineHelp/AAM-DAP/11.2/en/Content/Integrations/Kubernetes_deployApplicationsConjur-k8s-Secrets.htm) ### Vulnerabilities - Container runtime sandboxes How an attack with lateral movement and privesc could be done: ![](https://sickrov.github.io/media/Screenshot-161.jpg) Getting inside the container: ```bash kubectl get node kubectl run pod --image= kubectl exec pod -it -- bash ``` Once inside the container: ```text uname -r ``` When the attack achieves discovering the kernel version, he could run exploiting techniques to gather information or escalate into the OS. For secure sandboxes: * gVisor: [https://github.com/google/gvisor](https://github.com/google/gvisor) * Katakontainers: [https://katacontainers.io/](https://katacontainers.io/) ### Vulnerabilities - OS 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 ```bash kubectl run pod --image=busybox --command -oyaml --dry-run=client > -- sh -c 'sleep 1h' vi .yaml ``` Add the uncomment lines: ```yaml #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: ```bash kubectl -f .yaml delete --force kubectl -f .yaml create ``` Check permissions: ```bash kubectl exec -it -- sh ``` #### How to disable privilege escalation: ```bash vi .yaml ``` Set this line to false ```yaml allowPrivilegeEscalation: false ``` Save and: ```bash kubectl -f .yaml delete --force kubectl -f .yaml create ``` #### Modify PodSecurityPolicy 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/) Edit the kube-apiserver.yaml file: ```bash vi /etc/kubernetes/manifests/kube-apiserver.yaml ``` Inside you add in ```text - --enable-admission-plugins=NodeRestriction,PodSecurityPolicy ``` ### Vulnerabilities - mTLS Mutual authentication, two-way, pod to pod. ![](https://sickrov.github.io/media/Screenshot-165.jpg) 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 Create your .yaml ```bash kubectl run app --image=bash --comand -oyaml --dry-run=client > -- shj -c 'ping google.com' ``` Edit your .yaml and add the uncomment lines: ```yaml #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", "apt update && apt install iptables -y && iptables -L && sleep 1h" ] securityContext: capabilities: add: ["NET_ADMIN"] # volumeMounts: # - name: sec-ctx-vol # mountPath: /data/demo # securityContext: # allowPrivilegeEscalation: true ``` See the logs of the proxy: ```bash kubectl logs app -C proxy ``` More info at: [https://kubernetes.io/docs/tasks/configure-pod-container/security-context/](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/) ## CLUSTER HARDENING - RBAC Kubernetes has an **authorization module named Role-Based Access Control** \([**RBAC**](https://kubernetes.io/docs/reference/access-authn-authz/rbac/)\) that helps to set utilization permissions to the API server. The RBAC table is constructed from “**Roles**” and “**ClusterRoles**.” The difference between them is just where the role will be applied – a “**Role**” will grant access to only **one** **specific** **namespace**, while a “**ClusterRole**” can be used in **all namespaces** in the cluster. Moreover, ClusterRoles can also grant access to: * cluster-scoped resources \(like nodes\). * non-resource endpoints \(like /healthz\). * namespaced resources \(like Pods\), across all namespaces. Example of **Role** **configuration**: ```yaml 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"] ``` Example of **ClusterRole** configuration: For example you can use a **ClusterRole** to allow a particular user to run: ```text kubectl get pods --all-namespaces ``` ```yaml apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: # "namespace" omitted since ClusterRoles are not namespaced name: secret-reader rules: - apiGroups: [""] 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**. **RoleBinding** example: ```yaml 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: ```yaml 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 by default.** ### RBAC Structure RBAC’s permission is built from three individual parts: 1. **Role\ClusterRole ­–** The actual permission. It contains _**rules**_ that represent a set of permissions. Each rule contains [resources](https://kubernetes.io/docs/reference/kubectl/overview/#resource-types) and [verbs](https://kubernetes.io/docs/reference/access-authn-authz/authorization/#determine-the-request-verb). The verb is the action that will apply on the resource. 2. **Subject \(User, Group or ServiceAccount\) –** The object that will receive the permissions. 3. **RoleBinding\ClusterRoleBinding –** The connection between Role\ClusterRole and the subject. This is what it will look like in a real cluster: ![](https://www.cyberark.com/wp-content/uploads/2018/12/rolebiding_serviceaccount_and_role-1024x551.png) “**Fine-grained** role bindings **provide greater security**, but **require more effort to administrate**." From **Kubernetes** 1.6 onwards, **RBAC** policies are **enabled by default**. ****But to enable RBAC you can use something like: ```text kube-apiserver --authorization-mode=Example,RBAC --other-options --more-options ``` This is enabled by default. RBAC functions: * Restrict the access to the resources to users or ServiceAccounts. * An RBAC Role or ClusterRole contains rules that represent a set of permissions. * Permissions are purely additive \(there are no “deny” rules\). * RBAC works with Roles and Bindings {% hint style="info" %} When configuring roles and permissions it's highly important to always follow the principle of Least Privileges {% endhint %} ## SERVICE ACCOUNTS HARDENING **To learn about Service Accounts Hardenig read the page:** {% page-ref page="enumeration-from-a-pod.md" %} ## KUBERNETES API HARDENING It's very important to **protect the access to the Kubernetes Api Server** as a malicious actor with enough privileges could be able to abuse it and damage in a lot of way the environment. It's important to secure both the **access** \(**whitelist** origins to access the API Server and deny any otehr connection\) and the [**authentication**](https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-authentication-authorization/) \(following the principle of **least** **privilege**\). And definitely **never** **allow** **anonymous** **requests**. **Common 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. * [https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/\#noderestriction](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#noderestriction) * 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 You should update your Kubernetes environment as frequently as necessary to have: * Dependencies up to date. * Bug and security patches. \*\*\*\*[**Release cycles**](https://kubernetes.io/docs/setup/release/version-skew-policy/): Each 3 months there is a new minor release -- 1.20.3 = 1\(Major\).20\(Minor\).3\(patch\) **The best way to update a Kubernetes Cluster is \(from** [**here**](https://kubernetes.io/docs/tasks/administer-cluster/cluster-upgrade/)**\):** * Upgrade the Master Node components following this sequence: * etcd \(all instances\). * kube-apiserver \(all control plane hosts\). * kube-controller-manager. * kube-scheduler. * cloud controller manager, if you use one. * Upgrade the Worker Node components such as kube-proxy, kubelet. ## References {% embed url="https://sickrov.github.io/" %} {% embed url="https://www.youtube.com/watch?v=X48VuDVv0do" %}