Share my k8s research materials that I did two years ago.
This repo aims to how to secure your kubernetes (K8s) environment.
- Misconfiguration
- Docker Remote API unauthorized access port 2375 (HTTP) and 2376 (HTTPS) /containers/json
- Docker.sock is mounted inside the container
- Docker compose secret expose
- DIND(docker-in-docker) exploitation
- Docker high-risk startup parameters
- Privileged privileged mode
- Mount sensitive directories
- Safety issues related to startup parameters
- Escape by Docker software flaw
- Shocker attack, VMM-container breakout
- runC container escape vulnerability (CVE-2019-5736)
- Docker cp command (CVE-2019-14271)
- Abuse cgroup (release_agent)
- rkt enter (CVE-2019-10144, CVE-2019-10145 and CVE-2019-10146)
- Escape by Kernel vulnerability
- Dirty COW - (CVE-2016-5195) - Docker Container Escape
- Backdoor container
- Recon / Misconfiguration
- Service unauthorized access / Expose
- ETCD port 2379
- Maintains cluster state and secrets
- No authentication by default
- No encryption at rest by default
- REST & gRPC APIs
- Kubelet API port 10250/10255 (Misconfigured kubelets non-auth)
- API server port 443/6443/8443/8080
- Kube porxy port 10256
- Calico port 9099
- Weave 6782-4
- NodePort expose
- Cluster network recon
- Shodan/ZoomEye/Censys
- kubernetesDashboard
- kubernetes
- k8s
- kubernetes master
- openshift
- swarm
- product:etcd
- k8s.io
- apiserver
- k8s_node/k8s-cluster-etcd/kubeadm-master/kubemaster-etcd
- Bypass namespace restriction
- The namespaces within the cluster doesn't have any network security restrictions by default. By default, all pods in a Kubernetes cluster can communicate freely with each other without any issues
- Docker sock
- Container escape / replace host binary / reverse shell
- docker.sock expose
- Hostpath mount / chroot /host/ bash
- Privilege escalation
- Insecure deployment file
- Insecure pod security policy (AllowPrivilegeEscalation, MustRunAsNonRoot and privileged) Bypass the PSP to deploy a Pod
- Bad Pod #1: Everything allowed
- Bad Pod #2: Privileged and hostPid
- Bad Pod #3: Privileged only
- Bad Pod #4: hostPath only
- Bad Pod #5: hostPid only
- Bad Pod #6: hostNetwork only
- Bad Pod #7: hostIPC only
- Bad Pod #8: Nothing allowed
- Create pod into kube-system with automountServiceAccountToken: true
- Create malicious Admission controllers
- Shell Escape Sequences
- Git expose
- Secret leakage
- Config
- Secret
- SSH key
- Environment information
- DoS the memory/cpu resources
- No applied limit ranges for the containers
- Service unauthorized access / Expose
- Initial Access
- Using cloud credentials, instance metadata
- SSRF over web vulnerability
- In Container
- Gain access private registry
- Vulnerable application
- Backdooring CI/CD
- Discovering Routes and Hidden Consoles
- SSRF Impacts on Cloud Environments
- Command Injections
- SQL Injections
- Peirates for Container Escape
- Injecting Functionless Environments Using LambdaShell
- Vulnerable application - insecure deserialization
- Insecure secret management - no protection of encryption key
- Redis - no authentication
- Using cloud credentials, instance metadata
- Attack API over server account - Authorization
- /run/secrets/kubernetes.io/serviceaccount/token
- /var/lib/kubelet/kubeconfig
- $HOME/.kube/config
- get secret
- Bypass RBAC
- Seeking Extensive Privileges (kubernetes-rbac-audit)
- Exploit
- CVE-2018-1002105 (Unauthenticated user to perform privilege escalation)
- CVE-2020-8558 (kube-proxy route_localnet unauthenticated access node)
- CVE-2020-8555 (SSRF)
- kubelet-exploit
- Exec a command / shell in a container via the API server
- Launch a container onto the cluster via the API server
- Abuse or set up a "volume mount" to steal/modify data or the host itself
- Ask a Kubelet to exec a command / shell in an existing container
- Interact with the Docker daemon on the host
- Interact with the internal or external networks
- Image 3rd vulnerability
- Kubernetes CronJob
- helm2 exposes a Tiller gRPC interface (Default:No authentication)
- Pod compromise
- RCE into the Pod
- Steal Service Tokens
- Find the public IP of the cluster
- Setup kubectl with the compromised token
- Determine what you can do in the cluster
- Namespace compromise
- Bypass the PSP to deploy a Pod
- Port forwarding into the Pod
- Finding other services in the cluster
- Namespace tenant bypass
- Compromise the other Pod
- Steal account token in new namespace
- Deploy a privileged pod
- Node compromise
- Compromise the Node
- Deeper compromise
- Stealing the kubelet config
- Cluster compromise
- Creating mirror pods
- Accessing the shell in the kube-system namespace
- Helm v2 tiller to PwN the cluster (Retrieve tiller service account token)
- Combo
- No permission to get secret but you can create pod. Create pod that include secret
- From pod lateral movement
- Bypass the PSP to deploy a Pod
- Later movement - instance metadata
- Cluster Layer
- No network policy
- No authentication or access control
- No logical segmentation - namespaces
- No pod security controls
- Lack of monitoring
- Application Layer
- Vulnerable application - insecure deserialization
- Insecure secret management - no protection of encryption key
- Redis - no authentication
- More
- Container Layer
- Running as root
- No hardening of container runtime
- Insecure secret in container environment variables *High Privileged
- Privilege to Use Pods/Exec
- Privilege to Get/Patch Rolebindings
- Impersonating a Privileged Account
- Privileged Service Account Token
- Defense evasion
- Clear container logs
- Delete Kubernetes events
- Pod / container name similarity
- Secure EKS Cluster
- Cloud Infrastructure Security
- VPC Layout
- Dedicated IAM Role for EKS Cluster Creation
- Cluster Resource Tagging
- Control SSH Access to Nodes
- EC2 Security Groups for Nodes
- Don’t Install the Kubernetes Dashboard
- AWS Fargate for Nodeless EKS (AWS does not recommend running sensitive workloads on Fargate.)
- IAM Policies and the Principle of Least Privilege( cluster autoscaler by using the IAM policy Condition)
- Isolating Critical Cluster Workloads
- Manage IAM Credentials for Pods
- Authentication
- --anonymous-auth=false (Default:true)
- To enable X509 client certificate authentication to the kubelet's HTTPS endpoint
- Authorization (RBAC, Node, ABAC or Webhook)
- –authorization-mode is not set to AlwaysAllow, as the more secure Webhook mode will delegate authorization decisions to the Kubernetes API server.
- Do not grant write access to ConfigMaps in ClusterRoles, which apply globally across all namespaces. Use RoleBindings to limit these permissions to specific namespaces.
- Admission Control
- Gatekeeper
- Enable NodeRestriction admission plugin to limit a kubelet to modify its own node) pods and pod status
- AlwaysPullImages
- DenyEscalatingExec
- ResourceQuota
- LimitRanger
- Pod security. Admins can control specific actions.
- Pod security policy
- Restrict the containers that can run as privileged (Delete the default pod security policy)
- Do not run processes in containers as root
- Do not allow privileged escalation
- Restrict the use of hostPath or if hostPath is necessary restrict which prefixes can be used and configure the volume as read-only (By default pods that run as root will have write access to the file system exposed by hostPath) prevent symbolic links threat
- Set requests and limits for each container to avoid resource contention and DoS attacks Quality Of Service (QoS)
- Privileged: false
- runAsUser: rule: 'MustRunAsNonRoot'
- AllowPrivilegeEscalation=false
- Multi-tenancy
- Namespace / RBAC
- Node selector
- Anti-Affinity Rules
- Taints / Tolerations
- Network security
- Network policies. The default is that all pods talk to all pods. Consider changing it.
- Traffic control
- Network Policies (Calico)
- Create a default deny policy
- Create a rule to allow DNS queries
- Incrementally add rules to selectively allow the flow of traffic between namespaces/pods
- Log network traffic metadata
- Use encryption with AWS load balancers
- Security Groups
- Encryption in transit
- Service Mesh
- Container Network Interfaces (CNIs)
- Nitro Instances
- Kubernetes secrets. Use secrets to store sensitive data instead of config maps.
- ETCD
- PKI-based authentication for etcd
- Encryption at rest
- etcd peer-to-peer TLS
- Kubernetes API to etcd cluster TLS
- Image Security
- Private registries
- Image signing (use only signed images from trusted registry)
- Image vulnerability check
- Container security
- Dockerfile
- Do not expose the Docker daemon socket
- Set a non-root user
- Add –no-new-privileges flag
- Prevent Docker in docker (DIND)
- Docker Bench for Security
- Preventing containers from loading unwanted kernel modules
- /etc/modprobe.d/kubernetes-blacklist.conf
- Runtime security
- SELinux
- AppArmor (EX: enforce AppArmor profiles on pods via Pod Security Policies. Prevent the attack pods from writing to files in the host’s filesystem)
- Seccomp
- Falco
- Detective Controls (Audit logging. Watch them!)
- Auditing and logging
- Enable audit logs
- Create alarms for suspicious events
- Analyzing Log Data with CloudWatch Logs Insights
- Audit your CloudTrail logs (IRSA)
- Falco log
- Audit all the container's activity
- Infrastructure Security
- Use an OS optimized for running containers
- Treat your infrastructure as immutable and automate the replacement of your worker nodes
- Periodically run kube-bench to verify compliance with CIS benchmarks for Kubernetes
- Minimize access to worker nodes
- Deploy workers onto private subnets
- Run Amazon Inspector to assess hosts for exposure, vulnerabilities, and deviations from best practices
- Harden the host (always patch)
- Separate partitions for containers
- Defense
- Don’t allow privileged Pods
- Don't allow a container to become root
- Don’t allow host mounts at all
- Consider a network plugin or Network Policy for segmentation
- Only use images and registries that you trust and don’t rely on Docker Hub as a trusted source
- Keep roles and role bindings as strict as possible
- Don’t automount Service Tokens into Pods if your services don’t need to communicate to the API
- Consider abstracting direct console access to the cluster away (ie Terraform, Spinnaker) so that none of your developers have cluster-admin permission.
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