| insightCloudSec | RBAC Tool For Kubernetes

Kubernetes RBAC

Role-based access control (RBAC) is a method of regulating access to 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.

Permissions are purely additive (there are no “deny” rules).

A Role always sets permissions within a particular namespace ; when you create a Role, you have to specify the namespace it belongs in. ClusterRole, by contrast, is a non-namespaced resource. ClusterRoles have several uses. You can use a ClusterRole to:

• define permissions on namespaced resources and be granted within individual namespace(s)
• define permissions on namespaced resources and be granted across all namespaces
• define permissions on cluster-scoped resources

If you want to define a role within a namespace, use a Role; if you want to define a role cluster-wide, use a ClusterRole.

rbac-tool simplifies querying and creation RBAC policies.

Install

Standalone

Download the latest from the release page

curl https://raw.githubusercontent.com/alcideio/rbac-tool/master/download.sh | bash

kubectl plugin //

$ kubectl krew install rbac-tool

rbac-tool

A collection of Kubernetes RBAC tools to sugar coat Kubernetes RBAC complexity

rbac-tool

Usage:
  rbac-tool [command]

Available Commands:
  analysis        Analyze RBAC permissions and highlight overly permissive principals, risky permissions, etc.
  auditgen        Generate RBAC policy from Kubernetes audit events
  bash-completion Generate bash completion. source <(rbac-tool bash-completion)
  generate        Generate Role or ClusterRole and reduce the use of wildcards
  help            Help about any command
  lookup          RBAC Lookup by subject (user/group/serviceaccount) name
  policy-rules    RBAC List Policy Rules For subject (user/group/serviceaccount) name
  show            Generate ClusterRole with all available permissions from the target cluster
  version         Print rbac-tool version
  visualize       A RBAC visualizer
  who-can         Shows which subjects have RBAC permissions to perform an action
  whoami          Shows the subject for the current context with which one authenticates with the cluster
  
Flags:
  -h, --help      help for rbac-tool
  -v, --v Level   number for the log level verbosity

Use "rbac-tool [command] --help" for more information about a command.

• The rbac-tool viz command
• The rbac-tool analysis command
• The rbac-tool lookup command
• The rbac-tool who-can command
• The rbac-tool policy-rules command
• The rbac-tool auditgen command
• The rbac-tool gen command
• The rbac-tool show command
• The rbac-tool whoami command
• Command Line Reference
• Contributing

rbac-tool viz

A Kubernetes RBAC visualizer that generate a graph as dot file format or in HTML format.

By default 'rbac-tool viz' will connect to the local cluster (pointed by kubeconfig) Create a RBAC graph of the actively running workload on all namespaces except kube-system

See run options on how to render specific namespaces, other clusters, etc.

#Render Locally
rbac-tool viz --outformat dot && cat rbac.dot | dot -Tpng > rbac.png  && open rbac.png

# Render Online
https://dreampuf.github.io/GraphvizOnline

Examples:

# Scan the cluster pointed by the kubeconfig context 'myctx'
rbac-tool viz --cluster-context myctx

# Scan and create a PNG image from the graph
rbac-tool viz --outformat dot --exclude-namespaces=soemns && cat rbac.dot | dot -Tpng > rbac.png && google-chrome rbac.png

rbac-tool show

Generate sample ClusterRole with all available permissions from the target cluster.

rbac-tool read from the Kubernetes discovery API the available API Groups and resources, and based on the command line options, generate an explicit ClusterRole with available resource permissions. Examples:

# Generate a ClusterRole with all the available permissions for core and apps api groups
rbac-tool show  --for-groups=,apps

rbac-tool analysis

Analyze RBAC permissions and highlight overly permissive principals, risky permissions. The command allows to use a custom analysis rule set, as well as the ability to define custom exceptions (global and per-rule).

The default rule set can be found here

Examples:

# Analyze the cluster pointed by the kubeconfig context 'myctx' with the internal analysis rule set
rbac-tool analysis --cluster-context myctx

# Analyze the cluster pointed by kubeconfig with the the provided analysis rule set
rbac-tool analysis --config myruleset.yaml

rbac-tool lookup

Lookup of the Roles/ClusterRoles used attached to User/ServiceAccount/Group with or without regex

Examples:

# Search All Service Accounts
rbac-tool lookup

# Search Service Accounts that match myname exactly
rbac-tool lookup myname

# Search All Service Accounts that contain myname
rbac-tool lookup -e '.*myname.*'

# Lookup System Accounts (all accounts that start with system: )
rbac-tool lookup -e '^system:'
  SUBJECT                                         | SUBJECT TYPE | SCOPE       | NAMESPACE   | ROLE                                                                 | BINDING
+-------------------------------------------------+--------------+-------------+-------------+----------------------------------------------------------------------+---------------------------------------------------+
  system:anonymous                                | User         | Role        | kube-public | kubeadm:bootstrap-signer-clusterinfo                                 | kubeadm:bootstrap-signer-clusterinfo
  system:authenticated                            | Group        | ClusterRole |             | system:basic-user                                                    | system:basic-user
  system:authenticated                            | Group        | ClusterRole |             | system:public-info-viewer                                            | system:public-info-viewer
  system:authenticated                            | Group        | ClusterRole |             | system:discovery                                                     | system:discovery
  system:bootstrappers:kubeadm:default-node-token | Group        | ClusterRole |             | kubeadm:get-nodes                                                    | kubeadm:get-nodes
  system:bootstrappers:kubeadm:default-node-token | Group        | ClusterRole |             | system:node-bootstrapper                                             | kubeadm:kubelet-bootstrap
  system:bootstrappers:kubeadm:default-node-token | Group        | ClusterRole |             | system:certificates.k8s.io:certificatesigningrequests:nodeclient     | kubeadm:node-autoapprove-bootstrap
  system:bootstrappers:kubeadm:default-node-token | Group        | Role        | kube-system | kube-proxy                                                           | kube-proxy
  system:bootstrappers:kubeadm:default-node-token | Group        | Role        | kube-system | kubeadm:nodes-kubeadm-config                                         | kubeadm:nodes-kubeadm-config
  system:bootstrappers:kubeadm:default-node-token | Group        | Role        | kube-system | kubeadm:kubelet-config                                               | kubeadm:kubelet-config
  system:kube-controller-manager                  | User         | ClusterRole |             | system:kube-controller-manager                                       | system:kube-controller-manager
...

rbac-tool who-can

Shows which subjects have RBAC permissions to perform an action denoted by VERB on an object denoted as ( KIND | KIND/NAME | NON-RESOURCE-URL)

• VERB is a logical Kubernetes API verb like 'get', 'list', 'watch', 'delete', etc.
• KIND is a Kubernetes resource kind. Shortcuts and API groups will be resolved, e.g. 'po' or 'deploy'.
• NAME is the name of a particular Kubernetes resource.
• NON-RESOURCE-URL is a partial URL that starts with "/".

Examples:

# Who can read ConfigMap resources
rbac-tool who-can get cm

# Who can watch Deployments
rbac-tool who-can watch deployments.apps

# Who can read the Kubernetes API endpoint /apis
rbac-tool who-can get /apis

# Who can read a secret resource by the name some-secret
rbac-tool who-can get secret/some-secret

rbac-tool policy-rules

List Kubernetes RBAC policy rules for a given User/ServiceAccount/Group with or without regex

Examples:

# List policy rules for system unauthenicated group
rbac-tool policy-rules -e '^system:unauth'

Output:

  TYPE  | SUBJECT                | VERBS | NAMESPACE | API GROUP | KIND | NAMES | NONRESOURCEURI                              
+-------+------------------------+-------+-----------+-----------+------+-------+--------------------------------------------+
  Group | system:unauthenticated | get   | *         | -         | -    | -     | /healthz,/livez,/readyz,/version,/version/  

Leveraging JMESPath to filter and transform RBAC Policy rules.

For example: Who Can Read Secrets

rbac-tool policy-rules -o json  | jp "[? @.allowedTo[? (verb=='get' || verb=='*') && (apiGroup=='core' || apiGroup=='*') && (resource=='secrets' || resource == '*')  ]].{name: name, namespace: namespace, kind: kind}"

See https://jmespath.org/

rbac-tool auditgen

Generate RBAC policy from Kubernetes audit events. Audit source format can be:

• Kubernetes List Object that contains Audit Events
• Newline seperated Audit Event objects Audit source can be file, directory or http URL.

rbac-tool auditgen -f audit.log

This command is based on this prior work.

rbac-tool gen

Examples would be simplest way to describe how rbac-tool gen can help:

• Generate a ClusterRole policy that allows to read everything except secrets and services
• Generate a Role policy that allows create,update,get,list (read/write) everything except secrets, services, ingresses, networkpolicies
• Generate a Role policy that allows create,update,get,list (read/write) everything except statefulsets

rbac-tool generate RBAC Role or RBAC ClusterRole resource while reducing the use of wildcards, and support deny semantics for specific Kubernetes clusters.

rbac-tool whoami

Shows the subject for the current context with which one authenticates with the cluster.

Examples:

rbac-tool whoami --cluster-context myctx

How rbac-tool gen works?

rbac-tool reads from the Kubernetes discovery API the available API Groups and resources, which represents the "world" of resources. Based on the command line options, generate an explicit Role/ClusterRole that avoid wildcards by expanding wildcards to the available "world" resources.

Command Line Examples

Examples generated against Kubernetes cluster v1.16 deployed using KIND.

Generate a ClusterRole policy that allows to read everything except secrets and services

rbac-tool  gen  --deny-resources=secrets.,services. --allowed-verbs=get,list

Generate a Role policy that allows create,update,get,list (read/write) everything except secrets, services, networkpolicies in core,apps & networking.k8s.io API groups

rbac-tool  gen --generated-type=Role --deny-resources=secrets.,services.,networkpolicies.networking.k8s.io --allowed-verbs=* --allowed-groups=,extensions,apps,networking.k8s.io

Generate a Role policy that allows create,update,get,list (read/write) everything except statefulsets

rbac-tool  gen --generated-type=Role --deny-resources=apps.statefulsets --allowed-verbs=* 

Example Output

Generate a Role policy that allows create,update,get,list (read/write) everything except secrets, services, networkpolicies in core,apps & networking.k8s.io API groups

rbac-tool  gen --generated-type=Role --deny-resources=secrets.,services.,networkpolicies.networking.k8s.io --allowed-verbs=* --allowed-groups=,extensions,apps,networking.k8s.io

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  creationTimestamp: null
  name: custom-role
  namespace: mynamespace
rules:
- apiGroups:
  - ""
  resources:
  - events
  - componentstatuses
  - podtemplates
  - namespaces
  - replicationcontrollers
  - persistentvolumes
  - configmaps
  - persistentvolumeclaims
  - resourcequotas
  - limitranges
  - nodes
  - bindings
  - serviceaccounts
  - pods
  - endpoints
  verbs:
  - '*'
- apiGroups:
  - extensions
  resources:
  - ingresses
  verbs:
  - '*'
- apiGroups:
  - apps
  resources:
  - replicasets
  - daemonsets
  - deployments
  - controllerrevisions
  - statefulsets
  verbs:
  - '*'
- apiGroups:
  - networking.k8s.io
  resources:
  - ingresses
  verbs:
  - '*'

Command Line Reference

Generate Role or ClusterRole resource while reducing the use of wildcards.

rbac-tool read from the Kubernetes discovery API the available API Groups and resources, 
and based on the command line options, generate an explicit Role/ClusterRole that avoid wildcards

Examples:

# Generate a Role with read-only (get,list) excluding secrets (core group) and ingresses (extensions group) 
rbac-tool gen --generated-type=Role --deny-resources=secrets.,ingresses.extensions --allowed-verbs=get,list

# Generate a Role with read-only (get,list) excluding secrets (core group) from core group, admissionregistration.k8s.io,storage.k8s.io,networking.k8s.io
rbac-tool gen --generated-type=ClusterRole --deny-resources=secrets., --allowed-verbs=get,list  --allowed-groups=,admissionregistration.k8s.io,storage.k8s.io,networking.k8s.io

Usage:
  rbac-tool generate [flags]

Aliases:
  generate, gen

Flags:
      --allowed-groups strings   Comma separated list of API groups we would like to allow '*' (default [*])
      --allowed-verbs strings    Comma separated list of verbs to include. To include all use '* (default [*])
  -c, --cluster-context string   Cluster.use 'kubectl config get-contexts' to list available contexts
      --deny-resources strings   Comma separated list of resource.group
  -t, --generated-type string    Role or ClusteRole (default "ClusterRole")
  -h, --help                     help for generate

Contributing

Bugs

If you think you have found a bug please follow the instructions below.

• Please spend a small amount of time giving due diligence to the issue tracker. Your issue might be a duplicate.
• Open a new issue if a duplicate doesn't already exist.

Features

If you have an idea to enhance rbac-tool follow the steps below.

• Open a new issue.
• Remember users might be searching for your issue in the future, so please give it a meaningful title to helps others.
• Clearly define the use case, using concrete examples.
• Feel free to include any technical design for your feature.

Pull Requests

• Your PR is more likely to be accepted if it focuses on just one change.
• Please include a comment with the results before and after your change.
• Your PR is more likely to be accepted if it includes tests.
• You're welcome to submit a draft PR if you would like early feedback on an idea or an approach.