Security Posture

KubeArmor supports configurable default security posture. The security posture could be allow/audit/deny. Default Posture is used when there's atleast one Allow policy for the given deployment i.e. KubeArmor is handling policies in whitelisting manner (more about this in Considerations in Policy Action ).

There are two default mode of operations available block and audit. block mode blocks all the operations that are not allowed in the policy. audit generates telemetry events for operations that would have been blocked otherwise.

KubeArmor has 4 types of resources: Process, File, Network and Capabilities. Default Posture is configurable for each of the resources seperately except Process. Process based operations are treated under File resource only.

Configuring Default Posture

Global Default Posture

Note By default, KubeArmor set the Global default posture to audit

Global default posture is configured using configuration options passed to KubeArmor using configuration file

defaultFilePosture: block # or audit
defaultNetworkPosture: block # or audit
defaultCapabilitiesPosture: block # or audit

Or using command line flags with the KubeArmor binary

  -defaultFilePosture string
    	configuring default enforcement action in global file context [audit,block] (default "block")
  -defaultNetworkPosture string
    	configuring default enforcement action in global network context [audit,block] (default "block")
  -defaultCapabilitiesPosture string
    	configuring default enforcement action in global capability context [audit,block] (default "block")

Namespace Default Posture

We use namespace annotations to configure default posture per namespace. Supported annotations keys are kubearmor-file-posture,kubearmor-network-posture and kubearmor-capabilities-posture with values block or audit. If a namespace is annotated with a supported key and an invalid value ( like kubearmor-file-posture=invalid), KubeArmor will update the value with the global default posture ( i.e. to kubearmor-file-posture=block).

Example

Let's start KubeArmor with configuring default network posture to audit in the following YAML.

 sudo env KUBEARMOR_CFG=/path/to/kubearmor.yaml ./kubearmor

Contents of kubearmor.yaml

defaultNetworkPosture: audit

Here's a sample policy to allow tcp connections from curl binary.

apiVersion: security.kubearmor.com/v1
kind: KubeArmorPolicy
metadata:
  name: ksp-ubuntu-5-net-tcp-allow-curl
  namespace: multiubuntu
spec:
  severity: 8
  selector:
    matchLabels:
      container: ubuntu-5
  network:
    matchProtocols:
    - protocol: tcp
      fromSource:
      - path: /usr/bin/curl
  action:
    Allow

Note: This example is in the multiubuntu environment.

Inside the ubuntu-5-deployment, if we try to access tcp using curl. It works as expected with no telemetry generated.

root@ubuntu-5-deployment-7778f46c67-hk6k6:/# curl 142.250.193.46
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<TITLE>301 Moved</TITLE></HEAD><BODY>
<H1>301 Moved</H1>
The document has moved
<A HREF="http://www.google.com/">here</A>.
</BODY></HTML>

If we try to access udp using curl, a bunch of telemetry is generated for the udp access.

root@ubuntu-5-deployment-7778f46c67-hk6k6:/# curl google.com
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<TITLE>301 Moved</TITLE></HEAD><BODY>
<H1>301 Moved</H1>
The document has moved
<A HREF="http://www.google.com/">here</A>.
</BODY></HTML>

curl google.com requires UDP for DNS resolution.

Generated alert has Policy Name DefaultPosture and Action as Audit

== Alert / 2022-03-21 12:56:32.999475 ==
Cluster Name: default
Host Name: kubearmor-dev-all
Namespace Name: multiubuntu
Pod Name: ubuntu-5-deployment-7778f46c67-hk6k6
Container ID: 1f92eb4c9d730862174be04f319763a2c1ac2752669807051c42ddc78aa102d1
Container Name: ubuntu-5-container
Policy Name: DefaultPosture
Type: MatchedPolicy
Source: /usr/bin/curl google.com
Operation: Network
Resource: domain=AF_INET6 type=SOCK_DGRAM protocol=0
Data: syscall=SYS_SOCKET
Action: Audit
Result: Passed

Now let's update the default network posture to block for multiubuntu namespace.

~❯❯❯  kubectl annotate ns multiubuntu kubearmor-network-posture=block
namespace/multiubuntu annotated

Now if we try to access udp using curl, the action is blocked and related alerts are generated.

root@ubuntu-5-deployment-7778f46c67-hk6k6:/# curl google.com
curl: (6) Could not resolve host: google.com

Here curl couldn't resolve google.com due to blocked access to UDP.

Generated alert has Policy Name DefaultPosture and Action as Block

== Alert / 2022-03-21 13:06:27.731918 ==
Cluster Name: default
Host Name: kubearmor-dev-all
Namespace Name: multiubuntu
Pod Name: ubuntu-5-deployment-7778f46c67-hk6k6
Container ID: 1f92eb4c9d730862174be04f319763a2c1ac2752669807051c42ddc78aa102d1
Container Name: ubuntu-5-container
Policy Name: ksp-ubuntu-5-net-tcp-allow
Severity: 8
Type: MatchedPolicy
Source: /usr/bin/curl google.com
Operation: Network
Resource: domain=AF_INET6 type=SOCK_DGRAM protocol=0
Data: syscall=SYS_SOCKET
Action: Allow
Result: Permission denied

Let's try to set the annotation value to something invalid.

~❯❯❯  kubectl annotate ns multiubuntu kubearmor-network-posture=invalid --overwrite
namespace/multiubuntu annotated
~❯❯❯  kubectl describe ns multiubuntu
Name:         multiubuntu
Labels:       kubernetes.io/metadata.name=multiubuntu
Annotations:  kubearmor-network-posture: audit
Status:       Active

We can see that, annotation value was automatically updated to audit since that was global mode of operation for network in the KubeArmor configuration.

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