Security Policy Specification for Containers

Policy Specification

Here is the specification of a security policy.

apiVersion: security.accuknox.com/v1
kind:KubeArmorPolicy
metadata:
name: [policy name]
namespace: [namespace name]
spec:
severity: [1-10] # --> optional (1 by default)
tags: ["tag", ...] # --> optional
message: [message] # --> optional
selector:
matchLabels:
[key1]: [value1]
[keyN]: [valueN]
process:
matchPaths:
- path: [absolute executable path]
ownerOnly: [true|false] # --> optional
fromSource: # --> optional
- path: [absolute exectuable path]
- dir: [absolute directory path]
recursive: [true|false]
matchDirectories:
- dir: [absolute directory path]
recursive: [true|false] # --> optional
ownerOnly: [true|false] # --> optional
fromSource: # --> optional
- path: [absolute exectuable path]
- dir: [absolute directory path]
recursive: [true|false]
matchPatterns:
- pattern: [regex pattern]
ownerOnly: [true|false] # --> optional
file:
matchPaths:
- path: [absolute file path]
readOnly: [true|false] # --> optional
ownerOnly: [true|false] # --> optional
fromSource: # --> optional
- path: [absolute exectuable path]
- dir: [absolute directory path]
recursive: [true|false]
matchDirectories:
- dir: [absolute directory path]
recursive: [true|false] # --> optional
readOnly: [true|false] # --> optional
ownerOnly: [true|false] # --> optional
fromSource: # --> optional
- path: [absolute exectuable path]
- dir: [absolute directory path]
recursive: [true|false]
matchPatterns:
- pattern: [regex pattern]
readOnly: [true|false] # --> optional
ownerOnly: [true|false] # --> optional
network:
matchProtocols:
- protocol: [TCP|tcp|UDP|udp|ICMP|icmp]
fromSource: # --> optional
- path: [absolute exectuable path]
- dir: [absolute directory path]
recursive: [true|false]
capabilities:
matchCapabilities:
- capability: [capability name]
fromSource: # --> optional
- path: [absolute exectuable path]
- dir: [absolute directory path]
recursive: [true|false]
action: [Audit|Allow|Block|AllowWithAudit|BlockWithAudit] (Block by default)

Policy Spec Description

Now, we will briefly explain how to define a security policy.

  • Common

    A security policy starts with the base information such as apiVersion, kind, and metadata. The apiVersion and kind would be the same in any security policies. In the case of metadata, you need to specify the names of a policy and a namespace where you want to apply the policy.

    apiVersion: security.accuknox.com/v1
    kind:KubeArmorPolicy
    metadata:
    name: [policy name]
    namespace: [namespace name]
  • Severity

    The severity part is somewhat important. You can specify the severity of a given policy from 1 to 10. This severity will appear in alerts when policy violations happen.

    severity: [1-10]
  • Tags

    The tags part is optional. You can define multiple tags (e.g., WARNNING, SENSITIVE, MITRE, STIG, etc.) to categorize security policies.

    tags: ["tag1", ..., "tagN"]
  • Message

    The message part is optional. You can add an alert message, and then the message will be presented in alert logs.

    message: [message]
  • Selector

    The selector part is relatively straightforward. Similar to other Kubernetes configurations, you can specify (a group of) pods based on labels.

    selector:
    matchLabels:
    [key1]: [value1]
    [keyN]: [valueN]
  • Process

    In the process section, there are three types of matches: matchPaths, matchDirectories, and matchPatterns. You can define specific executables using matchPaths or all executables in specific directories using matchDirectories. In the case of matchPatterns, advanced operators may be able to determine particular patterns for executables by using regular expressions. However, the coverage of regular expressions is highly dependent on AppArmor (Policy Core Reference). Thus, we generally do not recommend using this match.

    process:
    matchPaths:
    - path: [absolute executable path]
    ownerOnly: [true|false] # --> optional
    fromSource: # --> optional
    - path: [absolute executable path]
    - dir: [absolute directory path]
    recursive: [true|false]
    matchDirectories:
    - dir: [absolute directory path]
    recursive: [true|false] # --> optional
    ownerOnly: [true|false] # --> optional
    fromSource: # --> optional
    - path: [absolute exectuable path]
    - dir: [absolute directory path]
    recursive: [true|false]
    matchPatterns:
    - pattern: [regex pattern]
    ownerOnly: [true|false] # --> optional

    In each match, there are three options.

    • ownerOnly (static action: allow owner only; otherwise block all)

      If this is enabled, the owners of the executable(s) defined with matchPaths and matchDirectories will be only allowed to execute.

    • recursive

      If this is enabled, the coverage will extend to the subdirectories of the directory defined with matchDirectories.

    • fromSource

      If a path or a directory is specified in fromSource, the executable of the path or those in the directory will be allowed/blocked to execute the executables defined with matchPaths or matchDirectories. For better understanding, let us say that an operator defines a policy as follows. Then, /bin/bash will be only allowed to execute /bin/sleep. Otherwise, the execution of /bin/sleep will be blocked.

      process:
      matchPaths:
      - path: /bin/sleep
      fromSource:
      - path: /bin/bash
  • File

    The file section is quite similar to the process section.

    file:
    matchPaths:
    - path: [absolute file path]
    readOnly: [true|false] # --> optional
    ownerOnly: [true|false] # --> optional
    fromSource: # --> optional
    - path: [absolute file path]
    - dir: [absolute directory path]
    recursive: [true:false]
    matchDirectories:
    - dir: [absolute directory path]
    recursive: [true|false] # --> optional
    readOnly: [true|false] # --> optional
    ownerOnly: [true|false] # --> optional
    fromSource: # --> optional
    - path: [absolute file path]
    - dir: [absolute directory path]
    recursive: [true:false]
    matchPatterns:
    - pattern: [regex pattern]
    readOnly: [true|false] # --> optional
    ownerOnly: [true|false] # --> optional

    The only difference between 'process' and 'file' is the readOnly option.

    • readOnly (static action: allow to read only; otherwise block all)

      If this is enabled, the read operation will be only allowed, and any other operations (e.g., write) will be blocked.

  • Network

    In the case of network, there is currently one match type: matchProtocols. You can define specific protocols among TCP, UDP, and ICMP.

    network:
    matchProtocols:
    - protocol: [protocol] # --> [ TCP | tcp | UDP | udp | ICMP | icmp ]
    fromSource: # --> optional
    - path: [absolute file path]
    - dir: [absolute directory path]
    recursive: [true:false]
  • Capabilities

    In the case of capabilities, there is currently one match type: matchCapabilities. You can define specific capability names to allow or block using matchCapabilities. You can check available capabilities in Capability List.

    capabilities:
    matchCapabilities:
    - capability: [capability name]
    fromSource: # --> optional
    - path: [absolute file path]
    - dir: [absolute directory path]
    recursive: [true:false]
  • Action

    The action could be Audit, Allow, or Block. Security policies would be handled in a blacklist manner or a whitelist manner according to the action. Thus, you need to define the action carefully. You can refer to Consideration in Policy Action for more details. In the case of the Audit action, we can use this action for policy verification before applying a security policy with the Block action.

When we use the Allow action, we do not get any logs for objects and operations allowed to access and conduct. Hence, if we want to get logs for such allowed accesses, we can use the AllowWithAudit action instead of the Allow action.

action: [Audit|Allow|Block|AllowWithAudit|BlockWithAudit]