Here is the specification of a security policy.
Note Please note that for system calls monitoring we only support audit action no matter what the value of action is
For better understanding, you can check the KubeArmorPolicy spec diagram.
Now, we will briefly explain how to define a security policy.
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.
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.
The tags part is optional. You can define multiple tags (e.g., WARNING, SENSITIVE, MITRE, STIG, etc.) to categorize security policies.
The message part is optional. You can add an alert message, and then the message will be presented in alert logs.
The selector part is relatively straightforward. Similar to other Kubernetes configurations, you can specify (a group of) pods based on labels.
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.
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 is specified in fromSource, the executable at the path 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 (blocked) to execute /bin/sleep. Otherwise, the execution of /bin/sleep will be blocked (allowed).
The file section is quite similar to the process section.
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.
In the case of network, there is currently one match type: matchProtocols. You can define specific protocols among TCP, UDP, and ICMP.
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.
In the case of syscalls, there are two types of matches, matchSyscalls and matchPaths. matchPaths can be used to target system calls targeting specific binary path or anything under a specific directory, additionally you can slice based on syscalls generated by a binary or a group of binaries in a directory. You can use matchSyscall as a more general rule to match syscalls from all sources or from specific binaries.
There is one options in each match.
fromSource
If a path is specified in fromSource, kubearmor will match only syscalls generated by the defined source. For better undrestanding, lets take the example below. Only unlink system calls generated by /bin/bash will be matched.
recursive
If this is enabled, the coverage will extend to the subdirectories of the directory.
Action
The action could be Allow, Audit, 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. For System calls monitoring, we only support audit mode no matter what the action is set to.