k8s-audit-filter 0.1.0

A tool to filter k8s audit logs

Filter K8s Audit Logs

Abstract

This library provides a simple way to filter Kubernetes audit logs, if you, whit some reason, are not able to apply audit policy directly at your cloud (e. g. in yandex cloud). The library does not provide any service, it just give you easy way to filter audit logs in your python script with AuditFilter class interfaces.

Instalation

pip install k8s-audit-filter

Usage

You can easly modify your python script to filter audit logs. Just import AuditFilter class, init it with your audit-policy.yaml file and use it's methods. See an example of modification of this script:

import json

import os
import boto3
import string
import random

from datetime import datetime

from k8s_audit_filter import AuditFilter  # import AuditFilter class


def get_random_alphanumeric_string(length):
    letters_and_digits = string.ascii_letters + string.digits
    result_str = ''.join((random.choice(letters_and_digits) for i in range(length)))
    return result_str


client = boto3.client(
    service_name='s3',
    endpoint_url='https://storage.yandexcloud.net',
    region_name='ru-central1'
)


def handler(event, context):
    for log_data in event['messages']:

        full_log = []
        for log_entry in log_data['details']['messages']:
            kubernetes_log = json.loads(log_entry['message'])
            full_log.append(json.dumps(kubernetes_log))

        audit_filter = AuditFilter('path/to/audit_policy.yaml')  # init AuditFilter class with path to audit policy file
        filtered_log = [line for line in full_log if audit_filter.filter(full_log)]  # filter audit logs

        bucket_name = os.environ.get('BUCKET_NAME')
        object_key = 'AUDIT/' + os.environ.get('CLUSTER_ID') + '/' + datetime.now().strftime(
            '%Y-%m-%d-%H:%M:%S') + '-' + get_random_alphanumeric_string(5)
        object_value = '\n'.join(filtered_log)  # prepare data to load
        client.put_object(Bucket=bucket_name, Key=object_key, Body=object_value,
                          StorageClass='COLD')  # load data to cloud storage

Also you can update your policy dinamically, just use add_rule and remove_rule method:

from k8s_audit_filter import AuditFilter

audit_filter = AuditFilter()  # init AuditFilter class with blink audit policy
audit_filter.add_rule({'level': 'Metadata'})
audit_filter.filter({'level': 'Metadata'})  # return True
audit_filter.remove_rule({'level': 'Metadata'})
audit_filter.filter({'level': 'Metadata'})  # return False

Describing Audit Policy

You can use find the way to describe k8s audit policy rules in Official Kubernetes Documentation at https://kubernetes.io/docs/reference/config-api/apiserver-audit.v1/

See example of audit policy:

apiVersion: audit.k8s.io/v1 # This is required.

kind: Policy
# Don't generate audit events for all requests in RequestReceived stage.

omitStages:
  - "RequestReceived"

rules:
  # Include line in the audit log which contains verb "get" and have level "Metadata"
  - level: Metadata
    verbs:
      - "get"

  # Exclude line in the audit log which contains verb "create"
  - level: None
    verbs:
      - "create"

Supported Rules

Please note, that level is required field for every rule, and should have of one of next values:

• None - do not log events that match this rule (this is ExcludeRule)
• Metadata - log line marked as "Metadata"
• Request - log line marked as "Request"
• RequestResponse - log line marked as "RequestResponse"

The library supports the following rules k8s audit PolicyRules:

• level
• verbs
• users
• userGroups

Limitations

Currently, the library does not support following rules:

• nonResourceURLs - will be supported in the future
• resources - will be supported in the future
• namespaces - will be supported in the future
• omitStages - now it does not distinguish any stages, and filter any string provided to AuditFilter.filter()
• omitManagedFields