A tool to filter k8s audit logs
Project description
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) and have to filter it with python script.
Also you can use this library to analyze audit logs.
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
# load data to cloud storage
client.put_object(Bucket=bucket_name, Key=object_key, Body=object_value, StorageClass='COLD')
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
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"
- level: Request
users:
- "admin"
- level: Request
userGroups:
- "system:admins"
Describing Audit Policy in Python
If you want to describe audit policy in python, you can describe it in the same way as in yaml file with dict:
from k8s_audit_filter import AuditFilter
audit_filter = AuditFilter()
rules = [
{'level': 'Metadata', 'verbs': ['get']},
{'level': 'None', 'verbs': ['create']},
{'level': 'Request', 'users': ['admin']},
{'level': 'Request', 'userGroups': ['system:admins']},
{'level': 'Request', 'namespaces': ['kube-system']},
{'level': 'RequestResponse',
'resources': [
{'group': '', 'resources': ['deployments'], 'resourceNames': ['pods']},
{'group': 'apps', 'resources': ['leases'], 'resourceNames': ['test']}
]
}
]
audit_filter.add_rules(rules)
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
namespaces
resources
- Partly supported. Please read about limitations below
Limitations
The library does not support following k8s Audit rules:
resources
- please note, that unlike original k8s audit policy, empty string "" in "group" field will not return "core" group, but will return all groupsnonResourceURLs
- notResourceURLs are not declared explicitly in audit logsomitStages
- now it does not discern any stagesomitManagedFields
- omitManagedFields is not declared explicitly in audit logs
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