Files
sigma-rules/detection_rules/ecs.py
T
Justin Ibarra 332ea40100 Cleanup rule survey code (#1923)
* Cleanup rule survey code

* default to only unique-ing on process name for lucene rules

* fix bug in kibana url parsing by removing redundant port from domain

* update search-alerts columns and nest fields

* fix rule.contents.data.index

Co-authored-by: Mika Ayenson <Mikaayenson@users.noreply.github.com>
2022-09-06 15:53:47 -06:00

270 lines
8.6 KiB
Python

# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
# or more contributor license agreements. Licensed under the Elastic License
# 2.0; you may not use this file except in compliance with the Elastic License
# 2.0.
"""ECS Schemas management."""
import copy
import glob
import os
import shutil
import json
from pathlib import Path
import requests
import eql
import eql.types
import yaml
from .semver import Version
from .utils import DateTimeEncoder, cached, load_etc_dump, get_etc_path, gzip_compress, read_gzip, unzip
ETC_NAME = "ecs_schemas"
ECS_SCHEMAS_DIR = get_etc_path(ETC_NAME)
def add_field(schema, name, info):
"""Nest a dotted field within a dictionary."""
if "." not in name:
schema[name] = info
return
top, remaining = name.split(".", 1)
if not isinstance(schema.get(top), dict):
schema[top] = {}
add_field(schema, remaining, info)
def _recursive_merge(existing, new, depth=0):
"""Return an existing dict merged into a new one."""
for key, value in existing.items():
if isinstance(value, dict):
if depth == 0:
new = copy.deepcopy(new)
node = new.setdefault(key, {})
_recursive_merge(value, node, depth + 1)
else:
new[key] = value
return new
def get_schema_files():
"""Get schema files from ecs directory."""
return glob.glob(os.path.join(ECS_SCHEMAS_DIR, '*', '*.json.gz'), recursive=True)
def get_schema_map():
"""Get local schema files by version."""
schema_map = {}
for file_name in get_schema_files():
path, name = os.path.split(file_name)
name = name.split('.')[0]
version = os.path.basename(path)
schema_map.setdefault(version, {})[name] = file_name
return schema_map
@cached
def get_schemas():
"""Get local schemas."""
schema_map = get_schema_map()
for version, values in schema_map.items():
for name, file_name in values.items():
schema_map[version][name] = json.loads(read_gzip(file_name))
return schema_map
def get_max_version(include_master=False):
"""Get maximum available schema version."""
versions = get_schema_map().keys()
if include_master and any([v.startswith('master') for v in versions]):
return list(Path(ECS_SCHEMAS_DIR).glob('master*'))[0].name
return str(max([Version(v) for v in versions if not v.startswith('master')]))
@cached
def get_schema(version=None, name='ecs_flat'):
"""Get schema by version."""
if version == 'master':
version = get_max_version(include_master=True)
return get_schemas()[version or str(get_max_version())][name]
@cached
def get_eql_schema(version=None, index_patterns=None):
"""Return schema in expected format for eql."""
schema = get_schema(version, name='ecs_flat')
str_types = ('text', 'ip', 'keyword', 'date', 'object', 'geo_point')
num_types = ('float', 'integer', 'long')
schema = schema.copy()
def convert_type(t):
return 'string' if t in str_types else 'number' if t in num_types else 'boolean'
converted = {}
for field, schema_info in schema.items():
field_type = schema_info.get('type', '')
add_field(converted, field, convert_type(field_type))
if index_patterns:
for index_name in index_patterns:
for k, v in flatten(get_index_schema(index_name)).items():
add_field(converted, k, convert_type(v))
return converted
def flatten(schema):
flattened = {}
for k, v in schema.items():
if isinstance(v, dict):
flattened.update((k + "." + vk, vv) for vk, vv in flatten(v).items())
else:
flattened[k] = v
return flattened
@cached
def get_non_ecs_schema():
"""Load non-ecs schema."""
return load_etc_dump('non-ecs-schema.json')
@cached
def get_index_schema(index_name):
return get_non_ecs_schema().get(index_name, {})
def flatten_multi_fields(schema):
converted = {}
for field, info in schema.items():
converted[field] = info["type"]
for subfield in info.get("multi_fields", []):
converted[field + "." + subfield["name"]] = subfield["type"]
return converted
class KqlSchema2Eql(eql.Schema):
type_mapping = {
"keyword": eql.types.TypeHint.String,
"ip": eql.types.TypeHint.String,
"float": eql.types.TypeHint.Numeric,
# "double": eql.types.TypeHint.Numeric,
# "long": eql.types.TypeHint.Numeric,
# "short": eql.types.TypeHint.Numeric,
"integer": eql.types.TypeHint.Numeric,
"boolean": eql.types.TypeHint.Boolean,
}
def __init__(self, kql_schema):
self.kql_schema = kql_schema
eql.Schema.__init__(self, {}, allow_any=True, allow_generic=False, allow_missing=False)
def validate_event_type(self, event_type):
# allow all event types to fill in X:
# `X` where ....
return True
def get_event_type_hint(self, event_type, path):
from kql.parser import elasticsearch_type_family
dotted = ".".join(path)
elasticsearch_type = self.kql_schema.get(dotted)
es_type_family = elasticsearch_type_family(elasticsearch_type)
eql_hint = self.type_mapping.get(es_type_family)
if eql_hint is not None:
return eql_hint, None
@cached
def get_kql_schema(version=None, indexes=None, beat_schema=None) -> dict:
"""Get schema for KQL."""
indexes = indexes or ()
converted = flatten_multi_fields(get_schema(version, name='ecs_flat'))
for index_name in indexes:
converted.update(**flatten(get_index_schema(index_name)))
if isinstance(beat_schema, dict):
converted = dict(flatten_multi_fields(beat_schema), **converted)
return converted
def download_schemas(refresh_master=True, refresh_all=False, verbose=True):
"""Download additional schemas from ecs releases."""
existing = [Version(v) for v in get_schema_map()] if not refresh_all else []
url = 'https://api.github.com/repos/elastic/ecs/releases'
releases = requests.get(url)
for release in releases.json():
version = Version(release.get('tag_name', '').lstrip('v'))
# we don't ever want beta
if not version or version < (1, 0, 1) or version in existing:
continue
schema_dir = os.path.join(ECS_SCHEMAS_DIR, str(version))
with unzip(requests.get(release['zipball_url']).content) as archive:
name_list = archive.namelist()
base = name_list[0]
# members = [m for m in name_list if m.startswith('{}{}/'.format(base, 'use-cases')) and m.endswith('.yml')]
members = ['{}generated/ecs/ecs_flat.yml'.format(base), '{}generated/ecs/ecs_nested.yml'.format(base)]
saved = []
for member in members:
file_name = os.path.basename(member)
os.makedirs(schema_dir, exist_ok=True)
# load as yaml, save as json
contents = yaml.safe_load(archive.read(member))
out_file = file_name.replace(".yml", ".json.gz")
compressed = gzip_compress(json.dumps(contents, sort_keys=True, cls=DateTimeEncoder))
new_path = get_etc_path(ETC_NAME, str(version), out_file)
with open(new_path, 'wb') as f:
f.write(compressed)
saved.append(out_file)
if verbose:
print('Saved files to {}: \n\t- {}'.format(schema_dir, '\n\t- '.join(saved)))
# handle working master separately
if refresh_master:
master_ver = requests.get('https://raw.githubusercontent.com/elastic/ecs/master/version')
master_ver = Version(master_ver.text.strip())
master_schema = requests.get('https://raw.githubusercontent.com/elastic/ecs/master/generated/ecs/ecs_flat.yml')
master_schema = yaml.safe_load(master_schema.text)
# prepend with underscore so that we can differentiate the fact that this is a working master version
# but first clear out any existing masters, since we only ever want 1 at a time
existing_master = glob.glob(os.path.join(ECS_SCHEMAS_DIR, 'master_*'))
for m in existing_master:
shutil.rmtree(m, ignore_errors=True)
master_dir = "master_{}".format(master_ver)
os.makedirs(get_etc_path(ETC_NAME, master_dir), exist_ok=True)
compressed = gzip_compress(json.dumps(master_schema, sort_keys=True, cls=DateTimeEncoder))
new_path = get_etc_path(ETC_NAME, master_dir, "ecs_flat.json.gz")
with open(new_path, 'wb') as f:
f.write(compressed)
if verbose:
print('Saved files to {}: \n\t- {}'.format(master_dir, 'ecs_flat.json.gz'))