SigmaHQ/tests/test_rules.py

#!/usr/bin/env python3
"""
Checks for noncompliance or common errors on all rules

Run using the command
# python -m unittest test_rules.py
"""

import os
import unittest
import yaml
import re
from colorama import init
from colorama import Fore

class TestRules(unittest.TestCase):
    MITRE_TECHNIQUES = [
             "t1002",
             "t1003",
             "t1003.001",
             "t1003.002",
             "t1003.003",
             "t1003.004",
             "t1003.005",
             "t1003.006",
             "t1004",
             "t1005",
             "t1006",
             "t1007",
             "t1009",
             "t1011",
             "t1012",
             "t1015",
             "t1016",
             "t1018",
             "t1020",
             "t1021",
             "t1021.001",
             "t1021.002",
             "t1021.003",
             "t1021.006",
             "t1023",
             "t1027",
             "t1028",
             "t1031",
             "t1033",
             "t1035",
             "t1036",
             "t1036.005",
             "t1037",
             "t1037.001",
             "t1038",
             "t1040",
             "t1041",
             "t1042",
             "t1043",
             "t1046",
             "t1047",
             "t1048",
             "t1049",
             "t1050",
             "t1053",
             "t1053.002",
             "t1053.005",
             "t1054",
             "t1055",
             "t1056",
             "t1057",
             "t1058",
             "t1059",
             "t1059.001",
             "t1059.003",
             "t1059.004",
             "t1059.005",
             "t1059.006",
             "t1060",
             "t1064",
             "t1066",
             "t1067",
             "t1068",
             "t1069",
             "t1070",
             "t1070.001",
             "t1070.002",
             "t1070.003",
             "t1070.004",
             "t1070.005",
             "t1070.006",
             "t1071",
             "t1071.004",
             "t1073",
             "t1074",
             "t1075",
             "t1076",
             "t1077",
             "t1078",
             "t1081",
             "t1082",
             "t1083",
             "t1084",
             "t1085",
             "t1086",
             "t1087",
             "t1088",
             "t1089",
             "t1090",
             "t1091",
             "t1096",
             "t1098",
             "t1099",
             "t1100",
             "t1102",
             "t1103",
             "t1105",
             "t1106",
             "t1107",
             "t1110",
             "t1112",
             "t1114",
             "t1117",
             "t1118",
             "t1121",
             "t1122",
             "t1123",
             "t1124",
             "t1125",
             "t1127",
             "t1128",
             "t1130",
             "t1133",
             "t1134",
             "t1134.005",
             "t1135",
             "t1136",
             "t1137",
             "t1138",
             "t1139",
             "t1140",
             "t1145",
             "t1146",
             "t1156",
             "t1158",
             "t1168",
             "t1169",
             "t1170",
             "t1171",
             "t1175",
             "t1177",
             "t1178",
             "t1182",
             "t1183",
             "t1190",
             "t1191",
             "t1193",
             "t1195",
             "t1195.001",
             "t1196",
             "t1197",
             "t1200",
             "t1201",
             "t1202",
             "t1203",
             "t1204",
             "t1207",
             "t1208",
             "t1210",
             "t1211",
             "t1212",
             "t1218",
             "t1218.001",
             "t1218.005",
             "t1218.010",
             "t1218.011",
             "t1219",
             "t1220",
             "t1222",
             "t1223",
             "t1482",
             "t1485",
             "t1487",
             "t1488",
             "t1489",
             "t1490",
             "t1492",
             "t1493",
             "t1495",
             "t1499",
             "t1500",
             "t1501",
             "t1505",
             "t1505.003",
             "t1537",
             "t1542.003",
             "t1543.002",
             "t1543.003",
             "t1546.001",
             "t1546.003",
             "t1546.004",
             "t1546.007",
             "t1546.008",
             "t1546.009",
             "t1546.010",
             "t1546.011",
             "t1546.012",
             "t1546.015",
             "t1547.001",
             "t1547.004",
             "t1547.008",
             "t1547.009",
             "t1548.002",
             "t1550.002",
             "t1551",
             "t1551.003",
             "t1551.004",
             "t1551.006",
             "t1552.001",
             "t1552.003",
             "t1552.004",
             "t1553.004",
             "t1557.001",
             "t1558",
             "t1558.003",
             "t1559.001",
             "t1560",
             "t1561.001",
             "t1561.002",
             "t1562.001",
             "t1562.006",
             "t1564.001",
             "t1564.004",
             "t1565.001",
             "t1565.002",
             "t1566.001",
             "t1569.002",
             "t1571",
             "t1574.001",
             "t1574.002",
             "t1574.011",
]
    MITRE_TECHNIQUE_NAMES = ["process_injection", "signed_binary_proxy_execution", "process_injection"] # incomplete list
    MITRE_TACTICS = ["initial_access", "execution", "persistence", "privilege_escalation", "defense_evasion", "credential_access", "discovery", "lateral_movement", "collection", "exfiltration", "command_and_control", "impact", "launch"]
    MITRE_GROUPS =  ["g0001", "g0002", "g0003", "g0004", "g0005", "g0006", "g0007", "g0008", "g0009", "g0010", "g0011", "g0012", "g0013", "g0014", "g0015", "g0016", "g0017", "g0018", "g0019", "g0020", "g0021", "g0022", "g0023", "g0024", "g0025", "g0026", "g0027", "g0028", "g0029", "g0030", "g0031", "g0032", "g0033", "g0034", "g0035", "g0036", "g0037", "g0038", "g0039", "g0040", "g0041", "g0042", "g0043", "g0044", "g0045", "g0046", "g0047", "g0048", "g0049", "g0050", "g0051", "g0052", "g0053", "g0054", "g0055", "g0056", "g0057", "g0058", "g0059", "g0060", "g0061", "g0062", "g0063", "g0064", "g0065", "g0066", "g0067", "g0068", "g0069", "g0070", "g0071", "g0072", "g0073", "g0074", "g0075", "g0076", "g0077", "g0078", "g0079", "g0080", "g0081", "g0082", "g0083", "g0084", "g0085", "g0086", "g0087", "g0088", "g0089", "g0090", "g0091", "g0092", "g0093", "g0094", "g0095", "g0096"]
    MITRE_SOFTWARE = ["s0001", "s0002", "s0003", "s0004", "s0005", "s0006", "s0007", "s0008", "s0009", "s0010", "s0011", "s0012", "s0013", "s0014", "s0015", "s0016", "s0017", "s0018", "s0019", "s0020", "s0021", "s0022", "s0023", "s0024", "s0025", "s0026", "s0027", "s0028", "s0029", "s0030", "s0031", "s0032", "s0033", "s0034", "s0035", "s0036", "s0037", "s0038", "s0039", "s0040", "s0041", "s0042", "s0043", "s0044", "s0045", "s0046", "s0047", "s0048", "s0049", "s0050", "s0051", "s0052", "s0053", "s0054", "s0055", "s0056", "s0057", "s0058", "s0059", "s0060", "s0061", "s0062", "s0063", "s0064", "s0065", "s0066", "s0067", "s0068", "s0069", "s0070", "s0071", "s0072", "s0073", "s0074", "s0075", "s0076", "s0077", "s0078", "s0079", "s0080", "s0081", "s0082", "s0083", "s0084", "s0085", "s0086", "s0087", "s0088", "s0089", "s0090", "s0091", "s0092", "s0093", "s0094", "s0095", "s0096", "s0097", "s0098", "s0099", "s0100", "s0101", "s0102", "s0103", "s0104", "s0105", "s0106", "s0107", "s0108", "s0109", "s0110", "s0111", "s0112", "s0113", "s0114", "s0115", "s0116", "s0117", "s0118", "s0119", "s0120", "s0121", "s0122", "s0123", "s0124", "s0125", "s0126", "s0127", "s0128", "s0129", "s0130", "s0131", "s0132", "s0133", "s0134", "s0135", "s0136", "s0137", "s0138", "s0139", "s0140", "s0141", "s0142", "s0143", "s0144", "s0145", "s0146", "s0147", "s0148", "s0149", "s0150", "s0151", "s0152", "s0153", "s0154", "s0155", "s0156", "s0157", "s0158", "s0159", "s0160", "s0161", "s0162", "s0163", "s0164", "s0165", "s0166", "s0167", "s0168", "s0169", "s0170", "s0171", "s0172", "s0173", "s0174", "s0175", "s0176", "s0177", "s0178", "s0179", "s0180", "s0181", "s0182", "s0183", "s0184", "s0185", "s0186", "s0187", "s0188", "s0189", "s0190", "s0191", "s0192", "s0193", "s0194", "s0195", "s0196", "s0197", "s0198", "s0199", "s0200", "s0201", "s0202", "s0203", "s0204", "s0205", "s0206", "s0207", "s0208", "s0209", "s0210", "s0211", "s0212", "s0213", "s0214", "s0215", "s0216", "s0217", "s0218", "s0219", "s0220", "s0221", "s0222", "s0223", "s0224", "s0225", "s0226", "s0227", "s0228", "s0229", "s0230", "s0231", "s0232", "s0233", "s0234", "s0235", "s0236", "s0237", "s0238", "s0239", "s0240", "s0241", "s0242", "s0243", "s0244", "s0245", "s0246", "s0247", "s0248", "s0249", "s0250", "s0251", "s0252", "s0253", "s0254", "s0255", "s0256", "s0257", "s0258", "s0259", "s0260", "s0261", "s0262", "s0263", "s0264", "s0265", "s0266", "s0267", "s0268", "s0269", "s0270", "s0271", "s0272", "s0273", "s0274", "s0275", "s0276", "s0277", "s0278", "s0279", "s0280", "s0281", "s0282", "s0283", "s0284", "s0330", "s0331", "s0332", "s0333", "s0334", "s0335", "s0336", "s0337", "s0338", "s0339", "s0340", "s0341", "s0342", "s0343", "s0344", "s0345", "s0346", "s0347", "s0348", "s0349", "s0350", "s0351", "s0352", "s0353", "s0354", "s0355", "s0356", "s0357", "s0358", "s0359", "s0360", "s0361", "s0362", "s0363", "s0364", "s0365", "s0366", "s0367", "s0368", "s0369", "s0370", "s0371", "s0372", "s0373", "s0374", "s0375", "s0376", "s0377", "s0378", "s0379", "s0380", "s0381", "s0382", "s0383", "s0384", "s0385", "s0386", "s0387", "s0388", "s0389", "s0390", "s0391", "s0393", "s0394", "s0395", "s0396", "s0397", "s0398", "s0400", "s0401", "s0402", "s0404", "s0409", "s0410", "s0412", "s0413", "s0414", "s0415", "s0416", "s0417"]
    MITRE_ALL = ["attack." + item for item in MITRE_TECHNIQUES + MITRE_TACTICS + MITRE_GROUPS + MITRE_SOFTWARE]

    path_to_rules = "rules"

    # Helper functions
    def yield_next_rule_file_path(self, path_to_rules:str) -> str:
        for root, _, files in os.walk(path_to_rules):
            for file in files:
                yield os.path.join(root, file)

    def get_rule_part(self, file_path:str, part_name:str):
        yaml_dicts = self.get_rule_yaml(file_path)
        for yaml_part in yaml_dicts:
            if part_name in yaml_part.keys():
                return yaml_part[part_name]

        return None

    def get_rule_yaml(self, file_path:str) -> dict:
        data = []

        with open(file_path) as f:
            yaml_parts = yaml.safe_load_all(f)
            for part in yaml_parts:
                data.append(part)

        return data

    # Tests
    def test_confirm_extension_is_yml(self):
        files_with_incorrect_extensions = []

        for file in self.yield_next_rule_file_path(self.path_to_rules):
            file_name_and_extension = os.path.splitext(file)
            if len(file_name_and_extension) == 2:
                extension = file_name_and_extension[1]
                if extension != ".yml":
                    files_with_incorrect_extensions.append(file)

        self.assertEqual(files_with_incorrect_extensions, [], Fore.RED + 
                        "There are rule files with extensions other than .yml")

    def test_confirm_correct_mitre_tags(self):
        files_with_incorrect_mitre_tags = []

        for file in self.yield_next_rule_file_path(self.path_to_rules):
            tags = self.get_rule_part(file_path=file, part_name="tags")
            if tags:
                for tag in tags:
                    if tag not in self.MITRE_ALL and tag.startswith("attack.") and len(split(".", tag)) < 3:
                        print(Fore.RED + "Rule {} has the following incorrect tag {}".format(file, tag))
                        files_with_incorrect_mitre_tags.append(file)

        self.assertEqual(files_with_incorrect_mitre_tags, [], Fore.RED + 
                         "There are rules with incorrect/unknown MITRE Tags. (please inform us about new tags that are not yet supported in our tests) and check the correct tags here: https://attack.mitre.org/ ")

    def test_look_for_duplicate_filters(self):
        def check_list_or_recurse_on_dict(item, depth:int) -> None:
            if type(item) == list:
                check_if_list_contain_duplicates(item, depth)
            elif type(item) == dict and depth <= MAX_DEPTH:
                for sub_item in item.values():
                    check_list_or_recurse_on_dict(sub_item, depth + 1)

        def check_if_list_contain_duplicates(item:list, depth:int) -> None:
            try:
                if len(item) != len(set(item)):
                    print(Fore.RED + "Rule {} has duplicate filters".format(file))
                    files_with_duplicate_filters.append(file)
            except:
                # unhashable types like dictionaries
                for sub_item in item:
                    if type(sub_item) == dict and depth <= MAX_DEPTH:
                        check_list_or_recurse_on_dict(sub_item, depth + 1)

        MAX_DEPTH = 3
        files_with_duplicate_filters = []

        for file in self.yield_next_rule_file_path(self.path_to_rules):
            detection = self.get_rule_part(file_path=file, part_name="detection")
            check_list_or_recurse_on_dict(detection, 1)

        self.assertEqual(files_with_duplicate_filters, [], Fore.RED + 
                         "There are rules with duplicate filters")

    def test_single_named_condition_with_x_of_them(self):
        faulty_detections = []

        for file in self.yield_next_rule_file_path(self.path_to_rules):
            yaml = self.get_rule_yaml(file_path = file)
            detection = self.get_rule_part(file_path = file, part_name = "detection")

            has_them_in_condition = "them" in detection["condition"]
            has_only_one_named_condition = len(detection) == 2
            not_multipart_yaml_file = len(yaml) == 1

            if has_them_in_condition and \
                has_only_one_named_condition and \
                    not_multipart_yaml_file:
                faulty_detections.append(file)

        self.assertEqual(faulty_detections, [], Fore.RED +
                         "There are rules using '1/all of them' style conditions but only have one condition")

    def test_duplicate_titles(self):
        def compare_detections(detection1:dict, detection2:dict) -> bool:

            # detections not the same length can't be the same
            if len(detection1) != len(detection2):
                return False

            for named_condition in detection1:
                # condition clause must be the same too 
                if named_condition == "condition":
                    if detection1["condition"] != detection2["condition"]:
                        return False
                    else:
                        continue

                # Named condition must exist in both rule files
                if named_condition not in detection2:
                    return False

                if len(detection1[named_condition]) != len(detection2[named_condition]):
                    return False

                for condition in detection1[named_condition]:
                    if type(condition) != str:
                        return False

                    if condition not in detection2[named_condition]:
                        return False

                    condition_value1 = detection1[named_condition][condition]
                    condition_value2 = detection2[named_condition][condition]

                    if condition_value1 != condition_value2:
                        return False

            return True

        faulty_detections = []
        files_and_their_detections = {}

        for file in self.yield_next_rule_file_path(self.path_to_rules):
            detection = self.get_rule_part(file_path = file, part_name = "detection")
            yaml = self.get_rule_yaml(file_path = file)

            is_multipart_yaml_file = len(yaml) != 1
            if is_multipart_yaml_file:
                continue

            for key in files_and_their_detections:
                if compare_detections(detection, files_and_their_detections[key]):
                    faulty_detections.append((key, file))

            files_and_their_detections[file] = detection

        self.assertEqual(faulty_detections, [], Fore.YELLOW + 
                         "There are rule files with exactly the same detection logic.")

    def test_source_eventlog(self):
        faulty_detections = []

        for file in self.yield_next_rule_file_path(self.path_to_rules):
            detection = self.get_rule_part(file_path = file, part_name = "detection")
            detection_str = str(detection).lower()
            if "'source': 'eventlog'" in detection_str:
                faulty_detections.append(file)

        self.assertEqual(faulty_detections, [], Fore.YELLOW + 
                         "There are detections with 'Source: Eventlog'. This does not add value to the detection.")

    def test_event_id_instead_of_process_creation(self):
        faulty_detections = []
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            with open(file) as f:
                for line in f:
                    if re.search(r'.*EventID: (?:1|4688)\s*$', line) and file not in faulty_detections:
                        faulty_detections.append(file)

        self.assertEqual(faulty_detections, [], Fore.YELLOW + 
                         "There are rules still using Sysmon 1 or Event ID 4688. Please migrate to the process_creation category.")

    def test_missing_id(self):
        faulty_rules = []
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            id = self.get_rule_part(file_path=file, part_name="id")
            if not id:
                print(Fore.YELLOW + "Rule {} has no field 'id'.".format(file))
                faulty_rules.append(file)
            elif len(id) != 36:
                print(Fore.YELLOW + "Rule {} has a malformed 'id' (not 36 chars).".format(file))
                faulty_rules.append(file)                

        self.assertEqual(faulty_rules, [], Fore.RED + 
                         "There are rules with missing or malformed 'id' fields. Create an id (e.g. here: https://www.uuidgenerator.net/version4) and add it to the reported rule(s).")
    
    def test_sysmon_rule_without_eventid(self):
        faulty_rules = []
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            logsource = self.get_rule_part(file_path=file, part_name="logsource")
            service = logsource.get('service', '')
            if service.lower() == 'sysmon':
                with open(file) as f:
                    found = False
                    for line in f:
                        if re.search(r'.*EventID:.*$', line):  # might be on a single line or in multiple lines
                            found = True
                            break
                    if not found:
                        faulty_rules.append(file)      

        self.assertEqual(faulty_rules, [], Fore.RED + 
                         "There are rules using sysmon events but with no EventID specified")


    def test_missing_date(self):
        faulty_rules = []
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            datefield = self.get_rule_part(file_path=file, part_name="date")
            if not datefield:
                print(Fore.YELLOW + "Rule {} has no field 'date'.".format(file))
                faulty_rules.append(file)
            elif len(datefield) != 10:
                print(Fore.YELLOW + "Rule {} has a malformed 'date' (not 10 chars, should be YYYY/MM/DD).".format(file))
                faulty_rules.append(file)                

        self.assertEqual(faulty_rules, [], Fore.RED + 
                         "There are rules with missing or malformed 'date' fields. (create one, e.g. date: 2019/01/14)")

    def test_references(self):
        faulty_rules = []
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            references = self.get_rule_part(file_path=file, part_name="references")
            # Reference field doesn't exist      
            #if not references:
                #print(Fore.YELLOW + "Rule {} has no field 'references'.".format(file))
                #faulty_rules.append(file)
            if references:
                # it exists but isn't a list
                if not isinstance(references, list):
                    print(Fore.YELLOW + "Rule {} has a references field that isn't a list.".format(file))
                    faulty_rules.append(file)     

        self.assertEqual(faulty_rules, [], Fore.RED + 
                         "There are rules with malformed 'references' fields. (has to be a list of values even if it contains only a single value)")

    def test_file_names(self):
        faulty_rules = []
        filename_pattern = re.compile('[a-z0-9_]{10,70}\.yml')
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            filename = os.path.basename(file)
            if not filename_pattern.match(filename) and not '_' in filename:
                print(Fore.YELLOW + "Rule {} has a file name that doesn't match our standard.".format(file))
                faulty_rules.append(file)     

        self.assertEqual(faulty_rules, [], Fore.RED + 
                         "There are rules with malformed file names (too short, too long, uppercase letters, a minus sign etc.). Please see the file names used in our repository and adjust your file names accordingly. The pattern for a valid file name is '[a-z0-9_]{10,70}\.yml' and it has to contain at least an underline character.")

    def test_title(self):
        faulty_rules = []
        allowed_lowercase_words = [
                'the',
                'for',
                'in',
                'with',
                'via',
                'on',
                'to',
                'without',
                'of',
                'through',
                'from',
                'by',
                'as',
                'a',
                'or',
                'at',
                'and',
                'an',
                'over',
                'new',
                ]
        for file in self.yield_next_rule_file_path(self.path_to_rules):
            title = self.get_rule_part(file_path=file, part_name="title")
            if not title:
                print(Fore.RED + "Rule {} has no field 'title'.".format(file))
                faulty_rules.append(file)
                continue
            elif len(title) > 70:
                print(Fore.YELLOW + "Rule {} has a title field with too many characters (>70)".format(file))
                faulty_rules.append(file)
            if title.startswith("Detects "):
                print(Fore.RED + "Rule {} has a title that starts with 'Detects'".format(file))
                faulty_rules.append(file)
            wrong_casing = []
            for word in title.split(" "):
                if word.islower() and not word.lower() in allowed_lowercase_words and not "." in word and not "/" in word and not word[0].isdigit():
                    wrong_casing.append(word)
            if len(wrong_casing) > 0:
                print(Fore.RED + "Rule {} has a title that has not title capitalization. Words: '{}'".format(file, ", ".join(wrong_casing)))
                faulty_rules.append(file)

        self.assertEqual(faulty_rules, [], Fore.RED + 
                         "There are rules with non-conform 'title' fields. Please check: https://github.com/Neo23x0/sigma/wiki/Rule-Creation-Guide#title")

if __name__ == "__main__":
    init(autoreset=True)
    unittest.main()