重构子域解析模块

oneforall/brute.py

@@ -10,11 +10,8 @@ OneForAll子域爆破模块
 import gc
 import json
 import time
-import stat
 import random
 import secrets
-import platform
-import subprocess
 
 import exrex
 import fire
@@ -24,7 +21,7 @@ from dns.resolver import NXDOMAIN, YXDOMAIN, NoAnswer, NoNameservers
 
 import config
 import dbexport
-from common import resolve, utils
+from common import utils
 from common.module import Module
 from config import logger
 
@@ -76,7 +73,7 @@ def detect_wildcard(domain, authoritative_ns):
     logger.log('INFOR', f'正在探测{domain}是否使用泛解析')
     token = secrets.token_hex(4)
     random_subdomain = f'{token}.{domain}'
-    resolver = resolve.dns_resolver()
+    resolver = utils.dns_resolver()
     resolver.nameservers = authoritative_ns
     resolver.rotate = True
     resolver.cache = None
@@ -114,15 +111,6 @@ def gen_fuzz_subdomains(expression, rule):
     return subdomains
 
 
-def gen_domains(iterable, place):
-    subdomains = set()
-    for _ in range(place.count('*')):
-        for item in iterable:
-            subdomain = place.replace('*', item)
-            subdomains.add(subdomain)
-    return subdomains
-
-
 def gen_word_subdomains(expression, path):
     """
     生成基于word模式的爆破子域
@@ -151,7 +139,7 @@ def query_domain_ns_a(ns_list):
     if not isinstance(ns_list, list):
         return list()
     ns_ip_list = []
-    resolver = resolve.dns_resolver()
+    resolver = utils.dns_resolver()
     for ns in ns_list:
         try:
             answer = resolver.query(ns, 'A')
@@ -168,7 +156,7 @@ def query_domain_ns_a(ns_list):
 
 def query_domain_ns(domain):
     domain = utils.get_maindomain(domain)
-    resolver = resolve.dns_resolver()
+    resolver = utils.dns_resolver()
     try:
         answer = resolver.query(domain, 'NS')
     except Exception as e:
@@ -218,7 +206,7 @@ def collect_wildcard_record(domain, authoritative_ns):
     logger.log('INFOR', f'正在收集{domain}的泛解析记录')
     if not authoritative_ns:
         return list(), int()
-    resolver = resolve.dns_resolver()
+    resolver = utils.dns_resolver()
     resolver.nameservers = authoritative_ns
     resolver.rotate = True
     resolver.cache = None
@@ -259,28 +247,6 @@ def get_nameservers_path(enable_wildcard, ns_ip_list):
     return path
 
 
-def get_massdns_path(massdns_dir):
-    path = config.brute_massdns_path
-    if path:
-        return path
-    system = platform.system().lower()
-    machine = platform.machine().lower()
-    name = f'massdns_{system}_{machine}'
-    if system == 'windows':
-        name = name + '.exe'
-        if machine == 'amd64':
-            massdns_dir = massdns_dir.joinpath('windows', 'x64')
-        else:
-            massdns_dir = massdns_dir.joinpath('windows', 'x84')
-    path = massdns_dir.joinpath(name)
-    path.chmod(stat.S_IXUSR)
-    if not path.exists():
-        logger.log('FATAL', '暂无该系统平台及架构的massdns')
-        logger.log('INFOR', '请尝试自行编译massdns并在配置里指定路径')
-        exit(0)
-    return path
-
-
 def check_dict():
     if not config.enable_check_dict:
         return
@@ -294,40 +260,6 @@ def check_dict():
         exit(0)
 
 
-def do_brute(massdns_path, dict_path, ns_path, output_path, log_path,
-             query_type='A', process_num=1, concurrent_num=10000,
-             quiet_mode=False):
-    quiet = ''
-    if quiet_mode:
-        quiet = '--quiet'
-    status_format = config.brute_status_format
-    socket_num = config.brute_socket_num
-    resolve_num = config.brute_resolve_num
-    cmd = f'{massdns_path} {quiet} --status-format {status_format} ' \
-          f'--processes {process_num} --socket-count {socket_num} ' \
-          f'--hashmap-size {concurrent_num} --resolvers {ns_path} ' \
-          f'--resolve-count {resolve_num} --type {query_type} ' \
-          f'--flush --output J --outfile {output_path} ' \
-          f'--error-log {log_path} {dict_path}'
-    logger.log('INFOR', f'执行命令 {cmd}')
-    subprocess.run(args=cmd, shell=True)
-
-
-def read_result(result_path):
-    result = list()
-    with open(result_path) as fd:
-        for line in fd:
-            line = line.strip()
-            try:
-                record = json.loads(line)
-            except Exception as e:
-                logger.log('ERROR', e.args)
-                logger.log('ERROR', f'解析行{line}出错跳过解析该行')
-                continue
-            result.append(record)
-    return result
-
-
 def gen_records(items, records, subdomains, ip_times, wc_ips, wc_ttl):
     qname = items.get('name')[:-1]  # 去出最右边的`.`点号
     reason = items.get('status')
@@ -474,8 +406,9 @@ def is_valid_subdomain(ip, ttl, times, wc_ips, wc_ttl):
     return 1, 'OK'
 
 
-def save_brute_dict(path, data):
-    if not utils.save_data(path, data):
+def save_brute_dict(dict_path, dict_set):
+    dict_data = '\n'.join(dict_set)
+    if not utils.save_data(dict_path, dict_data):
         logger.log('FATAL', '保存生成的字典出错')
         exit(1)
 
@@ -611,7 +544,7 @@ class Brute(Module):
         result_dir = config.result_save_dir
         temp_dir = result_dir.joinpath('temp')
         utils.check_dir(temp_dir)
-        massdns_path = get_massdns_path(massdns_dir)
+        massdns_path = utils.get_massdns_path(massdns_dir)
         timestring = utils.get_timestring()
 
         wildcard_ips = list()  # 泛解析IP列表
@@ -627,14 +560,11 @@ class Brute(Module):
 
         dict_set = self.gen_brute_dict(domain)
         dict_len = len(dict_set)
-        dict_data = '\n'.join(dict_set)
-        del dict_set
-        gc.collect()
 
         dict_name = f'generated_subdomains_{domain}_{timestring}.txt'
         dict_path = temp_dir.joinpath(dict_name)
-        save_brute_dict(dict_path, dict_data)
-        del dict_data
+        save_brute_dict(dict_path, dict_set)
+        del dict_set
         gc.collect()
 
         output_name = f'resolved_result_{domain}_{timestring}.json'
@@ -642,11 +572,9 @@ class Brute(Module):
         log_path = result_dir.joinpath('massdns.log')
         check_dict()
 
-        logger.log('INFOR', f'开始执行massdns')
-        do_brute(massdns_path, dict_path, ns_path, output_path, log_path,
-                 process_num=self.process_num,
-                 concurrent_num=self.concurrent_num)
-        logger.log('INFOR', f'结束执行massdns')
+        utils.call_massdns(massdns_path, dict_path, ns_path, output_path,
+                           log_path, process_num=self.process_num,
+                           concurrent_num=self.concurrent_num)
 
         ip_times = stat_ip_times(output_path)
         self.records, self.subdomains = deal_output(output_path, ip_times,
@@ -703,7 +631,3 @@ class Brute(Module):
 
 if __name__ == '__main__':
     fire.Fire(Brute)
-    # domain = 'example.com'
-    # result = queue.Queue()
-    # brute = AIOBrute(domain)
-    # brute.run(result)

oneforall/common/request.py

@@ -22,7 +22,7 @@ def get_limit_conn():
 
 
 def get_ports(port):
-    logger.log('DEBUG', f'正在获取请求探测端口范围')
+    logger.log('DEBUG', f'正在获取请求端口范围')
     ports = set()
     if isinstance(port, (set, list, tuple)):
         ports = port
@@ -30,12 +30,12 @@ def get_ports(port):
         if 0 <= port <= 65535:
             ports = {port}
     elif port in {'default', 'small', 'large'}:
-        logger.log('DEBUG', f'探测{port}等端口范围')
+        logger.log('DEBUG', f'请求{port}等端口范围')
         ports = config.ports.get(port)
     if not ports:  # 意外情况
-        logger.log('ERROR', f'指定探测端口范围有误')
+        logger.log('ERROR', f'指定请求端口范围有误')
         ports = {80}
-    logger.log('INFOR', f'探测端口范围：{ports}')
+    logger.log('INFOR', f'请求端口范围：{ports}')
     return set(ports)
 
 
@@ -202,7 +202,7 @@ async def bulk_request(data, port):
     no_req_data = utils.get_filtered_data(data)
     to_req_data = gen_req_data(data, ports)
     method = config.request_method
-    logger.log('INFOR', f'使用{method}请求方法')
+    logger.log('INFOR', f'请求使用{method}方法')
     logger.log('INFOR', f'正在进行异步子域请求')
     connector = get_connector()
     header = get_header()
@@ -224,8 +224,6 @@ async def bulk_request(data, port):
                                     desc='Request Progress',
                                     ncols=80):
                 await future
-
-    logger.log('INFOR', f'完成异步进行子域的GET请求')
     return to_req_data + no_req_data
 
 
@@ -239,6 +237,7 @@ def run_request(domain, data, port):
     :return: 请求后得到的结果列表
     :rtype: list
     """
+    logger.log('INFOR', f'开始执行子域请求模块')
     loop = asyncio.get_event_loop()
     asyncio.set_event_loop(loop)
     data = utils.set_id_none(data)

oneforall/common/resolve.py

@@ -1,110 +1,44 @@
-import socket
-import asyncio
-import functools
-import sys
-from multiprocessing import Manager
-
-import tqdm
-import aiomultiprocess as aiomp
-from dns.resolver import Resolver
+import gc
+import json
 
 import config
 from config import logger
 from common import utils
 from common.database import Database
 
-socket.setdefaulttimeout(20)
 
-
-def dns_resolver():
-    """
-    dns解析器
-    """
-    resolver = Resolver()
-    resolver.nameservers = config.resolver_nameservers
-    resolver.timeout = config.resolver_timeout
-    resolver.lifetime = config.resolver_lifetime
-    return resolver
-
-
-async def aio_resolve_a(hostname, loop=None):
-    """
-    异步解析A记录
-
-    :param str hostname: 主机名
-    :param loop: 事件循环
-    :return: 查询结果
-    """
-    if loop is None:
-        loop = asyncio.get_event_loop()
-    try:
-        answer = await loop.run_in_executor(None,
-                                            socket.gethostbyname_ex,
-                                            hostname)
-    except BaseException as e:
-        logger.log('TRACE', e.args)
-        answer = e
-    return hostname, answer
-
-
-def convert_results(result_list):
-    """
-    将结果列表类型转换为结果字典类型
-
-    :param result_list: 待转换的结果列表
-    :return: 转换后的结果字典
-    """
-    result_dict = {}
-    for result in result_list:
-        hostname, answer = result
-        value_dict = {'content': None, 'reason': None, 'resolve': None,
-                      'public': None, 'valid': None}
-        if isinstance(answer, tuple):
-            ip_list = answer[2]
-            value_dict['content'] = ','.join(ip_list)
-            value_dict['public'] = utils.check_ip_public(ip_list)
-            value_dict['resolve'] = 1
-            result_dict[hostname] = value_dict
-        elif isinstance(answer, Exception):
-            value_dict['reason'] = str(answer.args)
-            value_dict['resolve'] = 0
-            result_dict[hostname] = value_dict
-        else:
-            value_dict['resolve'] = 0
-            result_dict[hostname] = value_dict
-    return result_dict
-
-
-def filter_subdomain(data_list):
+def filter_subdomain(data):
     """
     过滤出无解析内容的子域到新的子域列表
 
-    :param list data_list: 待过滤的数据列表
+    :param list data: 待过滤的数据列表
     :return: 符合条件的子域列表
     """
+    logger.log('DEBUG', f'正在过滤出待解析的子域')
     subdomains = []
-    for data in data_list:
+    for data in data:
         if not data.get('content'):
             subdomain = data.get('subdomain')
             subdomains.append(subdomain)
     return subdomains
 
 
-def update_data(data_list, results_dict):
+def update_data(data, records):
     """
     更新解析结果
 
-    :param list data_list: 待更新的数据列表
-    :param dict results_dict: 解析结果字典
+    :param list data: 待更新的数据列表
+    :param dict records: 解析结果字典
     :return: 更新后的数据列表
     """
-    for index, data in enumerate(data_list):
-        if not data.get('content'):
-            subdomain = data.get('subdomain')
-            value_dict = results_dict.get(subdomain)
-            data.update(value_dict)
-            data_list[index] = data
-    return data_list
+    logger.log('DEBUG', f'正在更新解析结果')
+    for index, items in enumerate(data):
+        if not items.get('content'):
+            subdomain = items.get('subdomain')
+            record = records.get(subdomain)
+            items.update(record)
+            data[index] = items
+    return data
 
 
 def save_data(name, data):
@@ -114,6 +48,7 @@ def save_data(name, data):
     :param str name: 保存表名
     :param list data: 待保存的数据
     """
+    logger.log('INFOR', f'正在保存解析结果')
     db = Database()
     db.drop_table(name)
     db.create_table(name)
@@ -121,104 +56,111 @@ def save_data(name, data):
     db.close()
 
 
-def resolve_progress_func(done_obj, total_num):
-    """
-    解析进度函数
-
-    :param done_obj: 进程间共享的Value对象
-    :param int total_num: 待解析的子域个数
-    """
-    bar = tqdm.tqdm()
-    bar.total = total_num
-    bar.desc = 'Resolve Progress'
-    bar.ncols = 80
-    bar.smoothing = 0
-    while True:
-        done_num = done_obj.value
-        bar.n = done_num
-        bar.update()
-        if done_num == total_num:
-            break
-    bar.close()
+def save_subdomains(save_path, subdomain_list):
+    logger.log('DEBUG', f'正在保存待解析的子域')
+    subdomain_data = '\n'.join(subdomain_list)
+    if not utils.save_data(save_path, subdomain_data):
+        logger.log('FATAL', '保存待解析的子域出错')
+        exit(1)
 
 
-async def do_resolve(done_obj, hostname):
-    """
-    异步解析主机名的A记录
-
-    :param done_obj: 进程间共享的Value对象
-    :param str hostname: 主机名
-    :return: 查询结果
-    """
-    loop = asyncio.get_event_loop()
-    result = await aio_resolve_a(hostname, loop)
-    done_obj.value += 1
-    return result
+def deal_output(output_path):
+    logger.log('INFOR', f'正在处理解析结果')
+    records = dict()  # 用来记录所有域名解析数据
+    with open(output_path) as fd:
+        for line in fd:
+            line = line.strip()
+            try:
+                items = json.loads(line)
+            except Exception as e:
+                logger.log('ERROR', e.args)
+                logger.log('ERROR', f'解析行{line}出错跳过解析该行')
+                continue
+            record = dict()
+            record['resolver'] = items.get('resolver')
+            qname = items.get('name')[:-1]  # 去出最右边的`.`点号
+            status = items.get('status')
+            if status != 'NOERROR':
+                record['alive'] = 0
+                record['resolve'] = 0
+                record['reason'] = status
+                records[qname] = record
+                continue
+            data = items.get('data')
+            if 'answers' not in data:
+                record['alive'] = 0
+                record['resolve'] = 0
+                record['reason'] = 'NOANSWER'
+                records[qname] = record
+                continue
+            flag = False
+            cname = list()
+            ips = list()
+            public = list()
+            ttls = list()
+            answers = data.get('answers')
+            for answer in answers:
+                if answer.get('type') == 'A':
+                    flag = True
+                    cname.append(answer.get('name')[:-1])  # 去出最右边的`.`点号
+                    ip = answer.get('data')
+                    ips.append(ip)
+                    ttl = answer.get('ttl')
+                    ttls.append(str(ttl))
+                    is_public = utils.ip_is_public(ip)
+                    public.append(str(is_public))
+                    record['resolve'] = 1
+                    record['reason'] = status
+                    record['cname'] = ','.join(cname)
+                    record['content'] = ','.join(ips)
+                    record['public'] = ','.join(public)
+                    record['ttl'] = ','.join(ttls)
+                    records[qname] = record
+            if not flag:
+                record['alive'] = 0
+                record['resolve'] = 0
+                record['reason'] = 'NOARECORD'
+                records[qname] = record
+        return records
 
 
-async def aio_resolve(subdomain_list, process_num, coroutine_num):
-    """
-    异步解析子域A记录
-
-    :param list subdomain_list: 待解析的子域列表
-    :param int process_num: 解析进程数
-    :param int coroutine_num: 每个解析进程下的协程数
-    :return: 解析结果
-    """
-    m = Manager()
-    done_obj = m.Value('done', 0)  # 创建一个进程间可以共享的值
-    loop = asyncio.get_event_loop()
-    loop.run_in_executor(None, resolve_progress_func,
-                         done_obj, len(subdomain_list))
-    wrapped_resolve_func = functools.partial(do_resolve, done_obj)
-    result_list = list()
-    # macOS上队列大小不能超过2**15 - 1 = 32767
-    # https://stackoverflow.com/questions/5900985/multiprocessing-queue-maxsize-limit-is-32767
-    if sys.platform == 'darwin':
-        split_subdomain_list = utils.split_list(subdomain_list, 32767)
-        for current_subdomain_list in split_subdomain_list:
-            async with aiomp.Pool(processes=process_num,
-                                  childconcurrency=coroutine_num) as pool:
-                result = await pool.map(wrapped_resolve_func,
-                                        current_subdomain_list)
-                result_list.extend(result)
-        return result_list
-    async with aiomp.Pool(processes=process_num,
-                          childconcurrency=coroutine_num) as pool:
-        result_list = await pool.map(wrapped_resolve_func, subdomain_list)
-        return result_list
-
-
-async def run_aio_resolve(subdomain_list):
-    """
-    异步解析子域A记录
-
-    :param list subdomain_list: 待解析的子域列表
-    :return: 解析得到的结果列表
-    """
-    process_num = utils.get_process_num()
-    coroutine_num = utils.get_coroutine_num()
-    logger.log('INFOR', '正在异步查询子域的A记录')
-    result_list = await aio_resolve(subdomain_list, process_num, coroutine_num)
-    logger.log('INFOR', '完成异步查询子域的A记录')
-    return result_list
-
-
-def run_resolve(data):
+def run_resolve(domain, data):
     """
     调用子域解析入口函数
 
+    :param str domain: 待解析的主域
     :param list data: 待解析的子域数据列表
     :return: 解析得到的结果列表
     :rtype: list
     """
-    loop = asyncio.get_event_loop()
-    asyncio.set_event_loop(loop)
-    need_resolve_subdomains = filter_subdomain(data)
-    if not need_resolve_subdomains:
+    logger.log('INFOR', f'开始解析{domain}的子域')
+    subdomains = filter_subdomain(data)
+    if not subdomains:
         return data
-    resolve_coroutine = run_aio_resolve(need_resolve_subdomains)
-    results_list = loop.run_until_complete(resolve_coroutine)
-    results_dict = convert_results(results_list)
-    resolved_data = update_data(data, results_dict)
-    return resolved_data
+
+    massdns_dir = config.third_party_dir.joinpath('massdns')
+    result_dir = config.result_save_dir
+    temp_dir = result_dir.joinpath('temp')
+    utils.check_dir(temp_dir)
+    massdns_path = utils.get_massdns_path(massdns_dir)
+    timestring = utils.get_timestring()
+
+    save_name = f'collected_subdomains_{domain}_{timestring}.txt'
+    save_path = temp_dir.joinpath(save_name)
+    save_subdomains(save_path, subdomains)
+    del subdomains
+    gc.collect()
+
+    output_name = f'resolved_result_{domain}_{timestring}.json'
+    output_path = temp_dir.joinpath(output_name)
+    log_path = result_dir.joinpath('massdns.log')
+
+    ns_path = config.brute_nameservers_path
+
+    utils.call_massdns(massdns_path, save_path, ns_path,
+                       output_path, log_path, quiet_mode=True)
+
+    records = deal_output(output_path)
+    data = update_data(data, records)
+    logger.log('INFOR', f'结束解析{domain}的子域')
+    return data

oneforall/common/utils.py

@@ -4,13 +4,16 @@ import sys
 import time
 import random
 import platform
+import subprocess
 from ipaddress import IPv4Address, ip_address
+from stat import S_IXUSR
 
 import psutil
 
 import config
 from pathlib import Path
 from records import Record, RecordCollection
+from dns.resolver import Resolver
 
 from common.domain import Domain
 from config import logger
@@ -335,6 +338,17 @@ def export_all(format, path, datas):
     save_data(path, content)
 
 
+def dns_resolver():
+    """
+    dns解析器
+    """
+    resolver = Resolver()
+    resolver.nameservers = config.resolver_nameservers
+    resolver.timeout = config.resolver_timeout
+    resolver.lifetime = config.resolver_lifetime
+    return resolver
+
+
 def dns_query(qname, qtype):
     """
     查询域名DNS记录
@@ -344,7 +358,7 @@ def dns_query(qname, qtype):
     :return: 查询结果
     """
     logger.log('TRACE', f'尝试查询{qname}的{qtype}记录')
-    resolver = resolve.dns_resolver()
+    resolver = dns_resolver()
     try:
         answer = resolver.query(qname, qtype)
     except Exception as e:
@@ -485,3 +499,46 @@ def check_env():
 
 def get_maindomain(domain):
     return Domain(domain).registered()
+
+
+def call_massdns(massdns_path, dict_path, ns_path, output_path, log_path,
+                 query_type='A', process_num=1, concurrent_num=10000,
+                 quiet_mode=False):
+    logger.log('INFOR', f'开始执行massdns')
+    quiet = ''
+    if quiet_mode:
+        quiet = '--quiet'
+    status_format = config.brute_status_format
+    socket_num = config.brute_socket_num
+    resolve_num = config.brute_resolve_num
+    cmd = f'{massdns_path} {quiet} --status-format {status_format} ' \
+          f'--processes {process_num} --socket-count {socket_num} ' \
+          f'--hashmap-size {concurrent_num} --resolvers {ns_path} ' \
+          f'--resolve-count {resolve_num} --type {query_type} ' \
+          f'--flush --output J --outfile {output_path} ' \
+          f'--error-log {log_path} {dict_path}'
+    logger.log('INFOR', f'执行命令 {cmd}')
+    subprocess.run(args=cmd, shell=True)
+    logger.log('INFOR', f'结束执行massdns')
+
+
+def get_massdns_path(massdns_dir):
+    path = config.brute_massdns_path
+    if path:
+        return path
+    system = platform.system().lower()
+    machine = platform.machine().lower()
+    name = f'massdns_{system}_{machine}'
+    if system == 'windows':
+        name = name + '.exe'
+        if machine == 'amd64':
+            massdns_dir = massdns_dir.joinpath('windows', 'x64')
+        else:
+            massdns_dir = massdns_dir.joinpath('windows', 'x84')
+    path = massdns_dir.joinpath(name)
+    path.chmod(S_IXUSR)
+    if not path.exists():
+        logger.log('FATAL', '暂无该系统平台及架构的massdns')
+        logger.log('INFOR', '请尝试自行编译massdns并在配置里指定路径')
+        exit(0)
+    return path

oneforall/example.py

@@ -8,8 +8,8 @@
 import oneforall
 
 if __name__ == '__main__':
-    test = oneforall.OneForAll(target='example.com')
-    test.brute = True
+    test = oneforall.OneForAll(target='freebuf.com')
+    test.brute = False
     test.takeover = True
     test.run()
     result = test.datas

oneforall/modules/check/axfr.py

@@ -10,7 +10,7 @@ DNS域传送(DNS zone transfer)指的是一台备用域名服务器使用来自
 import dns.resolver
 import dns.zone
 
-from common import resolve, utils
+from common import utils
 from common.module import Module
 from config import logger
 
@@ -57,7 +57,7 @@ class CheckAXFR(Module):
         """
         正则匹配响应头中的内容安全策略字段以发现子域名
         """
-        resolver = resolve.dns_resolver()
+        resolver = utils.dns_resolver()
         try:
             answers = resolver.query(self.domain, "NS")
         except Exception as e:

oneforall/oneforall.py

@@ -189,7 +189,7 @@ class OneForAll(object):
             return self.export(self.domain)
 
         # 解析子域
-        self.data = resolve.run_resolve(self.data)
+        self.data = resolve.run_resolve(self.domain, self.data)
         # 保存解析结果
         resolve.save_data(self.resolve_table, self.data)
 

oneforall/takeover.py

@@ -18,7 +18,7 @@ from tqdm import tqdm
 
 import config
 from config import logger
-from common import resolve, utils
+from common import utils
 from common.module import Module
 from common.domain import Domain
 
@@ -31,7 +31,7 @@ def get_fingerprint():
 
 
 def get_cname(subdomain):
-    resolver = resolve.dns_resolver()
+    resolver = utils.dns_resolver()
     try:
         answers = resolver.query(subdomain, 'CNAME')
     except Exception as e: