Draft announcement: --------------------------------------------------------------------- fetchmail-SA-2008-01: Crash on large log messages in verbose mode Topics: Crash in large log messages in verbose mode. Author: Matthias Andree Version: 1.0 Announced: Type: Dereferencing garbage pointer trigged by outside circumstances Impact: denial of service possible Danger: low CVSS V2 vector: (AV:N/AC:M/Au:N/C:N/I:N/A:C/E:P/RL:O/RC:C) Credits: Petr Uzel (fix), Petr Cerny (analysis), Gunter Nau (bug report) CVE Name: XXX URL: http://www.fetchmail.info/fetchmail-SA-2008-01.txt Project URL: http://www.fetchmail.info/ Affects: fetchmail release < 6.3.9 exclusively Not affected: fetchmail release 6.3.9 and newer systems without varargs (stdargs.h) support. Corrected: 2008-06-13 fetchmail SVN (rev XXX) 0. Release history ================== 2008-06-13 1.0 first draft for MITRE/CVE (visible in SVN) 1. Background ============= fetchmail is a software package to retrieve mail from remote POP2, POP3, IMAP, ETRN or ODMR servers and forward it to local SMTP, LMTP servers or message delivery agents. fetchmail ships with a graphical, Python/Tkinter based configuration utility named "fetchmailconf" to help the user create configuration (run control) files for fetchmail. 2. Problem description and Impact ================================= Gunter Nau reported fetchmail crashing on some messages; further debugging by Petr Uzel and Petr Cerny at Novell/SUSE Czech Republic dug up that this happened when fetchmail was trying to print, in -v -v verbose level, headers exceeding 2048 bytes. In this situation, fetchmail would resize the buffer and fill in further parts of the message, but forget to reinitialize its va_list typed source pointer, thus reading data from a garbage address found on the stack at addresses above the function arguments the caller passed in; usually that would be the caller's stack frame. It is unknown whether code can be injected remotely, but given that the segmentation fault is caused by read accesses, the relevant data is not under the remote attacker's control and no buffer overrun situation is present that would allow altering program /flow/, it is deemed rather unlikely that code can be injected. Note that the required -vv configuration at hand is both non-default and also not common in automated (cron job) setups, but usually used in manual debugging, so not many systems would be affected by the problem. Nonetheless, in vulnerable configurations, it is remotely exploitable to effect a denial of service attack. 3. Solution =========== There are two alternatives, either of them by itself is sufficient: a. Apply the patch found in section B of this announcement to fetchmail 6.3.8, recompile and reinstall it. b. Install fetchmail 6.3.9 or newer when it becomes available. The fetchmail source code is available from <http://developer.berlios.de/project/showfiles.php?group_id=1824>. 4. Workaround ============= Run fetchmail at low verbosity, avoid using two or three -v arguments; internal messages are short and do not contain external message sources so they do not cause buffer resizing. It is recommended to replace the vulnerable code by a fixed version (see previous section 3. Solution) as soon as reasonably possible. A. Copyright, License and Warranty ================================== (C) Copyright 2008 by Matthias Andree, <matthias.andree@gmx.de>. Some rights reserved. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs German License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/2.0/de/ or send a letter to Creative Commons; 559 Nathan Abbott Way; Stanford, California 94305; USA. THIS WORK IS PROVIDED FREE OF CHARGE AND WITHOUT ANY WARRANTIES. Use the information herein at your own risk. B. Patch to remedy the problem ============================== diff --git a/report.c b/report.c index 31d4e48..2a731ac 100644 --- a/report.c +++ b/report.c @@ -238,11 +238,17 @@ report_build (FILE *errfp, message, va_alist) rep_ensuresize(); #if defined(VA_START) - VA_START (args, message); for ( ; ; ) { + /* + * args has to be initialized before every call of vsnprintf(), + * because vsnprintf() invokes va_arg macro and thus args is + * undefined after the call. + */ + VA_START(args, message); n = vsnprintf (partial_message + partial_message_size_used, partial_message_size - partial_message_size_used, message, args); + va_end (args); if (n >= 0 && (unsigned)n < partial_message_size - partial_message_size_used) @@ -254,7 +260,6 @@ report_build (FILE *errfp, message, va_alist) partial_message_size += 2048; partial_message = REALLOC (partial_message, partial_message_size); } - va_end (args); #else for ( ; ; ) { END OF fetchmail-SA-2008-01.txt ------------------------------------------------------------------------------------------
I know we did not handle bug 191154 as security bug, but I would consider fetchmail running in automated setups not "user" issues.
I added fetchmail-6.3.8-r2 which includes this patch.
Arches, please test and mark stable: =net-mail/fetchmail-6.3.8-r2 Target keywords : "alpha amd64 arm hppa ia64 ppc ppc64 release s390 sh sparc x86"
ppc64 done
Stable on alpha.
++++amd64++++ 1. Compiles. 2. Installs correctly. 3. Merges. 4. Killing fetchmail and restarting it results in the bugspam keeping on coming in ;-) 5. Starting in verbose mode and sending myself a large message does not result in a crash. Portage 2.1.4.4 (default-linux/amd64/2007.0, gcc-4.1.2, glibc-2.6.1-r0, 2.6.24-gentoo-r8 x86_64) ================================================================= System uname: 2.6.24-gentoo-r8 x86_64 AMD Athlon(tm) 64 Processor 3400+ Timestamp of tree: Sun, 15 Jun 2008 12:00:01 +0000 ccache version 2.4 [enabled] app-shells/bash: 3.2_p33 dev-lang/python: 2.4.4-r13 dev-python/pycrypto: 2.0.1-r6 dev-util/ccache: 2.4-r7 sys-apps/baselayout: 1.12.11.1 sys-apps/sandbox: 1.2.18.1-r2 sys-devel/autoconf: 2.13, 2.61-r1 sys-devel/automake: 1.5, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2, 1.10.1 sys-devel/binutils: 2.18-r1 sys-devel/gcc-config: 1.4.0-r4 sys-devel/libtool: 1.5.26 virtual/os-headers: 2.6.23-r3 ACCEPT_KEYWORDS="amd64" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=athlon64 -O2 -pipe" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/kde/3.5/env /usr/kde/3.5/share/config /usr/kde/3.5/shutdown /usr/kde/svn/env /usr/kde/svn/share/config /usr/kde/svn/shutdown /usr/share/config" CONFIG_PROTECT_MASK="/etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/terminfo /etc/texmf/web2c /etc/udev/rules.d" CXXFLAGS="-march=athlon64 -O2 -pipe" DISTDIR="/distfiles" FEATURES="ccache collision-protect distlocks metadata-transfer multilib-strict parallel-fetch sandbox sfperms strict test unmerge-orphans userfetch userpriv" GENTOO_MIRRORS="http://distfiles.gentoo.org http://distro.ibiblio.org/pub/linux/distributions/gentoo" MAKEOPTS="-j2" PKGDIR="/usr/portage/packages" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --stats --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" PORTDIR_OVERLAY="/usr/portage/local/layman/science /overlay" SYNC="rsync://raptor.gentoo.osuosl.org/gentoo-portage" USE="X acl aiglx aim amd64 berkdb branding cli cracklib crypt cups dri fortran gdbm gpm gtk iconv imap ipv6 isdnlog midi mmx mpeg3 mudflap ncurses nls nptl nptlonly nvidia opengl openmp pam pcre perl pppd python qt3 readline reflection session sockets spl sqlite3 sse sse2 ssl tcpd unicode vim xcomposite xine xorg zlib" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mulaw multi null plug rate route share shm softvol" APACHE2_MODULES="actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" ELIBC="glibc" INPUT_DEVICES="keyboard mouse evdev" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" USERLAND="GNU" VIDEO_CARDS="nvidia" Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LDFLAGS, LINGUAS, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS
ia64/sparc/x86 stable
ppc stable
Stable for HPPA.
amd64 stable, thanks Thomas. (All security relevant arches should be done)
GLSA vote, I vote NO.
voting NO too, and closing.