remote syslog PRI vulnerability =============================== CVE: CVE-2014-3634 Status of this report --------------------- FINAL Embargo Date ------------ Please keep this information private until after 2014-09-30, 12:00 CEDT Reporter ------- Rainer Gerhards <rgerhards@adiscon.com>, rsyslog project lead Affected -------- - rsyslog, most probably all versions (checked 5.8.6+) - sysklogd (checked most recent versions) - potentially others (see root cause) Root Cause ---------- Note: rsyslogd was forked from sysklogd, and the root cause applies to both. For simplicity, here I use sysklogd as this is the base code. The system header file /usr/include/*/syslog.h contains the following definitions #define LOG_NFACILITIES 24 /* current number of facilities */ #define LOG_FACMASK 0x03f8 /* mask to extract facility part */ /* facility of pri */ #define LOG_FAC(p) (((p) & LOG_FACMASK) >> 3) [This is from Ubuntu 12.04LTS, but can be found similarly in most, if not all, distributions]. The define LOG_NFACILITIES is used by sysklogd to size arrays for facility processing. In sysklogd, an array for selector matching is using this. Rsyslog has additional array. The macro LOG_FAC() is used to extract the facility from a syslog PRI [RFC3164, RFC 5424]. Its result is used to address the arrays. Unfortunately, the LOG_FACMASK permits PRI values up to 0x3f8 (1016 dec). This translates to 128 facilities. Consequently, for PRI values above 191 the LOG_NFACILITIES arrays are overrun. Other applications may have similar problems, as LOG_NFACILITES "sounds" like the max value that LOG_FAC() can return. It would probably make sense to check why there is a difference between LOG_NFACILITES and LOG_FACMASK, and if this really needs to stay. A proper fix would probably be to make LOG_FAC return a valid (maybe special) facility if an invalid one is provided. This is the route taken in rsyslog patches. Effect in Practice ------------------ General ~~~~~~~ Almost all distributions do ship rsyslog without remote reception by default and almost all distros also put firewall rules into place that prevent reception of syslog messages from remote hosts (even if rsyslog would be listening). With these defaults, it is impossible to trigger the vulnerability in v7 and v8. Older versions may still be vulnerable if a malicious user writes to the local log socket. Even when configured to receive remote message (on a central server), it is good practice to protect such syslog servers to accept only messages from trusted peers, e.g. within the relay chain. If setup in such a way, a trusted peer must be compromised to send malformed messages. This further limits the magnitude of the vulnerability. If, however, any system is permitted to send data unconditionally to the syslogd, a remote attack is possible. sysklogd ~~~~~~~~ Sysklogd is mildly affected. Having a quick look at the current git master branch, the wrong action may be applied to messages with invalid facility. A segfault seems unlikely, as the maximum misaddressing is 104 bytes of the f_pmask table, which is always within properly allocated memory (albeit to wrong data items). This can lead to triggering invalid selector lines and thus wrongly writing to files or wrongly forwarding to other hosts. rsyslogd ~~~~~~~~ Rsyslogd experiences the same problem as sysklogd. However, more severe effects can occur, BUT NOT WITH THE DEFAULT CONFIGURATION. The most likely and thus important attack is a remote DoS. Some of the additional tables are writable and can cause considerable misaddressing. This is especially true for versions 7 and 8. In those versions, remote code injection may also be possible by a carefully crafted package. It sounds hard to do, but it cannot be totally outruled [we did not check this in depth]. A segfault (and thus Dos) has the following preconditions: - the rsyslog property "pri-text" must be used, either in * templates * conditional statements (RainerScript and property-based filters) - the property must actually be accessed With traditional selector lines, this depends on the facility causing a misaddressing that leads to reading a 1 from the misaccessed location. When the preconditions are met, misaddressing happens. The code uses a string table and a table of string lengths. Depending on memory layout at time of misaddressing and depending on the actual invalid PRI value, the lookup to the string table can lead to a much to long length, which is the used in buffer copy calculations. High PRI values close to the max of 1016 potentially cause most problems, but we have also seen segfaults with very low invalid PRI values. Note that, as usual in such situations, a segfault may not happen immediately. Instead some data structures may be damaged (e.g. from the memory allocator) which will later on result in a segfault. In v5 and below, a segfault is very unlikely, as snprintf() is used to generate the pri-text property. As such, no write overrun can happen (but still garbage be contained inside the property). A segfault could theoretically happen if the name lookup table indices cause out-of-process misaddressing. We could not manage to produce a segfault with v5. Versions 7.6.3 and 7.6.4 already have partial fixes for the issue and will not be vulnerable to a segfault (but the mild other issues described). All other versions 7 and 8 are vulnerable. Version 6 was not checked as it seems no longer be used in practice (it was an interim version). No patch for version 6 will be provided. Note that a segfault of rsyslog can cause message loss. There are multiple scenarios for this, but likely ones are: - reception via UDP, where all messages arriving during downtime are lost - corruption of disk queue structures, which can lead to loss of all disk queue contents (manual recovery is possible). This list does not try to be complete. Note that disk queue corruption is likely to occur in default settings, because the important queue information file (.qi) is only written on successful shutdown. Without a valid .qi file, queue message files cannot be processed. How to Exploit -------------- A syslog message with an invalid PRI value needs to be sent. It is sufficient to send just the PRI as in this example "<201>" Any message starting with "<PRI>" where PRI is an integer greater than 191 can trigger the problem. The maximum offset that can be generated is with PRI equal to 1016, as this is the modulus used due to LOG_FACMASK. Note that messages with - PRI > 191 and - PRI modulus 1016 <= 191 will not lead to misaddressing but go into the wrong bin. Messages with - PRI > 191 - PRI modulus 1016 > 191 will go into the wrong bin and lead to misaddressing. Severity -------- Given the triggering scenarios, the fact that multiple changes must be made to default system configurations and potential problems we classify the severity of this vulnerability as MEDIUM Note that the probability of a successful attack is LOW. However, the risk of message loss is HIGH in those rare instances where an attack is successful. As mentioned above, it cannot totally be outruled that remote code injection is possible using this vulnerability. This vulnerability is at least not publicly know. Based on (no) bug reports, it seems unlikely that it is being exploited, but that's obviously hard to know for sure. Patches ------- Patches are available for versions known to be in wide-spread use. All patches and downloads can be found on http://www.rsyslog.com (after 2014-09-30 12:00 CEDT).
@ Security: I already prepared ebuilds for v8.4.1. Lars (polynomial-c) will commit the ebuild to portage when the advisory will be published (2014-09-30 12:00 CEDT). For people who may ask why we will replace v7 with a new major version: The versions in portage (v7.2) are heavily outdated. Version 7.6.x is EOL and has some quality issues. As proxy-maintainer I DO NOT RECOMMEND to patch v7.6. Version 8.4.x is the current stable version and best version to go. There wouldn't be such a jump if bug 520328 would have been already addressed. But UltraBug had no time within the last 30 days...
+*rsyslog-8.4.1 (30 Sep 2014) + + 30 Sep 2014; Lars Wendler <polynomial-c@gentoo.org> -rsyslog-7.2.7.ebuild, + -rsyslog-7.4.10.ebuild, -rsyslog-7.6.3-r1.ebuild, +rsyslog-8.4.1.ebuild, + -files/6-stable/rsyslog-6.6.0-fix-runtime.patch, + +files/8-stable/README.gentoo, +files/8-stable/rsyslog.confd, + -files/rsyslog-7.2.5-json-c-pkgconfig.patch, +files/8-stable/50-default.conf, + +files/8-stable/rsyslog.conf, +files/8-stable/rsyslog.initd, + +files/8-stable/rsyslog.logrotate, metadata.xml: + Security bump (bug #524058). Removed old. Remote syslog PRI vulnerability + (CVE-2014-3634). + How is further procedure now? Do we CC arches for stabilization while keeping the bug restricted or does someone from security team unrestrict the bug? AFAIK disclosure deadline has been expired.
Yep, the bug is now public, see http://thread.gmane.org/gmane.comp.security.oss.general/14065 Restriction can be removed.
@ Security: I am not sure if you will handle app-admin/sysklogd which is affected by the same bug in this bug or if somebody should fill an own bug for sysklogd. However, this is openSUSE's patch for sysklogd: https://build.opensuse.org/package/view_file/Base:System/syslogd/sysklogd-1.4.1-CVE-2014-3634.patch PS: Red Hat and Novell both have raised severity. =app-admin/rsyslog-8.4.1 should get stabilized very soon. Also, an GLSA should be issued. This bug affects systems relying on PCI-compliant logging. Please tell us how to proceed!
Arches, please test and mark stable: =app-admin/rsyslog-8.4.1 Target keywords : "amd64 hppa x86"
(In reply to Agostino Sarubbo from comment #5) > Arches, please test and mark stable: > > =app-admin/rsyslog-8.4.1 > > Target keywords : "amd64 hppa x86" We have some deps, the full list is: =app-admin/rsyslog-8.4.1 =dev-libs/liblogging-1.0.4 =dev-libs/libmongo-client-0.1.7 =dev-libs/liblognorm-1.0.1 =net-libs/rabbitmq-c-0.5.0 =dev-libs/librelp-1.2.7-r1
Stable for HPPA.
FYI: app-admin/rsyslog-8.4.1 fix for CVE-2014-3634 was incomplete. Therefore upstream released rsyslog-8.4.2, see bug #524290 (CVE-2014-3683).
Closing this... superseded by bug #524290, app-admin/rsyslog-8.4.2 is now available in portage (thank you Lars!).
Please don't close security bugs just because there's another one for the same package.
mancha released a patch for app-admin/sysklogd: http://seclists.org/oss-sec/2014/q4/79 Added app-admin/sysklogd to summary and CC'ed base-system due to sysklogd's metadata.xml.
Created attachment 386014 [details, diff] app-admin/sysklogd-1.5-r4 ebuild Adding ebuild for sysklogd-1.5-r4 which includes the patch from mancha for CVE-2014-3634. Please review and add it to portage.
+*sysklogd-1.5-r4 (04 Oct 2014) + + 04 Oct 2014; Lars Wendler <polynomial-c@gentoo.org> -sysklogd-1.5.ebuild, + -sysklogd-1.5-r1.ebuild, +sysklogd-1.5-r4.ebuild, + +files/sysklogd-1.5_CVE-2014-3634.diff: + Security bump (bug #524058). Remote syslog PRI vulnerability (CVE-2014-3634). + Removed old. +
Arches, please test and mark stable: =app-admin/sysklogd-1.5-r4 Target keywords : "alpha amd64 arm hppa ia64 ppc ppc64 s390 sh sparc x86"
*** Bug 524508 has been marked as a duplicate of this bug. ***
FYI, sysklogd 1.5.1 was just released which includes this fix: http://www.infodrom.org/projects/sysklogd/download/sysklogd-1.5.1.tar.gz --mancha
+*sysklogd-1.5.1 (06 Oct 2014) + + 06 Oct 2014; Lars Wendler <polynomial-c@gentoo.org> -sysklogd-1.5-r4.ebuild, + +sysklogd-1.5.1.ebuild, -files/sysklogd-1.5_CVE-2014-3634.diff: + Version bump which adds official upstream security release for CVE-2014-3634 + (bug #524058). + Arches pelase proceed but with =app-admin/sysklogd-1.5.1 instead of -1.5-r4.
+ 15 Oct 2014; Lars Wendler <polynomial-c@gentoo.org> -rsyslog-7.4.4.ebuild, + -rsyslog-8.4.1.ebuild, -files/7-stable/50-default.conf, + -files/7-stable/rsyslog.conf, + -files/7-stable/rsyslog-7.4.3-fix-runtime.patch, + -files/7-stable/README.gentoo, -files/7-stable/rsyslog.confd, + -files/7-stable/rsyslog-7.4.3-json-c-pkgconfig.patch, + -files/7-stable/bugfix_52.patch, -files/7-stable/rsyslog.confd-r1, + -files/7-stable/rsyslog-7.x-mmjsonparse.patch, + -files/7-stable/bugfix_73.patch, + -files/7-stable/fix-omruleset-default-value.patch, + -files/7-stable/rsyslog.initd, -files/7-stable/rsyslog.initd-r1, + -files/7-stable/rsyslog.logrotate, -files/7-stable/rsyslog.logrotate-r1, + -files/7-stable/rsyslog-gentoo.conf, metadata.xml: + Removed old vulnerable versions. + Readded arches for sysklogd stabilization.
Stable on alpha.
amd64 stable
x86 stable
ppc stable
ppc64 stable
ia64 stable
sparc stable
s390 stable
ARM, SH: ping
arm stable
sh will not go stable
Setting to GLSA, version is no longer in tree.
This issue was resolved and addressed in GLSA 201412-35 at http://security.gentoo.org/glsa/glsa-201412-35.xml by GLSA coordinator Yury German (BlueKnight).
