2003 hasn't been a banner year for computer security, and that includes
Linux. The CVS repository for the Linux kernel was attacked (if clumsily),
several servers related to the Debian project were compromised, and the GNU
Project's Savannah server was also
broken into recently. Since there has been little information published
about the nature of the Savannah compromise, we contacted Bradley Kuhn,
executive director of the Free Software Foundation for more information.
Kuhn described the Savannah compromise as "almost identical to what
happened to Debian." (A detailed account of the Debian compromise can be
found here.)
Kuhn said that he believes that the Savannah compromise and the Debian
attacks were related, and happened at about the same time. However, he said
that the project has not put a great deal of time and effort into analyzing
the attacks because it was more important to put Savannah back online and
to try to harden the system to see to it that a similar compromise doesn't
happen again. The hard drives from Savannah have been saved for future
reference, but the project is not putting its efforts into thoroughly
analyzing the attacks.
For the most part, Savannah has been restored
and changes have been made to try to ensure a similar attack will not be
possible. However, there are still some features that remain unavailable,
including Web CVS access and new projects are not being approved for the
time being. According to the Savannah website, new projects will probably
be accepted sometime before the end of January, 2004.
Has there been an attempt to insert a trojan into any of the code residing
on Savannah? Kuhn says that they've asked the owners of projects on
Savannah to go through and verify the code that is on Savannah to be sure
that it hasn't been trojaned. So far, there have been no reports of tainted
code. However, not all of the projects have reported their status. Kuhn
also noted that projects on the Savannah website will soon have an
indicator to report whether or not the developers have verified that they
have checked the integrity of their software.
We also asked if there was any sensitive information on Savannah that may
have been compromised. Kuhn said that the useful information on Savannah
mostly consists of the code for the various projects, and that the only
other information of interest would be developers' passwords. The passwords
on Savannah have been reset, of course, and the developers have been
encouraged to "investigate their own personal security."
For now, the GNU Project is not actively pursuing criminal prosecution of
the attacker or attackers. Kuhn says that the project is not "ethically
opposed" to prosecuting the intruder, but that with limited resources he'd
rather divert time and energy to restoring the services and trying to
harden systems to make future attacks more difficult and easier to contain.
To that end, the compromise may actually be a good thing in the long
run. Kuhn said that they have contacted the CVS maintainers and have
offered to pay for development of features that would allow GPG signing of
commits through CVS -- making it much more difficult for changes to be
inserted unnoticed into code held in a CVS repository. He said that they
have also contacted the GNU Arch maintainer about adding GPG
signing. Though it may take some time to develop, the addition of GPG
signing to commits would be a welcome feature.
Kuhn said that he expects that the future will bring more attacks on the
community, as free and open source software become more
prevalent. Opponents of the open development model will no doubt be using
these events as an illustration of the "dangers" of open source. Though the
recent intrusions have mostly been an inconvenience, it's important that
the community learn from these attacks, and redouble efforts to prevent
them in the future.
Stable CVS 1.11.11 has been released,
adding code to the CVS server to prevent it from continuing as root after a
user login, as an extra failsafe against a compromise of the CVSROOT/passwd
file.
A vulnerability was discovered in jabber, an instant messaging server,
whereby a bug in the handling of SSL connections could cause the
server process to crash, resulting in a denial of service.
Paul Starzetz discovered a flaw in bounds checking in mremap() in the Linux
kernel versions 2.4.23 and previous which may allow a local attacker to
gain root privileges. No exploit is currently available; however, it is
believed that this issue is exploitable (although not trivially.) The
Common Vulnerabilities and Exposures project has assigned the name
CAN-2003-0985 to this issue. There is also a minor information leak in the
real time clock (rtc) routines. The Common Vulnerabilities and Exposures
project has assigned the name CAN-2003-0984 to this issue. See this advisory for
more information.
A vulnerability was discovered in mpg321, a command-line mp3 player,
whereby user-supplied strings were passed to printf(3) unsafely. This
vulnerability could be exploited by a remote attacker to overwrite
memory, and possibly execute arbitrary code. In order for this
vulnerability to be exploited, mpg321 would need to play a malicious
mp3 file (including via HTTP streaming).
Multiple vulnerabilities were discovered in nd, a command-line WebDAV
interface, whereby long strings received from the remote server could
overflow fixed-length buffers. This vulnerability could be exploited
by a remote attacker in control of a malicious WebDAV server to
execute arbitrary code if the server was accessed by a vulnerable
version of nd.
Steve Kemp discovered a problem in xsok, a single player strategy game
for X11, related to the Sokoban game, which leads a user to execute
arbitrary commands under the GID of games.
Another buffer overflow in Apache 2.0.47 and earlier in mod_cgid's
mishandling of CGI redirect paths could result in CGI output going to the
wrong client when a threaded MPM is used.
CAN-2003-0789.
A problem was discovered in Apache2 where CGI scripts that write more than
4k to the standard error stream will hang the script's execution. This problem can lead to a
denial of service situation. See this bug
report for additional details.
Paul Mitcheson reported a situation where the CUPS Internet Printing
Protocol (IPP) implementation in CUPS versions prior to 1.1.19 would get
into a busy loop. This could result in a denial of service. In order to
exploit this bug an attacker would need to have the ability to make a TCP
connection to the IPP port (by default 631).
Serious issues have been discovered in two ethereal protocol dissectors.
Both vulnerabilities will make the Ethereal application crash. The Q.931
vulnerability also affects Tethereal. It is not known if either
vulnerability can be used to make Ethereal or Tethereal run arbitrary
code. (CAN-2003-1012 and CAN-2003-1013)
"fam" (file alteration monitor) watches files and directories for changes and lets interested applications know when something happens. This package has a flaw in its group handling that blocks some legitimate operations while, at the same time, exposing the names of files that should otherwise be invisible.
There is, it seems, an integer overflow vulnerability in "ls" which can be exploited via wu-ftpd to create a denial of service situation. See this advisory from Georgi Guninski for details.
DNS stub resolvers from multiple vendors contain a buffer overflow
vulnerability. The impact of this vulnerability appears to be limited to
denial of service. (See CERT Vulnerability Note
VU#738331)
The BIND 4 and BIND 8.2.x stub resolver libraries, and other libraries such
as glibc 2.2.5 and earlier, libc, and libresolv, uses the maximum buffer
size instead of the actual size when processing a DNS response, which
causes the stub resolvers to read past the actual boundary ("read buffer
overflow"), allowing remote attackers to cause a denial of service
(crash).
A severe vulnerability was discovered in GnuPG by Phong Nguyen relating to
ElGamal sign+encrypt keys. This
email message from Werner Koch contains more information. "Phong
Nguyen identified a severe bug in the way GnuPG creates and uses ElGamal
keys for signing. This is a significant security failure which can lead to
a compromise of almost all ElGamal keys used for signing. Note that this
is a real world vulnerability which will reveal your private key within a
few seconds."
GtkHTML is the HTML rendering widget used by the Evolution mail reader.
GtkHTML supplied with versions of Evolution prior to 1.2.4 contain a bug
when handling HTML messages. Alan Cox discovered that certain malformed
messages could cause the Evolution mail component to crash.
A vulnerability was discovered in the Linux kernel versions 2.4.22 and
previous. A flaw in bounds checking in the do_brk() function can allow a
local attacker to gain root privileges. This vulnerability is known to be
exploitable.
The 2.4.23 kernel contains the fix. For more details on how this vulnerability works, see this LWN article.
The kernel-utils package contains several utilities that can be used to
control the kernel or machine hardware. In Red Hat Linux 8.0 this package
contains user mode linux (UML) utilities.
The uml_net utility in kernel-utils packages with Red Hat Linux 8.0 was
incorrectly shipped setuid root. This could allow local users to control
certain network interfaces, add and remove arp entries and routes, and put
interfaces in and out of promiscuous mode.
All users of the kernel-utils package should update to these packages that
contain a version of uml_net that is not setuid root.
Alternatively, as a work-around to this vulnerability issue the following
command as root:
According to this advisory versions of lftp
prior to 2.6.10 are vulnerable to two exploitable buffer overflow
problems. Both occur when you connect to a web server with lftp using HTTP
or HTTPS, and then use lftp's "ls" or "rels" commands on specially prepared
directories on the web server.
libnids (a NIDS plugin which emulates the Linux 2.0 IP stack) contains a buffer overflow vulnerability which can be exploited remotely. Version 1.18 fixes the problem.
Glenn Randers-Pehrson discovered a problem in connection with 16-bit
samples from libpng, an interface for reading and writing PNG
(Portable Network Graphics) format files. The starting offsets for
the loops are calculated incorrectly which causes a buffer overrun
beyond the beginning of the row buffer.
A remotely exploitable buffer overflow vulnerability was found in
MPlayer. A malicious host can craft a harmful ASX header, and trick MPlayer
into executing arbitrary code upon parsing that header. Read the full advisory
for details.
Some some vulnerabilities exsist in the Nessus NASL scripting engine. To
exploit these flaws, an attacker would need to have a valid Nessus account
as well as the ability to upload arbitrary Nessus plugins in the Nessus
server (this option is disabled by default) or he/she would need to trick a
user somehow into running a specially crafted nasl script. Read the full
advisory for additional information.
The Net-SNMP project includes various Simple Network Management Protocol
(SNMP) tools. A security issue in Net-SNMP versions before 5.0.9 could
allow an existing user/community to gain access to data in MIB objects that
were explicitly excluded from their view.
Version 5.0.9 of Net-SNMP is not vulnerable to this issue. In addition,
Net-SNMP 5.0.9 fixes a number of other minor bugs.
Linux NFS utils package contains remotely exploitable off-by-one bug.
A local or remote attacker could exploit this vulnerability by sending
specially crafted request to rpc.mountd daemon. See this BugTraq post for more details.
From the advisory:
"During a pen-test we stumbled across a nasty bug in OpenSSH-portable
with PAM support enabled (via the --with-pam configure script switch). This
bug allows a remote attacker to identify valid users on vulnerable systems,
through a simple timing attack. The vulnerability is easy to exploit and
may have high severity, if combined with poor password policies and other
security problems that allow local privilege escalation."
The postfix MTA, versions through 1.1.12 (but not 2.0) is subject to two remotely exploitable denial of service vulnerabilities; see this advisory from Michal Zalewski for details.
The ASCII translation mechanism in ProFTPD 1.2.8 contains a vulnerability which will provide a remote attacker with a root shell - if the attacker is able to download a specially-crafted file. See this ISS advisory for more information.
An advisory has gone out warning of a
remotely exploitable heap overflow vulnerability in rsync versions 2.5.6
and prior. If you are running an rsync server, you will want to apply a
distributor patch or upgrade to 2.5.7 in the near future.
usePerl has a
description of a vulnerability in the Safe.pm Perl module. It seems
that if a Safe compartment is used more than once, it ceases to be safe.
The problem is fixed in Safe 2.08.
Alexander Hvostov, Julien Blache and Aurelien Jarno discovered several
security-related problems in the sane-backends package, which contains
an API library for scanners including a scanning daemon (in the
package libsane) that can be remotely exploited. These problems allow
a remote attacker to cause a segfault fault and/or consume arbitrary
amounts of memory. The attack is successful, even if the attacker's
computer isn't listed in saned.conf.
You are only vulnerable if you actually run saned e.g. in xinetd or
inetd. If the entries in the configuration file of xinetd or inetd
respectively are commented out or do not exist, you are safe.
Try "telnet localhost 6566" on the server that may run saned. If you
get "connection refused" saned is not running and you are safe.
The Common Vulnerabilities and Exposures project identifies the
following problems:
CAN-2003-0773: saned checks the identity (IP address) of the remote
host only after the first communication took place (SANE_NET_INIT). So
everyone can send that RPC, even if the remote host is not allowed to
scan (not listed in saned.conf).
CAN-2003-0774: saned lacks error checking nearly everywhere in the
code. So connection drops are detected very late. If the drop of the
connection isn't detected, the access to the internal wire buffer leaves
the limits of the allocated memory. So random memory "after" the wire
buffer is read which will be followed by a segmentation fault.
CAN-2003-0775: If saned expects strings, it mallocs the memory
necessary to store the complete string after it receives the size of the
string. If the connection was dropped before transmitting the size,
malloc will reserve an arbitrary size of memory. Depending on that size
and the amount of memory available either malloc fails (->saned quits
nicely) or a huge amount of memory is allocated. Swapping and OOM
measures may occur depending on the kernel.
CAN-2003-0776: saned doesn't check the validity of the RPC numbers
it gets before getting the parameters.
CAN-2003-0777: If debug messages are enabled and a connection is
dropped, non-null-terminated strings may be printed and segmentation
faults may occur.
CAN-2003-0778: It's possible to allocate an arbitrary amount of
memory on the server running saned even if the connection isn't dropped.
At the moment this can not easily be fixed according to the author.
Better limit the total amount of memory saned may use (ulimit).
According to
this advisory a buffer overflow in GNU screen allows privilege
escalation for local users. Usually screen is installed either setgid-utmp
or setuid-root.
It also has some potential for remote attacks or getting control of another
user's screen. The problem is that you have to transfer around 2-3 gigabytes
of data to user's screen to exploit this vulnerability. 4.0.1, 3.9.15 and
older versions are vulnerable.
The tar utility does not properly filter file names containing
"../", meaning that a hostile archive can, if unpacked by an
unsuspecting user, overwrite any file that is writable by that user. GNU
tar versions 1.13.19 and earlier are vulnerable; unzip through version 5.42
has the same vulnerability.
This vulnerability,
originally thought to be confined to BSD-derived systems, was first covered
in the July 26th Security
Summary. It is now known that Linux telnet daemons are vulnerable as
well.
VIM allows a user to set the modeline differently for each edited text file
by placing special comments in the files. Georgi Guninski found that these
comments can be carefully crafted in order to call external programs. This
could allow an attacker to create a text file such that when it is opened
arbitrary commands are executed.
Zebra an open source implementation of TCP/IP routing software.
Jonny Robertson reported that Zebra can be remotely crashed if a Zebra
password has been enabled and a remote attacker can connect to the Zebra
telnet management port. The Common Vulnerabilities and Exposures project
(cve.mitre.org) has assigned the name CAN-2003-0795 to this issue.
Herbert Xu reported that Zebra can accept spoofed messages sent on the
kernel netlink interface by other users on the local machine. This could
lead to a local denial of service attack. The Common Vulnerabilities and
Exposures project (cve.mitre.org) has assigned the name CAN-2003-0858 to
this issue.
