CERT Vendor-Initiated Bulletin VB-95:07 - lsof
cert-advisory at cert.org
Thu Sep 28 19:44:54 UTC 1995
CERT Vendor-Initiated Bulletin VB-95:07
September 28, 1995
Topic: Directory and file vulnerability from lsof 3.18 through 3.43
Source: Vic Abell (abe at cc.purdue.edu)
To aid in the wide distribution of essential security information, the CERT
Coordination Center is forwarding the following information from Vic Abell,
who urges you to act on this information as soon as possible. Please contact
Vic Abell if you have any questions or need further information.
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It may be possible to write lsof's private device cache file to
system locations that are normally inaccessible to the lsof user,
depending on the UNIX dialect where lsof is installed and how that
dialect grants permission to access kernel memory information.
The vulnerability affects lsof revisions 3.18 through 3.43, installed
on these UNIX dialects:
AIX 3.2.4, 3.2.5, 4.1, the IBM RISC/System 6000
4.1.1, and 4.1.2
EP/IX 2.1.1 the CDC 4680
FreeBSD 22.214.171.124, 2.0, and Intel-based systems
HP-UX 8.x, 9.x, and 10 HP systems (some combinations)
IRIX 4.0.5H, 5.2, 5.3, SGI systems
6.0, and 6.1
Linux through 1.3.0 Intel-based systems
Motorola V/88 R32V3, M88K systems
NetBSD 1.0 and 1.0A Intel and SPARC-based systems
NEXTSTEP 2.1 and 3. all NEXTSTEP architectures
OSF/1 1.3, 2.0, 3.0, and the DEC Alpha
RISC/os 4.52 MIPS R2000-based systems
SCO OpenDesktop or Intel-based systems
OpenServer 1.1, 3.0,
Sequent Dynix 3.0.12 the Sequent Symmetry
Sequent PTX 2.1. and Sequent systems
Solaris 2. and 2.5 Sun 4 and i86pc systems
SunOS 4.1. Sun 3 and 4
Ultrix 2.2, 4.2, 4.3, DEC RISC and VAX
I recommend that users of the affected revisions of lsof on these
dialects install lsof revision 3.44, 3.45 or later. Section III
describes its location and some appropriate installation considerations.
A private device cache file feature was introduced at lsof
revision 3.18 to speed up subsequent calls to lsof by reducing
the need for a full scan of the nodes in /dev (or /devices).
Accompanying the feature was an option (-D) that allowed the
lsof user to specify where the device cache file was to be
Since lsof normally runs with effective group ID permission
set to the group that can read kernel memory devices, the -D
option might allow lsof to write its device cache file to a
location not normally accessible to the real user or group
owning the lsof process. The locations where the lsof device
cache file might be inappropriately recorded depend on the
group that owns the memory devices and to what other files
and directories the group has write permission.
Here are two examples: 1) IBM's distribution of AIX sets group
ownership of /dev/kmem and /etc to the "system" group and
enables group write permission in /etc; and 2) Sun's Solaris
distribution does the same thing, using the "sys" group.
(Security conscious installations often create a new group --
e.g., "kmem" or "mem" -- that owns no files and is used solely
for enabling read access to kernel memory devices.)
A fix for this group ID vulnerability may be found in lsof
revisions 3.44, 3.45, and above.
A more serious vulnerability exists when lsof must run setuid
to the root user and also has device cache file support. This
happens for the lsof implementation that runs under Motorola's
V/88 UNIX dialects R40V4.1, R40V4.2, and R40V4.3. This gives
the lsof user an unlimited choice of places to record the
device cache file. A partial fix for this vulnerability was
introduced in lsof revision 3.43. The complete fix may be
found in lsof revisions 3.44, 3.45, and above.
Unauthorized users may be able to write the lsof device cache
file to normally-restricted locations, possibly in place of
important system files.
The vulnerability can be exploited only by users with a valid
account. It cannot be exploited by arbitrary remote users.
The vulnerability affects all lsof revisions 3.18 through 3.43
on UNIX dialects where device cache file support has been
Retrieve lsof revision 3.44, 3.45, or later and install it.
Compressed tar archive:
Gzip'd tar archive:
Lsof 3.44 eliminates the vulnerability for all relevant UNIX
dialects. However, its overly zealous restrictions for Solaris
and SunOS and are relaxed in revision 3.45.
Both tar archives are wrappers that contain authentication
information (MD5 checksums and PGP certificates) and a tar
archive of the lsof sources.
1. Retrieve the wrapper archive, extract its three files --
README.lsof_<revision>, lsof_<revision>.tar, and
lsof_<revision>.tar.asc -- and verify its authentication
information. (<revision> should be 3.44 or greater.)
2. Unpack the lsof source archive from lsof_<revision>.tar
and read its documentation files. Pay particular attention
to the 00DCACHE file that describes options for specifying
the location of the device cache, and the security section
in the 00README file.
3. Having selected the lsof options appropriate to the UNIX
dialect where you want to install it, run the Configure
script, use make to build lsof, and install the resulting
Vic Abell appreciates the advice and comments provided by members
of the bugtraq mailing list that led him to realize this vulnerability
existed. He thanks Katherine T. Fithen and Linda Hutz Pesante of the
CERT Coordination Center for their help in preparing this bulletin.
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