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__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Capability
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__________________________________________________________
INFORMATION BULLETIN
Solaris 2.x eject Buffer Overrun Vulnerability
March 14, 1997 18:00 GMT Number H-41
______________________________________________________________________________
PROBLEM: A vulnerability exists in eject(1).
PLATFORM: All platforms running Solaris 2.4, 2.5, and 2.5.1. Earlier
versions may also be vulnerable.
DAMAGE: This vulnerability may allow local users to gain root
privileges.
SOLUTION: Until patches are available, take the steps outlined in Section
3 as soon as possible.
______________________________________________________________________________
VULNERABILITY Exploit details involving this vulnerability have been made
ASSESSMENT: publicly available.
______________________________________________________________________________
[ Start AUSCERT Advisory ]
===========================================================================
AA-97.10 AUSCERT Advisory
Solaris 2.x eject Buffer Overrun Vulnerability
14 March 1997
Last Revised: --
- ----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in eject(1),
distributed under Solaris 2.4, 2.5 and 2.5.1. Earlier versions may be
vulnerable.
This vulnerability may allow local users to gain root privileges.
Exploit information involving this vulnerability has been made publicly
available.
At this stage, AUSCERT is unaware of any official vendor patches. AUSCERT
recommends that sites apply the workaround given in Section 3 until vendor
patches are made available.
This advisory will be updated as more information becomes available.
- ----------------------------------------------------------------------------
1. Description
eject(1) is a program used for those removable media devices that do
not have a manual eject button, or for those that do, but are managed
by Volume Management
Due to insufficient bounds checking on arguments which are supplied
by users, it is possible to overwrite the internal stack space of the
eject program while it is executing. By supplying a carefully designed
argument to the eject program, intruders may be able to force eject
to execute arbitrary commands. As eject is setuid root, this may
allow intruders to run arbitrary commands with root privileges.
Sites can determine if this program is installed by using:
% ls -l /usr/bin/eject
eject is installed by default in /usr/bin. Sites are encouraged to
check for the presence of this program regardless of the version of
Solaris installed.
Exploit information involving this vulnerability has been made publicly
available.
Sun Microsystems has informed AUSCERT that they are currently working
on this vulnerability.
2. Impact
Local users may gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites prevent the exploitation of this
vulnerability in eject by immediately applying the workaround given
in Section 3.1.
If the eject functionality is required AUSCERT recommends applying
the workaround given in Section 3.2.
Currently there are no vendor patches available that address this
vulnerability. AUSCERT recommends that official vendor patches be
installed when they are made available.
3.1 Remove setuid and non-root execute permissions
To prevent the exploitation of the vulnerability described in this
advisory, AUSCERT recommends that the setuid permissions be removed
from the eject program immediately. As eject will no longer work for
non-root users, it is recommended that the execute permissions also
be removed.
# ls -l /usr/bin/eject
-r-sr-xr-x 1 root other 5804 Mar 14 09:47 /usr/bin/eject
# chmod 500 /usr/bin/eject
# ls -l /usr/bin/eject
-r-x------ 1 root other 5804 Mar 14 09:47 /usr/bin/eject
3.2 Install eject wrapper
AUSCERT has developed a wrapper to help prevent programs from being
exploited using the vulnerability described in this advisory. Sites
which have a C compiler can obtain the source, compile and install
the wrapper as described in Section 3.2.1. For sites without a C
compiler, AUSCERT has made pre-compiled binaries available for Solaris
2.4, 2.5 and 2.5.1 (Section 3.1.2).
3.2.1 Installing the wrapper from source
The source for the wrapper, including installation instructions, can
be found at:
ftp://ftp.auscert.org.au/pub/auscert/tools/overflow_wrapper.c
This wrapper replaces the eject program and checks the length of the
command line arguments which are passed to it. If an argument exceeds
a certain predefined value (MAXARGLEN), the wrapper exits without
executing the eject command. The wrapper program can also be
configured to syslog any failed attempts to execute eject with
arguments exceeding MAXARGLEN. For further instructions on using this
wrapper, please read the comments at the top of overflow_wrapper.c.
When compiling overflow_wrapper.c for use with eject, AUSCERT
recommends defining MAXARGLEN to be 32.
The MD5 checksum for Version 1.0 of overflow_wrapper.c is:
MD5 (overflow_wrapper.c) = f7f83af7f3f0ec1188ed26cf9280f6db
3.2.2 Installing the wrapper binaries
Pre-compiled wrapper binaries are provided for sites that wish to
install the wrapper but do not have a C compiler available. AUSCERT
has compiled the wrapper on Solaris 2.4, 2.5 and 2.5.1. The following
compile time options have been used to the create the binaries:
REAL_PROG='"/usr/bin/eject.real"'
MAXARGLEN=32
SYSLOG
More information on these options can be found in Section 3.1.1 and
in the overflow_wrapper.c source code.
The pre-compiled binaries for the wrapper program can be retrieved from:
ftp://ftp.auscert.org.au/pub/auscert/tools/eject_wrapper.tar.Z
The MD5 checksum for eject_wrapper.tar.Z is:
MD5 (eject_wrapper.tar.Z) = 1ae34aea7a637d6464105cbec7ff4443
eject_wrapper.tar.Z contains a README file with installation
instructions, as well as pre-compiled binaries for Solaris 2.4, 2.5
and 2.5.1. The binaries have been linked statically so they are larger
than the default eject binary.
Sites are encouraged to carefully read the installation notes in the
README file before installation.
4. Additional measures
Most Unix systems ship with numerous programs which have setuid or
setgid privileges. Often the functionality supplied by these
privileged programs is not required by many sites. The large number
of privileged programs that are shipped by default are to cater for
all possible uses of the system.
AUSCERT encourages sites to examine all the setuid/setgid programs
and determine the necessity of each program. If a program does not
absolutely require the setuid/setgid privileges to operate (for
example, it is only run by the root user), the setuid/setgid
privileges should be removed. Furthermore, if a program is not
required at your site, then all execute permissions should be removed.
A sample command to find all setuid/setgid programs is (run as root):
# find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -l {} \;
It is AUSCERT's experience that many vulnerability are being discovered
in setuid/setgid programs which are not necessary for the correct
operation of most systems. Sites can increase their security by
removing unnecessary setuid/setgid programs.
For example, the functionality provided by the eject program is not
needed by many sites. If sites had previously disabled this program,
they would not have been susceptible to this latest vulnerability.
[ End AUSCERT Advisory ]
______________________________________________________________________________
CIAC wishes to acknowledge the contributions of AUSCERT, Brian Meilak
(Queensland University of Technology) and Sun Microsystems for the information
contained in this bulletin.
______________________________________________________________________________
CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
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