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__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Capability
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__________________________________________________________
INFORMATION BULLETIN
Solaris 2.x passwd buffer Overrun Vulnerability
March 3, 1997 21:00 GMT Number H-37
______________________________________________________________________________
PROBLEM: A vulnerability exists in the passwd(1) program.
PLATFORM: All platforms with Solaris 2.x.
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-97.09 AUSCERT Advisory
Solaris 2.x passwd buffer Overrun Vulnerability
26 February 1997
Last Revised: 3 March 1997
Fixed information regarding versions prior to Solaris 2.5.
Added information on getting binary versions of the wrapper.
- ----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in the
passwd(1) program under Solaris 2.x.
This vulnerability may allow local users to gain root privileges.
Exploit information involving this vulnerability has been made
publicly available.
Currently there are no vendor patches available that address this
vulnerability. AUSCERT recommends that sites take the steps outlined in
section 3 as soon as possible.
This advisory will be updated as more information becomes available.
- ----------------------------------------------------------------------------
1. Description
AUSCERT has received information that a vulnerability exists in the
Solaris 2.x passwd(1) program. Under Solaris 2.5, yppasswd(1) and
nispasswd(1) are hard links to the passwd program, and as such are
also vulnerable. Under Solaris 2.3 and 2.4, passwd, yppasswd and
nispasswd are separate programs. Of these, only passwd is known to
be exploitable.
Due to insufficient bounds checking on arguments which are supplied
by users, it is possible to overwrite the internal stack space of the
passwd program while it is executing. By supplying a carefully
designed argument to the passwd program, intruders may be able to
force passwd to execute arbitrary commands. As passwd is setuid
root, it may allow intruders to run arbitrary commands with root
privileges.
Exploit information involving this vulnerability has been made
publicly available.
passwd, yppasswd and nispasswd under Solaris 2.x are located by
default in /usr/bin/.
2. Impact
Local users may gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites limit the possible exploitation of
this vulnerability by immediately applying the workaround given in
Section 3.1.
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 Install passwd 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 3.1.1. 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).
3.1.1 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 passwd 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 passwd command. The wrapper program can also be
configured to syslog any failed attempts to execute passwd with
arguments exceeding MAXARGLEN. For further instructions on using this
wrapper, please read the comments at the top of overflow_wrapper.c.
Applying this wrapper program to passwd, following the instructions
given in the comments at the start of the wrapper program, will also
fix the overflow problems with yppasswd and nispasswd under Solaris
2.5, since these programs are merely hard links to passwd.
When compiling overflow_wrapper.c for use with passwd, AUSCERT
recommends defining MAXARGLEN to be 32.
The MD5 checksum for Version 1.0 of overflow_wrapper.c is:
MD5 (overflow_wrapper.c) = f7f83af7f3f0ec1188ed26cf9280f6db
3.1.2 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/passwd.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/passwd_wrapper.tar.Z
The MD5 checksum for passwd_wrapper.tar.Z is:
MD5 (passwd_wrapper.tar.Z) = 9b49f5522ef4a481c7e4b4c1fb4f816f
passwd_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.
Sites are encouraged to carefully read the installation notes in
the README file before installation.
[ End AUSCERT Advisory ]
______________________________________________________________________________
CIAC wishes to acknowledge the contributions of AUSCERT, Jim Gifford (Board of
Regents of the University System of Georgia) 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
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.
CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
Voice: +1 510-422-8193
FAX: +1 510-423-8002
STU-III: +1 510-423-2604
E-mail: ciac@llnl.gov
For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 510-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.
Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.
World Wide Web: http://ciac.llnl.gov/
Anonymous FTP: ciac.llnl.gov (128.115.19.53)
Modem access: +1 (510) 423-4753 (28.8K baud)
+1 (510) 423-3331 (28.8K baud)
CIAC has several self-subscribing mailing lists for electronic
publications:
1. CIAC-BULLETIN for Advisories, highest priority - time critical
information and Bulletins, important computer security information;
2. CIAC-NOTES for Notes, a collection of computer security articles;
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(SPI) software updates, new features, distribution and
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following request as the E-mail message body, substituting
CIAC-BULLETIN, CIAC-NOTES, SPI-ANNOUNCE or SPI-NOTES for list-name and
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subscribe list-name LastName, FirstName PhoneNumber
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You will receive an acknowledgment containing address, initial PIN,
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PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
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This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
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