__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Capability
___ __ __ _ ___
/ | /_\ /
\___ __|__ / \ \___
__________________________________________________________
INFORMATION BULLETIN
HP-UX Security Vulnerabilities (passwd, fpkg2swpkg, newgrp)
December 6, 1996 23:00 GMT Number H-10
______________________________________________________________________________
PROBLEM: Three vulnerabilities have been found in the HP-UX operating
system: 1) passwd buffer overrun, 2) fpkg2swpkg program, and
3) newgrp buffer overrun.
PLATFORM: HP-UX 9.x and HP-UX 10.x
DAMAGE: Vulnerabilities may allow local users to gain root privileges.
SOLUTION: Install the proper patches and/or use the workarounds provided
below.
______________________________________________________________________________
VULNERABILITY Exploit information involving these vulnerabilities have been
ASSESSMENT: made publicly available.
______________________________________________________________________________
[ Begin AUSCERT Advisories ]
1. passwd Buffer Overrun Vulnerability
===========================================================================
AA-96.13 AUSCERT Advisory
HP-UX passwd Buffer Overrun Vulnerability
28 November 1996
Last Revised: 5 December 1996
Remove permissions on /sbin/passwd as it is also
vulnerable.
Replace wrapper program with pointer to
overflow_wrapper.c (no change in functionality).
----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in the
passwd(1) program under HP-UX 9.x and HP-UX 10.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
HP-UX passwd(1) program.
This vulnerability is known to affect HP-UX 9.x and 10.x.
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.
By default, a dynamically linked version of the passwd program is
found in /bin under HP-UX 9.x and in /usr/bin under HP-UX 10.x. A
statically linked version is also available under HP-UX 10.x and is
located in /sbin.
Exploit information involving this vulnerability has been made
publicly available.
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 workarounds given in Sections
3.1.1 and 3.1.2. Sites using either HP-UX 9.x or HP-UX 10.x will need
to apply the workaround given in Section 3.1.1. In addition, sites
using HP-UX 10.x will also need to apply the workaround given in
Section 3.1.2.
Currently there are no vendor patches available that address this
vulnerability. AUSCERT recommends that official vendor patches be
installed when they are made available.
3.1.1 Install passwd wrapper
AUSCERT has developed a wrapper to help prevent programs from being
exploited using the vulnerability described in this advisory. This
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.
When compiling overflow_wrapper.c for use with HP-UX passwd, AUSCERT
recommends defining MAXARGLEN to be 64.
The MD5 checksum for Version 1.0 of overflow_wrapper.c is:
MD5 (overflow_wrapper.c) = f7f83af7f3f0ec1188ed26cf9280f6db
AUSCERT recommends that until vendor patches can be installed,
sites apply this workaround.
The overflow_wrapper.c program provides functionality identical to
passwd_wrapper.c included in the previous version of this advisory.
Sites that have already installed passwd_wrapper.c do not need to
install overflow_wrapper.c.
Sites using HP-UX 10.x will need to additionally apply the workaround
given in Section 3.1.2.
3.1.2 Remove setuid and non-root execute permissions on /sbin/passwd
Under HP-UX 10.x, a statically linked copy of the passwd program is
located in /sbin. This copy of the passwd program is available for
root to use when only the root partition is mounted, for example, when
in single user mode. There is no need for non-root users to use this
copy of the passwd program, so setuid and non-root execute permissions
should be removed.
# ls -l /sbin/passwd
-r-sr-xr-x 1 root bin 487424 Jun 10 17:00 /sbin/passwd
# chmod 500 /sbin/passwd
# ls -l /sbin/passwd
-r-x------ 1 root bin 487424 Jun 10 17:00 /sbin/passwd
Note this will remove the ability for non-root users to execute
/sbin/passwd.
4. Additional measures
During the installation of HP-UX patches, copies of files being
replaced are saved in case the patches need to be backed out of. The
original versions of patched files are stored in the following
locations:
HP-UX 9.x: /system/<PATCH-NAME>/orig/
HP-UX 10.x: /var/adm/sw/patch/PATCH_NAME>/
If patches for vulnerable programs have been previously installed,
copies of the vulnerable programs may be available in the above
locations. Sites should ensure the directories have permissions
which restrict access to the patch areas.
----------------------------------------------------------------------------
AUSCERT thanks Hewlett-Packard for their continued assistance and technical
expertise essential for the production of this advisory. AUSCERT also
thanks Information Technology Services of the University of Southern
Queensland, Albert Lunde (Northwestern University) and CERT/CC for
their assistance.
----------------------------------------------------------------------------
2. fpkg2swpkg Program Vulnerability
===========================================================================
AA-96.14 AUSCERT Advisory
HP-UX fpkg2swpkg Vulnerability
29 November 1996
Last Revised: --
----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in the
HP-UX 10.x program fpkg2swpkg.
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
The HP-UX 10.x fpkg2swpkg(1m) program is used to translate fpkg (HP-UX
9.x) network media or Product Specification Files (PSFs) to SD
swpackage (HP-UX 10.x) PSFs.
The fpkg2swpkg program creates files in an insecure manner. As this
program executes with root privileges, it is possible for local users
to create or append to arbitrary files on the system.
Exploit information involving this vulnerability has been made publicly
available.
The default location for fpkg2swpkg is /usr/sbin/fpkg2swpkg.
2. Impact
Local users may be able to create or append to arbitrary files on
the system. This can be leveraged to gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites prevent the exploitation of the
vulnerability in fpkg2swpkg 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 Remove setuid and execute permissions
Until official vendor patches are made available, sites should remove
the setuid root and execute permissions from fpkg2swpkg. To do this,
the following command should be run as root:
# chmod 400 /usr/sbin/fpkg2swpkg
# ls -l /usr/sbin/fpkg2swpkg
-r-------- 1 root bin 57344 May 30 1996 /usr/sbin/fpkg2swpkg
Note that this will remove the ability for any user to run this
program. If only the setuid permissions are removed, it is still
possible for users to gain privileges when fpkg2swpkg is executed
by the root user.
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 / \( -perm -4000 -o -perm -2000 \) -exec ls -ld {} \;
It is AUSCERT's experience that many vulnerabilities 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 fpkg2swpkg program is
not needed by most sites. If sites had previously disabled the
fpkg2swpkg program, they would not have been vulnerable to this latest
exploit.
----------------------------------------------------------------------------
AUSCERT thanks Hewlett-Packard for their continued assistance and technical
expertise essential for the production of this advisory. AUSCERT also
thanks Information Technology Services of the University of Southern
Queensland for their assistance.
----------------------------------------------------------------------------
3. newgrp Buffer Overrun Vulnerability
===========================================================================
AA-96.16 AUSCERT Advisory
HP-UX newgrp Buffer Overrun Vulnerability
3 December 1996
Last Revised: --
----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in the
newgrp(1) program under HP-UX 9.x and 10.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
HP-UX newgrp(1) program. The newgrp command is used to change a users
group identification, and is installed by default.
Due to insufficient bounds checking on arguments which are supplied
by users, it is possible to overwrite the internal stack space of the
newgrp program while it is executing. By supplying a carefully
designed argument to the newgrp program, intruders may be able to
force newgrp to execute arbitrary commands. As newgrp is setuid
root, this may allow intruders to run arbitrary commands with root
privileges.
This vulnerability is known to affect both HP-UX 9.x and 10.x.
By default, newgrp is located in /bin under HP-UX 9.x and in
/usr/bin under HP-UX 10.x.
Exploit information involving this vulnerability has been made
publicly available.
2. Impact
Local users may gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites limit the possible exploitation of this
vulnerability by immediately removing the setuid permissions as stated
in Section 3.1. If the newgrp command is required, AUSCERT recommends
the newgrp wrapper program given in Section 3.2 be installed.
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 the
advisory, AUSCERT recommends that the setuid permissions be removed
from the newgrp program immediately. As the newgrp program will no
longer work for non-root users, it is recommended that the execute
permissions also be removed. Before doing so, the original permissions
for newgrp should be noted as they will be needed if sites choose to
install the newgrp wrapper program (Section 3.2).
For HP-UX 9.x:
# ls -l /bin/newgrp
-r-sr-xr-x 1 root sys 16384 Dec 2 13:45 /bin/newgrp
# chmod 500 /bin/newgrp
# ls -l /bin/newgrp
-r-x------ 1 root sys 16384 Dec 2 13:45 /bin/newgrp
For HP-UX 10.x:
# ls -l /usr/bin/newgrp
-r-sr-xr-x 1 root sys 12288 Dec 2 13:27 /usr/bin/newgrp
# chmod 500 /usr/bin/newgrp
# ls -l /usr/bin/newgrp
-r-x------ 1 root sys 12288 Dec 2 13:27 /usr/bin/newgrp
Note that this will remove the ability for any non-root user to run the
newgrp program.
3.2 Install newgrp wrapper
AUSCERT has developed a wrapper to help prevent programs from being
exploited using the vulnerability described in this advisory. This
wrapper, including installation instructions, can be found at:
ftp://ftp.auscert.org.au/pub/auscert/tools/overflow_wrapper.c
This replaces the newgrp program with a wrapper which checks the
length of the command line arguments passed to it. If an argument
exceeds a certain predefined value (MAXARGLEN), the wrapper exits
without executing the newgrp command. The wrapper program can also
be configured to syslog any failed attempts to execute newgrp 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 HP-UX newgrp, AUSCERT
recommends defining MAXARGLEN to be 16.
The MD5 checksum for Version 1.0 of overflow_wrapper.c is:
MD5 (overflow_wrapper.c) = f7f83af7f3f0ec1188ed26cf9280f6db
AUSCERT recommends that until vendor patches can be installed, sites
requiring the newgrp functionality apply this workaround.
----------------------------------------------------------------------------
AUSCERT thanks Hewlett-Packard for their continued assistance and technical
expertise essential for the production of this advisory. AUSCERT also
thanks Information Technology Services of the University of Southern
Queensland for their assistance.
----------------------------------------------------------------------------
[ End AUSCERT Advisories ]
_______________________________________________________________________________
CIAC wishes to acknowledge the contributions of AUSCERT for the
information contained in this bulletin.
_______________________________________________________________________________
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