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__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Capability
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__________________________________________________________
INFORMATION BULLETIN
SGI IRIX ordist, login/scheme Buffer Overrun Vulnerability
May 28, 1997 18:00 GMT Number H-62
______________________________________________________________________________
PROBLEM: Two vulnerabilities have been identified on the SGI IRIX
operating system: (1) ordist program, and the (2) login
program.
PLATFORM: All SGI systems running IRIX 6.2. Other versions (including
IRIX 5.x) may be vulnerable.
DAMAGE: These vulnerabilities may allow local users to gain root
privileges.
SOLUTION: Apply the suggested workarounds listed below.
______________________________________________________________________________
VULNERABILITY Exploit information involving these vulnerabilities have been
ASSESSMENT: made publicly available.
______________________________________________________________________________
[ Start AUSCERT Advisories ]
1. ordist Buffer Overrun Vulnerability
===========================================================================
AA-97.23 AUSCERT Advisory
SGI IRIX ordist Buffer Overrun Vulnerability
28 May 1997
Last Revised: --
- ----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in ordist(1c),
distributed under IRIX 6.2. Other versions of IRIX may also 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
ordist(1c) is a program used to maintain identical copies of files over
multiple hosts. It preserves the owner, group, mode and mtime of
a file if possible.
Due to insufficient bounds checking on arguments which are supplied
by users, it is possible to overwrite the internal stack space of the
ordist program while it is executing. By supplying a carefully designed
argument to the ordist program, intruders may be able to force ordist to
execute arbitrary commands. As ordist is setuid root, this may allow
intruders to run arbitrary commands with the privileges of root.
Sites can determine if this program is installed by using:
% ls -l /usr/bsd/ordist
ordist is installed by default in /usr/bsd. Sites are encouraged to check
for the presence of this program regardless of the version of IRIX
installed.
Exploit information involving this vulnerability has been made publicly
available.
2. Impact
This vulnerability may allow local users to gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites prevent the exploitation of this
vulnerability in ordist by immediately applying the workaround given in
Section 3.1.
If the ordist functionality is required by non-root users, 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 ordist program immediately. As ordist will no longer work for
non-root users, it is recommended that the execute permissions for
them also be removed.
# ls -l /usr/bsd/ordist
-rwsr-xr-x 1 root sys 70564 Nov 28 15:07 /usr/bsd/ordist
# chmod 500 /usr/bsd/ordist
# ls -l /usr/bsd/ordist
-r-x------ 1 root sys 70564 Nov 28 15:07 /usr/bsd/ordist
3.2 Install ordist 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
(Section 3.2.2).
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/
overflow_wrapper.c
This wrapper replaces the ordist 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 ordist command. The wrapper program can also be configured
to syslog any failed attempts to execute ordist 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 ordist, AUSCERT recommends
defining MAXARGLEN to be 32.
The MD5 checksum for the current version of overflow_wrapper.c can be
retrieved from:
ftp://ftp.auscert.org.au/pub/auscert/tools/overflow_wrapper/CHECKSUM
The CHECKSUM file has been digitally signed using the AUSCERT PGP key.
3.2.2 Installing the wrapper binaries
A pre-compiled wrapper binary is provided for sites that wish to
install the wrapper but do not have a C compiler available. AUSCERT
has compiled the wrapper on IRIX 5.3, however later versions of IRIX
should be able to use the wrapper binary without recompilation. The
following compile time options have been used to create the binaries:
REAL_PROG='"/usr/bsd/ordist.real"'
MAXARGLEN=32
SYSLOG
More information on these options can be found in Section 3.2.1 and
in the overflow_wrapper.c source code.
The pre-compiled binary for the wrapper program can be retrieved from:
ftp://ftp.auscert.org.au/pub/auscert/tools/
AA-97.23-ordist_wrapper.tar.Z
The MD5 checksum for AA-97.23-ordist_wrapper.tar.Z is:
MD5 (AA-97.23-ordist_wrapper.tar.Z) = 0eed9d9a52658181a1ce9b4ce2ed7fd2
AA-97.23-ordist_wrapper.tar.Z contains a README file with installation
instructions, as well as a pre-compiled 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 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 ordist program is not
needed by many sites. If sites had previously disabled this program,
they would not have been susceptible to this latest vulnerability.
- ----------------------------------------------------------------------------
2. login/scheme Buffer Overrun Vulnerability
===========================================================================
AA-97.22 AUSCERT Advisory
SGI IRIX login/scheme Buffer Overrun Vulnerability
28 May 1997
Last Revised: --
- ----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in login(1),
distributed under IRIX 6.2. Other versions (including IRIX 5.x) may also
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
login(1) is a program used at the beginning of each terminal session
that allows users to identify themselves to the session. Under current
versions of IRIX this functionality is supplied by the program
/usr/lib/iaf/scheme. The login program is a symbolic link to
/usr/lib/iaf/scheme.
Due to insufficient bounds checking on arguments which are supplied
by users, it is possible to overwrite the internal stack space of the
scheme program while it is executing. By supplying a carefully designed
argument to the scheme program, intruders may be able to force scheme to
execute arbitrary commands. As scheme is setuid root, this may allow
intruders to run arbitrary commands with root privileges.
The login program is installed in /usr/bin/login. Under default
configurations this is a symbolic link to /usr/lib/iaf/scheme.
% ls -l /usr/bin/login
lrwxr-xr-x 1 root sys 17 Nov 22 1994 /usr/bin/login ->
../lib/iaf/scheme
% ls -l /usr/lib/iaf/scheme
-rwsr-xr-x 1 root sys 65832 Nov 22 1994 /usr/lib/iaf/scheme
Exploit information involving this vulnerability has been made publicly
available.
Although AUSCERT has only verified this vulnerability under IRIX 6.2,
this vulnerability is believed to affect other versions of IRIX,
including IRIX 5.x.
2. Impact
This vulnerability may allow local users to gain root privileges.
3. Workarounds/Solution
AUSCERT recommends that sites prevent the exploitation of this
vulnerability in login/scheme by immediately applying the workaround
given in Section 3.1.
To maintain the full login/scheme functionality, 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 scheme program immediately.
# ls -l /usr/lib/iaf/scheme
-rwsr-xr-x 1 root sys 58324 Nov 28 1996 /usr/lib/iaf/scheme
# chmod 500 /usr/lib/iaf/scheme
# ls -l /usr/lib/iaf/scheme
-r-x------ 1 root sys 58324 Nov 28 1996 /usr/lib/iaf/scheme
3.2 Install scheme 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
(Section 3.2.2).
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/
overflow_wrapper.c
This wrapper replaces the scheme 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 scheme command. The wrapper program can also be configured
to syslog any failed attempts to execute scheme 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 scheme, AUSCERT recommends
defining MAXARGLEN to be 32.
The MD5 checksum for the current version of overflow_wrapper.c can be
retrieved from:
ftp://ftp.auscert.org.au/pub/auscert/tools/overflow_wrapper/CHECKSUM
The CHECKSUM file has been digitally signed using the AUSCERT PGP key.
3.2.2 Installing the wrapper binaries
A pre-compiled wrapper binary is provided for sites that wish to install
the wrapper but do not have a C compiler available. AUSCERT has
compiled the wrapper on IRIX 5.3, however later versions of IRIX should
be able to use the wrapper binary without recompilation. The following
compile time options have been used to create the binaries:
REAL_PROG='"/usr/lib/iaf/scheme.real"'
MAXARGLEN=32
SYSLOG
More information on these options can be found in Section 3.2.1 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/
AA-97.22-scheme_wrapper.tar.Z
The MD5 checksum for AA-97.22-scheme_wrapper.tar.Z is:
MD5 (AA-97.22-scheme_wrapper.tar.Z) = dc302aa275a4009d1545180bfce8ebf4
AA-97.22-scheme_wrapper.tar.Z contains a README file with installation
instructions, as well as a pre-compiled binary.
Sites are encouraged to carefully read the installation notes in the
README file before installation.
- ----------------------------------------------------------------------------
[ End AUSCERT Advisories ]
______________________________________________________________________________
CIAC wishes to acknowledge the contributions of AUSCERT, Ian Farquhar, and
the Prentice Center, University of Queensland for 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
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