TUCoPS :: SunOS/Solaris :: ciach056.txt

TUCoPS :: SunOS/Solaris :: ciach056.txt
Solaris 2x Lp Vulnerability

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__________________________________________________________

The U.S. Department of Energy
Computer Incident Advisory Capability
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__________________________________________________________

INFORMATION BULLETIN

Solaris 2.x lp Print Service Vulnerability

May 13, 1997 16:00 GMT Number H-56
______________________________________________________________________________
PROBLEM: A vulnerability exists in the lp print service temporary files
creation.
PLATFORM: Solaris 2.4, 2.5 and 2.5.1. Earlier versions of Solaris may
also be vulnerable.
DAMAGE: This vulnerability may allow local users to gain lp privileges,
which may be leveraged to gain root access.
SOLUTION: Until vendor patches are made available, apply the workaround
in Section 3.1.
______________________________________________________________________________
VULNERABILITY Exploit details involving this vulnerability have been made
ASSESSMENT: publicly available.
______________________________________________________________________________

[ Start AUSCERT Advisory ]

===========================================================================
AA-97.15 AUSCERT Advisory
Solaris 2.x lp temporary files creation vulnerability
13 May 1997

Last Revised: --

- ----------------------------------------------------------------------------

AUSCERT has received information that a vulnerability exists in the lp
print service under Solaris 2.4, 2.5 and 2.5.1. Earlier versions of
Solaris may also be vulnerable.

This vulnerability may allow local users to gain lp privileges. This may be
leveraged to gain root privileges.

Exploit information involving this vulnerability has been made publicly
available.

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 lp print service. The lp print service is used to print
files on local and remote printers.

This problem is known to be present in the lp print service distributed
with Solaris 2.4, 2.5 and 2.5.1. Earlier versions of Solaris may also
be vulnerable.

Due to a problem with insecure file creation, it is possible to force
the lp print service to create, or overwrite arbitrary files with the
privileges of the lp user. This may be leveraged to gain root
privileges.

Exploit information involving this vulnerability has been made publicly
available.

2. Impact

Local users may create arbitrary files as the lp user. This may be
leveraged to gain root access.

3. Workarounds/Solution

AUSCERT recommends that sites prevent the exploitation of this
vulnerability in the lp print service 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 Modify lp configuration

To prevent the exploitation of the vulnerability described in this
advisory, AUSCERT recommends applying the following steps:

1. su to root

2. Before continuing, all printing services must be stopped and the
printing queue emptied.

To reject any new jobs to the printing queue use the command:

# /usr/sbin/reject printer_queue

and wait until the printing queue is emptied.

To stop the print service use the command:

# /etc/init.d/lp stop
Print services stopped.

3. The file /etc/init.d/lp needs to be edited to set the umask for
this service to 022. Files created by lp printing service will
now inherit this umask and not be created as world writable.

Using your favorite editor, edit the file /etc/init.d/lp and
change the line

state=$1

umask 022
state=$1

4. The original log files may have been created with insecure
permission settings, therefore containing information that cannot
be trusted. Its best to rename or remove these files.

The files will be re-created by lp printing service with the
correct permissions after the printing service is re-started.

Before executing the following commands make sure that there are
no jobs pending on the queue.

# mv -i /var/lp/logs/lpNet /var/lp/logs/lpNet.previous
# mv -i /var/lp/logs/lpsched /var/lp/logs/lpsched.previous
# mv -i /var/lp/logs/requests /var/lp/logs/requests.previous

5. Change the default location of the temporary files to /var/lp/

# echo 'Options: PRINTER * = -L/var/lp/*.log' | lpfilter -f postio -
# echo 'Options: PRINTER * = -L/var/lp/*.log' | lpfilter -f postior -

6. Re-start printing services:

# /etc/init.d/lp start
Print services started.

7. If you used the command reject on step 2, use the following command
to allow printing queue to be re-enabled:

# /usr/sbin/accept printer_queue

[ End AUSCERT Advisory ]

______________________________________________________________________________

CIAC wishes to acknowledge the contributions of AUSCERT 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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