*ALERT* BID 3581: Wu-Ftpd File Globbing Heap Corruption Vulnerability

2001-11-29T00:00:00
ID SECURITYVULNS:DOC:2218
Type securityvulns
Reporter Securityvulns
Modified 2001-11-29T00:00:00

Description


                          Security Alert

Subject: Wu-Ftpd File Globbing Heap Corruption Vulnerability BUGTRAQ ID: 3581 CVE ID: CVE-MAP-NOMATCH Published: Nov 27, 2001 Updated: Nov 28, 2001 01:12:56

Remote: Yes Local: No Availability: Always Authentication: Not Required Credibility: Vendor Confirmed Ease: No Exploit Available Class: Failure to Handle Exceptional Conditions

Impact: 10.0 Severity: 10.0 Urgency: 8.2

Last Change: Initial analysis.

Vulnerable Systems:

Washington University wu-ftpd 2.6.1 + Caldera OpenLinux Server 3.1 + Caldera OpenLinux Workstation 3.1 + Cobalt Qube 1.0 + Conectiva Linux 7.0 + Conectiva Linux 6.0 + MandrakeSoft Corporate Server 1.0.1 + MandrakeSoft Linux Mandrake 8.1 + MandrakeSoft Linux Mandrake 8.0 ppc + MandrakeSoft Linux Mandrake 8.0 + MandrakeSoft Linux Mandrake 7.2 + MandrakeSoft Linux Mandrake 7.1 + MandrakeSoft Linux Mandrake 7.0 + MandrakeSoft Linux Mandrake 6.1 + MandrakeSoft Linux Mandrake 6.0 + RedHat Linux 7.2 noarch + RedHat Linux 7.2 ia64 + RedHat Linux 7.2 i686 + RedHat Linux 7.2 i586 + RedHat Linux 7.2 i386 + RedHat Linux 7.2 athlon + RedHat Linux 7.2 alpha + RedHat Linux 7.1 noarch + RedHat Linux 7.1 ia64 + RedHat Linux 7.1 i686 + RedHat Linux 7.1 i586 + RedHat Linux 7.1 i386 + RedHat Linux 7.1 alpha + RedHat Linux 7.0 sparc + RedHat Linux 7.0 i386 + RedHat Linux 7.0 alpha + TurboLinux TL Workstation 6.1 + TurboLinux Turbo Linux 6.0.5 + TurboLinux Turbo Linux 6.0.4 + TurboLinux Turbo Linux 6.0.3 + TurboLinux Turbo Linux 6.0.2 + TurboLinux Turbo Linux 6.0.1 + TurboLinux Turbo Linux 6.0 + Wirex Immunix OS 7.0-Beta + Wirex Immunix OS 7.0 Washington University wu-ftpd 2.6.0 + Cobalt Qube 1.0 + Conectiva Linux 5.1 + Conectiva Linux 5.0 + Conectiva Linux 4.2 + Conectiva Linux 4.1 + Conectiva Linux 4.0es + Conectiva Linux 4.0 + Debian Linux 2.2 sparc + Debian Linux 2.2 powerpc + Debian Linux 2.2 arm + Debian Linux 2.2 alpha + Debian Linux 2.2 68k + Debian Linux 2.2 + RedHat Linux 6.2 sparc + RedHat Linux 6.2 i386 + RedHat Linux 6.2 alpha + RedHat Linux 6.1 sparc + RedHat Linux 6.1 i386 + RedHat Linux 6.1 alpha + RedHat Linux 6.0 sparc + RedHat Linux 6.0 i386 + RedHat Linux 6.0 alpha + RedHat Linux 5.2 sparc + RedHat Linux 5.2 i386 + RedHat Linux 5.2 alpha + S.u.S.E. Linux 6.4ppc + S.u.S.E. Linux 6.4alpha + S.u.S.E. Linux 6.4 + S.u.S.E. Linux 6.3 ppc + S.u.S.E. Linux 6.3 alpha + S.u.S.E. Linux 6.3 + S.u.S.E. Linux 6.2 + S.u.S.E. Linux 6.1 alpha + S.u.S.E. Linux 6.1 + TurboLinux Turbo Linux 4.0 + Wirex Immunix OS 6.2 Washington University wu-ftpd 2.5.0 + Caldera eDesktop 2.4 + Caldera eServer 2.3.1 + Caldera eServer 2.3 + Caldera OpenLinux 2.4 + Caldera OpenLinux Desktop 2.3 + RedHat Linux 6.0 sparc + RedHat Linux 6.0 i386 + RedHat Linux 6.0 alpha

Summary:

Wu-Ftpd contains a remotely exploitable heap corruption bug.

Impact:

A remote attacker may execute arbitrary code on the vulnerable server.

Technical Description:

Wu-Ftpd is an ftp server based on the BSD ftpd that is maintained by Washington University.

Wu-Ftpd allows for clients to organize files for ftp actions based on "file globbing" patterns. File globbing is also used by various shells. The implementation of file globbing included in Wu-Ftpd contains a heap corruption vulnerability that may allow for an attacker to execute arbitrary code on a server remotely.

During the processing of a globbing pattern, the Wu-Ftpd implementation creates a list of the files that match. The memory where this data is stored is on the heap, allocated using malloc(). The globbing function simply returns a pointer to the list. It is up to the calling functions to free the allocated memory.

If an error occurs processing the pattern, memory will not be allocated and a variable indicating this should be set. The calling functions must check the value of this variable before attempting to use the globbed filenames (and later freeing the memory).

When certain globbing patterns are processed, the globbing function does not set this variable when an error occurs. As a result of this, Wu-Ftpd may eventually attempt to free uninitialized memory. There are a number of possibly exploitable conditions.

If this region of memory contained user-controllable data before the free call, it may be possible to have an arbitrary word in memory overwritten with an arbitrary value. This can lead to execution of arbitrary code if function pointers or return addresses are overwritten.

If anonymous FTP is not enabled, valid user credentials are required to exploit this vulnerability.

This vulnerability was initially scheduled for public release on December 3, 2001. However, Red Hat has made details public as of November 27, 2001. As a result, we are forced to warn other users of the vulnerable product, so that they may take appropriate actions.

Attack Scenarios:

To exploit this vulnerability, an attacker must have either valid credentials required to log in as an FTP user, or anonymous access must be enabled.

The attacker must ensure that a maliciously constructed malloc header containing the target address and it's replacement value are in the right location in the uninitialized part of the heap. The attacker must also place shellcode in server process memory.

The attacker must send an FTP command containing a specific globbing pattern that does not set the error variable.

When the server attempts to free the memory used to store the globbed filenames, the target word in memory will be overwritten.

If an attacker overwrites a function pointer or return address with a pointer to the shellcode, it may be executed by the server process.

Exploits:

The following (from the CORE advisory) demonstrates the existence of this vulnerability:

ftp> open localhost
Connected to localhost (127.0.0.1).
220 sasha FTP server (Version wu-2.6.1-18) ready.
Name (localhost:root): anonymous
331 Guest login ok, send your complete e-mail address as password.
Password:
230 Guest login ok, access restrictions apply.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls ~{
227 Entering Passive Mode (127,0,0,1,241,205)
421 Service not available, remote server has closed connection

1405 ?        S      0:00 ftpd: accepting connections on port 21
7611 tty3     S      1:29 gdb /usr/sbin/wu.ftpd
26256          ?                 S               0:00           ftpd:

sasha:anonymous/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 26265 tty3 R 0:00 bash -c ps ax | grep ftpd (gdb) at 26256 Attaching to program: /usr/sbin/wu.ftpd, process 26256 Symbols already loaded for /lib/libcrypt.so.1 Symbols already loaded for /lib/libnsl.so.1 Symbols already loaded for /lib/libresolv.so.2 Symbols already loaded for /lib/libpam.so.0 Symbols already loaded for /lib/libdl.so.2 Symbols already loaded for /lib/i686/libc.so.6 Symbols already loaded for /lib/ld-linux.so.2 Symbols already loaded for /lib/libnss_files.so.2 Symbols already loaded for /lib/libnss_nisplus.so.2 Symbols already loaded for /lib/libnss_nis.so.2 0x40165544 in __libc_read () from /lib/i686/libc.so.6 (gdb) c Continuing.

Program received signal SIGSEGV, Segmentation fault.
__libc_free (mem=0x61616161) at malloc.c:3136
3136    in malloc.c

Currently the SecurityFocus staff are not aware of any exploits for this issue. If you feel we are in error or are aware of more recent information, please mail us at: vuldb@securityfocus.com <mailto:vuldb@securityfocus.com>

Mitigating Strategies:

This vulnerability is remotely exploitable. Restricting access to the network port, (TCP port 21 is standard for FTP), will block clients from unauthorized networks.

With some operating systems, anonymous FTP is enabled by default. Anonymous FTP is often in use on public FTP sites, most often software repositories. It is basically a guest account with access to download files from within a restricted environment. This vulnerability is exploitable by clients logged in through anonymous FTP. Anonymous FTP should be disabled immediately until fixes are available, as it would allow any host on the Internet who can connect to the service to exploit this vulnerability. It is a good idea to disable it normally unless it is absolutely necessary (in which case the FTP server should be on a dedicated, isolated host).

Stack and other memory protection schemes may complicate exploitability, and/or prevent commonly available exploits from working. This should not be relied upon for security. This vulnerability involves 'poking' words in memory. This means that there are many different ways that it may be exploited. Making the stack non-executable or checking the integrity of stack variables may not be enough to prevent all possibile methods of exploitation.

It is advised to disable the service and use alternatives until fixes are available.

Solutions:

Vendor notified on Nov 14, 2001.

Fixes will be available from the author as well as from vendors who ship products that include Wu-Ftpd as core or optional components.

This vulnerability was initially scheduled for public release on December 3, 2001. Red Hat pre-emptively released an advisory on November 27, 2001. As a result, other vendors may not yet have fixes available.

This record will be updated as fixes from various vendors become available.

For Washington University wu-ftpd 2.6.1:

Red Hat RPM 6.2 alpha wu-ftpd-2.6.1-0.6x.21.alpha.rpm
ftp://updates.redhat.com/6.2/en/os/alpha/wu-ftpd-2.6.1-0.6x.21.alpha.rpm

Red Hat RPM 6.2 sparc wu-ftpd-2.6.1-0.6x.21.sparc.rpm
ftp://updates.redhat.com/6.2/en/os/sparc/wu-ftpd-2.6.1-0.6x.21.sparc.rpm

Red Hat RPM 7.0 alpha wu-ftpd-2.6.1-16.7x.1.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/wu-ftpd-2.6.1-16.7x.1.alpha.rpm

Red Hat RPM 7.0 i386 wu-ftpd-2.6.1-16.7x.1.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/wu-ftpd-2.6.1-16.7x.1.i386.rpm

Red Hat RPM 7.1 alpha wu-ftpd-2.6.1-16.7x.1.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/wu-ftpd-2.6.1-16.7x.1.alpha.rpm

Red Hat RPM 7.1 i386 wu-ftpd-2.6.1-16.7x.1.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/wu-ftpd-2.6.1-16.7x.1.i386.rpm

Red Hat RPM 7.1 ia64 wu-ftpd-2.6.1-16.7x.1.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/wu-ftpd-2.6.1-16.7x.1.ia64.rpm

Red Hat RPM 7.2 i386 wu-ftpd-2.6.1-20.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/wu-ftpd-2.6.1-20.i386.rpm

Red Hat RPM 6.2 i386 wu-ftpd-2.6.1-0.6x.21.i386.rpm
ftp://updates.redhat.com/6.2/en/os/i386/wu-ftpd-2.6.1-0.6x.21.i386.rpm

Credit:

Condition first reported by Matt Power, deemed non-exploitable. Rediscovered and exploitability later confirmed by Luciano Notarfrancesco and Juan Pablo Martinez Kuhn from Core Security Technologies, Buenos Aires, Argentina.

References:

advisory: RedHat RHSA-2001:157-06: Updated wu-ftpd packages are available http://www.securityfocus.com/advisories/3680

web page: CORE SDI Homepage (CORE) http://www.core-sdi.com

web page: Wu-Ftpd Homepage (Washington University) http://www.wu-ftpd.org

ChangeLog:

Nov 26, 2001: Initial analysis.


HOW TO INTERPRET THIS ALERT

        BUGTRAQ ID: This  is  a  unique  identifier  assigned  to   the
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           Updated: The date the information was last updated.

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       Credibility: Describes how credible the  information  about  the
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                    vulnerability.

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                    existence and details of the vulnerability.

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       Last Change: The  last  change   made   to   the   vulnerability
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Vulnerable Systems: The list of vulnerable systems. A &#39;+&#39;  preceding  a
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                    Windows 98 ships with Internet Explorer.  So  if  a
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           Summary: A concise summary of the vulnerability.

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 Related Resources: Resources that might be of additional value.

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                 Copyright 2001 SecurityFocus.com

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