A Security Vulnerability in the Solaris X Window System (X(5)) PCF Font Handler  (see details below)

A security vulnerability in the Solaris X Window System (X(5)) PCF font handler in libfont and libXfont libraries may allow a remote unprivileged user to crash the application or execute arbitrary code with the privileges of the application which dynamically links to one of these libraries. The ability to crash an application is a type of Denial of Service (DoS).

This issue is described in the following document:

CERT VU#203220 at http://www.kb.cert.org/vuls/id/203220

This issue can occur in the following releases:

SPARC Platform

• Solaris 8 without patch 119067-09
• Solaris 9 without patch 112785-63 (for Xsun(1))
• Solaris 10 without patch119059-37 (for Xsun(1))
• Solaris 10 without patch 125719-07 (for Xorg(1))

x86 Platform

• Solaris 8 without patch 119068-09
  
• Solaris 9 without patch 112786-52 (for Xsun(1))
• Solaris 9 without patch 118908-04 (for Xorg(1))
• Solaris 10 without patch119060-36 (for Xsun(1))
• Solaris 10 without patch125720-16 (for Xorg(1))

Note: The Xorg(1) X server only ships on the x86 platform for Solaris 9 with the Sun Java Desktop System (JDS) release 2 installed, and on Solaris 10.

To determine if JDS release 2 is installed on a Solaris 9 x86 system, the following command can be run:

    % grep distributor-version /usr/share/gnome-about/gnome-version.xml 
    <distributor-version>Sun Java Desktop System, Release 2</distributor-version>

To determine if an application is linked with the libXfont or libfont library, the ldd(1) utility can be utilized as in the following examples:

    $ ldd /usr/openwin/bin/Xsun | grep libfont
    libfont.so.1 =>  /usr/openwin/server/lib/libfont.so.1

    $ ldd /usr/X11/bin/Xorg | grep libXfont
    libXfont.so.1 =>  /usr/X11/lib/X11/xserver/libXfont.so.1

There are no predictable symptoms that would indicate the described issue has been exploited to execute arbitrary code with elevated privileges.

If the described issue is exploited to cause a Denial of Service (DoS) to an application which links to the libfreetype library, the application will exit and may generate a segmentation fault error, potentially writing a core(4) file.

To work around this issue, the "noexec_user_stack" options can be used to defeat the most common form of buffer overflow attacks that store executable exploit code on the stack. This can be achieved by editing the "/etc/system" file and adding the following lines:

    set noexec_user_stack = 1
    set noexec_user_stack_log = 1

A reboot will be necessary in order for the above change to take effect. See system(4) for information on modifying the system configuration information file.

5. Resolution

This issue is addressed in the following releases:

SPARC Platform

• Solaris 8 with patch 119067-09 or later (for Xsun(1))
• Solaris 9 with patch 112785-63 or later (for Xsun(1))
• Solaris 10 with patch119059-37 or later (for Xsun(1))
• Solaris 10 with patch 125719-07 or later (for Xorg(1))

x86 Platform

• Solaris 8 with patch 119068-09 or later (for Xsun(1))
• Solaris 9 with patch 112786-52 or later (for Xsun(1))
• Solaris 9 with patch118908-04 or later (for Xorg(1))
• Solaris 10 with patch119060-36 or later (for Xsun(1))
• Solaris 10 with patch125720-16 or later (for Xorg(1))

For more information on Security Sun Alerts, see Sun Infodoc 91209.

Copyright 2000-2008 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, CA 95054 U.S.A. All rights reserved.

18-JAN-2008: Updated Contributing Factors, Relief/Workaround, Resolution sections
31-JAN-2008: Updated Contributing Factors and Resolution sections
01-FEB-2008: Updated Contributing Factors, Resolution sections: Resolved

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