From proff Thu Jun 27 02:18:56 1996 Received: (proff@localhost) by suburbia.net (8.7.4/Proff-950810) id CAA08016 for best-of-security; Thu, 27 Jun 1996 02:18:56 +1000 Received: from why.cert.org (why.cert.org [192.88.210.60]) by suburbia.net (8.7.4/Proff-950810) with SMTP id CAA07377 for ; Thu, 27 Jun 1996 02:01:05 +1000 Received: (from cert-advisory@localhost) by why.cert.org (8.6.12/CERT-ecd.1) id LAA06948 for cert-advisory-queue-4; Wed, 26 Jun 1996 11:34:33 -0400 Date: Wed, 26 Jun 1996 11:34:33 -0400 Message-Id: <199606261534.LAA06948@why.cert.org> From: CERT Advisory To: cert-advisory@cert.org Subject: CERT Advisory CA-96.12 - Vulnerability in suidperl Reply-To: cert-advisory-request@cert.org Organization: CERT(sm) Coordination Center - +1 412-268-7090 Sender: proff -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT(sm) Advisory CA-96.12 June 26, 1996 Topic: Vulnerability in suidperl - ----------------------------------------------------------------------------- The CERT Coordination Center has received reports of a vulnerability in systems that contain the suidperl program and that support saved set-user-ID and saved set-group-ID. By exploiting this vulnerability, anyone with access to an account on such a system may gain root access. Saved set-user-IDs and set-group-IDs are sometimes referred to as POSIX saved IDs. suidperl is also known as sperl followed by a version number, as in sperl5.002. Perl versions 4 and 5 can be compiled and installed in such a way that they will be vulnerable on some systems. If you have installed the suidperl or sperl programs on a system that supports saved set-user-ID and set-group-ID, you may be at risk. The CERT Coordination Center recommends that you first disable the suidperl and sperl programs (Section III.A). If you need the functionality, we further recommend that you either apply a patch for this problem or install Perl version 5.003 (Section III.B). If neither a patch nor a new version are viable alternatives, we recommend installing the wrapper written by Larry Wall as a workaround for this problem (Section III.C). As we receive additional information relating to this advisory, we will place it in ftp://info.cert.org/pub/cert_advisories/CA-96.12.README We encourage you to check our README files regularly for updates on advisories that relate to your site. - ----------------------------------------------------------------------------- I. Description On some systems, setuid and setgid scripts (scripts written in the C shell, Bourne shell, or Perl, for example, with the set user or group ID permissions enabled) are insecure due to a race condition in the kernel. For those systems, Perl versions 4 and 5 attempt to work around this vulnerability with a special program named suidperl, also known as sperl. Even on systems that do provide a secure mechanism for setuid and setgid scripts, suidperl may also be installed--although it is not needed. suidperl attempts to emulate the set-user-ID and set-group-ID features of the kernel. Depending on whether the script is set-user-ID, set-group-ID, or both, suidperl achieves this emulation by first changing its effective user or group ID to that of the original Perl script. suidperl then reads and executes the script as that effective user or group. To do these user and group ID changes correctly, suidperl must be installed as set-user-ID root. On systems that support saved set-user-ID and set-group-ID, suidperl does not properly relinquish its root privileges when changing its effective user and group IDs. II. Impact On a system that has the suidperl or sperl program installed and that supports saved set-user-ID and saved set-group-ID, anyone with access to an account on the system can gain root access. III. Solution The command in Section A helps you determine if your system is vulnerable and, if it is, optionally disables the suidperl and sperl programs that it locates. After you have run this command on all of your systems, your system will no longer be vulnerable. If you find that your system is vulnerable, then you need to replace the suidperl and sperl programs with new versions. Section B describes how to do that. Finally, Section C identifies a wrapper that can be used in place of the suidperl program. A. How to determine if your system is vulnerable To determine if a system is vulnerable to this problem and to disable the programs that are believed to be vulnerable, use the following find command or a variant. Consult your local system documentation to determine how to tailor the find program on your system. You will need to run the find command on each system you maintain because the command examines files on the local disk only. Substitute the names of your local file systems for FILE_SYSTEM_NAMES in the example. Example local file system names are /, /usr, and /var. You must do this as root. Note that this is one long command, though we have separated it onto three lines using back-slashes. find FILE_SYSTEM_NAMES -xdev -type f -user root \ \( -name 'sperl[0-9].[0-9][0-9][0-9]' -o -name \ 'suidperl' \) -perm -04000 -print -ok chmod ug-s '{}' \; This command will find all files on a system that are - only in the file system you name (FILE_SYSTEM_NAMES -xdev) - regular files (-type f) - owned by root (-user root) - named appropriately (-name 'sperl[0-9].[0-9][0-9][0-9]' -o -name 'suidperl') - setuid root (-perm -04000) Once found, those files will - have their names printed (-print) - have their modes changed, but only if you type `y' in response to the prompt (-ok chown ug-s '{}' \;) B. Obtain and install the appropriate patch according to the instructions included with the patch. Vendor patches -------------- You may be vulnerable if your vendor supports saved set-user-ID and set-group-ID and ships suidperl or sperl. You need to get a patched version from your vendor. Appendix A contains information provided by vendors as of the date of this advisory. When we receive updated information, we will put it in CA-96.12.README. Until you can install a patch, we recommend disabling suidperl. The find command above will help you do that. If you need suidperl or sperl, an alternative is to install the wrapper described in Section C. Source code patches ------------------- If you have installed Perl from source code, you should install source code patches. Patches are available from the CPAN (Comprehensive Perl Archive Network) archives. Patch for Perl Version 4: File src/fixsuid4-0.pat MD5 Checksum af3e3c40bbaafce134714f1381722496 Patch for Perl Version 5: File src/fixsuid5-0.pat MD5 Checksum 135c96ee400fd37a38a7ef37edd489e9 In addition, Perl version 5.003 contains this patch, so installing it on your system also addresses this vulnerability. Perl 5.003 is available from the CPAN archives. Here are the specifics: File src/5.0/perl5.003.tar.gz MD5 Checksum b1bb23995cd25e5b750585bfede0e8a5 The CPAN archives can be found at the following locations: CPAN master site ftp://ftp.funet.fi/pub/languages/perl/CPAN/ Africa ftp://ftp.is.co.za/programming/perl/CPAN/ Asia ftp://dongpo.math.ncu.edu.tw/perl/CPAN/ ftp://ftp.lab.kdd.co.jp/lang/perl/CPAN/ Australasia ftp://coombs.anu.edu.au/pub/perl/ ftp://ftp.mame.mu.oz.au/pub/perl/CPAN/ ftp://ftp.tekotago.ac.nz/pub/perl/CPAN/ Europe ftp://ftp.arnes.si/software/perl/CPAN/ ftp://ftp.ci.uminho.pt/pub/lang/perl/ ftp://ftp.cs.ruu.nl/pub/PERL/CPAN/ ftp://ftp.demon.co.uk/pub/mirrors/perl/CPAN/ ftp://ftp.funet.fi/pub/languages/perl/CPAN/ ftp://ftp.ibp.fr/pub/perl/CPAN/ ftp://ftp.leo.org/pub/comp/programming/languages/perl/CPAN/ ftp://ftp.pasteur.fr/pub/computing/unix/perl/CPAN/ ftp://ftp.rz.ruhr-uni-bochum.de/pub/programming/languages/perl/CPAN/ ftp://ftp.sunet.se/pub/lang/perl/CPAN/ ftp://ftp.switch.ch/mirror/CPAN/ ftp://unix.hensa.ac.uk/mirrors/perl-CPAN/ North America ftp://ftp.cis.ufl.edu/pub/perl/CPAN/ ftp://ftp.delphi.com/pub/mirrors/packages/perl/CPAN/ ftp://ftp.sedl.org/pub/mirrors/CPAN/ ftp://ftp.sterling.com/programming/languages/perl/ ftp://ftp.uoknor.edu/mirrors/CPAN/ ftp://uiarchive.cso.uiuc.edu/pub/lang/perl/CPAN/ C. If you need setuid or setgid Perl scripts and are unable to apply the source code patches listed in Section B, we suggest that you retrieve Larry Wall's fixsperl script noted below. fixsperl is a script that replaces the suidperl and sperl programs with a wrapper that eliminates the vulnerability. The script is available from the CPAN archives as File src/fixsperl-0 MD5 Checksum f13900d122a904a8453a0af4c1bdddc6 Note that this script should be run one time, naming every suidperl or sperl file on your system. If you add another version of suidperl or sperl to your system, then you must run fixsperl on those newly installed versions. - --------------------------------------------------------------------------- The CERT Coordination Center staff thanks Paul Traina, Larry Wall, Eric Allman, Tom Christiansen, and AUSCERT for their support in the development of this advisory. - --------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in the Forum of Incident Response and Security Teams (FIRST). We strongly urge you to encrypt any sensitive information you send by email. The CERT Coordination Center can support a shared DES key and PGP. Contact the CERT staff for more information. Location of CERT PGP key: ftp://info.cert.org/pub/CERT_PGP.key CERT Contact Information - ------------------------ Email cert@cert.org Phone +1 412-268-7090 (24-hour hotline) CERT personnel answer 8:30-5:00 p.m. EST (GMT-5)/EDT(GMT-4), and are on call for emergencies during other hours. Fax +1 412-268-6989 Postal address CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 USA CERT publications, information about FIRST representatives, and other security-related information are available for anonymous FTP from http://www.cert.org/ ftp://info.cert.org/pub/ CERT advisories and bulletins are also posted on the USENET newsgroup comp.security.announce To be added to our mailing list for CERT advisories and bulletins, send your email address to cert-advisory-request@cert.org Copyright 1996 Carnegie Mellon University This material may be reproduced and distributed without permission provided it is used for non-commercial purposes and the copyright statement is included. CERT is a service mark of Carnegie Mellon University. ......................................................................... Appendix A: Vendor Information Current as of June 26, 1996 See CA-96.12.README for updated information. Below is information we have received from vendors concerning the vulnerability described in this advisory. If you do not see your vendor's name, please contact the vendor directly for information. Apple Computer, Inc. ==================== A/UX 3.1.1 and earlier support saved set-{user,group}-ids. A/UX 3.1.1 and earlier do not have Perl as part of the standard product. Data General Corporation ======================== Data General does support saved set-user-IDs and set-group-IDs on DG/UX. Data General does not ship suidperl or sperl* with DG/UX. Hewlett-Packard Company ======================= HP/UX versions 8.X, 9.X, and 10.X all support saved set-user-id. None of HP/UX versions 8.X, 9.X, and 10.X have Perl as part of the standard product. IBM Corporation =============== AIX versions 3.2.5 and 4.X support saved set-user-id. AIX versions 3.2.5 and 4.X do not have Perl as part of the standard product. However, the SP2's PSSP software does contain suidperl, but the program is not installed with the setuid bit set. Linux ===== Linux 1.2 and 2.0 support saved set-user-id. Most distributions of Linux provide suidperl and sperl. The fixsperl script works on linux, and it is recommended that this fix be applied until a new Perl release is made. Open Software Foundation ======================== OSF/1 1.3 or later support saved set-user-id OSF/1 1.3 or later does not have Perl as part of the standard product. Sony Corporation ================ NEWS-OS 4.X does not support saved set-user-id and therefore any version of Perl on that system is not vulnerable. NEWS-OS 6.X does support saved set-user-id. X.org ===== None of X.org's development systems are vulnerable to the saved set-user-IDs and set-group-IDs problems, and suidperl is not shipped with either of our products. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMdE8tnVP+x0t4w7BAQF2eQQAlpH/zOBMFK3/TQ+TAbfAkkULJORsvPTs Hv2aJtInooObGNlT8NThg+7DBOUTcNQ7allPtNRzDE9xIDsn/ZGQZSUMtuSiVqI5 F9vgXZgDFNMknRW35ae6E9zJ3R/FJGIVxQyA6BB2YhbyvnaMrzKqE0nGDy1GZsPl mhGAXh3CZYw= =o+Jl -----END PGP SIGNATURE-----