Date: Thu Nov 21 12:03:19 PST 1991 Subject: Security Digest V3 #15 Security Digest Volume 3 Issue 15 subject(s): undesirable ftpd behavior errata for "Practical Unix Security" CERT Advisory - AIX TFTP Daemon Vulnerability CERT Advisory - /usr/ucb/rdist Vulnerability The unix security mailing list is by invitation only and often contains sensitive material which IS NOT INTENDED FOR PUBLIC DISSEMINATION. PLEASE DO NOT PUT ANY SECURITY LIST CONTENTS IN LOCATIONS ACCESSABLE TO NON-MEMBERS. PLEASE SEND NEW SECURITY HOLES TO: holes@uninet.cpd.com PLEASE POST NORMAL MESSAGES TO: security@uninet.cpd.com PLEASE SEND EMERGENCY ALERTS TO: security-emergency@uninet.cpd.com PLEASE SEND REQUESTS TO: security-request@uninet.cpd.com Postings that describe security holes/fixes have a * in their subject. ------------------------------------------------------------------------ Date: Wed, 02 Oct 91 08:11:00 EDT From: Thomas Narten Subject: undesirable ftpd behavior I don't believe I have seen this discussed here before, if so, please ignore this message. Sun's (and old Berkeley versions) of ftpd do not tinker with umask. Result: ftp's "put" command may create files with world write permissions. On our SunOS 4.1 system, ftpd is started by inetd, which is started at boot time in the /etc/rc file. The problem is that because ftpd doesn't set the umask, it inherits it from init. On our machines, the result is that ftpd creates new files with world read and write permissions. The simple fix is to add an explicit umask() call in ftpd. The latest version of ftpd on ucbarpa.berkeley.edu (5.1) appears to have fixed this problem. However, the ftpd distributed with SunOS 4.1.1 does have the problem. Older versions of Berkeley ftpd (we were running version 4.1) also have the problem. No doubt, many other vendor's ftpds will display this feature. Thomas Narten ------------------------------------------------------------------------ Date: Sun, 6 Oct 91 18:22:05 PDT From: irving@happy-man.com Subject: errata for "Practical Unix Security" > [ A highly recomended book. - neil ] Neil, I'd be happy to put together a group order that would let me re-sell them at a discount of close to 20%, postage included. I once made a similar offer to the Perl newsgroup and saved quite a few people $5 and some inconvenience. If you think it would fly here, I'll come up with an exact price. Irving_Wolfe@happy-man.com Happy Man Corp. 206/463-9399 x101 4410 SW Pt. Robinson Rd., Vashon Island, WA 98070-7399 fax x108 ------------------------------------------------------------------------ Date: Thu, 17 Oct 91 16:42:51 EDT From: CERT Advisory Subject: CERT Advisory - AIX TFTP Daemon Vulnerability CA-91:19 CERT Advisory October 17, 1991 AIX TFTP Daemon Vulnerability The Computer Emergency Response Team/Coordination Center (CERT/CC) has received information concerning a vulnerability in the TFTP daemon in all versions of AIX for IBM RS/6000 machines. IBM is aware of this problem and a fix is available as apar number "ix22628". This patch is available for all AIX releases from "GOLD" to the current release. NOTE: THIS IS AN UPDATED PATCH FROM ONE RECENTLY MADE AVAILABLE and fixes a security hole in the original patch. The SCCS id of the correct patch is tftpd.c 1.13.1.3 (*not* 1.13.1.2 or earlier versions). This can be checked using the following "what" command. % what /etc/tftpd /etc/tftpd: 56 1.13.1.3 tftpd.c, tcpip, tcpip312 10/10/91 09:01:48 tftpsubs.c 1.2 com/sockcmd/tftpd,3.1.2,9048312 10/8/89 17:40:55 IBM customers may call IBM Support (800-237-5511) and ask that the fix be shipped to them. The fix will appear in the upcoming 2009 update and the next release of AIX. I. Description Previous versions of tftpd did not provide a method for restricting TFTP access. II. Impact If TFTP is enabled at your site, anyone on the Internet can retrieve copies of your site's world-readable files, such as /etc/passwd. III. Solution A. Sites that do not need to allow tftp access should disable it. This can be done by editing /etc/inetd.conf and deleting or commenting out the tftpd line: #tftp dgram udp wait nobody /etc/tftpd tftpd -n and then, as root, restarting inetd with the "refresh" command. # refresh -s inetd For more details on starting/stopping tftp, refer to documentation for the System Resource Controller (SRC) or the System Management Interface Tool (SMIT). B. Sites that must run tftpd (for example, to support X terminals) should obtain and install the above patch AND create a /etc/tftpaccess.ctl file to restrict the files that are accessible. The /etc/tftpaccess.ctl file should be writable only by root. Although the new /etc/tftpaccess.ctl mechanism provides a very general capability, the CERT/CC strongly recommends that sites keep this control file simple. For example, the following tftpaccess.ctl file is all that is necessary to support IBM X terminals: # /etc/tftpaccess.ctl # By default, all files are restricted if /etc/tftpaccess.ctl exists. # Allow access to X terminal files. allow:/usr/lpp/x_st_mgr/bin NOTE: Be CERTAIN to create the /etc/tftpaccess.ctl file. If it does not exist then all world-readable files are accessible as in the current version of tftpd. Installation Instructions: 1. Create an appropriate /etc/tftpaccess.ctl file. 2. From the directory containing the new tftpd module, issue the following commands as root. # chmod 644 /etc/tftpaccess.ctl # chown root.system /etc/tftpaccess.ctl # mv /etc/tftpd /etc/tftpd.old # cp tftpd /etc # chmod 755 /etc/tftpd # chown root.system /etc/tftpd # refresh -s inetd The CERT/CC wishes to thank Karl Swartz of the Stanford Linear Accelerator Center for bringing this vulnerability to our attention. If you believe that your system has been compromised, contact CERT/CC via telephone or e-mail. Computer Emergency Response Team/Coordination Center (CERT/CC) Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 Internet E-mail: cert@cert.sei.cmu.edu Telephone: 412-268-7090 24-hour hotline: CERT/CC personnel answer 7:30a.m.-6:00p.m. EST/EDT, on call for emergencies during other hours. Past advisories and other computer security related information are available for anonymous ftp from the cert.sei.cmu.edu (192.88.209.5) system. ------------------------------------------------------------------------ Date: Tue, 22 Oct 91 13:05:02 EDT From: CERT Advisory Subject: CERT Advisory - /usr/ucb/rdist Vulnerability CA-91:20 CERT Advisory October 22, 1991 /usr/ucb/rdist Vulnerability The Computer Emergency Response Team/Coordination Center (CERT/CC) has received information concerning a vulnerability in /usr/ucb/rdist (the location of rdist may vary depending on the operating system). This vulnerability is present in possibly all versions of rdist. Vendors responding with patches are listed below. Additionally, some vendors who do not include rdist in their operating systems are identified. Operating systems from vendors not listed in either of the two categories below will probably be affected and the CERT/CC has proposed a workaround for those systems. VENDORS THAT DO NOT SHIP rdist (Note: Even though these vendors do not ship rdist, it may have been added later (for example, by the system administrator). It is also possible that vendors porting one of these operating systems may have added rdist. In both cases corrective action must be taken.) Amdahl AT&T System V Data General DG/UX for AViiON Systems VENDORS PROVIDING PATCHES Cray Research, Inc. UNICOS 6.0/6.E/6.1 Field Alert #132 SPR 47600 For further information contact the Support Center at 1-800-950-CRAY or 612-683-5600 or e-mail support@crayamid.cray.com. NeXT Computer, Inc. NeXTstep Release 2.x A new version of rdist may be obtained from your authorized NeXT Support Center. If you are an authorized support center, please contact NeXT through your normal channels. NeXT also plans to make this new version of rdist available on the public NeXT FTP archives. Silicon Graphics IRIX 3.3.x/4.0 (fixed in 4.0.1) Patches may be obtained via anonymous ftp from sgi.com in the sgi/rdist directory. Sun Microsystems, Inc. SunOS 4.0.3/4.1/4.1.1 Patch ID 100383-02 Patches may be obtained via anonymous ftp from ftp.uu.net or from local Sun Answer Centers worldwide. The CERT/CC is hopeful that other patches will be forthcoming. We will be maintaining a status file, rdist-patch-status, on the cert.sei.cmu.edu system. We will add patch availability information to this file as it becomes known. The file is available via anonymous ftp to cert.sei.cmu.edu and is found in pub/cert_advisories/rdist-patch-status. All trademarks are the property of their respective holders. I. Description A security vulnerability exists in /usr/ucb/rdist that can be used to gain unauthorized privileges. Under some circumstances /usr/ucb/rdist can be used to create setuid root programs. II. Impact Any user logged into the system can gain root access. III. Solution A. If available, install the appropriate patch provided by your operating system vendor. B. If no patch is available, restrict the use of /usr/ucb/rdist by changing the permissions on the file. # chmod 711 /usr/ucb/rdist The CERT/CC wishes to thank Casper Dik of the University of Amsterdam, The Netherlands, for bringing this vulnerability to our attention. We would also like to thank the vendors who have responded to this problem. If you believe that your system has been compromised, contact CERT/CC via telephone or e-mail. Computer Emergency Response Team/Coordination Center (CERT/CC) Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 Internet E-mail: cert@cert.sei.cmu.edu Telephone: 412-268-7090 24-hour hotline: CERT/CC personnel answer 7:30a.m.-6:00p.m. EST(GMT-5)/EDT(GMT-4), on call for emergencies during other hours. Past advisories and other computer security related information are available for anonymous ftp from the cert.sei.cmu.edu (192.88.209.5) system. ------------------------------------------------------------------------ End of Security Digest Volume 3 Issue 15 **********************