-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =============================================================================== >> CERT-NL, 01-Mar-2000 << >> All CERT-NL information has been moved to http://cert.surfnet.nl. Links << >> to CERT-NL information contained in this advisory are therefore outdated. << >> << >> CERT-NL also has stopped the CERT-CC-Mirror service. Due to this the << >> links to the CERT-CC mirror are obsolete. Visit the CERT-CC site for the << >> complete CERT-CC advisory texts: http://www.cert.org << =============================================================================== =============================================================================== Security Advisory CERT-NL =============================================================================== Author/Source : CERT-NL (Gert Meijerink) Index : S-94-07 Distribution : World Page : 1 Classification: External Version: Final Subject : Writable /etc/utmp Vulnerability Date : 01-Apr-94 =============================================================================== CERT-NL received information on a vulnerability that exists on systems where the file /etc/utmp is writable by any user on the system The vulnerability is being actively exploited, so take care. All honours to CERT/CC as provider of the following information (slightly abridged version): =============================================================================== The CERT Coordination Center has received information concerning a vulnerability that exists on systems where the file /etc/utmp is writable by any user on the system. This vulnerability is being actively exploited; please review: CERT-NL Advisory S-94-02 "Ongoing Network Monitoring Attacks". The problem is known to affect Sun Microsystems, Inc. SunOS 4.1.X operating systems. Solbourne Computer, Inc. and other Sparc products using SunOS 4.1.X are also affected. Solaris 1.1.1 and 2.x are not affected by this problem. Patches can be obtained from local Sun Answer Centers worldwide as well as through anonymous FTP from: ftp.nic.surfnet.nl in the surfnet/net-security/cert-nl/patches/sun-fixes directory. CERT queried several vendors in addition to Sun. The following vendors reported that their operating systems, as distributed by the vendor, are not affected by this problem: Convex Computer Corporation Digital Equipment Corporation Data General Corporation Hewlett-Packard Company IBM Intergraph Motorola, Inc. NeXT, Inc. Pyramid Technology Corporation Sequent Computer Systems Sony Corporation Currently, we are not aware of /etc/utmp being writable on other systems. If your operating system is not explicitly mentioned above, and if you determine that /etc/utmp is writable by someone other than root, we encourage you to contact your vendor. If /etc/utmp on your system is writable only by the root account, you need not be concerned about the vulnerability. CERT recommends that sites check their /etc/utmp file to be sure it is not writable by users other than root. If it is generally writable, you should obtain patches from the system vendor or protect /etc/utmp as described below. - ----------------------------------------------------------------------------- I. Description If the file /etc/utmp is writable by users other than root, programs that trust the information stored in that file can be subverted. II. Impact This vulnerability allows anyone with access to a user account to gain root access. III. Solution The solutions to this vulnerability are to either (a) protect the file, or (b) patch all the programs that trust it. A. To protect the file, make /etc/utmp writable only by root: # chown root /etc/utmp # chmod 644 /etc/utmp B. Patches from Sun Microsystems Program Patch ID Patch File Name ------- --------- --------------- in.comsat 100272-07 100272-07.tar.Z dump 100593-03 100593-03.tar.Z syslogd 100909-02 100909-02.tar.Z in.talkd 101480-01 101480-01.tar.Z shutdown 101481-01 101481-01.tar.Z write 101482-01 101482-01.tar.Z Program BSD SVR4 MD5 Digital Signature Checksum Checksum ------- --------- --------- -------------------------------- in.comsat 26553 39 64651 78 912ff4a0cc8d16a10eecbd7be102d45c dump 52095 242 41650 484 cdba530226e8735fae2bd9bcbfa47dd0 syslogd 61539 108 38239 216 b5f70772384a3e58678c9c1f52d81190 in.talkd 47917 44 32598 88 5c3dfd6f90f739100cfa4aa4c97f01df shutdown 46562 80 56079 159 bfc257ec795d05646ffa733d1c03855b write 61148 41 48636 81 f93276529aa9fc25b35679ebf00b2d6f ============================================================================== CERT-NL is the Computer Emergency Response Team for SURFnet customers. SURFnet is the Dutch network for educational, research and related institutes. CERT-NL is a member of the Forum of Incident Response and Security Teams (FIRST). All CERT-NL material is available under: http://cert.surfnet.nl/ In case of computer or network security problems please contact your local CERT/security-team or CERT-NL (if your institute is NOT a SURFnet customer please address the appropriate (local) CERT/security-team). CERT-NL is one/two hour(s) ahead of UTC (GMT) in winter/summer, i.e. UTC+0100 in winter and UTC+0200 in summer (DST). Email: cert-nl@surfnet.nl ATTENDED REGULARLY ALL DAYS Phone: +31 302 305 305 BUSINESS HOURS ONLY Fax: +31 302 305 329 BUSINESS HOURS ONLY Snailmail: SURFnet bv Attn. CERT-NL P.O. Box 19035 NL - 3501 DA UTRECHT The Netherlands NOODGEVALLEN: 06 22 92 35 64 ALTIJD BEREIKBAAR EMERGENCIES : +31 6 22 92 35 64 ATTENDED AT ALL TIMES CERT-NL'S EMERGENCY PHONENUMBER IS ONLY TO BE USED IN CASE OF EMERGENCIES: THE SURFNET HELPDESK OPERATING THE EMERGENCY NUMBER HAS A *FIXED* PROCEDURE FOR DEALING WITH YOUR ALERT AND WILL IN REGULAR CASES RELAY IT TO CERT-NL IN AN APPROPRIATE MANNER. CERT-NL WILL THEN CONTACT YOU. =============================================================================== -----BEGIN PGP SIGNATURE----- Version: PGP 6.5.1i iQA/AwUBOL6WETSYjBqwfc9jEQJ0sgCfanhY4PqVRcdZS3v6LHnQhcFc0zQAoM7Y FbtgEqEZgEp2R38K7zuEEMDB =j+Rr -----END PGP SIGNATURE-----