-----BEGIN PGP SIGNED MESSAGE----- =============================================================================== Security Advisory CERT-NL =============================================================================== Author/Source : Don Stikvoort Index : S-97-21 Distribution : World Page : 1 Classification: External Version: 1 Subject : Solaris 2.x fdformat Buffer Overflow Date : 24-Mar-97 Vulnerability =============================================================================== By courtesy of AUSCERT and Christian Schipor (via BUGTRAQ) we received information on a vulnerability in Solaris 2.x fdformat, allowing for root access. CERT-NL recommends to apply the workaround suggested in AUSCERT's text below. ============================================================================== AA-97.11 AUSCERT Advisory Solaris 2.x fdformat Buffer Overflow Vulnerability 24 March 1997 Last Revised: -- - ---------------------------------------------------------------------------- AUSCERT has received information that a vulnerability exists in fdformat(1), distributed under Solaris 2.4, 2.5 and 2.5.1. Earlier versions may be vulnerable. This vulnerability may allow local users to gain root privileges. Exploit information involving this vulnerability has been made publicly available. At this stage, AUSCERT is unaware of any official vendor patches. AUSCERT recommends that sites apply the workaround given in Section 3 until vendor patches are made available. This advisory will be updated as more information becomes available. - ---------------------------------------------------------------------------- 1. Description fdformat(1) is a utility for formatting both diskettes and PCMCIA memory cards. Due to insufficient bounds checking on arguments which are supplied by users, it is possible to overwrite the internal stack space of the fdformat program while it is executing. By supplying a carefully designed argument to the fdformat program, intruders may be able to force fdformat to execute arbitrary commands. As fdformat is setuid root, this may allow intruders to run arbitrary commands with root privileges. Sites can determine if this program is installed by using: % ls -l /usr/bin/fdformat fdformat is installed by default in /usr/bin. Sites are encouraged to check for the presence of this program regardless of the version of Solaris installed. Exploit information involving this vulnerability has been made publicly available. Sun Microsystems has informed AUSCERT that they are currently working on this vulnerability. 2. Impact Local users may gain root privileges. 3. Workarounds/Solution AUSCERT recommends that sites prevent the exploitation of this vulnerability in fdformat by immediately applying the workaround given in Section 3.1. Currently there are no vendor patches available that address this vulnerability. AUSCERT recommends that official vendor patches be installed when they are made available. 3.1 Remove setuid execute permissions To prevent the exploitation of the vulnerability described in this advisory, AUSCERT recommends that the setuid permissions be removed from the fdformat program immediately. # ls -l /usr/bin/fdformat -r-sr-xr-x 1 root bin 26284 Oct 25 1995 /usr/bin/fdformat # chmod 555 /usr/bin/fdformat # ls -l /usr/bin/fdformat -r-xr-xr-x 1 root bin 26284 Oct 25 1995 /usr/bin/fdformat 4. Additional measures Most Unix systems ship with numerous programs which have setuid or setgid privileges. Often the functionality supplied by these privileged programs is not required by many sites. The large number of privileged programs that are shipped by default are to cater for all possible uses of the system. AUSCERT encourages sites to examine all the setuid/setgid programs and determine the necessity of each program. If a program does not absolutely require the setuid/setgid privileges to operate (for example, it is only run by the root user), the setuid/setgid privileges should be removed. Furthermore, if a program is not required at your site, then all execute permissions should be removed. A sample command to find all setuid/setgid programs is (run as root): # find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -l {} \; It is AUSCERT's experience that many vulnerability are being discovered in setuid/setgid programs which are not necessary for the correct operation of most systems. Sites can increase their security by removing unnecessary setuid/setgid programs. For example, the functionality provided by the fdformat program is not needed by many sites. If sites had previously disabled this program, they would not have been susceptible to this latest vulnerability. - ---------------------------------------------------------------------------- AUSCERT thanks to Sun Microsystems for their assistance in this matter. - ---------------------------------------------------------------------------- ============================================================================== 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: 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 Phone: +31 302 305 305 Fax: +31 302 305 329 Snailmail: SURFnet bv Attn. CERT-NL P.O. Box 19035 NL - 3501 DA UTRECHT The Netherlands A 7 * 24 hours phone number is available to SURFnet SSC's and FIRST members on request. ============================================================================== -----BEGIN PGP SIGNATURE----- Version: 2.6.2i iQCVAwUBMzZys0U5nQkWIq1FAQH79AQAulzP+dQ01zg0WC9uH7wHOv8iMYgAZXtG TF7OCW1kRxxuRLbbsjCV1K3UXqCUFaS2L7s7T+FLI/tdNCaaJG6HzGHcjjp3ygl0 +/8D93HqYI4dfOGLp/EiBVbRPIhufpJJB03KbkrmIBQh16vcneyV1CGDcqP+aPyf 5gNDvXkw5yE= =bSiU -----END PGP SIGNATURE-----