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FreeBSD Security Advisory FreeBSD-SA-02:39.libkvm


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Date: Mon, 16 Sep 2002 09:15:45 -0700 (PDT)
From: FreeBSD Security Advisories <security-advisories@freebsd.org.>
To: Bugtraq <bugtraq@securityfocus.com.>
Subject: FreeBSD Security Advisory FreeBSD-SA-02:39.libkvm

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FreeBSD-SA-02:39.libkvm Security Advisory The FreeBSD Project Topic: Applications using libkvm may leak sensitive descriptors Category: core Module: libkvm Announced: 2002-09-16 Credits: David Endler <DEndler@iDefense.com.>, <badc0ded@badc0ded.com.> Affects: All releases prior to and including 4.6.2-RELEASE. Security branch releases prior to 4.4-RELEASE-p27, 4.5-RELEASE-p20, and 4.6.2-RELEASE-p2. Corrected: 2002-09-13 14:53:43 UTC (RELENG_4) 2002-09-13 15:04:22 UTC (RELENG_4_6) 2002-09-13 15:07:26 UTC (RELENG_4_5) 2002-09-13 15:09:07 UTC (RELENG_4_4) FreeBSD only: NO I. Background The kvm(3) library provides a uniform interface for accessing kernel virtual memory images, including live systems and crash dumps. Access to live systems is via /dev/mem and /dev/kmem. Memory can be read and written, kernel symbol addresses can be looked up efficiently, and information about user processes can be gathered. The kvm_openfiles(3) function opens the special device files /dev/mem and /dev/kmem, and returns an opaque handle that must be passed to the other library functions. II. Problem Description Applications that wish to present system information such as swap utilization, virtual memory utilization, CPU utilization, and so on may use the kvm(3) library to read kernel memory directly and gather this information. Such applications typically must be run set-group-ID kmem so that the call to kvm_openfiles(3) can access /dev/mem and /dev/kmem. If the application then uses exec(2) to start another application, the new application will continue to have open file descriptors to /dev/mem and /dev/kmem. This is usually avoided by marking file descriptors as close-on-exec, but since the handle returned by kvm_openfiles(3) is opaque, there is no direct way for the application to determine what file descriptors have been opened by the library. As a result, application writers may neglect to take these file descriptors into account. III. Impact Set-group-ID kmem applications which use kvm(3) and start other applications may leak /dev/mem and /dev/kmem file descriptors. If those applications can be specified by a local user, they may be used to read kernel memory, resulting in disclosure of sensitive information such as file, network, and tty buffers, authentication tokens, and so on. Several applications in the FreeBSD Ports Collection were identified that are affected: asmon, ascpu, bubblemon, wmmon, and wmnet2. There may be other applications as well. IV. Workaround Remove the set-group-ID bit on affected applications. This will result in the applications losing some functionality. V. Solution Do one of the following: 1) Upgrade your vulnerable system to 4.6-STABLE; or to the RELENG_4_6, RELENG_4_5, or RELENG_4_4 security branch dated after the correction date (4.6.2-RELEASE-p2, 4.5-RELEASE-p20, or 4.4-RELEASE-p27). 2) To patch your present system: The following patch has been verified to apply to FreeBSD 4.4, FreeBSD 4.5, FreeBSD 4.6, and FreeBSD 4.6.2 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:39/libkvm.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:39/libkvm.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch # cd /usr/src/lib/libkvm # make depend && make && make install VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. Path Revision Branch - ------------------------------------------------------------------------- src/lib/libkvm/kvm.c RELENG_4 1.12.2.3 RELENG_4_6 1.12.2.2.8.1 RELENG_4_5 1.12.2.2.6.1 RELENG_4_4 1.12.2.2.4.1 src/sys/conf/newvers.sh RELENG_4_6 1.44.2.23.2.19 RELENG_4_5 1.44.2.20.2.21 RELENG_4_4 1.44.2.17.2.26 - ------------------------------------------------------------------------- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (FreeBSD) iQCVAwUBPYXz/1UuHi5z0oilAQGNGAP/cpg8s9L034EbrJriQDicHptv/2QgSnrw 2BvOaUXRIEweDz7FAoLstbxDFVE3Hx9+zN4gn7S49WIbFjATFRcL2FT/1yBhrbBx Yp20/gveFQSU+AnjsriKVDrH9ksBO4/ZX6lBxjvxD0Hbyj4ATd027jNAXl7WeLbq 2DN6Lf4FB1Y= =699Y -----END PGP SIGNATURE-----

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