-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NetBSD Security Advisory 2006-027 ================================= Topic: libc glob(3) buffer overflow Version: NetBSD-current: source prior to September 13, 2005 NetBSD 4.0_BETA2: not affected NetBSD 3.1: affected NetBSD 3.0.*: affected NetBSD 3.0: affected NetBSD 2.1: affected NetBSD 2.0.*: affected NetBSD 2.0: affected pkgsrc: 20040810 and earlier Severity: Potential remote root for systems providing the ftpd service with a custom configuration. Fixed: NetBSD-current: September 13, 2005 NetBSD-3-0 branch: December 2, 2006 NetBSD-3 branch: December 2, 2006 NetBSD-2-1 branch: December 2, 2006 NetBSD-2-0 branch: December 2, 2006 NetBSD-2 branch: December 2, 2006 pkgsrc: tnftpd-20040810nb1 corrects this issue Abstract ======== A flaw in glob(3) could potentially allow for the execution of untrusted code. Currently the NetBSD ftp daemon that ships with the base distribution uses glob(3) which has been found to be potentially vulnerable to attack. In addition to this there may be other applications/network services which use glob(3) which are also potentially vulnerable. In the case of ftpd the server must be configured to allow remote users to create directories in order for attackers to exploit this issue. Technical Details ================= The limit computation of an internal buffer was done incorrectly. The size of the buffer in byte was used as element count, even though the elements of the buffer are 2 bytes long. Long expanded path names would therefore overflow the buffer. Solutions and Workarounds ========================= * Determining if you could be vulnerable (inetd): By default ftpd is not enabled in the default install of NetBSD. To confirm if the host in question is running ftpd, check the ftp entries in /etc/inetd.conf. By default, the entries look like this: #ftp stream tcp nowait root /usr/libexec/ftpd ftpd -ll #ftp stream tcp6 nowait root /usr/libexec/ftpd ftpd -ll If the comment character (#) has been removed from the start of the lines, then ftpd has been enabled on this host. Hosts not running ftpd are not vulnerable, but libc should be updated to prevent future exposure if ftpd is enabled at a later date. * Disable ftpd (inetd): As root, comment out the ftp lines in /etc/inetd.conf, and execute the following command to disable ftpd: % /etc/rc.d/inetd reload * Determining if you could be vulnerable (standalone): On NetBSD-current it is also possible to run ftpd in standalone mode by adding the following to rc.conf: ftpd=YES If this entry exists then ftpd is being run in standalone mode. * Disable ftpd (standalone): As root, comment out the ftpd line in rc.conf, and execute the following command to disable ftpd: % /etc/rc.d/ftpd forcestop * Limit directory creation: Another possible workaround is to not allow remote users to create directories of their choice on the ftpd server. * Directory names: If you allow users to create directories of their own choice check for very long directory names. * Drop root privileges: As root, add -r to the command line options for any ftp entry in /etc/inetd.conf. Then run: % /etc/rc.d/inetd reload This option may not be acceptable at all sites, since client compatibility issues are possible. See the ftpd(8) man page for more details about -r. The following instructions describe how to upgrade your libc binaries by updating your source tree and rebuilding and installing a new version of libc. * NetBSD-current: Systems running NetBSD-current dated from before 2005-09-13 should be upgraded to NetBSD-current dated 2005-09-14 or later. The following files need to be updated from CVS HEAD: lib/libc/gen/glob.c To update from CVS, re-build, and re-install libc: # cd src # cvs update lib/libc/gen/glob.c # cd lib/libc # make USETOOLS=no cleandir dependall # make USETOOLS=no install # cd ../../libexec/ftpd # make USETOOLS=no cleandir dependall # make USETOOLS=no install * NetBSD 3.*: Systems running NetBSD 3.* sources dated from before 2006-12-02 should be upgraded from NetBSD 3.* sources dated 2006-12-03 or later. The following files need to be updated from the netbsd-3, netbsd-3-0, netbsd-3-1 CVS branches: lib/libc/gen/__glob13.c To update from CVS, re-build, and re-install libc: # cd src # cvs update lib/libc/gen/__glob13.c # cd lib/libc # make USETOOLS=no cleandir dependall # make USETOOLS=no install # cd ../../libexec/ftpd # make USETOOLS=no cleandir dependall # make USETOOLS=no install * NetBSD 2.*: Systems running NetBSD 2.* sources dated from before 2006-12-02 should be upgraded from NetBSD 2.* sources dated 2006-12-03 or later. The following files need to be updated from the netbsd-2, netbsd-2-0 or netbsd-2-1 CVS branches: lib/libc/gen/__glob13.c To update from CVS, re-build, and re-install libc: # cd src # cvs update lib/libc/gen/__glob13.c # cd lib/libc # make USETOOLS=no cleandir dependall # make USETOOLS=no install # cd ../../libexec/ftpd # make USETOOLS=no cleandir dependall # make USETOOLS=no install Thanks To ========= Tomas Skare for reporting this issue and the initial analysis. Revision History ================ 2006-12-14 Initial release More Information ================ Advisories may be updated as new information becomes available. The most recent version of this advisory (PGP signed) can be found at ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2006-027.txt.asc Information about NetBSD and NetBSD security can be found at http://www.NetBSD.org/ and http://www.NetBSD.org/Security/. Copyright 2006, The NetBSD Foundation, Inc. All Rights Reserved. Redistribution permitted only in full, unmodified form. $NetBSD: NetBSD-SA2006-027.txt,v 1.4 2006/12/14 20:13:16 adrianp Exp $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (NetBSD) iQCVAwUBRYGx2T5Ru2/4N2IFAQJbLAQAhHlwMkZdBnPhI2hFnp89DkfXvrDDQF8h i0R4kO1BpLLFUmFfwNyQeNbRPLvfO6L5XNXMo03xAoXvbm/idhcIBXc14aysP1zG g9HnRmthejogSI96KDtng/AWBWl3qMxIALTaOqe6uhQrYIqPbi+ITyKx3YB/gbO9 SJ28zBZQcQ0= =4daO -----END PGP SIGNATURE-----