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UNIRAS Brief - 382/06 - FreeBSD - Vulnerabilities in ypserv and smbfs



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   UNIRAS (UK Govt CERT) Briefing Notice - 382/06 dated 05.06.06  Time: 10:01  
  UNIRAS is part of NISCC (National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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Title
=====
FreeBSD Security Advisories:
Inoperative access controls in ypserv(8)
smbfs chroot escape

Detail
====== 

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=============================================================================
FreeBSD-SA-06:15.ypserv                                     Security Advisory
                                                          The FreeBSD Project

Topic:          Inoperative access controls in ypserv(8)

Category:       core
Module:         ypserv
Announced:      2006-05-31
Credits:        Hokan
Affects:        All FreeBSD 5.x and FreeBSD 6.x releases
Corrected:      2006-05-31 22:31:21 UTC (RELENG_6, 6.1-STABLE)
                2006-05-31 22:31:42 UTC (RELENG_6_1, 6.1-RELEASE-p1)
                2006-05-31 22:32:04 UTC (RELENG_6_0, 6.0-RELEASE-p8)
                2006-05-31 22:32:22 UTC (RELENG_5, 5.5-STABLE)
                2006-05-31 22:32:49 UTC (RELENG_5_5, 5.5-RELEASE-p1)
                2006-05-31 22:33:17 UTC (RELENG_5_4, 5.4-RELEASE-p15)
                2006-05-31 22:33:41 UTC (RELENG_5_3, 5.3-RELEASE-p30)
CVE Name:       CVE-2006-2655

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

The ypserv(8) utility is a server which distributes NIS databases to client
systems within an NIS domain.

II.  Problem Description

There are two documented methods of restricting access to NIS maps through
ypserv(8): through the use of the /var/yp/securenets file, and through the
/etc/hosts.allow file.  While both mechanisms are implemented in the server,
a change in the build process caused the "securenets" access restrictions
to be inadvertantly disabled.

III. Impact

ypserv(8) will not load or process any of the networks or hosts specified in
the /var/yp/securenets file, rendering those access controls ineffective.

IV.  Workaround

One possible workaround is to use /etc/hosts.allow for access control, as
shown by examples in that file.

Another workaround is to use a firewall (e.g., ipfw(4), ipf(4), or pf(4))
to limit access to RPC functions from untrusted systems or networks, but
due to the complexities of RPC, it might be difficult to create a set of
firewall rules which accomplish this without blocking all access to the
machine in question.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE or 6-STABLE, or to the
RELENG_6_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, or RELENG_5_3 security
branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 5.3, 5.4,
5.5, 6.0, and 6.1 systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch http://security.FreeBSD.org/patches/SA-06:15/ypserv.patch
# fetch http://security.FreeBSD.org/patches/SA-06:15/ypserv.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/usr.sbin/ypserv
# make obj && make depend && make && make install

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- - -------------------------------------------------------------------------
RELENG_5
  src/usr.sbin/ypserv/yp_access.c                                1.22.6.1
RELENG_5_5
  src/UPDATING                                             1.342.2.35.2.1
  src/sys/conf/newvers.sh                                   1.62.2.21.2.3
  src/usr.sbin/ypserv/yp_access.c                               1.22.18.1
RELENG_5_4
  src/UPDATING                                            1.342.2.24.2.24
  src/sys/conf/newvers.sh                                  1.62.2.18.2.20
  src/usr.sbin/ypserv/yp_access.c                               1.22.10.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.33
  src/sys/conf/newvers.sh                                  1.62.2.15.2.35
  src/usr.sbin/ypserv/yp_access.c                                1.22.8.1
RELENG_6
  src/usr.sbin/ypserv/yp_access.c                               1.22.12.1
RELENG_6_1
  src/UPDATING                                             1.416.2.22.2.3
  src/sys/conf/newvers.sh                                   1.69.2.11.2.3
  src/usr.sbin/ypserv/yp_access.c                               1.22.16.1
RELENG_6_0
  src/UPDATING                                             1.416.2.3.2.13
  src/sys/conf/newvers.sh                                    1.69.2.8.2.9
  src/usr.sbin/ypserv/yp_access.c                               1.22.14.1
- - -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2655

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-06:15.ypserv.asc
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=============================================================================
FreeBSD-SA-06:16.smbfs                                      Security Advisory
                                                          The FreeBSD Project

Topic:          smbfs chroot escape

Category:       core
Module:         smbfs
Announced:      2006-05-31
Credits:        Mark Moseley
Affects:        All FreeBSD releases.
Corrected:      2006-05-31 22:31:21 UTC (RELENG_6, 6.1-STABLE)
                2006-05-31 22:31:42 UTC (RELENG_6_1, 6.1-RELEASE-p1)
                2006-05-31 22:32:04 UTC (RELENG_6_0, 6.0-RELEASE-p8)
                2006-05-31 22:32:22 UTC (RELENG_5, 5.5-STABLE)
                2006-05-31 22:32:49 UTC (RELENG_5_5, 5.5-RELEASE-p1)
                2006-05-31 22:33:17 UTC (RELENG_5_4, 5.4-RELEASE-p15)
                2006-05-31 22:33:41 UTC (RELENG_5_3, 5.3-RELEASE-p30)
                2006-05-31 22:34:32 UTC (RELENG_4, 4.11-STABLE)
                2006-05-31 22:34:53 UTC (RELENG_4_11, 4.11-RELEASE-p18)
                2006-05-31 22:35:32 UTC (RELENG_4_10, 4.10-RELEASE-p24)
CVE Name:       CVE-2006-2654

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

smbfs is a network file-system used to access file servers using the
SMB/CIFS protocol.  chroot(2) is system call designed to limit a
process's access to a particular subset of a file-system.

II.  Problem Description

smbfs does not properly sanitize paths containing a backslash
character; in particular the directory name '..\' is interpreted as
the parent directory by the SMB/CIFS server, but smbfs handles it in
the same manner as any other directory.

III. Impact

When inside a chroot environment which resides on a smbfs mounted
file-system it is possible for an attacker to escape out of this
chroot to any other directory on the smbfs mounted file-system.

IV.  Workaround

Mount the smbfs file-systems which need to be used with chroot on top,
in a way so the chroot directory is exactly on the mount point and not
a sub directory.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, RELENG_5_3,
RELENG_4_11, or RELENG_4_10 security branch dated after the correction
date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.10,
4.11, 5.3, 5.4, 5.5, 6.0, and 6.1 systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch http://security.FreeBSD.org/patches/SA-06:16/smbfs.patch
# fetch http://security.FreeBSD.org/patches/SA-06:16/smbfs.patch.asc

b) Apply the patch.

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- - -------------------------------------------------------------------------
RELENG_4
  src/sys/fs/smbfs/smbfs_vnops.c                                 1.2.2.11
RELENG_4_11
  src/UPDATING                                             1.73.2.91.2.19
  src/sys/conf/newvers.sh                                  1.44.2.39.2.22
  src/sys/fs/smbfs/smbfs_vnops.c                             1.2.2.10.4.1
RELENG_4_10
  src/UPDATING                                             1.73.2.90.2.25
  src/sys/conf/newvers.sh                                  1.44.2.34.2.26
  src/sys/fs/smbfs/smbfs_vnops.c                             1.2.2.10.2.1
RELENG_5
  src/sys/fs/smbfs/smbfs_vnops.c                                 1.46.2.2
RELENG_5_5
  src/UPDATING                                             1.342.2.35.2.1
  src/sys/conf/newvers.sh                                   1.62.2.21.2.3
  src/sys/fs/smbfs/smbfs_vnops.c                             1.46.2.1.4.1
RELENG_5_4
  src/UPDATING                                            1.342.2.24.2.24
  src/sys/conf/newvers.sh                                  1.62.2.18.2.20
  src/sys/fs/smbfs/smbfs_vnops.c                             1.46.2.1.2.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.33
  src/sys/conf/newvers.sh                                  1.62.2.15.2.35
  src/sys/fs/smbfs/smbfs_vnops.c                                 1.46.4.1
RELENG_6
  src/sys/fs/smbfs/smbfs_vnops.c                                 1.61.2.2
RELENG_6_1
  src/UPDATING                                             1.416.2.22.2.3
  src/sys/conf/newvers.sh                                   1.69.2.11.2.3
  src/sys/fs/smbfs/smbfs_vnops.c                             1.61.2.1.2.1
RELENG_6_0
  src/UPDATING                                             1.416.2.3.2.13
  src/sys/conf/newvers.sh                                    1.69.2.8.2.9
  src/sys/fs/smbfs/smbfs_vnops.c                                 1.61.4.1
- - -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2654

The following three references correspond to independent bugs which
affect the Linux kernel but have the same impact:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-1863
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-1864
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=189434

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-06:16.smbfs.asc
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UNIRAS wishes to acknowledge the contributions of FreeBSD for the information 
contained in this Briefing. 
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This Briefing contains the information released by the original author. Some 
of the information may have changed since it was released. If the vulnerability 
affects you, it may be prudent to retrieve the advisory from the site of the
original source to ensure that you receive the most current information concerning 
that problem.

Reference to any specific commercial product, process, or service by trade 
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not be liable for any loss or damage whatsoever, arising from or in connection 
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and has contacts with other international Incident Response Teams (IRTs) in 
order to foster cooperation and coordination in incident prevention, to prompt 
rapid reaction to incidents, and to promote information sharing amongst its 
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<End of UNIRAS Briefing>

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