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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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