FreeBSD Security Advisory FreeBSD-SA-02:28.resolv

Type securityvulns
Reporter Securityvulns
Modified 2002-06-28T00:00:00



============================================================================= FreeBSD-SA-02:28.resolv Security Advisory The FreeBSD Project

Topic: buffer overflow in resolver

Category: core Module: libc Announced: 2002-06-26 Credits: Joost Pol <> Affects: All releases prior to and including 4.6-RELEASE Corrected: 2002-06-26 06:34:18 UTC (RELENG_4) 2002-06-26 08:44:24 UTC (RELENG_4_6) 2002-06-26 18:53:20 UTC (RELENG_4_5) FreeBSD only: NO

I. Background

The resolver implements functions for making, sending and interpreting query and reply messages with Internet domain name servers. Hostnames, IP addresses, and other information are queried using the resolver.

II. Problem Description

DNS messages have specific byte alignment requirements, resulting in padding in messages. In a few instances in the resolver code, this padding is not taken into account when computing available buffer space. As a result, the parsing of a DNS message may result in a buffer overrun of up to a few bytes for each record included in the message.

III. Impact

An attacker (either a malicious domain name server or an agent that can spoof DNS messages) may produce a specially crafted DNS message that will exploit this bug when parsed by an application using the resolver. It may be possible for such an exploit to result in the execution of arbitrary code with the privileges of the resolver-using application. Though no exploits are known to exist today, since practically all Internet applications utilize the resolver, the severity of this issue is high.

IV. Workaround

There is currently no workaround.

V. Solution

Do one of the following:

1) Upgrade your vulnerable system to 4.6-STABLE; or to the RELENG_4_6 or RELENG_4_5 security branch dated after the correction date (4.6-RELEASE-p1 or 4.5-RELEASE-p7).

2) To patch your present system:

The following patch has been verified to apply to FreeBSD 4.5 and FreeBSD 4.6 systems.

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



b) Execute the following commands as root:

cd /usr/src

patch < /path/to/patch

c) Recompile the operating systems as described in <URL:>.

Note that any statically linked applications that are not part of the base system (i.e. from the Ports Collection or other 3rd-party sources) must be recompiled.

VI. Correction details

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

Path Revision Branch

src/lib/libc/net/gethostbydns.c RELENG_4 RELENG_4_6 RELENG_4_5 src/lib/libc/net/getnetbydns.c RELENG_4 RELENG_4_6 RELENG_4_5 src/lib/libc/net/name6.c RELENG_4 RELENG_4_6 RELENG_4_5 src/sys/conf/ RELENG_4_6 RELENG_4_5

VII. References

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