Re: [squid-users] [UPDATED] Advisory SQUID-2010:1 - Denial of Service issue in DNS handling

Hi, Amos

> Workarounds:
>
> Using all of the following steps are required to protect a
> vulnerable Squid from this and other forms of DNS attack.
>
> * Ensuring the ignore_unknown_nameservers is turned on.
>
> * Ensuring that DNS packets cannot be sent to Squid from
> untrusted nameservers or other machines.
>
> The most secure implementation of these requirements is to use
> a nameserver running on the localhost IP dedicated for secure use
> by Squid and any other services on the Squid machine.

I'd like to make sure above. "The most secure implementation" mean that

 - The ignore_unknown_nameservers is turned on (default)

 - The /etc/resolv.conf on squid server is following
   nameserver 127.0.0.1

 - The localhost nameserver on squid server is just only cache
   server which is like BIND.

Is is correct ?

Sincerely,

--
Mikio Kishi
On Tue, Feb 2, 2010 at 7:33 PM, Amos Jeffries <squid3_at_treenet.co.nz> wrote:
> CHANGES from previous advisory:
>  * Corrected Squid-3.0 patch and release details.
>
> __________________________________________________________________
>
>      Squid Proxy Cache Security Update Advisory SQUID-2010:1
> __________________________________________________________________
>
> Advisory ID:            SQUID-2010:1
> Date:                   January 28, 2010
> Summary:                Denial of Service issue in DNS handling
> Affected versions:      Squid 2.x,
>                        Squid 3.0 -> 3.0.STABLE22,
>                        Squid 3.1 -> 3.1.0.15
> Fixed in version:       Squid 3.0.STABLE23, 3.1.0.16
> __________________________________________________________________
>
>     http://www.squid-cache.org/Advisories/SQUID-2010_1.txt
> __________________________________________________________________
>
> Problem Description:
>
>  Due to incorrect data validation Squid is vulnerable to a denial
>  of service attack when processing specially crafted DNS packets.
>
> __________________________________________________________________
>
> Severity:
>
>  This problem allows any trusted client or external server who can
>  determine the squid receiving port to perform a short-term denial
>  of service attack on the Squid service.
>
> __________________________________________________________________
>
> Updated Packages:
>
>  This bug is fixed by Squid versions 3.0.STABLE23 and 3.1.0.16
>
>  In addition, patches addressing these problems can be found In
>  our patch archives.
>
> Squid 2.x:
>  http://www.squid-cache.org/Versions/v2/HEAD/changesets/12597.patch
>
> Squid 3.0:
>  http://www.squid-cache.org/Versions/v3/3.0/changesets/squid-3.0-9163.patch
>
> Squid 3.1:
>  http://www.squid-cache.org/Versions/v3/3.1/changesets/squid-3.1-9853.patch
>
>  If you are using a prepackaged version of Squid then please refer
>  to the package vendor for availability information on updated
>  packages.
>
> __________________________________________________________________
>
> Determining if your version is vulnerable:
>
>  Squid still using the obsolete dnsserver are not vulnerable.
>
>  The ignore_unknown_nameservers option affects the severity of
>  this vulnerability. When set to "on" (the default) risk is low.
>  When set to "off" the vulnerability risk is increased.
>
>  All unpatched Squid-3.0 versions up to and including 3.0.STABLE22
>  are vulnerable.
>
>  All unpatched Squid-3.1 versions up to and including 3.1.0.15 are
>  vulnerable.
>
>  All unpatched Squid-2.x versions are vulnerable.
>
> __________________________________________________________________
>
> Workarounds:
>
>  Using all of the following steps are required to protect a
>  vulnerable Squid from this and other forms of DNS attack.
>
>  * Ensuring the ignore_unknown_nameservers is turned on.
>
>  * Ensuring that DNS packets cannot be sent to Squid from
>   untrusted nameservers or other machines.
>
>  The most secure implementation of these requirements is to use
>  a nameserver running on the localhost IP dedicated for secure use
>  by Squid and any other services on the Squid machine.
> __________________________________________________________________
>
> Contact details for the Squid project:
>
>  For installation / upgrade support on binary packaged versions
>  of Squid: Your first point of contact should be your binary
>  package vendor.
>
>  If your install and build Squid from the original Squid sources
>  then the squid-users_at_squid-cache.org mailing list is your primary
>  support point. For subscription details see
>  <http://www.squid-cache.org/Support/mailing-lists.html>.
>
>  For reporting of non-security bugs in the latest STABLE release
>  the squid bugzilla database should be used
>  <http://www.squid-cache.org/bugs/>.
>
>  For reporting of security sensitive bugs send an email to the
>  squid-bugs_at_squid-cache.org mailing list. It's a closed list
>  (though anyone can post) and security related bug reports are
>  treated in confidence until the impact has been established.
>
> __________________________________________________________________
>
> Credits:
>
>  Zero-Day attributed to work by Fabian Yamaguchi.
>
>  The vulnerability was reported by Tomas Hoger of RedHat.
>
> __________________________________________________________________
>
> Revision history:
>
>  2010-01-14 18:05 GMT Initial Report
>  2010-01-16 03:51 GMT Patches released.
>  2010-02-01 04:49 GMT Squid-3 bundled fixes and advisory released.
>  2010-02-02 07:42 GMT Updated 3.0 patch and bundle
> __________________________________________________________________
> END
>