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Date: Thu, 04 Apr 2013 11:01:13 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Vincent Danen <vdanen@...hat.com>
Subject: Re: CVE request: rpc-gssd is vulnerable to DNS spoofing

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On 04/03/2013 04:43 PM, Vincent Danen wrote:
> This has been discussed on the linux-nfs mailing list, so fully
> public. Just cutting and pasting from our bugzilla:
> 
> It was reported [1],[2] that rpc.gssd in nfs-utils is vulnerable to
> DNS spoofing due to it depending on PTR resolution for GSSAPI 
> authentication.  Because of this, if a user where able to poison
> DNS to a victim's computer, they would be able to trick rpc.gssd
> into talking to another server (perhaps with less security) than
> the intended server (with stricter security).  If the victim has
> write access to the second (less secure) server, and the attacker
> has read access (when they normally might not on the secure
> server), the victim could write files to that server, which the
> attacker could obtain (when normally they would not be able to).
> To the victim this is transparent because the victim's computer
> asks the KDC for a ticket to the second server due to reverse DNS
> resolution; in this case Krb5 authentication does not fail because
> the victim is talking to the "correct" server.
> 
> A patch that prevents this issue has been posted [3].
> 
> To workaround this issue, set the IP/host pair in /etc/hosts so
> that it cannot be spoofed.
> 
> A good explanation is also available here [4].
> 
> [1] http://marc.info/?l=linux-nfs&m=136491998607561&w=2 [2]
> http://marc.info/?l=linux-nfs&m=136500502805121&w=2 [3]
> http://marc.info/?l=linux-nfs&m=136493115612397&w=2 [4]
> http://ssimo.org/blog/id_015.html
> 
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=948072
> 
> 
> Since this is fairly new, I don't think a CVE would have been
> requested already.  Could one be assigned to this?

Please use CVE-2013-1923 for this issue.


- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
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