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Date:      Mon, 18 Feb 2008 10:23:14 -0800
From:      Wes Peters <wes@opensail.org>
To:        Guy Helmer <ghelmer@palisadesys.com>
Cc:        src-committers@FreeBSD.org, d@delphij.net, ache@nagual.pp.ru, cvs-all@FreeBSD.org, delphij@FreeBSD.org, cvs-src@FreeBSD.org, "M. Warner Losh" <imp@bsdimp.com>
Subject:   Re: cvs commit: src/lib/libc/resolv res_comp.c
Message-ID:  <F9A908A1-6C73-45EE-BCD1-43AC5A37FF45@opensail.org>
In-Reply-To: <47B99880.1060306@palisadesys.com>
References:  <200802160016.m1G0GnFB046558@repoman.freebsd.org>	<20080216024541.GA31498@nagual.pp.ru> <20080215.233427.1598351542.imp@bsdimp.com> <47B7746A.8080403@delphij.net> <47B99880.1060306@palisadesys.com>

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On Feb 18, 2008, at 6:38 AM, Guy Helmer wrote:

> Xin LI wrote:
>>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> M. Warner Losh wrote:
>> I don't think it would be the end of world if we allow _ in host  
>> names.
>> All other (lame) OSes allows it, their resolver just accepts this
>> character and give the answer, actually, I would be very surprised  
>> if it
>> can still cause any real world attack nowadays.
>>
> Are we talking about hostnames specifically, or domain name  
> components in general?
>
> I've been recently looking at DomainKeys, and underscores appear to  
> be typically used in the domain components for domain keys TXT  
> records (example below from http://www.elandsys.com/resources/sendmail/domainkeys.html) 
> :
> mail._domainkey.example.com. IN TXT "k=rsa; t=y;
>            
> p=MEwwPQRJKoZIhvcNADAQCQADOwAwOAIxANPpYHdE2tevfEpvL1Tk2dDYv0pF28/ 
> f5MxU83x/0b
>           sn4R4p7waPaz1IbOGs/6bm5QIDAQAB"

Other systems, including mDNS and zeroconf, rely on underscores in  
domain components as well. Underscores in domain names are a de jure  
standard, in the hostname a de facto standard.

--
            Where am I, and what am I doing in this handbasket?
Wes Peters                                                     wes@opensail.org





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