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Date: Wed, 17 Mar 2010 14:00:43 +0000
From: Brian Stafford <brian@...fford.uklinux.net>
To: Ludwig Nussel <ludwig.nussel@...e.de>
Cc: oss-security@...ts.openwall.com, libesmtp@...fford.uklinux.net,
	security@...ntu.com, Pawel Salek <pawsa@...ochem.kth.se>,
	jskarvad@...hat.com
Subject: Re: CVE Request: libesmtp does not check NULL bytes
 in commonName

Ludwig Nussel wrote:
> Brian Stafford wrote:
>   
>> Since both the original and patched versions of match_component() 
>> implement wildcards rather less liberally than RFC 2818 implies, I 
>> decided to move towards the approach in the I-D.  match_component() now 
>> accepts either a string or a single wildcard '*'.  Matched characters 
>> are validated against the set of valid domain name component characters 
>> , that is, *.example.org will not match %.example.org, nor for that 
>> matter will the pattern %.example.org.  Question: should underline '_' 
>> be in the set of valid characters?
>>     
>
> AFAIK underlines are not allowed in DNS. I'm sure someone knows the
> RFC for that too :-)
>   
They are permitted in some contexts but not in actual domain names, for 
example a SRV record question to a name server contains stuff like 
_smtp._tcp.host.example.org  The host.example.org section is forbidden 
from using _ but obviously the name server itself supports it so it can 
handle the _smtp._tcp components.  I am assuming that since we're 
validating domain names and not name server queries, the _ is forbidden 
but if anyone out there can clarify it might be useful :-)
> cu
> Ludwig
>
>   
Brian

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