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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