[405] in Hesiod
Don Lewis: hesiod aliases for illegal DNS names
daemon@ATHENA.MIT.EDU (Greg Hudson)
Fri Sep 8 15:04:21 2000
Message-Id: <200009081903.PAA01686@egyptian-gods.MIT.EDU>
To: hesiod@MIT.EDU
Date: Fri, 08 Sep 2000 15:03:47 -0400
From: Greg Hudson <ghudson@MIT.EDU>
This is an interesting issue and I thought I would forward it to this
list for the record. (It was subsequently pointed out that ".." is
illegal in the local part of an address, but the general issue of
Hesiod lookups for strings which cannot be made into valid DNS labels
remains valid.)
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Date: Fri, 8 Sep 2000 07:32:33 -0700 (PDT)
From: Don Lewis <Don.Lewis@tsc.tdk.com>
Message-Id: <200009081432.HAA06345@salsa.gv.tsc.tdk.com>
To: bind-workers@isc.org, sendmail-beta@sendmail.org
Subject: hesiod aliases for illegal DNS names
Cc: nectar@FreeBSD.ORG
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We've been using a somewhat modified version hesiod to distribute our
sendmail alias database and would now like to migrate to a publicly
distributed version of the hesiod code. A problem that we initially
ran into was that we had some names, such as "foo..bar" that could not
be legally represented in DNS. The standard hesiod library translates
this into "foo..bar.ns.example.com" for the DNS lookup. The problem
is that the zero length label indicates the end of the domain name.
The way we solved this problem was to hack our copy of the hesiod
library to escape all the periods in the name being looked up, so
that the DNS name would be "foo\.\.bar.ns.example.com".
What is the best solution to this problem? Should the hesiod library
do this translation, or should should sendmail handle this before
calling hesiod? Doing this also limits the maximum length of a name
that can be looked up to 63 characters, even if the name has embedded
periods, so should all periods be escaped, or only sequential ones,
and if the latter, should it be the first or second of each pair?
Other users of hesiod could run into this problem as well. For
instance, someone distributing the passwd database might want to
enter a user name containing sequential periods.
--- Truck
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