Subject: TXT records, are they alive?

From: "Mohammad Awad" <[email-masked]>
Date: Sat, 12 Apr 2003 08:08:50 +0200

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Hi all,
I'm doing some research that I'll get it dependant on the TXT record in 
RFC1464 of 1993. I've noticed that there was no further drafts, RFCs, nor 
comments about that RR.
So:
1- Is the TXT record still considered a standard and is it really 
implemented in nowadays server?
2- if yes, do the servers really respond to queries that necessitate 
searching inside the RDATA cell of that TXT records?
Thank you all
Moh Awad

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---

From: Paul Vixie <[email-masked]>
Date: Sat, 12 Apr 2003 18:24:31 +0000

> > Yup.  They've worked fine in BIND for a while.  (On the server side,
> > there's been some issue about how much control a zone file has over the
> > boundaries between the text labels.  I don't know the status of that.)
> 
> The original BIND 4.x implementation of TXT RRs treated the entire
> RDATA as one big string.  If memory serves, this was fixed circa 1996.

yes.  both when parsing zone files and when handling it in cache, bind4
before 4.9.3b17 failed to deal with the inner segmentation of txt rdata's.
this meant an incompatibility when it was fixed, since

	FOO	IN	TXT	abc def

used to create

	rdlen	8
	rdata	\07 a b c \020 d e f

and now it creates

	rdlen	8
	rdata	\03 a b c \03 d e f

to get the prior behaviour, quotes are needed (per the standard), i.e.,

	FOO	IN	TXT	"abc def"

---

From: Dean Anderson <[email-masked]>
Date: Sat, 12 Apr 2003 15:10:28 -0400 (EDT)

Supposedly this is a protocol list, not a bind list.  The standards are
not defined by bind behavior.

TXT records certainly are current standard, and should be implemented in a
standards-compliant server. I note that AFS, DCE, CODA, and other
applications use TXT records.

		--Dean

On Sat, 12 Apr 2003, Rob Austein wrote:

> At 12 Apr 2003 10:40:37 -0400, Greg Hudson wrote:
> >
> > On Sat, 2003-04-12 at 02:08, Mohammad Awad wrote:

---

From: Greg Hudson <[email-masked]>
Date: 12 Apr 2003 15:48:33 -0400

> not defined by bind behavior.

Of course not, but it's information relevant to the question at hand. 
(In particular, it's useful to know that TXT records passing through an
old BIND cache may have their boundaries rewritten; depending on the
number of such caches out there, that might be an obstacle to using RFC
1464 on a wide scale.)

> applications use TXT records.

This statement doesn't agree with my understanding, although it's tough
to prove a negative.  AFS uses AFSDB records, and does not make any use
of TXT records that I can determine.  Coda does not appear to use either
AFSDB or TXT from a search of the current source code.  I don't know
about DCE, but I imagine it would use the DCE registry for anything you
might consider using TXT records for.

---

From: Dean Anderson <[email-masked]>
Date: Sat, 12 Apr 2003 17:41:13 -0400 (EDT)

> number of such caches out there, that might be an obstacle to using RFC

Sounds like an operational problem to me.  Since these old versions of
bind have pretty severe security problems, it seems unlikely that there
are enough around to be concerned about.

> might consider using TXT records for.

I think OpenAFS has some differences to transarc AFS. Now that you mention
it, TXT was deprecated after the AFSDB record type was approved. Most of
my afs administration was in the old days. I don't have the transarc
source online anymore, due to disk failure on the old ri.osf.org cell. DCE
uses a TXT record to locate other cells. It doesn't have anything similar
to the old CellServDB file. The registry is used by the cell itself to
find RPC endpoints.  I have old sets of DCE and AFS manuals in the office.
I'll be happy to fax you a copy of the relevant pages on monday, if you
want.

		--Dean

---

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Sun, 20 Apr 2003 19:36:00 -0700

Some of the spam blacklists use A records to encode their opinion of the
domain in question.

> -----Original Message-----
> From: Derek Atkins [mailto:[email-masked]]
> Sent: Sunday, April 20, 2003 7:00 PM
> To: Florian Weimer
> Cc: Peter Koch; Mohammad Awad; [email-masked]
> Subject: Re: TXT records, are they alive?
> 
> 
> Florian Weimer <[email-masked]> writes:
> 
> > However, as far as I can tell, stub resolvers lack convenient
> > interfaces for extracting TXT RRs.  This might explain why a lot of
> > DNS applications use A RRs to encode things which actually aren't IP
> > addresses. 8-/
> 
> What applications do something like this?  An A record is extremely
> limited in what it can hold (namely, a 4 octet address).  So, I'd be
> interested in hearing about "DNS applications" that hold something
> else or somehow use A records differently.
> 
> -derek
> 
> -- 
>        Derek Atkins
>        Computer and Internet Security Consultant
>        [email-masked]             www.ihtfp.com
> 
> --