Subject: Re: Reject vs. fix

From: Frank Ellermann <[email-masked]>
Date: Tue, 01 May 2007 09:23:12 +0200

Harald Alvestrand wrote:
 
> My technical opinion:
 
> I think it's reasonable for a posting agent (under the control of the
> poster) to "fix" articles.
> I think it's unreasonable for an injecting agent (under the control of
> the news admin) to do so.

We didn't disagree, or did we ?  Maybe we're in violent agreement.

Frank

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From: Harald Alvestrand <[email-masked]>
Date: Wed, 02 May 2007 16:08:34 +0200

Charles Lindsey wrote:
>
>> After writing the text, I think it's weird, but it's not quite as bad as I
>> thought it was going to be.  It does have the merit of closely mirroring
>> how Date works today, and if we're going to change something in this area,
>> sticking as close to what we know works as possible seems like a good idea
>> to me.
>>     
>
> +1
>
> It may well be that most 'normal' posting agents leave it to the injecting
> agent, but for the guy who is doing something slightly out of the ordinary
> (multiple injection, delayed injection, etc) it does have some advantages,
> and I can't see any disadvantage.
>   
As long as we assume that no posting agent ever sees an advantage to 
creating an injection-date with false information, and that the number 
of posting agents who generate wrong injection-date parameters is not 
significantly higher than the number of injecting agents to do so, there 
are no disadvantages I can see.

Those two assumptions are fairly big.

                  Harald

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From: Russ Allbery <[email-masked]>
Date: Wed, 02 May 2007 10:40:46 -0700

> Those two assumptions are fairly big.

I don't see any possible advantage for a posting agent creating a false
Injection-Date header over a posting agent right now creating a false Date
header.  They should be equivalent.  The Injection-Date header is
functional, rather than a trace header.

Trace information should be put in Injection-Info instead.

-- 
Russ Allbery ([email-masked])             <http://www.eyrie.org/~eagle/>

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From: Harald Alvestrand <[email-masked]>
Date: Thu, 03 May 2007 09:54:54 +0200

> Trace information should be put in Injection-Info instead.
one (contrived) example would be someone who wishes to make a posting 
that is visible at one site, but not at another site, where he knows 
that one site discards based on Date: and the other side discards based 
on Injection-Date:

He would then put either Date: or Injection-Date: a week or so in the 
past, depending on which site he wishes his message to be "invisible" at.

If the WG thinks that this isn't very worrying (I can't say I find it 
very worrying either), it's fine.

(minor guard against this particular kind of mischief: Insist that 
Injection-Date: is no earlier than Date:, and check BOTH of them against 
the 72-or-so-hour limit....)

                       Harald

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From: "Charles Lindsey" <[email-masked]>
Date: Thu, 3 May 2007 10:46:52 GMT

>are no disadvantages I can see.

A fair question that needs to be examined.

First, let us look at the presently used Date.

We are agreed (I think) that Dates up to 24 hours in the future do little
harm, and injecting agents are supposed to reject anything longer.
Clearly, they SHOULD reject Injection-Dates over 24 hours into the future
(I think I already suggested that needed to be added to Russ's text).

If a man, with hindsight, uses a Date header months into the past, then he
may be able to claim, falsely, "See, I already said that months ago". Of
course, that may also cause his article to propagate poorly (which is his
problem). But, in any case, this is not really a protocol issue.

But if a man uses an Injection-Date into the past, then the only effect
will be that his article propagates worse, so I do not see how that can
possibly give him any advantage, except possibly when he knows the exact
cutoff policy of his immediate peers, and is trying to ensure that his
scam is only seen by sites very close to himself (e.g. by colleagues in
his own organization). I think I could live with that.

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131 Fax: +44 161 436 6133   Web: http://www.cs.man.ac.uk/~chl
Email: [email-masked]      Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K.
PGP: 2C15F1A9      Fingerprint: 73 6D C2 51 93 A0 01 E7 65 E8 64 7E 14 A4 AB A5

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From: Russ Allbery <[email-masked]>
Date: Fri, 18 May 2007 17:25:43 -0700

> very worrying either), it's fine.

Ah, I see what you're saying.  Yes, I don't find that particularly
worrying.  I could see mentioning it in the Security Considerations
section, though, since a few similar things are already mentioned.  How do
you feel about that?

> the 72-or-so-hour limit....)

In the current draft, we are checking the Date header field, so that would
limit this (although that isn't the main reason why it's being done).
This is one of the things that Charles feels should be changed.

---

From: Russ Allbery <[email-masked]>
Date: Fri, 18 May 2007 17:33:00 -0700

Charles Lindsey <[email-masked]> writes:

> We are agreed (I think) that Dates up to 24 hours in the future do
> little harm, and injecting agents are supposed to reject anything
> longer.  Clearly, they SHOULD reject Injection-Dates over 24 hours into
> the future (I think I already suggested that needed to be added to
> Russ's text).

I must have missed that.  Indeed.

Okay, my proposed draft text now has:

   3.   It SHOULD reject any article whose Injection-Date or Date header
        field is more than 24 hours into the future (and MAY use a
        margin less than 24 hours).  It SHOULD reject any article whose
        Injection-Date header field is too far in the past (older than
        the cutoff interval of a relaying agent the injecting agent is
        using, for example).  It SHOULD similarly reject any article
        whose Date header field is too far in the past, since not all
        news servers support Injection-Date and only the injecting agent
        can provide a useful error message to the posting agent.  In
        either case, this interval SHOULD NOT be any shorter than 72
        hours into the past.

to be very clear about what header field we're talking about here.  I've
explicitly mentioned rejecting based on a stale Injection-Date because
injecting agents that accept articles and then have their upstream
relaying agent reject them may have lost the opportunity to return a
meaningful error message and injecting agents that just proxy to the
relaying agent and return its error message satisfy this requirement.

The third sentence is the one that remains controversial.  I think we're
fairly comfortable with the rest of the paragraph.

---

From: "Charles Lindsey" <[email-masked]>
Date: Mon, 21 May 2007 15:51:42 GMT

>   ....  It SHOULD similarly reject any article

>fairly comfortable with the rest of the paragraph.

The wording is now much weaker than in the present draft. It is more of a
recommendation to "think of a number greater than 72 hours", which does
not preclude thinking of "infinity". So I still marginally do not like it,
but will not press the point if others are happy.