Subject: Re: SUN and the Content-Length header field

From: Tomas Kullman <[email-masked]>
Date: Fri, 24 Mar 1995 11:05:19 +0100

> AT&T and SUN do not use standard Unix format mail.  Instead, they use
> something that looks like Unix format mail, but depends upon an extremely
> fragile and unrobust octet count.  Details are in a paper I wrote
> "Content-Length Considered Harmful"; among other aspects of bad design
> this count is generated by the originating MUA. 

Ah, is it really so? I thought it was generated at delivery. Wow, then
I understand your stand better. It sure is bad design not to regenerate
this at final delivery.
Is your paper available online somewhere or can you send it to me?

> It is technically infeasible to support Content-Length without making the
> Unix format mail algorithms considerably slower and less robust.  What is
> worse, on systems whose mailers do *not* use Content-Length, it would
> become a security bug (actually, two different bugs).

Well, large mailboxes in berkeley format isn't that blindingly fast either.
I thought content-length was invented to overcome this by allowing to skip
large messages without a need to parse through it all.

> The means to deal with this is, if you are using a SUN or AT&T system, to
> replace the broken mail delivery agent invoked by sendmail (generally this
> is /bin/mail) with a program that does the right thing, such as Steve
> Hubert's sendit.  Many sites have done this and have reported good results.
> 
> I think that sendit is available for ftp'ing, but if not I'll look into
> making it available. 

This sounds to be a reasonable approach, can you provide a pointer?

-- Tomas

---

From: "Barton E. Schaefer" <[email-masked]>
Date: Fri, 24 Mar 1995 12:05:37 -0800

On Mar 24, 11:05am, Tomas Kullman wrote:
} Subject: Re: SUN and the Content-Length header field
}
} > AT&T and SUN do not use standard Unix format mail.  Instead, they use
} > something that looks like Unix format mail, but depends upon an extremely
} > fragile and unrobust octet count.  Details are in a paper I wrote
} > "Content-Length Considered Harmful"; among other aspects of bad design
} > this count is generated by the originating MUA. 
} 
} Ah, is it really so? I thought it was generated at delivery.

It's normally recomputed on delivery if the receiving system is one that
supports content-length headers.  However, some sending systems insert
it into outgoing messages as well, which causes problems if the receiver
does not recompute it.

-- 
Bart Schaefer                     Vice President, Technology, Z-Code Software
[email-masked]               Division of Network Computing Devices, Inc.