Re: [exim-dev] [Bug 1684] Malformed headers which exceed len…

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著者: Viktor Dukhovni
日付:  
To: exim-dev
題目: Re: [exim-dev] [Bug 1684] Malformed headers which exceed length spec willingly passed to remote servers
On Wed, Sep 30, 2015 at 07:39:11PM +0000, admin@??? wrote:

> We should also consider body lines; the spec (rfc 5322 section 2.3) says the
> same limit applies. Probably the same variable should control behaviour and
> the name should reflect this.


Yes, the Postfix SMTP client (outgoing SMTP) folds all overly long
message lines (header and body) by inserting "<CRLF><SPACE>". Some
care *may* then be necessary to get "SMTP transparency" right by
not inserting "." at the first position in output line fragments
that start with "." when the line already starts with the inserted
<SPACE>.

One could arguably use MIME parser state to distinguish between
primary/MIME/nested headers vs. MIME bodies and fold MIME bodies
with "<SPACE><CRLF>" rather than "<CRLF><SPACE>", but is a lot more
work (Postfix only engages the MIME parser on SMTP output when
doing 8bit->7bit downgrade or output header-checks.

Hope that's useful background.

-- 
    Viktor.