Re: [exim] local_user section with check_local_user removed …

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Author: Graeme Fowler
Date:  
To: Luke Kenneth Casson Leighton
CC: exim-users
Subject: Re: [exim] local_user section with check_local_user removed (as advised
OK, gloves off.

On 01/02/2007 16:06, Luke Kenneth Casson Leighton wrote:
> i will endeavour to track down the scope of this problem a bit
> further, because i have just tried this:
>
> HELO localhost
> MAIL FROM:<>
> RCPT TO:llllllllllllltotallyfakeaddress@localhost
>
> and _that_ was accepted (!)


In that case, YOUR copy of Exim is not checking against YOUR copy of
Cyrus - or anyhting else, in fact - to see if the local_part is valid.

> it's the fact that the mail gets accepted - without even being
> checked against the cyrus mailbox, and THEN it gets attempted
> to be delivered by LMTP, that bothers me. is that... just...
> too much to ask?


No. But then you haven't given us your ACL details, you haven't
described the files your Cyrus installation is using, you... well,
obviously you haven't done much apart from follow, blindly,
recommendations you found somewhere (in HOWTOs, but are they official
ones?) and they *don't do what you want them to*

> and this issue smells veeerrry slightly, to me, like a bug or
> limitation in exim4 itself, with a limitation in the config file
> format (of not being able to specify empty users, for sure).


Incorrect. It is a misconfiguration in YOUR Exim config.

> unless that _is_ possible, of course, and i just haven't found it,
> in which case, it's a bug in the exim4 documentation (nothing
> to do with cyrus or debian).


Also incorrect. There is the official documentation here:

http://www.exim.org/

Which a couple of minutes of probing would have led you to:

http://www.exim.org/eximwiki/CyrusImap

Which in turn would lead you to:

http://anfi.homeunix.net/exim/rtvcyrus.html

which uses a COMPLETELY DIFFERENT METHOD to the one you are trying, and
failing, to understand.

> and the reason _why_ you (plural - that is, the exim4 developers)
> should consider helping me is not because i will be the only person
> to benefit but because i am the only person who has the expertise
> and willingness to track it down, and also because _every_
> debian/exim4/cyrus2 administrator will benefit from the problem
> being fixed and resolved.


It has been. See previous link. Help yourself.

> i shouldn't _really_ have to point this out. but given that the
> issue hasn't been fully researched to confirm that it's not a bug
> in exim4, and you are already trying to refer me to the cyrus
> team who aren't experts in exim4 configuration, i _do_ have to point
> it out.


No, we were trying to refer you to the Debian Cyrus package maintainers
who may well have produced the documentation *you chose to follow* but
which didn't work as you wanted or expected.

> regarding the hack-suggestion, to use a flat file, it is a good
> starting point as a temporary hack.


Hack? Merely a suggestion; there are many more lookup methods, that was
only one. I know nothing whatsoever of Cyrus so was giving a "simple case".

> the key issue for me isn't so much that the destination user mailbox
> doesn't exist: the key is, i believe, that the mailbox user doesn't
> even get _checked_ when some idiot tries to send mail from a blank
> recipient (part of the issue is that i don't really understand why
> that's happening).


That's because you blindly uncommented an option in a router *without
understanding the consequences*.

> _and_ the mail gets accepted into the queue - and that's the worst
> bit about it. it definitely shouldn't be accepted, and i can't find
> out how to stop it.


Correct, it shouldn't. But that's... ah, never mind.

> now, that might be easy to fix with the right configuration changes -
> but i haven't found out how.
>
> and that's what i believe that i specifically need your help with.
>
> _how_ do i do 'blank user, containing no characters whatsoever,
> please bugger off' in exim configspeak?


You can't. Your MTA is REQUIRED by the relevant RFC to accept messages
with MAIL FROM:<> - that's how you get bounce messages through.

The issue for you is that you are NOT verifying your local users at RCPT
time, because you have *commented out the bit that checks for them*.

Please, read the Exim documentation and understand what options do what
before blindly following some outdated guidance (clearly it is outdated,
since it has the effect you are seeing) which leads you to point fingers
at "bugs".

Have a nice day. And do us a favour - if you want to discuss things on
this list, subscribe.

Graeme