dovecot - Aug 2008 - Dovecot and fake users

Hi everyone,

    Our company has decided to make a fake POP3 (and possibly IMAP) 
server, which accepts any user name and password combination and shows 
there are no new messages. This is for the purpose that when our mail 
cluster passes out, we can redirect our clients to this server while  we 
fix our mail system. This way we can prevent our users from getting 
errors. We are using the latest dovecot server with Ubuntu (currently), 
but perhaps will migrate to CentOS (if this is important)

    I am trying to use the following configuration for testing, but it 
doesn't seem to work (don't laugh :) )

-------8<------------
  passdb pam {
    args = dovecot
  }

  userdb static {
    args = uid=0 gid=0 home=/var/mail/empty allow_all_users=yes
    }

-------8<------------



cat /etc/pam.d/dovecot:
-------------------
#%PAM-1.0

auth required pam_permit.so
-------------------


I will be very thankful for pointing the way to do this and any thoughts.


P.S. Sorry for my english.

--
Vytenis

On Tue, 2008-08-19 at 10:05 +0300, Vytenis Sabaliauskas
wrote:
>     I am trying to use the following configuration for testing, but it 
> doesn't seem to work (don't laugh :) )
Set auth_debug=yes and look at the logs. But here are some suggestions:
> -------8<------------
>   passdb pam {
>     args = dovecot
>   }
Another possibility could be SQLite with:

password_query = select '%u' as user, null as password, 'y' as
nopassword
>   userdb static {
>     args = uid=0 gid=0 home=/var/mail/empty allow_all_users=yes
>     }
With uid=0 you're telling Dovecot to run the mail process as root.
That's not going to work. Use some other uid.
> cat /etc/pam.d/dovecot:
> -------------------
> #%PAM-1.0
> 
> auth required pam_permit.so
> -------------------
I don't know what pam_permit does, but would pam_allow work?

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On Tue, Aug 19, 2008 at 9:05 AM, Vytenis Sabaliauskas
<vytenis.sabaliauskas at gmail.com> wrote:
>       Hi everyone,
>
>   Our company has decided to make a fake POP3 (and possibly IMAP) server,
> which accepts any user name and password combination and shows there are no
> new messages. This is for the purpose that when our mail cluster passes
out,
> we can redirect our clients to this server while  we fix our mail system.
> This way we can prevent our users from getting errors. We are using the
I wonder if this leads into problems if you have users who use the
option "leave messages on server for X days". The email client might
get confused by having/not having a list of UIDLs/messages in the
inbox.

?

Chris

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On 2008-08-19, at 0305, Vytenis Sabaliauskas wrote:
>
> Our company has decided to make a fake POP3 (and possibly IMAP)  
> server, which accepts any user name and password combination and  
> shows there are no new messages. This is for the purpose that when  
> our mail cluster passes out, we can redirect our clients to this  
> server while  we fix our mail system. This way we can prevent our  
> users from getting errors. We are using the latest dovecot server  
> with Ubuntu (currently), but perhaps will migrate to CentOS (if this  
> is important)
>
> I am trying to use the following configuration for testing, but ...
it was easier to just throw together a quick script, rather than  
configuring dovecot to simulate what you're looking for.

http://qmail.jms1.net/scripts/#fake-pop3

you can run this under daemontools, using "tcpserver" (both of which  
are normal djb tools- if you're using qmail you should already have  
them on your system.) a "run" script might look like this:

#!/bin/sh
PATH=/usr/bin:/bin:/usr/local/bin
exec tcpserver -vR 1.2.3.4 110 fake-pop3 2>&1

if you're not using qmail, you may need the links...

daemontools: http://cr.yp.to/daemontools.html
tcpserver: http://cr.yp.to/ucspi-tcp.html

you *could* also run it under something like inetd, although i haven't  
personally done this- i don't use inetd or xinetd on any of my servers.

==
the other item i should probably mention... i don't recommend you even  
think about trying to make an IMAP version of this.

remember that many IMAP clients keep a copy of the server's contents  
on their local systems. if one of these clients were to connect and  
see what looks like an empty mailbox with no folders, they would  
proceed to make their local system "look like" what's on the
server...
empty. basically you would end up forcing a bunch of clients to delete  
their own local copies of what they have stored on the server.

of course, when the real server comes back, their messages and folders  
will "appear" again... but that means the clients will re-download all
of it (which might be a bandwidth or CPU issue, especially for a busy  
server where many users keep many messages stored on the server, and  
all of them are downloading their entire mailboxes at the same time)  
and will probably force the users to re-configure which folders they  
do and don't want to be subscribed to.

it's probably easier to just deal with the support calls. IMAP clients  
know that if they can't connect to the server, they shouldn't delete  
their local copy of the messages and folders...

- --------------------------------------------------------
| John M. Simpson  --  KG4ZOW  --  Programmer At Large |
| http://www.jms1.net/                 <jms1 at jms1.net> |
- --------------------------------------------------------
|   Hope for America  --  http://www.ronpaul2008.com/  |
- --------------------------------------------------------





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