dovecot - Jun 2007 - using 'socat' to relay Dovecot SASL's auth socket over TCP?

hi,

i've been running Exim & Dovecot together on the same box.

Exim's been sharing Dovecot/SASL auth info over a local unix socket.
works great.

i'm now splitting Exim & Dovecot onto two different boxes.

iiuc, Dovecot ONLY provides a UNIX (local) socket; *not* a TCP socket
for over-the-network access.  SUre, I could mount the Dovecot socket's
volume over NFS ... but just don't want to go there.

i've just discovered,

	socat - Multipurpose relay
	http://www.dest-unreach.org/socat/

	"Socat is a command line based utility that establishes two
bidirectional byte streams and transfers data between them. Because
the streams can be constructed from a large set of different types of
data sinks and sources (see address types), and because lots of
address options may be applied to the streams, socat can be used for
many different purposes. It might be one of the tools that one `has
already needed'."

which, iiuc (?), can bidirectionally bridge the Dovecot unix-socket to
a TCP socket that Exim can talk/listen to.

reading further, "address types"
(http://www.dest-unreach.org/socat/doc/socat.html#ADDRESS_TYPES) seem
to include BOTH unix & tcp sockets ...

can anyone here comment further on this?

known to work? possible? no way? etc etc

thanks!

snowcrash wrote:
> which, iiuc (?), can bidirectionally bridge the Dovecot unix-socket to
> a TCP socket that Exim can talk/listen to.
I've used socat extensively on a completely unrelated project in order
to bridge UNIX domain sockets across machines.

I assume you currently have this:

  exim ->  /some/unix/socket -> dovecot-auth

If you want to use socat, then make sure it is installed on both
machines.  You can bridge using ssh (recommended) or just plain TCP/IP.

For ssh, run the following command on eximhost:

  socat -t 10 UNIX-LISTEN:/some/unix/socket,fork  \
    EXEC:"ssh user at dovecot-auth-host STDIO UNIX:/some/unix/socket"

The ssh will need to be able to complete without any form of prompting
(ie you need private/authorized keys setup).

If you don't care about security then you can use TCP connections
between the machines.

On eximhost run this replacing 9999 with your chosen port number:

 socat -t 10 UNIX-LISTEN:/some/unix/socket,fork \
    TCP4:dovecot-auth-host:9999

On dovecot-auth-host run:

 socat TCP4-LISTEN:9999,fork \
    UNIX:/some/unix/socket

The -t 10 option waits for 10 seconds after one direction is closed
before closing the other direction.  The socat default is .5 seconds
which I found problematic on higher latency links.

Roger