logging TLS SNI hostname

[Arkadiusz Miśkiewicz]

On Thursday 20 of October 2016, Aki Tuomi wrote:
> On 18.10.2016 14:16, Arkadiusz Miśkiewicz wrote:
> > On Monday 17 of October 2016, KT Walrus wrote:
> >>> On Oct 17, 2016, at 2:41 AM, Arkadiusz Miśkiewicz <arekm at maven.pl>
> >>> wrote:
> >>> 
> >>> On Monday 30 of May 2016, Arkadiusz Miśkiewicz wrote:
> >>>> Is there a way to log SNI hostname used in TLS session? Info is there
> >>>> in SSL_CTX_set_tlsext_servername_callback, dovecot copies it to
> >>>> ssl_io->host.
> >>>> 
> >>>> Unfortunately I don't see it expanded to any variables (
> >>>> http://wiki.dovecot.org/Variables ). Please consider this to be a
> >>>> feature request.
> >>>> 
> >>>> The goal is to be able to see which hostname client used like:
> >>>> 
> >>>> May 30 08:21:19 xxx dovecot: pop3-login: Login: user=<abc>,
> >>>> method=PLAIN, rip=1.1.1.1, lip=2.2.2.2, mpid=17135, TLS,
> >>>> SNI=pop3.somehost.org, session=<hfS9Qwk03sBTBnrN>
> >>> 
> >>> Dear dovecot team, would be possible to add such variable ^^^^^ ?
> >>> 
> >>> That would be neat feature because server operator would know what
> >>> hostname client uses to connect to server (which is really usefull in
> >>> case of many hostnames pointing to single IP).
> >> 
> >> I’d love to be able to use this SNI domain name in the Dovecot IMAP
> >> proxy for use in the SQL password_query. This would allow the proxy to
> >> support multiple IMAP server domains each with their own set of users.
> >> And, it would save me money by using only the IP of the proxy for all
> >> the IMAP server domains instead of giving each domain a unique IP.
> > 
> > It only needs to be carefuly implemented on dovecot side as TLS SNI
> > hostname is information passed directly by client.
> > 
> > So some fqdn name validation would need to happen in case if client has
> > malicious intents.
> > 
> >> Kevin
> 
> Hi!
> 
> I wonder if this would be of any help? It provides %{local_name}
> passdb/userdb variable, you can use it for some logging too...
> 
> https://github.com/dovecot/core/commit/fe791e96fdf796f7d8997ee0515b163dc5ed
> dd72

Should it work for such usage, too?

login_log_format_elements = user=<%u> method=%m rip=%r lip=%l mpid=%e 
local_name=%{local_name} %c session=<%{session}>

Because I'm not getting local_name logged at all (dovecot -a shows its there).

> Aki

Thanks,
-- 
Arkadiusz Miśkiewicz, arekm / ( maven.pl | pld-linux.org )