dovecot - Oct 2009 - Capability info in hello message not complete?

Hi,

one Fedora user complains about not some troubles after update to dovecot 1.2. 
He suspects wrong capability information given by dovecot 1.2

In dovecot.conf he uses imap_capability= option. While response to 'A 
CAPABILITY' respects imap_capability value, the capability info in hello 
message does not.

for imap_capability=IMAP4 IMAP4rev1 ACL NAMESPACE CHILDREN SORT QUOTA 
THREAD=ORDEREDSUBJECT UNSELECT IDLE STARTTLS AUTH=PLAIN

A CAPABILITY response is:
* CAPABILITY IMAP4 IMAP4rev1 ACL NAMESPACE CHILDREN SORT QUOTA 
THREAD=ORDEREDSUBJECT UNSELECT IDLE STARTTLS AUTH=PLAIN

but hello message is:
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE STARTTLS 
AUTH=PLAIN] Dovecot ready.

But it seems even when imap_capability is not used capability in hello message 
is not complete:
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE STARTTLS 
AUTH=PLAIN] Dovecot ready.

vs.

* CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE SORT 
THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT IDLE CHILDREN NAMESPACE 
UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES 
WITHIN CONTEXT=SEARCH STARTTLS AUTH=PLAIN

is this expected? Do you think capability information in hello message really 
can befool clients?

Regards,
Michal Hlavinka

On Thu, 2009-10-01 at 14:59 +0200, Michal Hlavinka
wrote:
> Hi,
> 
> one Fedora user complains about not some troubles after update to dovecot
1.2.
> He suspects wrong capability information given by dovecot 1.2
> 
> In dovecot.conf he uses imap_capability= option. While response to 'A 
> CAPABILITY' respects imap_capability value, the capability info in
hello
> message does not.
> 
> for imap_capability=IMAP4 IMAP4rev1 ACL NAMESPACE CHILDREN SORT QUOTA 
> THREAD=ORDEREDSUBJECT UNSELECT IDLE STARTTLS AUTH=PLAIN
I suppose he's using Dovecot as a proxy? Because Dovecot doesn't support
IMAP4 or THREAD=ORDEREDSUBJECT.
> but hello message is:
> * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE
STARTTLS
> AUTH=PLAIN] Dovecot ready.
Hmm. Yeah..
> But it seems even when imap_capability is not used capability in hello
message
> is not complete:
..
> is this expected? Do you think capability information in hello message
really
> can befool clients?
The capability in greeting message is short on purpose. It's only enough
capabilities to get client logged in. After login Dovecot sends an
updated full capability list to the client. It uses a few different
tricks to get most clients understand the change.

So the only potential problem I see here is if client understands the
greeting capability and permanently remembers that the server supports
LITERAL+, ID and ENABLE after login but the destination server actually
doesn't. The other capabilities are relevant only before login. I'm not
entirely sure what, if anything, I should do about this.

I'd anyway like to hear what exactly is the problem and with what
client, preferably with IMAP traffic logs showing what's happening
wrong.
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On Thursday 01 October 2009 15:15:09 Timo Sirainen
wrote:
> On Thu, 2009-10-01 at 14:59 +0200, Michal Hlavinka wrote:
> > Hi,
> >
> > one Fedora user complains about not some troubles after update to
dovecot
> > 1.2. He suspects wrong capability information given by dovecot 1.2
> >
> > In dovecot.conf he uses imap_capability= option. While response to
'A
> > CAPABILITY' respects imap_capability value, the capability info in
hello
> > message does not.
> >
> > for imap_capability=IMAP4 IMAP4rev1 ACL NAMESPACE CHILDREN SORT QUOTA
> > THREAD=ORDEREDSUBJECT UNSELECT IDLE STARTTLS AUTH=PLAIN
> 
> I suppose he's using Dovecot as a proxy? Because Dovecot doesn't
support
> IMAP4 or THREAD=ORDEREDSUBJECT.
yes, dovecot is used as proxy
> 
> > but hello message is:
> > * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE
> > STARTTLS AUTH=PLAIN] Dovecot ready.
> 
> Hmm. Yeah..
> 
> > But it seems even when imap_capability is not used capability in hello
> > message is not complete:
> 
> ..
> 
> > is this expected? Do you think capability information in hello message
> > really can befool clients?
> 
> The capability in greeting message is short on purpose. It's only
enough
> capabilities to get client logged in. After login Dovecot sends an
> updated full capability list to the client. It uses a few different
> tricks to get most clients understand the change.
> 
> So the only potential problem I see here is if client understands the
> greeting capability and permanently remembers that the server supports
> LITERAL+, ID and ENABLE after login but the destination server actually
> doesn't. The other capabilities are relevant only before login. I'm
not
> entirely sure what, if anything, I should do about this.
> 
> I'd anyway like to hear what exactly is the problem and with what
> client, preferably with IMAP traffic logs showing what's happening
> wrong.
forwarded info:
The imap-server is dbmail which supports "IMAP4 IMAP4rev1 ACL NAMESPACE
CHILDREN SORT QUOTA THREAD=ORDEREDSUBJECT UNSELECT IDLE" and with dovecot 
version 1.1 it worked fine

The problem sue is "LITERAL+" what dbmail does not support.
The problem client was apple iphone