Quoting Timo Sirainen <tss@iki.fi>:

On 21.5.2013, at 9.40, Michael M Slusarz <slusarz@curecanti.org> wrote:

...

Using 2.2.2, I see this:

C: 6 APPEND "INBOX" (\seen) "16-May-2013 22:05:14 -0600" CATENATE
(URL "/INBOX;UIDVALIDITY=1255685337/;UID=48812/;SECTION=HEADER"
TEXT ~{40} S: 6 NO [UNKNOWN-CTE] Binary input allowed only when the first part
is binary.

Why is there this limitation? It seems to me that CATENATE is
confusing the content-type encoding of the data/part itself with
the encoding of the IMAP literal.

A literal 8 is nothing more than a series of OCTET's that *may*
contain nulls, but not necessarily. i.e., in the above example the
40 octets of data are US-ASCII text, which is perfectly acceptable
to send as a literal8. (Client rationale: If BINARY exists on the
server, we don't bother to scan IMAP literal's for null data -- we
just send them as literal8's. It's an optimization that I would
hate to get rid of.)

Well, the problem is that if it does contain NULs, the MIME part
needs to be converted to something that doesn't. And to do that it
needs to modify the previous header, which with current code was
already read..

Is altering the header something that BINARY/CATENATE is allowed to
do? Especially regarding the header. I know there is language about
the server changing the CTE, but this is potentially troubling since
cryptographic signatures may rely on the header text. Changing things
will break the message.

I can see the server altering the body text to match the header. But
I think the reverse is bothersome.

Or are you saying that the error is fine if the text contains NULs,
but simply should be allowed as long as it doesn't?

This. As mentioned before, it seems the code is simply assuming that
the text part contains NULs without ever checking it. My reading of
the literal8 is that there is no requirement that NULs MUST exist in
the string.

In our code, the append data is often from code that the IMAP library
doesn't have access to. So at APPEND time, it is unaware whether the
data contains NUL or not - it just has a blob of data and a length.
If BINARY exists, it is much easier for us to simply send as literal8
and stream the data - no extra overhead is needed on our side. Since
each individual byte need to be handled by the server as it comes in,
it seems much more efficient to do NUL checking there.

michael

Quoting Timo Sirainen <tss@iki.fi>:

Anyway .. the BINARY APPEND converts only the MIME parts that you
send with "Content-Transfer-Encoding: binary". Are you sending such
header to Dovecot?

I don't think so. I noticed the CATENATE error when I was stripping a
simple text/html part out of a multipart/alternative message. The
"master" message header has a single MIME header:

Content-Type: multipart/alternative;
boundary="----WPFVNCCY4GPWDK6HNJXHWWE7J94BSS"

For the record, here's the entire transaction, along with the fallback
APPEND w/out using literal8 that was successful on the identical data:

C: 6 APPEND "INBOX" (\seen) "16-May-2013 22:05:14 -0600" CATENATE (URL
"/INBOX;UIDVALIDITY=1255685337/;UID=48812/;SECTION=HEADER" TEXT ~{40} S: 6 NO [UNKNOWN-CTE] Binary input allowed only when the first part is binary. C: 8 APPEND "INBOX" (\seen) "16-May-2013 22:05:14 -0600" CATENATE (URL
"/INBOX;UIDVALIDITY=1255685337/;UID=48812/;SECTION=HEADER" TEXT {40+} C: [LITERAL DATA: 40 bytes] C: URL "/INBOX;UIDVALIDITY=1255685337/;UID=48812/;SECTION=1.MIME" URL
"/INBOX;UIDVALIDITY=1255685337/;UID=48812/;SECTION=1" TEXT {40+} C: [LITERAL DATA: 40 bytes] C: TEXT {113+} C: [LITERAL DATA: 113 bytes] C: TEXT {42+} C: [LITERAL DATA: 42 bytes] C: ) S: 8 OK [APPENDUID 1255685337 48885] Append completed.

If a non-binary MIME part contains NUL, what is Dovecot supposed to
do? Change it to some other character? Fail the APPEND? Should there
be a difference between how literal vs literal8 is handled in such
case?

I would say there is no doubt: fail the APPEND. It should be the
client's responsibility to correctly format the data.

I appreciate that Dovecot does its best to try to Do The Right Thing
(Cyrus is much stricter about input, for example). But at some point
us client authors have to be at least somewhat competent, and it is
not asking to much for us to accept that GIGO.

michael

On Wed, 2013-05-22 at 09:38 -0600, Michael M Slusarz wrote:

Quoting Michael M Slusarz <slusarz@curecanti.org>:

...

Quoting Timo Sirainen <tss@iki.fi>:

...

Anyway .. the BINARY APPEND converts only the MIME parts that you
send with "Content-Transfer-Encoding: binary". Are you sending such
header to Dovecot?

I can verify this isn't working as you described above:

1 APPEND "INBOX" CATENATE (TEXT {49+} Content-Type: multipart/alternative; boundary="A" TEXT ~{1} 1 NO [UNKNOWN-CTE] Binary input allowed only when the first part is binary.

What do you do then if server advertises CATENATE but not BINARY?

Anyway for the other possibilities Dovecot could:

a) Put all CATENATEd messages through the istream-binary-converter, but just not do any actual C-T-E:binary conversion until the first ~{binary} part is found.

b) Just treat ~{n} exactly the same as ~{n}, unless it's the first part of CATENATE.

Maybe this should be aked about in IMAP mailing list .. (Didn't I already ask something about CATENATE+BINARY combination?)

Quoting Michael M Slusarz <slusarz@curecanti.org>:

It is concerning because RFC 4466 indicates that literal8's are
allowed for both APPEND and MULTIAPPEND, which is essentially an
extended APPEND. But RFC 4469 defines CATENATE TEXT as literal only:

RFC 4466: append-data = literal / literal8 / append-data-ext

RFC 4469: append-data =/ "CATENATE" SP "(" cat-part *(SP cat-part) ")" cat-part = text-literal / url text-literal = "TEXT" SP literal

To me CATENATE =~ MULTIAPPEND - it is just another form of an
extended APPEND. Not sure why it shouldn't be allowed there.

Answered my own question here - sure enough, it was an oversight:

http://osdir.com/ml/ietf.imapext/2006-03/msg00030.html

michael