dovecot - May 2017 - Issue with parsing of forwarded messages with attachments and quotes in the subject

Hi all,
           at work we use Roundcube acting as a mail client for the  Dovecot
Imap server.

In Roundube the messages are parsed through the Imap BODYSTRUCTURE command
If a message contains forwarded messages and attachments and some of the
messages contains
a quote (") in the subject, then the resulting BODYSTRUCTURE appears to be
malformed.
---
After some digging through the code of Dovecot, it seems to me that the problem
is related to the
function: imap_append_string_for_humans
defined at the line 120 of the file src/lib-imap/imap-quote.c  (dovecot sources
v. 2.2.29)

Said function is supposed to return a quoted version of the input string while
removing unwanted
characters from the input data.

But,  if I call it with a string containing quotes as argument (eg: I am a lazy
" programmer)  in
the resulting output the quotes aren't escaped and the output string is not
quoted.
----

This is related to the stated issue through the function calls in:
part_write_body   [ defined at line 142 of imap-bodystructure.c ]
which calls imap_envelope_write [defined at line 46 of imap-envelope.c]
which finally calls imap_append_string_for_humans
----

Thank you for your time.

Best regards,
Giovanni S. Fois

On 2 May 2017, at 11.21, Giovanni Salvatore Fois <giovannisalvatore.fois at
eng.it> wrote:
> 
> Hi all,
>          at work we use Roundcube acting as a mail client for the  Dovecot
Imap server.
> 
> In Roundube the messages are parsed through the Imap BODYSTRUCTURE command
> If a message contains forwarded messages and attachments and some of the
messages contains
> a quote (") in the subject, then the resulting BODYSTRUCTURE appears
to be malformed.
> ---
> After some digging through the code of Dovecot, it seems to me that the
problem is related to the function: imap_append_string_for_humans
> defined at the line 120 of the file src/lib-imap/imap-quote.c  (dovecot
sources v. 2.2.29)
> 
> Said function is supposed to return a quoted version of the input string
while removing unwanted
> characters from the input data.
> 
> But,  if I call it with a string containing quotes as argument (eg: I am a
lazy " programmer)  in
> the resulting output the quotes aren't escaped and the output string is
not quoted.
It's then written as a literal, so it actually looks correct to me.

On 05/02/2017 11:13 AM, Timo Sirainen wrote:
> On 2 May 2017, at 11.21, Giovanni Salvatore Fois <giovannisalvatore.fois
at eng.it> wrote:
>>
>> Hi all,
>>          at work we use Roundcube acting as a mail client for the 
Dovecot Imap server.
>>
>> In Roundube the messages are parsed through the Imap BODYSTRUCTURE
command
>> If a message contains forwarded messages and attachments and some of
the messages contains
>> a quote (") in the subject, then the resulting BODYSTRUCTURE
appears to be malformed.
>> ---
>> After some digging through the code of Dovecot, it seems to me that the
problem is related to the function: imap_append_string_for_humans
>> defined at the line 120 of the file src/lib-imap/imap-quote.c  (dovecot
sources v. 2.2.29)
>>
>> Said function is supposed to return a quoted version of the input
string while removing unwanted
>> characters from the input data.
>>
>> But,  if I call it with a string containing quotes as argument (eg: I
am a lazy " programmer)  in
>> the resulting output the quotes aren't escaped and the output
string is not quoted.
>
> It's then written as a literal, so it actually looks correct to me.
>
I have done some further analysis of my real world cases and the problem arises
when the subject
line contains also a closed parenthesis, as in:

I'm a really ) bad "message"


In that case, part of the bodystructure is rendered as:

("Mon, 27 Mar 2017 11:18:04 +0000" I'm a really ) bad
"message" (("First Address" NIL "username"
"domain.com"))(( "Second Address" NIL "othername"
"otherdomain.com")) ... and so on ...

That lonely parenthesis confuses the parser and so the resulting structure is
slightly messed up.

I'm pretty positive that I can overcome the issue working on the client
side.

Thank you for your time and please keep going with the good job.

Best regards,
Giovanni S. Fois