[Dovecot] Possible mbox corruption if mail is saved with wrong Content-Length header (2.1.6)

[Timo Sirainen]

On 3.9.2012, at 17.11, Jost Krieger wrote:

>>> imap(x1234567): Error: Cached message size larger than expected (6796 > 2844)
>> 
>> This looks like it does. Existing emails must not be changed, IMAP
>> protocol forbids it (and Dovecot internals don't support it either).
>> The only safe way to drop attachments is to assign a new UID for the
>> mail, which basically means saving a new message without attachments
>> and deleting the old one. The Content-Length header doesn't really
>> have anything to do with this error.
> 
> Sorry if I was unclear. This is exactly what the plugin does. It builds
> a new message, starting with the old message and leaving out the
> unwanted attchment(s). Then it saves the new message, deletes the old
> message and finally copies over the flags.
> 
> I had a look at the handling of "Content-Length" in dovecot and had the
> impression that a new header was added but the old was not removed (if
> formally ok) and on reading the first header wins. But I'm not sure, of
> course.

Any Content-Length header sent by IMAP client or via LDA input should always get dropped (among some other headers) and replaced with the correct value. So if there's a bug, I doubt it has anything to do with that. But if you can easily reproduce this failure it would be nice to get it fixed..