AW: Re: Message contains NUL characters - howto dump?

[Markus Rebensburg]

Klemens Puritscher schrieb:
> Phil Brutsche schrieb:
>   
>> The error message is being created by the LMTP service - NUL characters
>> aren't valid in ASCII messages. The email in question is being generated
>> incorrectly somewhere, somehow.
>>     
>
> thanks for your reply.
> I know that in the email must be a NUL character, but I cannot see this NUL character during a tcpdump.
>
> Do you know, or someone else in this list, who can I safe find this NUL character?
>
>   
Maybe it is a problem of lines ine the email which are longer than the
standard allows. Cyrus has a fixed buffer for each line in the email. If
the line is longer than this buffer lmtp inserts a terminating string
character (NUL) itself. This could be the reason you cannot see the
Character in the tcp stream of your mail.
We have the same problem with the NUL character here produced by replies
to emails with some HTML Attachments which have only one linebreak in
the whole file.

Regards,
     Markus
>> What you need to do is either have the MTA reject the message during the
>> DATA portion of the SMTP transaction, or have the MTA remove the NUL
>> characters before it passes the message on to the LMTP service.
>>     
>
> Yes, this will be the next step.
>
>   
>> Your email headers indicate you are using Postfix as your MTA, and I am
>> not familiar enough with that to tell you how to do what is necessary.
>>     
>
> Yes, that's right for outgoing emails.
> The MTA for incoming emails (mx host) is exim.
>
> regards,
> Klemens
>
>
>   
>> Klemens Puritscher wrote:
>>     
>>> Hello,
>>>
>>> I have a problem with one of our customers.
>>> When he forwards an email with the thunderbird email client (windows
>>> version), the lmtp-daemon on my cyrus-imapd (v2.3.13) rejects those
>>> emails with the error "554 5.6.0 Message contains NUL characters".
>>> ...ok, that's clear, there are "NUL" characters in the email.
>>>
>>> But I would show my customer, where the "NUL" character is.
>>>
>>> For tests, I generate a testmail, with "echo -e
>>> "From:<sender at example.com>\nTo:<recipient at example.com>\nSubject:
>>> test\n\ntest\0000test\n.\n" > mail_with_NUL.txt
>>>
>>> Now I dump the lmtp-session on the cyrus-imapd host with:
>>> tcpdump -vv -XX -s 65535 -n -i eth1 "port lmtp
>>>
>>> and I see the "NUL" character:
>>> ...
>>>         0x0230:  7065 6564 2e61 740d 0a0d 0a74 6573 7400  peed.at....
>>>       
>> test.
>>     
>>>         0x0240:  7465 7374 0d0a 2e0d 0a                   test.....
>>> ...
>>> 65 = e
>>> 73 = s
>>> 74 = t
>>> 00 = NUL
>>>
>>> ...ok, fine, I can find the "NUL" character.
>>>
>>> But when I dump the lmtp-session with the customer email (which get's
>>> the error "554 5.6.0 Message contains NUL characters"), I cannot find
>>> this "NUL" character.
>>>
>>> Can someone tell me, what I did wrong?
>>>
>>> Thanks in advance.
>>>
>>> Klemens
>>>
>>> ----
>>> Cyrus Home Page: http://cyrusimap.web.cmu.edu/
>>> Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki
>>> List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
>>>       
>> -- 
>>
>> Phil Brutsche
>> phil at optimumdata.com
>>     
>
> ----
> Cyrus Home Page: http://cyrusimap.web.cmu.edu/
> Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki
> List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
>
>   

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