[Djigzo users] [OT] Invalid signature because of "Content-Transfer-Encoding: 8bit"

lst_hoe02 at kwsoft.de lst_hoe02 at kwsoft.de
Wed Apr 20 15:48:46 CEST 2011


Zitat von Martijn Brinkers <martijn at djigzo.com>:

>> today i got a mail fro a well known German Trustcenter with a invalid
>> signature warning (content altered). A former mail to an other account
>> from the same Trustcenter was valid. On inspection it looks like someone
>> altered the encoding because the valid mail has
>> "Content-Transfer-Encoding: 8bit" and the broken one
>> "Content-Transfer-Encoding: quoted-printable". As far as i know a SMTP
>> server should only pass 8bit if the remote site announces 8BITMIME, so i
>> suspect this is the trouble maker because neither Djigzo nor our Virus
>> scan announces 8BITMIME :-(
>>
>> Any comments on this?
>
> The application that added the signature is not RFC 3851 compliant.
> before signing a message the mail agent should convert 8bit mime bodies
> to 7bit. This is important because if SMTP sees that a server does not
> support 8bit, it should convert the message to 7bit. Because of this
> conversion the message has been changed and therefore the signature is
> no longer valid. So the trouble maker is the application that signed the
> message :). The problem is that there is not much you can do. In
> principle you can disable the conversion from 8bit to 7bit in your own
> gateway (not that I recommend that ;) but you cannot control other
> intermediate gateways.
>

Lead me straight to another question: What does Djigzo do if it is  
feed with 8bit content to sign? Oh, wait... It does not announce  
8BITMIME so this should not happen at all, no?

Regards

Andreas


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