Re: [Endymail] Improvements to S/MIME

[Wei Chuang <[e-mail]>]

On Sun, Sep 14, 2014 at 1:13 AM, Wei Chuang <[e-mail]> wrote:

>
>
> On Sat, Sep 13, 2014 at 10:54 AM, Werner Koch <[e-mail]> wrote:
>
>> On Fri, 12 Sep 2014 19:48, [e-mail] said:
>>
>> > 1) S/MIME doesn't fully protect users mail envelope metadata.  For
>> example
>> > the recipient and envelope-sender must be visible to the intermediate
>> SMTP
>>
>> If you want that, it is easy to put the messaqge into a message/rfc822
>> mail container and use faked subject and other mailer header.
>>
>
> Right I agree that there is a RFC5751 sec 3.1 (
> http://tools.ietf.org/html/rfc5751#page-18 ) that mentions the
> message/rfc822, but unless I'm missing something one still has to specify
> the intended recipient, and a return path.  Even if the body and most
> headers were wrapped hence private, an adversary could still find the
> sender/recipient information very useful.
>
> Another issue albeit a small one with message/rfc822, was what to do if
> the headers conflicted between the outer and inner messages.
>

Just wanted to point out that wrapping using message/rfc822 may have
problems.  In another thread regarding DMARC damage, one proposed
mitigation is also to wrap the message but was noted that this could open
the recipient to phishing attacks due to mishandling of headers by the
recipients MUA.

See http://www.ietf.org/mail-archive/web/ietf/current/msg89601.html

John Levine suggested there using other options for mitigating against
DMARC.  In the S/MIME context I don't think that's possible to avoid
wrapping if one wants to protect the headers, so work will have to be done
to prevent opening a phishing vector.

-Wei


>
> -Wei
>
>
>>
>>
>> Salam-Shalom,
>>
>>    Werner
>>
>> --
>> Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.
>>
>>
>