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Re: [lamps] S/MIME fix

Phillip Hallam-Baker <phill@hallambaker.com> Fri, 18 May 2018 02:04 UTC

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From: Phillip Hallam-Baker <phill@hallambaker.com>
Date: Thu, 17 May 2018 22:04:26 -0400
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To: Russ Housley <housley@vigilsec.com>
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Subject: Re: [lamps] S/MIME fix
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On Thu, May 17, 2018 at 9:42 AM, Russ Housley <housley@vigilsec.com> wrote:

> On May 16, 2018, at 1:51 PM, Alexey Melnikov <alexey.melnikov@isode.com>
> wrote:
>
> On 16/05/2018 18:35, Jim Schaad wrote:
>
> I will note that unless multipart/mixed has some special text associated
> with it.  Text/html is defined by RFC 1866 to only hold a single HTML
> document.  Thus building an HTML document from multiple parts is not
> according to Hoyle.
>
> Yes, but people do this anyway, as separate HTML body parts are frequently
> valid HTML documents. So building from pieces works most(*) of the time.
>
> (*) spam and phishing nonwithstanding.
>
>
> I do not see a way to totally thwart eFail unless each portion of a
> multi-part is processed in its own sandbox.
>

​I concur with Russ on this. Though defining what a sandbox is may be a
challenge.​

​While I don't doubt that spammers are abusing multipart/related, is there
a circumstance in which an end user is likely to generate an email with
text/html split across several multipart/related blocks? I think that is
really rather unlikely.


The gadget attack is less of a concern to me since encryption never assures
authentication, thats why you need authenticated encryption or a MAC.

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