bugtraq - Re: Mozilla Thunderbird SMTP down-negotiation weakness

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Date: Wed, 26 Oct 2005 22:35:27 +1300
From: Jason Haar <Jason.Haar@...mble.co.nz>
To: bugtraq@...urityfocus.com
Subject: Re: Mozilla Thunderbird SMTP down-negotiation weakness

Thomas Henlich wrote:

>Sequence of attack
>
>- S sends EHLO response with STARTTLS advertisement.
>- A4 discards S's STARTTLS advertisement.
>- PLAIN authentication takes place.
>- A4 can read cleartext password.
>
>RESOLUTION
>
>For A1-A3 no resolution is known. For A4, set user preference to
>enforce TLS.
>
>  
>
Comment about A4.

Thunderbird explicitly allows you "TLS, if available" - which appears to 
be what you refer to. However, there is a "TLS" - which means only do 
TLS - and alert if the TLS certificate presented doesn't match a known 
one (which would happen in a MITM).

Are you referring to a bug in their "TLS" mode - or implying that "TLS, 
if available" is somehow not... what it says it is...???

Doesn't sound like a hole to me.

-- 
Cheers

Jason Haar
Information Security Manager, Trimble Navigation Ltd.
Phone: +64 3 9635 377 Fax: +64 3 9635 417
PGP Fingerprint: 7A2E 0407 C9A6 CAF6 2B9F 8422 C063 5EBB FE1D 66D1