Re: Mozilla Thunderbird SMTP down-negotiation weakness

[Jason Haar <Jason.Haar () trimble co nz>]

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