Bug#684340: exim tls fails: Diffie-Hellman prime too short

[Suresh Ramasubramanian]

On 12-Sep-2013, at 1:18, Florian Weimer <fw at deneb.enyo.de> wrote:

> I suppose the simplest mitigation would be to avoid ephemeral
> Diffie-Hellman key agreement altogether, that is, remove it from the
> cipher suite default.

Dispensing with gnutls and using openssl like most other distros do would possibly make more sense, but that is a license war dating back to 2008 and still open on bts.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=446036

and of course these
http://blog.zugschlus.de/archives/585-exim4-vs.-OpenSSL-vs.-GnuTLS.html
http://blog.josefsson.org/2007/11/09/response-to-gnutls-in-exim-debate/

> 512 bits DH probably allows passive attacks, so IMHO it's unsuitable
> even if the peer's certificate isn't validated in some way (because
> like strong DH, this still provides security against passive
> eavesdroppers).

It is a fig leaf but still better than transporting email en clair.

--srs
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