[Ach] Applied Crypto PDF - postfix config

[christian mock]

On Wed, Feb 12, 2014 at 08:43:20PM +0100, Axel Hübl wrote:

> Would it be out-of-scope to add a further config how to remove the
> local IP of the initially connected client from the mails headers?

Yes, I think it would be out of scope.

It is still a worthwhile thing to do, but please...

> Maybe one could start like that blog entry
> 
> http://major.io/2013/04/14/remove-sensitive-information-from-email-headers-with-postfix/

...completely ignore that one, because he does it dangerously wrong. 

NEVER EVER REMOVE A "RECEIVED" HEADER.

(Sorry for shouting, but I've been fighting too many mail loops caused
by that type of stuff).

"Received" headers are counted and used to break mail loops. 

The solution is to replace the content of those headers with some
fixed string; I have that working in production at customer sites
since forever.

The postfix solution probably would be with header_checks:

/^Received:/  REPLACE Received: hidden

Now only use those header_checks in your outgoing path, and you should
be fine. Maybe by defining an SMTP transport that does outgoing, and
use smtp_header_checks on that...

HTH,

cm.

-- 
Christian Mock                          Wiedner Hauptstr. 15
Senior Security Engineer                1040 Wien
CoreTEC IT Security Solutions GmbH      +43-1-5037273
FN 214709 z

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