OSEC

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Subject: Re: removing Receiced: headers
From: brian moore (bemrom.org)
Date: Wed Aug 23 2000 - 21:11:32 CDT

On Wed, Aug 23, 2000 at 11:29:27PM +0400, Michael Tokarev wrote:
> This exact question popped up again and again.
> Postfix will not remove Received:. You're free to
> modify it so it will do that to you, but this is
> not a Good Thing to do. Search the archives for
> more information on this.

I pointed him at my header-(de)munging trick, which allows discarding
arbitrary headers. I didn't realize it at the time, but Wietse did...
it does provide a simple mechanism for dropping Receieved headers to
hide an internal network.

I must have missed prior threads on it, but if done wisely, it can be
useful (some corporations have truly bizarre internal networks that add
a stack of useless RFC-1918 machines ... there's really no reason to
send anything but the bastion machine to the real world).

Since there is existing code to fondle headers from a table, the
complexity of this one is pretty low, so should have no impact on
security (basically a strcmp and a return... :)) unless, of course
you do '/Received: .*/ DROP' and discard -all- received lines... but if
you do that, you're silly. :)