Mailinglists35 via Postfix-users:
>
> Hi
>
> I run a postfix 3.5.9 smtp relay for a webserver that sends user signup and
> forgot password emails. That's the only use case and the server does not
> receive any other emails and neither generates any locally.
>
> I'm trying to prevent leaking internal information (hostname & IP) in
> Received header.
If the use case is sending "signup" and "reset" email messages, you
cuold drop all Received: headers that match your pattern (the pattern
can then be simplified because it only needs to look at the first line).
But wait, there is more.
> For this, I've setup `smtp_header_checks = regexp:/etc/postfix/header_checks`
> with the contents:
>
> /^(Received: from \[127\.0\.0\.1\] \(web\d\w+
> \[\d+\.\d+\.\d+\.\d+\]\))((.|\n|\t)*)/m REPLACE Received: from
> email.domain.tld (email.domain.tld. [1.2.3.4])$2
> The postmap input looks like this:
>
> echo -e "Received: from [127.0.0.1] (web1dev [10.11.12.13])\n\tby
> email.domain.tld (Postfix) with ESMTPS id C9056
> 7E002\n\tfor <em...@gmail.com>; Fri, 8 Mar 2024 19:20:29 +0200 (EET)"
> | postmap -q - pcre:/etc/postfix/header_checks
> Received: from [127.0.0.1] (web1dev [10.11.12.13]) REPLACE Received:
> from email.domain.tld (email.domain.tld. [1.2.3.4])
>
> What I am doing wrong?
The postmap command reads input from stdin one line at a time, and
applies each input line to all the header_checks patterns. It can't
be used for multiline inputs.
However, it can handle multiline input when used like this, but the
details may be bash specific.
$ cat header_checks
/^Received: from \S+ \(web\d\w+ [^)]+\)(.+)/m REPLACE Received: from
email.domain.tld (email.domain.tld. [1.2.3.4])$1
input=$(echo -e "Received: from [127.0.0.1] (web1dev [10.11.12.13])\n\tby
email.domain.tld (Postfix) with ESMTPS id C90567E002\n\tfor <em...@gmail.com>;
Fri, 8 Mar 2024 19:20:29 +0200 (EET)")
$ postmap -q "$input" pcre:header_checks
REPLACE Received: from email.domain.tld (email.domain.tld. [1.2.3.4])
by email.domain.tld (Postfix) with ESMTPS id C90567E002
for <em...@gmail.com>; Fri, 8 Mar 2024 19:20:29 +0200 (EET)
It took me a while to figure that out.
Wietse
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