[hashcash] Re: hashcash integration on MTA level for postfix
- From: Dr Adam Back <adam@xxxxxxxxxxxxxxx>
- To: hashcash@xxxxxxxxxxxxx
- Date: Fri, 18 Aug 2006 14:52:35 -0400
Hi
I took a look at your hashcash postfix filter. And I looked again at
hc-sendmail http://www.hashcash.org/mail/mua/hc-sendmail/
after looking at how they work, hashcash-sendmail seems quite similar
in some ways to your postfix filter.
hc-sendmail delivers by invoking sendmail when its finished adding
stamps. (However it creates stamps as a background task, and delivers
them back to sendmail later; in the mean time it'll return
immediately). I see you also invoke sendmail, but do it in the
foreground if I read it right. (Actually hc-sendmail manages a queue
of tasks, to avoid more than one hashcash minter running at once, if
one is already running it queues the rest).
The difference is in the logic used to decide whether to mint a stamp
or not -- in hc-sendmail case it always makes a stamp, in your case
you have to avoid making stamps for other people which you by
examining the Received headers.
What about the calling api I guess teh filter api is a little bit
different to sendmail invocation, but not that much I think?
There is also Tom Ruddicks hashcash-filter which does foreground
hashcash minting. Maybe that has even closer similarities -- there
the difference would be just the command line API (sendmail-like vs
postfix-filter api) and also lacking the exclusion of creating stamps
for remote mail.
All 3 are written in perl.
Adam
On Wed, Aug 16, 2006 at 08:59:53PM +0200, decoder wrote:
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> Hash: SHA1
>
> Hello there,
>
> I'm new to hashcash and noticed that there isn't much MTA support for
> it. From my point of view, starting this at MUA level is pointless so
> I wrote a content_filter for postfix which stamps all outgoing mails.
> I've put a first (alpha) version online at
>
> http://users.own-hero.net/~decoder/hashcash/
>
> The script is integrated into the master cf like every other
> content_filter, for example with these 2 lines:
>
> smtp inet n - n - - smtpd
> -o content_filter=hashcash:dummy
>
> hashcash unix - n n - - pipe
> flags=Rq user=hashcashuser argv=/usr/local/bin/hashcash.pl -f
> ${sender} -- ${recipient}
>
>
> It checks if the mail it currently processes is an outgoing mail (from
> field contains specified domain(s) and last Received: line contains an
> SMTP from a given list), then it stamps it and requeues the mail for
> sending.
>
> The only thing that doesn't work yet is Bcc: (All mails are delivered
> but every mail contains all hashcash headers). I am currently working
> on this, together with a major restructuring as this version is really
> ugly (proof of concept only).
>
> Hope someone has use for this :)
>
> Chris
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