[hashcash] Re: hashcash-sendmail breaks up long stamps
- From: Andreas Mattheiss <please.post@xxxxxxxxxxxxxxxx>
- To: hashcash@xxxxxxxxxxxxx
- Date: Thu, 30 Jun 2011 19:24:30 +0200
Hello,
thanks for getting back.
You're effectively saying that splitting the stamp into short portions on
individual lines is not a bug but a feature. Having read the source you
quoted and having run a few more checks I strongly agree with you.
But why is procmail then not verifying the stamp? Well, it's apparently
the way procmail deals with line breaks in header lines. If I set up a
trivial provmail recepie
VERBOSE=yes
#hashcash
:0 Hfh
* ^X-Hashcash:
* $? cat > /tmp/zzz
|sed 's/\(^Subject:\)\(.*\)/\1<HC OK> \2/'
it should, one would assume, simply pipe the complete header into a file.
The content is however
<SNIP>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.5.9i
X-Hashcash:
1:20:110629:lvzwlcykh5uctsy5.t.hadvabvobs@xxxxxxxxxxxx::MukaRTmGN+xq
J5RO:00000000000000000003lEb
X-GMX-Antivirus: 0 (no virus found)
X-GMX-Antispam: 0 (Mail was not recognized as spam);
Detail=5D7Q89H36p6hEpf6ttqws02bSs/CL6nBCZcAzW/pD0kbT/BaZcLmAWMxrJq35NjII8ZYU
X6M6dwR6Ld/uk+5aGcGL8xTX1Cl/Uh1R+vjLtpoaQbFzoPu8EETGu03jarAu/l2iyZz9smJc5lih
xkatzETLXnSyLsDWmnxz3m1lJvMVJSJXatjcwrZzxGUPS7Rz22x8xy81Kh5NFAk5xgnqRNapFZyC
cbrAqiptWKyQ40fy/o7xI1R+w==V1;
X-Virus-Status: No
<SNIP>
whereas the true header is
<SNIP>
Content-Disposition: inline
User-Agent: Mutt/1.5.9i
X-Hashcash: 1:20:110629:lvzwlcykh5uctsy5.t.hadvabvobs@xxxxxxxxxxxx::MukaRTmGN+xq
J5RO:00000000000000000003lEb
X-GMX-Antivirus: 0 (no virus found)
X-GMX-Antispam: 0 (Mail was not recognized as spam);
Detail=5D7Q89H36p6hEpf6ttqws02bSs/CL6nBCZcAzW/pD0kbT/BaZcLmAWMxrJq35NjII8ZYU
X6M6dwR6Ld/uk+5aGcGL8xTX1Cl/Uh1R+vjLtpoaQbFzoPu8EETGu03jarAu/l2iyZz9smJc5lih
xkatzETLXnSyLsDWmnxz3m1lJvMVJSJXatjcwrZzxGUPS7Rz22x8xy81Kh5NFAk5xgnqRNapFZyC
cbrAqiptWKyQ40fy/o7xI1R+w==V1;
X-Virus-Status: No
<SNIP>
Watch the spaces/tab in the procmail-generated variant - looks like
procmail tries to stuff all lines of a header item into one line,
substituting <whitespace><tab> for the split. Of course hashcash can't
recognise this crap any more, and comes back with
examining stamp: X-Hashcash:
1:20:110629:lvzwlcykh5uctsy5.t.hadvabvobs@xxxxxxxxxxxx::MukaRTmGN+xq
J5RO:00000000000000000003lEb
skipped: stamp invalid
since it can't deal with the spaces.
Way out: wipe out the <whitespace><tab> with sed before feeding this to
hashcash:
#hashcash
:0 Hfh
* ^X-Hashcash:
* $? sed 's/ \t//g' |hashcash -cqXdp 1d -b20 -f $HOME/hashcash.db -Er \
'.**whatever'
|sed 's/\(^Subject:\)\(.*\)/\1<HC OK> \2/'
this works then reliably even for very long stamps.
So, no problem with hashcash or hashcash-sendmail, but with the way
procmail does business with multi-line header items. I'm sure a
procmail-guru would firmly claim his ground by stating that there are
"many good reasons for doing it that way" - to the humble end user who
doesn't have a Ph.D. from the Faculty of Procmail this is a bit hard to
swallow. The problem only arises when the stamp is broken into more than
one line, but still funny no one else has stumbled over this yet,
apparently.
Regards
Andreas
--
BAXTER: Can't reach anyfin' with them little arms.
RIMMER: That's probably why they're always a bit grumpy...
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