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Re: list

  • To: Xander Jansen < >
  • From: Piet Beertema < >
  • Date: Thu, 12 Feb 1998 13:24:33 +0100
  • Cc:

	I don't know which version of majordomo you're running,
    	but the version I picked up some 2 months ago and which
    	was then the latest version has a very serious flaw: it
    	looks *only* at the header From: line to extract the
    	sender's address from, but that line if by far the most
    	easy to fake. So I can subscribe hundreds of users by
    	sending as many subscribe messages with forged From:
    	lines. Majordomo really should at least check a Sender:
    	line (when present) too and take that as the sender's
    	address in case of discrepancy with the From: address.
    Mmm, I also don't trust the Sender: field anymore.
    There are quite a few popular UA's around (including
    the one I'm using now) that tend to put some kind of
    'POP/IMAP server user' in the Sender field.
You're right. But even so the From: line is a far
more widespread forging target/tool and therefore
really shouldn't be used by majordomo for issues
of 'confidence'.

    For example in this message there is a header X-X-Sender
How about an XXX-Sender? :-)
    Cross-checking RFC822-headers doesn't solve the forgery
    of addresses, even the SMTP-originator can be easily forged
I know. There is simply no fool-proof solution.
But that doesn't mean you shouldn't be able to
choose the less frequently used forging method
to base a 'confidence decision' on.

    cross-checking should be done on the SMTP-originator since
    that's more or less the 'most trustworthy address' (relatively
    speaking of course
Indeed. That's what I meant above.

    the number of double bounces I get as postmaster since people
    don't seem to understand that delivery errors are send to the
    SMTP-originators and they fail to have valid addresses in the
    MAIL FROM, is growing each day)).
Same here. And my guess is that there is a 1:1
correspondence with the number of nitwits that
joins the Internet every day... ;-)


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