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Subject: Re: Is it impossible to moderate a list?
From: Dave Wolfe <dwolfe @ risc . sps . mot . com>
Date: Tue, 24 Sep 1996 15:35:00 -0500 (CDT)
To: noah @ baysystems . com (Noah White)
Cc: majordomo-users @ greatcircle . com
In-reply-to: <3248373C.66EB@baysystems.com> from "Noah White" at Sep 24, 96 03:32:12 pm
Reply-to: Dave Wolfe <david_wolfe @ risc . sps . mot . com>

[ Noah White writes: ]
> 
> I'm trying to set up a list from which only certain people can post
> to.  I set it up such that in the config file it looks for a file to get
> a list of authorized addresses.  In doing so I noticed that X-Sender
> gets tacked on to the headers and that anyone with Netscape can forge
> this address nullifying any protection this gives.

Resend doesn't pay any attention to X-Sender.

> So I decided to use the approval header as a further protection.
> This works but I've come across a broader flaw in that in the Recieved
> header shows what the outgoing alias is.  Anyone who wishes to post to
> the list could bypass the resend alias and go directly to the outgoing
> aliases (which as I said it posted in the Recieved header). Thus
> bypassing all checks.

Note that if you put the Approval header in the body and don't provide a
subsequent To header (in the body, separated from the real body by a
blank line) you'll get Apparently-To headers. Stick with restrict_post.

> Is there any whay to protect from this?

[ This is a canned message ]

Here's how you hide your actual mail list alias from list spammers:

1.  Pick a non-obvious outgoing list alias name, e.g. "testlist-uzpl"
    instead of "testlist-outgoing".

2.  Turn off EXPN and VRFY in sendmail.cf (Opnoexpn,novrfy).

3.  Use a parameter file for resend parameters:

	testlist: "|/.../wrapper resend @/.../testlist.parms"

4.  In the parameter file, specify more recipients than just the
    outgoing list alias, e.g.:

	-l testlist
	-h foo.bar.com
	testlist-uzpl,nobody

    (Don't forget to alias "nobody" to /dev/null.)

5.  Don't allow any more file permissions than absolutely necessary on
    any of the Mj files and/or don't allow user logons on the Mj server
    machine and don't export the file system where the Mj files live.
    I.e., is it *really* necessary to have world read permissions on
    anything but the subscriber list file itself? I get along fine with
    0660 on all the list.* files and 0664 on the list files.

-- 
 Dave Wolfe    *Not a spokesman for Motorola*
 Motorola MMTG  6501 Wm. Cannon Dr. W. OE112  Austin  TX  78735-8598


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