From: Adam Shostack <adam@homeport.org>
Date: Mon, 23 Sep 1996 00:49:24 +0800
To: ichudov@algebra.com
Subject: Re: How to use procmail
In-Reply-To: <199609220423.XAA00811@manifold.algebra.com>
Message-ID: <199609221455.JAA15169@homeport.org>
MIME-Version: 1.0
Content-Type: text


Igor Chudov @ home wrote:

| Adam Shostack wrote:
| > :0
| > * From bal@swissnet.ai.mit.edu
| > {
| >    :0E
| >    | pgp +batchmode -fka
| 
| Isn't this vulnerable to "deadbeef" attacks? I can also see an attack when 
| someone sends you an email with the spooofed "From " address and a user
| name that is the same (or almost the same) as that of your trusted parties.

| Then I can send you a bogus email containing a key for mrx@bogus.com 
| and next time you encrypt something for your friend nrx@provider.com,
| you will actually encrypt it with the wron key. If I intercept your
| email, your message to mrx can be compromised.

	Yes its vulnerable.  I might see it in the logs, but I've
personally verified most of the keys I care about, and they carry my
signature, at least on my local keyring.

| > # basic file server.  Only sends whats in .outbound
| > :0 
| > * ^Subject: (SEND|get) [0-9a-z][-_/0-9a-z.]+$
| > * !^Subject:.*[ /.]\.
| > * !^FROM_DAEMON
| > {
| >    # FILE=`formail -x Subject: | sed 's/.* //'`
| >    FILE=`sed -n -e '/Subject:/s/.* //p' -e '/^$/q'`
| > 
| >   :0c 
| >   | (formail -rt -A"Precedence: junk";\
| >      cat $HOME/.outbound/$FILE) | $SENDMAIL -t
| 
| *If* .outbound has some subdirectories (say subdir), How about this email: 
| 
| From: dumbass@aol.com
| Subject: GET subdir/../../../../etc/passwd
| Reply-To: blin@algebra.com

That will fail in the second subject line:
 * !^Subject:.*[ /.]\.
 Subject: does not match '/' or '.' followed by '.'

The first Subject: line prevents absolute pathnames.
 * ^Subject: (SEND|get) [0-9a-z][-_/0-9a-z.]+$

So, AFAIK, you can't get anything but real subdirectories.  Feel free
to install it on localhost & experiment.  I was pretty careful when I
wrote it to make it safe.

Adam

-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume