🚀 go-pugleaf

barmar@think.com (Barry Margolin) writes:
>In article <1992Oct13.172459.28720@zip.eecs.umich.edu> ayman@eecs.umich.edu (Ayman I. Kayssi) writes:
>>I posted a question on comp.unix.questions about how to get a shell by email,
>>that is a shell that would execute what's in the body of an email message.
>>All the details have been worked out except for one thing: security.

>How about this:

>Include in the header a string in both plaintext and encrypted form.  The
>receiving system would decrypt the encrypted form and compare it to the
>plaintext.

>One problem with this is that it's quite amenable to known-plaintext
>attacks.  And it also requires a decryption key to be stored on the
>destination system, unless you use a public-key encryption system.

Such a system would be easily spoofed by a "replay" attack.  If I ever get
hold of one of the messages, I just take the header (which has a valid key
on it) attach a different shell script, and send it!  Bang!

To keep this kind of system secure you either need to encrypt the message,
or use some kind of digital signature stuff to provide a way of verifying
that the contents of the message have not been corrupted in transit.


-Tony Luck <aegl@ossi.com>