PPP configuration

Archaic archaic at linuxfromscratch.org
Fri Apr 7 09:00:40 PDT 2006

On Fri, Apr 07, 2006 at 06:51:44AM -0500, Randy McMurchy wrote:
> Anything more should be offered up by Archaic, as he is the resident
> security pundit, and if I recall correctly, is employed in a capacity
> of overseeing connectivity and mail issues for an ISP.

LOL. I don't really see how my job relates, but here goes! :) Unix uses
user/group/world file-based permissions. While certainly spartan, it
works and it is safe. [1] PPP has historically used cleartext passwords
for as long as I can remember. I don't personally have a problem with it
(though linking PPP to libcrypt and hashing sure would be a nice touch).

>From my experience, ADSL is not persistant. My company serves DSL via 3
different phone companies. One of those three has a subset of its
customers doing something a bit different in that they are MAC
authenticated. I don't know the trends, but from my experience, this is
the exception, not the rule, and isn't changing anytime soon. So the
problem becomes that if the password isn't stored anywhere, and you are
not at a local keyboard, you're hosed if/when the connection drops
because of the inability for PPP to re-auth. If PPP were to cache the
PW, you're still in the same boat WRT cleartext passwords because the
password would be readable in memory.

[1] By safe, I mean exploiting of the user/group/world feature mechanism
itself is not known (at least by me) to work. This doesn't mean someone
can't pop a livecd in and effectively bypass all security models in use.
Physical security is a different beast. Mobile laptops (i.e. laptops
that you do actually take places) can avoid the password because there
is a strong likelihood that it isn't meant to be run unattended like a
server or desktop left on at home, but that should be an exercise left
to the reader. The book can teach a few safe ideas, but can't create a
product safer than the admin running it.


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