Question about ftp and NIS (YP)

Question about ftp and NIS (YP)

Post by Russell J Fulton;ccc03 » Sat, 25 May 1991 14:04:24

I am about to put up a patched version of ftpd on our system. I was testing
it on a workstation when I noticed that I could not log on to it using
my normal login. The workstation is diskless and uses NIS to access the
password file from the main system. I relinked ftpd with -lsun to get the
NIS aware versions of getpwent etc and all worked fine.

I then checked the distributed versions of ftpd to see if they were NIS aware
(this is Irix 3.3.2) and found that it was not. I then tried to ftp to a
SUN (SUNOS 4.1.1) that also shares the main password file by NIS with the
same result.

My question is this: Is there some special reason why SGI and SUN both
distribute their ftpds so that only people with entries in the local
/etc/passwd file can get access to the system via ftp? Or to put it another
way is there some good reason for me not to link my version -lsun.

Thanks, Russell.

Russell Fulton, Computer Center, University of Auckland, New Zealand.


1. Reasonable nis security between Solaris & Linux (was Re: Is nis (yp) a security worry?

My original question was basically a "should I worry" concerning Solaris
sending encrypted passwords via nis to PC's running Linux.  The response I
got was that I should worry, e.g. about spoofing and ypcat passwd. The full
answer seems more complicated - ypcat passwd doesn't return the encrypted
passwords (rather "*" or "*NP*") for the two systems I looked at, and the
shadow file isn't in the "compatibility" list for nis+ under Solaris 2 so it
a question of yp make cobbling together the passwd and shadow file information to
make one backwards-compatible yp file.

But all this does seem to depend on the setup, and of course doesn't get me
any closer to some method of getting encrypted password to Linux clients, who
should have at least the level of security of the Solaris host from which the
passwords are kept - i.e. the /etc/shadow file is not world-readable there
so it shouldn't be readable (via ypcat or whatever) on the clients.

This *must* be something people have solved before?  I cannot run nis+ (some
of the clients, such as Linux, Sunos 4.x cannot run that), I cannot run Novell's
NDS on Solaris yet (even though Linux supports it) - besides I'm not sure that
sort of thing is what I want, and being outside the US some security options
are limited anyway.

I am scared of reducing the security of the main system with Linux satellites;
but I appreciate that "reasonable" security is always a compromise, and that
having the encrypted paswords available to Joe User is only a problem if people
choose crackable passwords anyway.  What is appropriate for the situation isn't
ultra-high security anyway, e.g. the main worry would be if academic staff's
home directories were readable (due to their encrypted passwords being distributed
to lots of computers they probably will never use) and therefore having to redo
some exam questions.  Not that I expect the students will try to break the security
but the new Linux systems are a sensitive issue and I don't want people to *fear*
them as a security loophole.

Perhaps the answer is nis 1.2 on the server, with restricted distribution of
all (? or some??) of these passwords to hosts based on IP or subnet. Again, has
anybody done this already and lived to tell the tale?
Mark Aitchison, Physics & Astronomy   \_  Phone : +64 3 3642-947 a.h. 3371-225
University of Canterbury,             </  Fax   : +64 3 3642-469  or  3642-999

#include <disclaimer.std>           (/'

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