Need help on UUCP connection (4.2 <--> Ultrix)

[Michael Thompson]

In article <636 at decuac.UUCP> avolio at decuac.UUCP (Frederick M. Avolio) writes:
>I article <98 at cholula.UUCP>, tim at cholula.UUCP writes:
>>In article <132 at illogica.UUCP> mickey at illogica.UUCP (Michael Thompson)writes:
>> =>  My bet is that your login name "UOurMachine" does not have a unique
>> =>  UID.  Some versions of UUCP (I've seen it in system V derivitives) do
>> =>  a getuid() call and search linearly through the password file until
>> =>  they find the *first* entry with a matching UID. The login name
>> =>  associated with that UID is what is used to check against entries
>> =>  in the USERFILE.
>> 
>> Thanks Michael for the fix to the problem.  Never even crossed my mind since
>> 4.2 systems don't care about that.  Apparently Ultrix UUCP is a mixture of
>> SYS5 and 4.[23] UUCP.
>
>I am glad a fix was found, but based on the LOGFILE entries and our
>experience the problem was not on the Ultrix system side.  We talk to 13
>or so other sites -- Ultrix systems and non-Ultrix systems -- using the
>Ultrix-32 UUCP.  On our system as well as on some of the others, the uucp
>login names are different but are all the same UID for different systems.
>We have no problems.  I suspect the problem -- based on the LOGFILE
>entries -- was in the USERFILE of the other system.  In fact, the problem
>might be with a UUCP that didn't recognize system names of more than 6
>characters.
>
>Fred.

Please keep in mind that as long as there *is* an entry in the remote
USERFILE which corresponds to the first matching login name that is
associated with the UID of the uucp account, then things will *appear*
to work properly. But the implications of this can be illustrated
thus:

USERFILE:

	uucp, /
	pubuucp,somesys /usr/spool/uucppublic

/etc/passwd:

	uucp:xCXK46Ju1PE1Q:4:4:UUCP account: ...
	pubuucp:rSL55Z9flVWhs:4:4:some other uucp account: ...

Since both `pubuucp' and `uucp' have the same UID, the protections implied
by entries in the USERFILE are *not properly enforced*. Since these
certain versions of UUCP determine the login name by associating it
with the first matching UID, any system logging into `pubuucp' would
be givin access to / .

A simple test to determine whether or not you have this type of UUCP
or not is to remove, say, `pubuucp' from the remote USERFILE and see
if you still have a UUCP link through that account.

Or, you can remove the entry in the remote USERFILE which
corresponds to `uucp' in my example.  If you have this type of UUCP,
all of your UUCP links which share UID's with `uucp' will fail.

I don't know if this should be classified as a bug or not, but it
certainly presents some security problems as well as other possible
headaches -

USERFILE:

	uucp, /usr/spool/uucppublic
	myuucp,mysys /usr/mickey

/etc/passwd:

	uucp:xCXK46Ju1PE1Q:4:4:UUCP account: ...
	myuucp:rSL55Z9flVWhs:4:4:my own private UUCP account ...

I could be banging my head against the wall trying to figure out
why UUCP denies me access to my home directory even though I explicitly
grant access in the USERFILE.

		    mickey m.
		    (Michael Thompson)
		    {decwrl,ucbvax}!dual!vecpyr!altos86!illogica!mickey