Bug in /bin/su?

DoN Nichols dnichols at ceilidh.beartrack.com
Tue Mar 5 12:48:28 AEST 1991

In article <1299 at kosman.UUCP> kevin at kosman.UUCP (Kevin O'Gorman) writes:
>I'm not sure I understand all the issues here, but I'm having trouble
>with /bin/su.

	[ ... ]
>For instance, if I want to su to 'news', which is generally unavailable
>for normal login, on most systems you can su to root and then su to
>news.  On the 3b1 this doesn't work -- you're stuck as root.

	I just shelled out of trn, su'ed from my personal account (dnichols)
to root, ran id(1), and got the expected response, and then su'ed to news,
ran id(1), and got the expected response (news), (news).  I than backed out,
doing id(1) at each step, and got the expected response.  On my system, it
does not seem to be broken!

	I'm running 3.51m, on a 7300 with 1MB on the motherboard, 1.5MB on a
combo board.

>On this system, it seems that to work as 'news' I have to log in originally
>as 'root' and use /bin/su only once.  This does seem to work.
>The reasons that I think this is a bug are (1) there's no error report
>and (2) the second /bin/su does actually leave you running a subshell,
>just not as the user you expect.

	Yes, it is a bug if it behaves as you describe, but is it due to the
software (su), or to some system configuration item?  Is there a valid home
directory for news?  What shell are you running?  Which version of the os?
How much core?  What are the modes on /bin/su?  On my system they are as

-rwsr-xr-x  1 root    sys        3488 Apr 18  1987 /bin/su

	Note the suid bit on owner, and the owner is root.  It SHOULD be
this way on your system, or you shouldn't be able to su TO root.

>Anyone with more insight?

	Give us more facts, then we'll try.  Since I can't duplicate the
behavior on my system, I don't know what is happening.

	Good Luck

Donald Nichols (DoN.)		| Voice (Days):	(703) 664-1585
D&D Data			| Voice (Eves):	(703) 938-4564
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