[comp.unix.admin] Bug in su

mrn@eplunix.UUCP (Mark R. Nilsen) (05/30/91)

I hope this posting is relevent here.  I do not regularly read this group.
I have encountered a problem when using su with rsh.  This is what happens.

I type from one of our vaxen:

	rsh earlobe su

I get:

	Password:

I start typing and my keystrokes are echoed!!

If noone is looking over my shoulder and I type the correct password
I get stuck in a very strange state.  I can do everything I want, 
but I have no visible prompt.  The environment variable says my
prompt is "#" though.  I went to our local guru and he poked around
for a while.  He noticed several interesting things in the source
that would explain parts of this problem.  My question to the net is
is there documentation or this?  Why hasn't it been fixed.

Thank-you in advance for any information regarding this.  You may
respond by email, but I will also check for postings.  Flames will be read
with pitty.

--Mark.  
-- 
"To skilled assembly language	      |	Mark Nilsen.	
programmers, the 8088 is perhaps the  |
most wonderful processor ever	      |	mrn%eplunix.UUCP@eddie.mit.edu	
created, ..."-Dr Dobb's Journal, 3/91 |

subbarao@phoenix.Princeton.EDU (Kartik Subbarao) (05/30/91)

In article <1086@eplunix.UUCP> mrn@eplunix.UUCP (Mark R. Nilsen) writes:
>I hope this posting is relevent here.  I do not regularly read this group.
>I have encountered a problem when using su with rsh.  This is what happens.
>
>I type from one of our vaxen:
>
>	rsh earlobe su
>
>I get:
>
>	Password:
>
>I start typing and my keystrokes are echoed!!
>
>If noone is looking over my shoulder and I type the correct password
>I get stuck in a very strange state.  I can do everything I want, 
>but I have no visible prompt.  The environment variable says my

Relax. There's no bug in su. The reason that you're seeing echoing is 
because there's no way to turn it off. when you say 'rsh foo su', the
rsh process is not associated with a tty on machine foo, therefore when
getpass() tries to ioctl() a tty, it can't find one, so things are echoed.
As to the shell after that, since isatty(0) is not true, it assumes that
it's not interactive and therefore does not print a prompt. (right, there's
no need to print a prompt in the general case if input is not from a tty).
If you wanted a prompt, all you have to say is 'rsh foo su -c "csh -i"', or
whatever your favorite shell is. Realize now that you won't be able to
interactively edit something via 'vi' or the likes. If you want a tty in the 
first place, you can have a kludge by saying say 'rsh foo pty -d su', if
you have Dan Bernstein's pty program. This, however, is not a really clean
approach, and if you want a darn tty in the first place, then you might as
well rlogin to the machine, get a shell, then su from the shell.

>"To skilled assembly language	      |	Mark Nilsen.	
>programmers, the 8088 is perhaps the  |
>most wonderful processor ever	      |	mrn%eplunix.UUCP@eddie.mit.edu	
>created, ..."-Dr Dobb's Journal, 3/91 |

Nah. It's not CISCy enough. The M680*0 series is a lot more nicer. Gotta
love that BFEXTU instruction!


			-Kartik


--
internet% whoami

subbarao@phoenix.Princeton.EDU -| Internet
kartik@silvertone.Princeton.EDU (NeXT mail)  
SUBBARAO@PUCC.BITNET			          - Bitnet

craig@attcan.UUCP (Craig Campbell) (05/31/91)

In article <1086@eplunix.UUCP> mrn@eplunix.UUCP (Mark R. Nilsen) writes:
 
>I type from one of our vaxen:
 
>	rsh earlobe su
 
>I get:
 
>	Password:
 
>I start typing and my keystrokes are echoed!!
 
>If noone is looking over my shoulder and I type the correct password
>I get stuck in a very strange state.  I can do everything I want, 
>but I have no visible prompt.  
>--Mark.  

This situation also exists as Mark describes on/in Unix 4.0.2.1 (AT&T)
{I just checked}.

I would suspect that this is in some way a rsh bug, but it is just a 
suspicion.

craig

jb3o+@andrew.cmu.edu (Jon Allen Boone) (06/06/91)

craig@attcan.UUCP (Craig Campbell) writes:
> This situation also exists as Mark describes on/in Unix 4.0.2.1 (AT&T)
> {I just checked}.
> 
> I would suspect that this is in some way a rsh bug, but it is just a 
> suspicion.

Under Ultrix 3.1, the characters are also echoed - however, a good
passwd will leave you su'ed, but the prompt won't show up!  however,
commands seem to work...

I'd say that it is NOT a bug for rsh to pass your characters clearly
through your remote connection.  I'm not sure where this behavior is
coming from (Ultrix?), but it would seem that if passwd wasn't sending
the text back, it wouldn't be displayed.

----------------------------------|++++++++++++++++++++++++++++++++++++++++
| "He divines remedies against injuries;   | "Words are drugs."           |
|  he knows how to turn serious accidents  |     -Antero Alli             |
|  to his own advantage; whatever does not |                              |
|  kill him makes him stronger."           | "Culture is for bacteria."   |
|                   - Friedrich Nietzsche  |     - Christopher Hyatt      |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

baier@r2d2.fmi.uni-passau.de (Joern Baier) (06/07/91)

In article <1086@eplunix.UUCP> mrn@eplunix.UUCP (Mark R. Nilsen) writes:
>[...]
>I type from one of our vaxen:
>
>	rsh earlobe su
>[...]

Type instead:
	
	rlogin -l root earlobe


Joern.
-- 
Joern Baier     (baier@unipas.fmi.uni-passau.de) 
Jesuitengasse 9 
D-W8390 Passau 
Tel.:   +49/851/35239