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From: notes@ucf-cs.UUCP
Newsgroups: net.sources
Subject: Re: Setidle Program
Message-ID: <2078@ucf-cs.UUCP>
Date: Wed, 24-Jul-85 23:17:19 EDT
Article-I.D.: ucf-cs.2078
Posted: Wed Jul 24 23:17:19 1985
Date-Received: Sun, 28-Jul-85 04:47:47 EDT
Sender: notes@ucf-cs.UUCP
Organization: Univ. of Central Florida, Orlando
Lines: 82
Nf-ID: #R:dadla:-32900:ucf-cs:69600001:000:2256
Nf-From: ucf-cs!goldfarb    Jul 24 12:37:00 1985

>This is a program which allows a user to set and maintain a specified idle
>time on his tty.  The default (giving no parameters) sets the idle time to
>zero every 10 minutes.  It is useful for those who need to maintain control
>on their idle time without being present at their terminals.

So who needs to do that?  Generally, users who want to circumvent an
automatic logout program.  I have such a program here and I have a set
of users who sometimes rambunctiously attempt to circumvent such controls
by using programs like this one.  So in retaliation, I offer the following
diff representing a 4.2bsd kernel change to disallow this kind of thing.
The file is ufs_syscalls.c.

(We use RCS, so line numbers may differ from yours.)
  
*** /tmp/,RCSt1001235	Wed Jul 24 12:29:27 1985
--- /tmp/,RCSt2001235	Wed Jul 24 12:29:30 1985
***************
*** 20,25
  
  /*
   * $Log:	ufs_syscalls.c,v $
   * Revision 1.1  84/09/25  10:01:00  root
   * Initial revision
   * 

--- 20,29 -----
  
  /*
   * $Log:	ufs_syscalls.c,v $
+  * Revision 1.2  84/09/25  11:54:59  root
+  * Fixed to disallow utimes() calls to modify char special device
+  * times for non-super-user.
+  * 
   * Revision 1.1  84/09/25  10:01:00  root
   * Initial revision
   * 
***************
*** 651,656
  
  	if ((ip = owner(1)) == NULL)
  		return;
  	u.u_error = copyin((caddr_t)uap->tptr, (caddr_t)tv, sizeof (tv));
  	if (u.u_error == 0) {
  		ip->i_flag |= IACC|IUPD|ICHG;

--- 655,665 -----
  
  	if ((ip = owner(1)) == NULL)
  		return;
+ 	/* no utimes on char spec. devices except superuser */
+ 	if ((ip->i_ic.ic_mode & IFCHR) && !suser()) {
+ 		u.u_error = EACCES;
+ 		goto utbad;
+ 	}
  	u.u_error = copyin((caddr_t)uap->tptr, (caddr_t)tv, sizeof (tv));
  	if (u.u_error == 0) {
  		ip->i_flag |= IACC|IUPD|ICHG;
***************
*** 656,661
  		ip->i_flag |= IACC|IUPD|ICHG;
  		iupdat(ip, &tv[0], &tv[1], 0);
  	}
  	iput(ip);
  }
  

--- 665,671 -----
  		ip->i_flag |= IACC|IUPD|ICHG;
  		iupdat(ip, &tv[0], &tv[1], 0);
  	}
+ utbad:
  	iput(ip);
  }
  
----------------
				Ben Goldfarb
				University of Central Florida
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