Messages in this thread | | | Date | Wed, 24 Nov 1999 16:28:55 +0100 (MEZ) | From | "Dr. Michael Weller" <> | Subject | Re: UNIX98 Ptys and chroot bug/question |
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On Wed, 24 Nov 1999, Valentin Podlovchenko wrote:
> crw--w---- 1 valya tty 136, 0 Nov 24 13:25 0 > crw--w--w- 1 root root 136, 1 Nov 24 13:25 1 > > in chroot: > >chroot /web/ !! > chroot /web/ ls -l /dev/pts/ > total 0 > crw--w--w- 1 root root 136, 0 Nov 24 12:16 0 > crw--w---- 1 valya tty 136, 1 Nov 24 13:25 1 [...] > so any user from basic root system can write to chrooted pty and > any user from chroot can write to basic root ptys. > > It seems to me slightly wrong ;)
I'm surprised that you say /dev/pts/1 (or 0) is rw--w--w- in partition and rw--w---- in the other. However, it might be a typo or ok, if the Unix98ptys just take the permissions of the filesystem, and the corresponding login process sets the permissions
Anyway, its simply ok that anyone has write only permission on the pty. The intentional result is that anyuser can send you a message into you login session. And, almost any full screen unix program (editor etc) has a screen refresh key (very often ^V) to redraw teh screen and purge any messages. ( The key is exactly to remove such msges, not to redraw when the screen was garbled due to a bug ;-) )
If you want peace from msgs of other people, the 'mesg' command allows you to enable/disable this. All it does is: Remove the write permission for group and others from the corresponding tty.
Note that others have no read permission, so they can neither modify control parameters by ioctl, nor rob keystrokes. They can only print something to you.
> And one problem too: > After some days work well my server in chrooted partition loose possibility > to log users in by telnet. I think it is because of some problems with ptys but > I wouldn't say it with certainty... ;)
I've no idea about that. It might be related to having those two mounts of Unix98 ptys, maybe something with ownership permission goes wrong, I dunno.
Michael.
--
Michael Weller: eowmob@exp-math.uni-essen.de, eowmob@ms.exp-math.uni-essen.de, or even mat42b@spi.power.uni-essen.de. If you encounter an eowmob account on any machine in the net, it's very likely it's me.
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