[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: problem using screen after running /bin/su
From: |
David Balazic |
Subject: |
RE: problem using screen after running /bin/su |
Date: |
Mon, 30 Aug 2004 09:27:06 +0200 |
>From your explanation I don't see why all other programs work ( can read and
write the tty ),
while screen can't.
> ----------
> From:
> address@hidden:screen-users-bou
> address@hidden on behalf of Juergen
> Weigert[SMTP:address@hidden
> Reply To: address@hidden
> Sent: 27. avgust 2004 18:45
> To: Felix E. Klee
> Cc: address@hidden
> Subject: Re: problem using screen after running /bin/su
>
> On Aug 27, 04 17:50:33 +0200, Felix E. Klee wrote:
> > On Fri, 27 Aug 2004 08:39:48 -0700 (PDT) Edward Quillen wrote:
> > > Cannot open your terminal '/dev/pts/4' - please check.
> >
> > I have the same problem under Linux. I found out that the device is
> > owned by the user who started the terminal (emulator). Ordinary users
> > cannot read/write from/to that device.
>
> And this is very good, the way it is. Otherwise, your 'ordinary user'
> could
> try to read from the device while you were typing your password.
>
> > The device seems to be central
> > for IO; for example issuing
> >
> > echo "hello" > /dev/pts/4
>
> Writing to a foreign tty is only a mild annouyance.
> But reading is a security risk.
>
> > should output "hello" in the terminal. It's a while ago that I searched
> > the web. All I could find were people saying that the above problem is a
> > bug in screen.
>
> What looks like a bug is actually a hand-crafted security feature.
> Annoying sometimes, but protecting the innocent.
>
> >
> > A workaround may involve setting the needed permissions before su'ing.
>
> Correct. Best is to chown the device. A group or world readable tty is an
> invitation to hackers. Or simply have your 'su' shell within the screen
> session, if that is possible.
>
> cheers,
> Jw.
>
> --
> o \ Juergen Weigert unix-software __/ _=======.=======_
> <V> | address@hidden creator __/ _---|____________\/
> \ | 0179/2069677 __/ (____/ /\
> (/) | ____________________________/ _/ \_ vim:set sw=2 wm=8
>
>
> _______________________________________________
> screen-users mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/screen-users
>