bugtraq - Re: GNU screen buffer overflow

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Date: Wed, 03 Dec 2003 22:17:40 +0100
From: Casper Dik <casper@...land.sun.com>
To: Pavel Kankovsky <peak@...o.troja.mff.cuni.cz>
Cc: Kyle Sallee <cromwell@...alab.unc.edu>, bugtraq@...urityfocus.com
Subject: Re: GNU screen buffer overflow



>On Mon, 1 Dec 2003, Kyle Sallee wrote:
>
>> > With devpts and libutempter it is possible to install fully functional
>> > screen without suid/sgid.
>> 
>> Does that mean any program that links with libutempter gains
>> complete suid/sgid root functionality, or only when executing 
>> the functions in the libutempter library, please?
>
>This means you do not need setuid root because devpts sets up the slave
>pty owner and group automatically and you do not need direct access to
>utmp/wtmp, e.g. via setgid utmp, because libtempter functions call an
>external setgid utmp helper called utempter to modify those files (the
>calling process is required to hold a corresponding master pty).


Nearly exactly like in generic SVR4 where ptys are setup using
/usr/lib/pt_chmod; and in Solaris there's the additional "utmp_update"
programs which allows you to set utmp entries; this is all hidden behind the
libc routines.

Casper