subbarao@phoenix.Princeton.EDU (Kartik Subbarao) (12/05/90)
In article <KHERA.90Dec4095322@thneed.cs.duke.edu> khera@thneed.cs.duke.edu (Vick Khera) writes: >In article <4453@idunno.Princeton.EDU> subbarao@phoenix.Princeton.EDU (Kartik Subbarao) writes: > The other questions is this. Is there a way to prevent a user from telneting > on to the machine while I am using it, and do an xloadimage on my display? > >which, to me at least, puts us into the world of X. to his first >question, there was already given an answer. to the second, i >responded. Okay - yes you are right. Within the world of X, this is true. >under SunOS 4.1, when you log in at the console, the /dev/console, >/dev/fb, as well as all the other graphics display devices are changed >to be owned by the person logging into the console, with read/write >permissions tightly controlled. thus unless you are root or the >person logged into the console, you cannot simply open /dev/fb and >scribble on it or read it. so, once you secure your X server, you are >pretty safe from people messing up your screen. Not necessarily the case here. The default case of SunOS 4.1, /dev/fb and all of /dev/win's are left owned by root, and are in readable/writable mode (i.e rw-rw-rw). You can uncomment lines in /etc/fbtab if you want, but that's something that a normal user can't do. And even then, there's the problem of of non - exclusive resources unlike /dev/audio, where a person can have a process continually running which is opening that resource. The argument is something simliar to tty's. It would be useful to chown those devices, but thats not necessarily the case and it may not help sometimes. >in summary, to prevent people from mucking up your screen by using the >devices directly, use SunOS 4.1. Be serious :-) -Kartik (I need a new .signature -- any suggestions?) subbarao@{phoenix or gauguin}.Princeton.EDU -|Internet kartik@silvertone.Princeton.EDU (NeXT mail) -| SUBBARAO@PUCC.BITNET - Bitnet (I need a new .signature -- any suggestions?) subbarao@{phoenix or gauguin}.Princeton.EDU -|Internet kartik@silvertone.Princeton.EDU (NeXT mail) -| SUBBARAO@PUCC.BITNET - Bitnet