asked on

Permission denied

I'm using a SUN server and while using

echo "Yoh" > /dev/pts/x (x is a number)

I can send the message to myself, or when I'm root, I can send mesg to user but user cannot send message to each other, error message is "permission denied", what can I do with this ?

jlevie

Well you're not supposed to be able to do that as an ordinary user. If you could write to just any user's terminal a lot of malicious things would be possible and there wouldn't be any way for the user to control it. Don't do it that way.

There are facilities within Unix specifically for this purpose. Look at the man pages for wall(1M), write(1), mesg(1), and talk(1). Probably the one you want is write(1).

ahTri

ASKER

it gotta be something relate to tty because currently every user have mesg on, can talk, can write ...

Mark Parr

Have you checked the permissions on the /dev/pts/#? I just checked my nonsecure development machine (IBM RS/6000) and the permissions are set to rw--w--w- so everyone has write access to my tty so a "echo message > /dev/pts/#" would work.

ahTri

ASKER

I did try but onn SUN /dev/pts/# is just a link to ../devices/pseudo/..... so cannot change access right

ASKER CERTIFIED SOLUTION

festive

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jlevie

I don't think you need suid on write(1) and I know that you don't on talk(1).

ahTri

ASKER

festive, is that a script to run on root ?

#!/bin/sh -p

this line doesn't run, maybe I don't have sh

festive

this script to run needs to be setuid root, and the top line means that it is a bourne shell script.