FreeBSD 6.3-PRERELEASE unable to change file permission

[Robert Watson]

On Mon, 3 Dec 2007, Anjang Aki wrote:

> hi!.. i'm not able to change file permission to disable rlogin and login on 
> my box even as root
>
> # ls -lo /usr/bin/login /usr/bin/rlogin
> -r-sr-xr-x  1 root  wheel  schg 19996 Dec  1 13:04 /usr/bin/login
> -r-sr-xr-x  1 root  wheel  schg 10140 Dec  1 13:04 /usr/bin/rlogin
>
> # chflags -R nouchg login rlogin
> chflags: /usr/bin/login: Operation not permitted
> chflags: /usr/bin/rlogin: Operation not permitted
>
> # chmod a=rx /usr/bin/login /usr/bin/rlogin
> chmod: /usr/bin/login: Operation not permitted
> chmod: /usr/bin/rlogin: Operation not permitted
>
> it makes me uneasy as my users can still use login and rlogin to gain access 
> to the box

Others have already addressed the chflags issue, but there's a larger concern 
here.

First off, 'rlogin' is the client, not the server for the rlogin protocol, so 
chmodding the file limits the ability to rlogin *from* your system, not rlogin 
*to* your system.  The ability to login via rlogin is controlled via 
inetd.conf, which enables or disables the rlogind daemon.  By default we 
neither run inetd nor rlogind, and even if you enable inetd, you still need to 
also enable rlogind explicitly.  Probably for the reasons you have in mind.

Second, I'm not sure what you're trying to do by disabling 'login', but keep 
in mind that 'login' is used on the console to allow login to the system on 
the console, so you may lock yourself out of the console if you disable it. 
On the other hand, 'login' is *not* used for sshd, so if your goal is to deny 
network access, it won't have that effect.

In general, what you want to do to prevent login over the network is not 
enable network services that allow remote login -- sshd, telnetd, rlogind, 
ftpd, etc.  By default, we disable all those services.  You can look in a 
combination of /etc/rc.conf and /etc/inetd.conf to see what is enabled.

Robert N M Watson
Computer Laboratory
University of Cambridge

>
> my system:
> # uname -a
> FreeBSD k3.college.edu 6.3-PRERELEASE FreeBSD 6.3-PRERELEASE #1: Sun
> Dec  2 18:51:02 MYT 2007     root at college.edu:/usr/obj/usr/src/sys/EDU
> i386
>
> thanks for advice
>
> -- 
> -- Anjang Aki --
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