Home Directory Jail for Users

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1

Hi,

I am looking for a shell script (or any other way), that puts a user in a home directory jail. So for example, I have a user named richard and I don't want him wandering outside /usr/users/richard. I don't want him to cd to anywhere including cd ..

Somebody said you can do that with chroot, but I looked it up on the man pages and it says it is used to change the root directory.

Any help will be greatly appreciated.

Thanks
.Michael

2

Hi, mz043.
As far as I know, you have two options:

  • One is to create a chroot jail for your users (As you've been told). This involves several tasks: create a dummy "root filesystem", copy libs, binaries, etc... The use of sudo, and some shell scripting among others. There are lots of info on the Net, depending on your OS.

  • The other is the use of a restricted shell. I don't know what OS you are using but perhaps a "man -k restricted" would give you some clues :wink:

Regards.

3

Thanks for the reply.

I want to avoid chroot, as I don't have much experience with UNIX sysadmin and chroot sounds like the kinda thing that if you get wrong, you quietly pack up your stuff, take a cab to the airport and board the first avail flight :slight_smile:

I use tru64 unix --- to be honest I think I'll use Access Control Lists. With them I can restrict access to areas I want. I can do that on the group level as well, so no need to do it for each user individually.

Thanks anyway.
M

4

what's about rksh?

$ rksh
$ cd ..
rksh: cd: restricted
$ cd /
rksh: cd: restricted
$ /usr/sbin/ifconfig
rksh: /usr/sbin/ifconfig: restricted
$

from the man page:

 rksh is used to set up login names  and  execution  environ-
 ments  whose  capabilities are more controlled than those of
 the standard shell. The actions of  rksh  are  identical  to
 those of ksh, except that the following are disallowed:

    o  changing directory \(see cd\(1\)\)

    o  setting the value of SHELL, ENV, or PATH

    o  specifying path or command names containing /

    o  redirecting output \(>, >|, <>, and >>\)

    o  changing group \(see newgrp\(1\)\).

 The restrictions above are enforced after .profile  and  the
 ENV files are interpreted.

 When a command to be executed is found to be  a  shell  pro-
 cedure,  rksh invokes ksh to execute it.  Thus, it is possi-
 ble to provide to the end-user shell  procedures  that  have
 access to the full power of the standard shell, while impos-
 ing a limited menu of commands; this scheme assumes that the
 end-user  does not have write and execute permissions in the
 same directory.
 The net effect of these rules is  that  the  writer  of  the
 .profile has complete control over user actions, by perform-
 ing guaranteed setup actions and  leaving  the  user  in  an
 appropriate directory \(probably not the login directory\).

 The system administrator often sets up a directory  of  com-
 mands  \(that  is,  /usr/rbin\)  that can be safely invoked by
 rksh.

still it's not perfect, but a good way to start...

regards pressy