[sudo-users] Sudo for groups?

Ladner, Eric (Eric.Ladner) Eric.Ladner at chevrontexaco.com
Wed Apr 6 14:12:29 EDT 2005

Oh..  I misunderstood.  I still think I misunderstand..

So if you just need to change the group membership instead of the user,
why use sudo at all?

If user fred is in "users" as his main group and "yourapp" as a
secondary group that owns the application you can do this:

$ newgrp yourapp # they're in this group in the first place, right?
$ /some/application/command

Ah, but then you have the problem that they are actually IN the group
and they can modify the files anyway.  I see your point. 

I don't think sudo can do that (or at least I can't see how it could
from the sudoers man page).  Best bet is probably a sgid executable
wrapper that forces the group to the application group.

Eric Ladner, Systems Analyst 
RFMS IT Support

-----Original Message-----
From: Rogan Dawes [mailto:lists at dawes.za.net] 
Sent: Wednesday, April 06, 2005 12:00 PM
To: Ladner, Eric (Eric.Ladner)
Cc: sudo-users at courtesan.com
Subject: Re: [sudo-users] Sudo for groups?

Ladner, Eric (Eric.Ladner) wrote:
> I think you're in luck.
> According to the sudoers man page
> (http://www.courtesan.com/sudo/man/sudoers.html):
> A User_List is made up of one or more usernames, system groups 
> (prefixed with '%'), netgroups (prefixed with '+') and other aliases. 
> Each list item may be prefixed with one or more '!' operators. An odd 
> number of '!' operators negate the value of the item; an even number 
> just cancel each other out.
> Eric Ladner, Systems Analyst
> RFMS IT Support

Hi Eric,

Thanks for your response.

But doesn't this simply control WHICH users are allowed to do things? 
i.e. members of the specified group, rather than listing them

I am trying to allow users to gain controlled access to a specific group
rather than to a specific user, which is what sudo normally does.

I think that I am looking for group support in the Runas_Alias /
Runas_List / Runas_Spec keywords.



> -----Original Message-----
> From: sudo-users-bounces at courtesan.com 
> [mailto:sudo-users-bounces at courtesan.com] On Behalf Of 
> lists at dawes.za.net
> Sent: Wednesday, April 06, 2005 5:19 AM
> To: sudo-users at courtesan.com
> Subject: [sudo-users] Sudo for groups?
> Hi folks,
> I have a situation that I am trying to correct as best I can.
> A company has a legacy application that needs world-writable 
> permissions on its data files to operate. I think this is bad 
> practice, and am trying to limit this to group writable for a specific
application group.
> There are then a couple of possibilities:
> 1) Add all application users to the application group
> 2) Use a setuid/setgid wrapper that calls the application.
> 1) has the disadvantage that the user is then still able to modify the

> data files directly.
> 2) seems to me to be a workable solution.
> Trying not to reinvent the wheel (and fall into the same security 
> traps that everyone else has already climbed out of), I thought that 
> maybe sudo could let me do this.
> One thing that I would like to have, though, is that the userid should

> not be changed, just the group. This is because the application checks

> the uid when deciding what operations the user should be allowed to 
> perform.
> Were it not for the "own userid" condition, I could just create an 
> "appuser"
> user who is a member of the "appgrp" group, and allow members of the 
> "appusers"
> group to execute /opt/app/bin/app as "appuser".
> SetGID directories could even control the permissions and ownership of

> spool files . . .
> Is such a thing possible with sudo? I have checked the archives, and 
> saw a post last year referring to an application called "hat" that set

> hardcoded groups.
> Unfortunately, it seems to be a private app, and there was no further 
> discussion on the list.
> Ideally, what I would like is something like:
> %appusers    ALL = (%appgrp) NOPASSWD: /opt/app/bin/app
> Where member of the appusers group would be permitted to run 
> /opt/app/bin/app with the primary group set to be appgrp, but their 
> UID still their own.
> Any suggestions? Am I out of luck?
> I should mention that the platform is Tru64 Unix V40.F and V5.1B, so 
> the Linuxish alternative of allowing the users to execute /usr/bin/sg 
> appgrp /opt/app/bin/app is not available. Thinking about it, though, I

> don't think that would work anyway, due to the uid issue :-(
> Many thanks for any assistance.
> Rogan
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Rogan Dawes

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