Re: syscall: sys_promote

[Bernd Petrovitsch <bernd@firmix.at>]

On Mon, 2005-08-29 at 11:55 +0800, qiyong wrote:
> Erik Mouw wrote:
> >On Fri, Aug 26, 2005 at 05:25:37PM +0800, Coywolf Qi Hunt wrote:
> >>I just wrote a tool with kernel patch, which is to set the uid's of a running
> >>process without FORK.
> >>
> >>The tool is at http://users.freeforge.net/~coywolf/pub/promote/
> >>Usage: promote <pid> [uid]
> >>
> >>I once need such a tool to work together with my admin in order to tune my web
> >>configuration.  I think it's quite convenient sometimes. 
> >>
> >>The situations I can image are:
> >>
> >>1) root processes can be set to normal priorities, to serve web
> >>service for eg.
> >
> >Most (if not all) web servers can be told to drop all privileges and
> >run as a normal user. If not, you can use selinux to create a policy
> >for such processes (IIRC that's what Fedora does).
> 
> In this way, it's that the web servers themselves drop the privileges, 
> not forced by sysadmin.  sys_promote is a new approach different from 

The sysadmin selects the tool and writes the configuration file. So for
the purpose of this discussion, it is effectively the same.

> selinux or sudo.  sys_promote is manipulating a already running process, 
> while selinux or sudo is for the next launching process.

Kill the process and start it again. Problem solved.

> >>2) admins promote trusted users, so they can do some system work without knowing
> >>   the password
> >>
> >Use sudo for that, it allows even much finer grained control.
> 
> sudo may become a security problem.  Sysadmin and the user don't like 

(almost) every tool may become a security problem.
If you fear a bug in sudo, then write a minimal setuid wrapper for
yourself which checks for the user it started and exec's a binary (with
the full path name specified).
And even then - dependent on other details of the setup - you have the
gap of security problems (or misuse) because of holes in the security.

> the user's account
> always have priorities.  My sysadmin Hommel says this to me:

What does the user do if the process terminates (for whatever reason)
and must be restarted by the user (manually or auutomatically)?
Basically I can see no need for "one time in history" actions. A daemon
can terminate and must be restarted (it may even be a software bug that
causes this and this doesn't change anything that the daemon's admin
must restart it *now*). The machine may reboot for whatever reason ....


	Bernd
-- 
Firmix Software GmbH                   http://www.firmix.at/
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          Embedded Linux Development and Services

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