linux security - May 1997 - Re: Re: Re: Re: Buffer Overflows: A Summary

Phexro <ieure@linknet.kitsap.lib.wa.us> writes:
> chroot()''d processes. So, important system calls could be modified
thus:
Since there are tons of syscalls and new ones appearing all the time,
"Fixing"
some of them doesn''t seem like a good idea. It seems more reasonbale to
deny
access to all of them, except for a few specific ones (that can moreover be
modified so as to limit their strength). Still, it would be a big hassle
and probably not worth it.
> [mod: We thought about this, and always Linus could come up with
> another way to break out of the "jail". Feel free to delve in and
I''m fairly convinced that to really get something reasonable, you need
to
totally redesign the OS with this "virtual machine" in mind. Several
research
projects follow such a path (with further expectation also, of course).

[mod: Yes. One "catchall" would be to modify "suser()" to
return
(uid==0) && (current->root == THE_ROOT). That would make a uid==0 in
a
chrooted environment just another user. Just with a special uid. But
still you would have to review the WHOLE system to be sure that no
holes remain.... --REW]


        Stefan

> [mod: Yes. One "catchall" would be to modify "suser()"
to return
> (uid==0) && (current->root == THE_ROOT). That would make a
uid==0 in a
> chrooted environment just another user. Just with a special uid. But
> still you would have to review the WHOLE system to be sure that no
> holes remain.... --REW]
Another would be to adopt the linux-privs (POSIX.1e aka. POSIX 6) model

    http://parc.power.net/morgan/Orange-Linux/linux-privs/index.html

and adopt individual capabilities/privileges instead of having a single
omnipotent superuser.

By removing capability sets from the files in your chroot prison cell it
should be possible to secure it against escape by any user...

Cheers

Andrew
--
               Linux-PAM, libpwdb, Orange-Linux and Linux-GSS
                  http://parc.power.net/morgan/index.html
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