From: Casey Schaufler <casey@schaufler-ca.com>
To: "Serge E. Hallyn" <serue@us.ibm.com>,
Casey Schaufler <casey@schaufler-ca.com>
Cc: Andrew Morgan <morgan@kernel.org>,
"Serge E. Hallyn" <serue@us.ibm.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
Chris Wright <chrisw@sous-sol.org>,
Andrew Morgan <agm@google.com>, Andrew Morton <akpm@google.com>,
Stephen Smalley <sds@tycho.nsa.gov>,
James Morris <jmorris@namei.org>,
linux-security-module@vger.kernel.org,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: implement-file-posix-capabilities.patch
Date: Thu, 28 Jun 2007 08:56:57 -0700 (PDT) [thread overview]
Message-ID: <325190.92239.qm@web36610.mail.mud.yahoo.com> (raw)
In-Reply-To: <20070628153844.GA1977@sergelap.austin.ibm.com>
--- "Serge E. Hallyn" <serue@us.ibm.com> wrote:
> Quoting Casey Schaufler (casey@schaufler-ca.com):
> >
> > --- Andrew Morgan <morgan@kernel.org> wrote:
> >
> > > -----BEGIN PGP SIGNED MESSAGE-----
> > > Hash: SHA1
> > >
> > > Serge E. Hallyn wrote:
> > > >> Does that explain it?
> > > >
> > > > Yes, thanks, but then it still could come in handy to have fE be a full
> > > > bitset, so the application gets some eff caps automatically, while
> > > > others it has to manually set...
> > >
> > > [We touched on this a number of emails back.]
> > >
> > > If an application is capability aware, it can manipulate its own
> > > capabilities and should have fE=0.
> > >
> > > If an application is not capability aware, it needs to have *all* of its
> > > capabilities enabled at exec() time. Otherwise, it won't work.
> >
> > The intent of the fE vector in the POSIX draft is that those capabilities
> > are set on exec (lower vectors permitting). There are cases where it
> > does make sense to raise just some (e.g. ping).
> >
> > > The only reason for having an fE bitmap is to allow a capability-aware
> > > program (you really trust to do its privileged operations carefully) to
> > > be lazy and get some of its capabilities raised for free. Perhaps you
> > > can clarify why this is a desirable thing? :-)
> >
> > No, it's to allow you to grant a subset of the available capabilities
> > to a program that is not aware of capabilities. You can give "date"
> > the capability to reset the clock without giving it the capability
> > to remove other people's files without changing the code or running
> > it setuid.
>
> Would there be a difference between that and setting either fI or fP
> (depending on your intent) to those caps, and setting fE=1 in Andrew's
> scheme?
Arg, you're making me think. The POSIX group went through this,
let me see if I can reconstruct the logic.
The main issue is one if there being a possible case where you
have a capability ignorant program that you want to exec with
a different fP and fE. On first glance it seems that since the
program is capability ignorant it can't matter. But what if your
capability ignorant program exec's a capability aware program
to perform a helper function? You may well want the first program
to have a capability that it does not use in fP (but not fE)
to pass along to the helper program. True, you could probably
come up with a way to set the capabilities on the helper program
to account for this use, but there may be design and security
constraints that make doing so complicated.
Casey Schaufler
casey@schaufler-ca.com
next prev parent reply other threads:[~2007-06-28 15:57 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20070611123714.GA2063@sergelap.austin.ibm.com>
[not found] ` <878322.98602.qm@web36606.mail.mud.yahoo.com>
[not found] ` <afff21250706110926l244ddc28i44289cb08a6721e2@mail.gmail.com>
[not found] ` <20070617135239.GA17689@sergelap>
[not found] ` <4676007F.7060503@kernel.org>
[not found] ` <20070618044017.GW3723@sequoia.sous-sol.org>
[not found] ` <20070620171037.GA28670@sergelap.ibm.com>
[not found] ` <20070620174613.GF3723@sequoia.sous-sol.org>
2007-06-21 16:00 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-06-23 8:13 ` implement-file-posix-capabilities.patch Andrew Morgan
2007-06-24 15:51 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-06-24 16:18 ` implement-file-posix-capabilities.patch James Morris
2007-06-24 20:58 ` [PATCH][RFC] security: Convert LSM into a static interface James Morris
2007-06-24 22:09 ` Chris Wright
2007-06-24 22:37 ` James Morris
2007-06-25 1:38 ` Chris Wright
2007-06-24 23:40 ` Casey Schaufler
2007-06-25 1:39 ` Chris Wright
2007-06-25 3:37 ` Casey Schaufler
2007-06-25 3:57 ` Chris Wright
2007-06-25 13:02 ` Casey Schaufler
2007-06-25 14:24 ` Roberto De Ioris
2007-06-25 4:33 ` [PATCH try #2] " James Morris
2007-06-25 4:48 ` Petr Vandrovec
2007-06-25 4:58 ` James Morris
2007-06-25 16:59 ` Stephen Smalley
2007-06-25 23:56 ` [PATCH try #3] " James Morris
2007-06-25 20:37 ` [PATCH try #2] " Andreas Gruenbacher
2007-06-25 21:14 ` James Morris
2007-06-26 3:57 ` Serge E. Hallyn
2007-06-26 13:15 ` Adrian Bunk
2007-06-26 14:06 ` Serge E. Hallyn
2007-06-26 14:59 ` Adrian Bunk
2007-06-26 15:53 ` Serge E. Hallyn
2007-06-26 18:52 ` Adrian Bunk
2007-06-26 18:18 ` Greg KH
2007-06-26 18:40 ` Serge E. Hallyn
2007-06-26 4:09 ` Kyle Moffett
2007-06-26 4:25 ` Kyle Moffett
2007-06-26 13:47 ` Serge E. Hallyn
2007-06-27 0:07 ` Kyle Moffett
2007-06-27 0:57 ` Crispin Cowan
2007-06-27 1:22 ` Kyle Moffett
2007-06-27 4:24 ` Chris Wright
2007-06-27 13:41 ` Serge E. Hallyn
2007-06-27 14:36 ` James Morris
2007-06-27 17:21 ` Serge E. Hallyn
2007-06-27 18:51 ` Serge E. Hallyn
2007-06-27 19:28 ` James Morris
2007-06-28 2:48 ` Serge E. Hallyn
2007-06-25 3:57 ` [PATCH][RFC] " Serge E. Hallyn
2007-06-25 4:10 ` Chris Wright
2007-06-25 4:54 ` Serge E. Hallyn
2007-06-25 13:50 ` Casey Schaufler
2007-06-25 13:54 ` James Morris
2007-06-25 14:32 ` Serge E. Hallyn
2007-06-25 15:08 ` Casey Schaufler
2007-06-27 5:00 ` implement-file-posix-capabilities.patch Andrew Morgan
2007-06-27 13:16 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-06-28 6:19 ` implement-file-posix-capabilities.patch Andrew Morgan
2007-06-28 13:36 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-06-28 15:14 ` implement-file-posix-capabilities.patch Casey Schaufler
2007-06-28 15:38 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-06-28 15:56 ` Casey Schaufler [this message]
2007-06-29 5:30 ` implement-file-posix-capabilities.patch Andrew Morgan
2007-06-29 13:24 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-06-29 14:46 ` implement-file-posix-capabilities.patch Casey Schaufler
2007-06-28 15:50 ` implement-file-posix-capabilities.patch Andrew Morgan
2007-07-02 14:38 ` implement-file-posix-capabilities.patch Serge E. Hallyn
2007-07-04 21:29 ` implement-file-posix-capabilities.patch Andrew Morgan
2007-07-04 23:00 ` implement-file-posix-capabilities.patch Casey Schaufler
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