From: "Serge E. Hallyn" <serge@hallyn.com>
To: Christoph Lameter <cl@linux.com>
Cc: "Andrew G. Morgan" <morgan@kernel.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Serge Hallyn <serge.hallyn@ubuntu.com>,
Serge Hallyn <serge.hallyn@canonical.com>,
Andy Lutomirski <luto@amacapital.net>,
Jonathan Corbet <corbet@lwn.net>,
Aaron Jones <aaronmdjones@gmail.com>, "Ted Ts'o" <tytso@mit.edu>,
linux-security-module@vger.kernel.org,
lkml <linux-kernel@vger.kernel.org>,
akpm@linuxfoundation.org
Subject: Re: [capabilities] Allow normal inheritance for a configurable set of capabilities
Date: Wed, 4 Feb 2015 16:56:17 +0100 [thread overview]
Message-ID: <20150204155617.GE16726@mail.hallyn.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1502040946080.16341@gentwo.org>
Quoting Christoph Lameter (cl@linux.com):
> On Wed, 4 Feb 2015, Andrew G. Morgan wrote:
>
> > I'm not generally in favor of this. Mostly because this seems to be a
> > mini-root kind of inheritance that propagates privilege to binaries
> > that aren't prepared for privilege. I don't really buy the mmap code
> > concern because the model as it stands says that you trust the binary
> > (and all of the various ways it was programmed to execute code) with
> > specific privileges. If the binary mmap's some code (PAM modules come
> > to mind) then that is part of what it was programmed to/allowed to do.
> >
> > That being said, if you really really want this kind of thing, then
> > make it a single secure bit (with another lock on/off bit) which, when
> > set, makes: fI default to X.
> >
> > pP' = (X & fP) | (pI & fI)
> >
> > That way the per-process bounding set still works as advertised and
> > you don't need to worry about the existing semantics being violated.
>
> Ok but then also fI needs to be set to X so that the binary f invokes
> can also inherit. So if we copy the inheritable flags to fI then we
> wont be needing the bounding set anymore.
>
> The changes to brpm_caps_from_vfs_cap would then
> be only the following? (substitute capable(CAP_INHERIT_BY_DEFAULT through
> any other means like PRCTL if wanted).
>
>
> Index: linux/security/commoncap.c
> ===================================================================
> --- linux.orig/security/commoncap.c 2015-02-04 09:44:25.000000000 -0600
> +++ linux/security/commoncap.c 2015-02-04 09:45:59.381572756 -0600
> @@ -350,6 +350,9 @@ static inline int bprm_caps_from_vfs_cap
> __u32 permitted = caps->permitted.cap[i];
> __u32 inheritable = caps->inheritable.cap[i];
>
> + if (capable(CAP_INHERIT_BY_DEFAULT)
> + new->cap_inheritable.cap[i] = inheritable;
> +
> /*
> * pP' = (X & fP) | (pI & fI)
> */
Not quite - I think more like
if (secure(SECURE_AMBIENT_PRIVS))
new->cap_inheritable.cap[i] = inheritable;
Then ns_capable(CAP_INHERIT_BY_DEFAULT), or perhaps rather
ns_capable(CAP_SETPCAP), would be required in order to set
SECURE_AMBIENT_PRIVS, which is off by default.
next prev parent reply other threads:[~2015-02-04 15:56 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-02 16:21 [capabilities] Allow normal inheritance for a configurable set of capabilities Christoph Lameter
2015-02-02 17:12 ` Serge Hallyn
2015-02-02 17:18 ` Andy Lutomirski
2015-02-02 18:09 ` Serge Hallyn
2015-02-03 15:16 ` Christoph Lameter
2015-02-03 15:23 ` Christoph Lameter
2015-02-03 15:55 ` Serge E. Hallyn
2015-02-03 17:18 ` Christoph Lameter
2015-02-03 17:26 ` Serge E. Hallyn
2015-02-04 15:15 ` Andrew G. Morgan
2015-02-04 15:50 ` Christoph Lameter
2015-02-04 15:56 ` Serge E. Hallyn [this message]
2015-02-04 16:12 ` Andrew G. Morgan
2015-02-04 16:34 ` Andy Lutomirski
2015-02-04 16:54 ` Andrew G. Morgan
2015-02-04 17:34 ` Serge E. Hallyn
2015-02-04 18:12 ` Christoph Lameter
2015-02-04 16:43 ` Christoph Lameter
2015-02-04 16:27 ` Andy Lutomirski
2015-02-05 0:34 ` Serge E. Hallyn
2015-02-05 15:23 ` Serge E. Hallyn
2015-02-25 21:50 ` Pavel Machek
2015-02-25 23:59 ` Christoph Lameter
2015-02-26 12:27 ` Pavel Machek
2015-02-27 20:15 ` Andy Lutomirski
2015-02-27 20:48 ` Pavel Machek
2015-02-27 20:56 ` Andy Lutomirski
2015-02-27 22:47 ` Pavel Machek
2015-02-02 17:54 ` Casey Schaufler
2015-02-02 18:08 ` Serge Hallyn
2015-02-02 18:47 ` Mimi Zohar
2015-02-02 19:05 ` Austin S Hemmelgarn
2015-02-02 20:35 ` Casey Schaufler
2015-02-03 16:04 ` Serge E. Hallyn
2015-02-02 19:00 ` Casey Schaufler
2015-02-05 0:20 ` Serge E. Hallyn
2015-02-02 20:37 ` Andy Lutomirski
2015-02-02 20:54 ` Casey Schaufler
2015-02-03 15:51 ` Serge E. Hallyn
2015-02-03 16:37 ` Casey Schaufler
2015-02-03 17:28 ` Serge E. Hallyn
2015-02-03 17:50 ` Casey Schaufler
2015-02-03 19:45 ` Christoph Lameter
2015-02-03 20:13 ` Andy Lutomirski
2015-02-03 23:14 ` Christoph Lameter
2015-02-03 23:17 ` Andy Lutomirski
2015-02-04 2:27 ` Christoph Lameter
2015-02-04 6:05 ` Markku Savela
2015-02-04 13:17 ` Christoph Lameter
2015-02-04 13:41 ` Markku Savela
2015-02-04 14:56 ` Jarkko Sakkinen
2015-02-03 15:17 ` Christoph Lameter
2015-02-03 15:40 ` Casey Schaufler
2015-02-03 15:46 ` Serge E. Hallyn
2015-02-03 17:19 ` Christoph Lameter
2015-02-03 17:29 ` Serge E. Hallyn
2015-02-25 21:50 ` Pavel Machek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150204155617.GE16726@mail.hallyn.com \
--to=serge@hallyn.com \
--cc=aaronmdjones@gmail.com \
--cc=akpm@linuxfoundation.org \
--cc=cl@linux.com \
--cc=corbet@lwn.net \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=morgan@kernel.org \
--cc=serge.hallyn@canonical.com \
--cc=serge.hallyn@ubuntu.com \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).