Re: [RFC 01/18] capabilities: track actually used capabilities
[Posted July 13, 2016 by jake]
| From: |
| Andy Lutomirski <luto-AT-amacapital.net> |
| To: |
| Topi Miettinen <toiwoton-AT-gmail.com> |
| Subject: |
| Re: [RFC 01/18] capabilities: track actually used capabilities |
| Date: |
| Mon, 13 Jun 2016 14:12:37 -0700 |
| Message-ID: |
| <CALCETrW3SwYPzA5HUKMhpRET4pht-4+eOjHiXFzRqync9Hx3yg@mail.gmail.com> |
| Cc: |
| "linux-kernel-AT-vger.kernel.org" <linux-kernel-AT-vger.kernel.org>, Alexander Viro <viro-AT-zeniv.linux.org.uk>, Ingo Molnar <mingo-AT-redhat.com>, Peter Zijlstra <peterz-AT-infradead.org>, Serge Hallyn <serge.hallyn-AT-canonical.com>, Andrew Morton <akpm-AT-linux-foundation.org>, Kees Cook <keescook-AT-chromium.org>, Christoph Lameter <cl-AT-linux.com>, "Serge E. Hallyn" <serge.hallyn-AT-ubuntu.com>, Andy Shevchenko <andriy.shevchenko-AT-linux.intel.com>, "Richard W.M. Jones" <rjones-AT-redhat.com>, =?UTF-8?Q?Iago_L=C3=B3pez_Galeiras?= <iago-AT-endocode.com>, Chris Metcalf <cmetcalf-AT-ezchip.com>, Andy Lutomirski <luto-AT-kernel.org>, Jann Horn <jann-AT-thejh.net>, "open list:FILESYSTEMS (VFS and infrastructure)" <linux-fsdevel-AT-vger.kernel.org>, "open list:CAPABILITIES" <linux-security-module-AT-vger.kernel.org> |
| Archive‑link: | |
Article |
On Mon, Jun 13, 2016 at 1:45 PM, Topi Miettinen <toiwoton@gmail.com> wrote:
> On 06/13/16 20:32, Andy Lutomirski wrote:
>> On Mon, Jun 13, 2016 at 12:44 PM, Topi Miettinen <toiwoton@gmail.com> wrote:
>>> Track what capabilities are actually used and present the current
>>> situation in /proc/self/status.
>>
>> What for?
>
>
> Capabilities
> [RFC 01/18] capabilities: track actually used capabilities
>
> Currently, there is no way to know which capabilities are actually used.
> Even
> the source code is only implicit, in-depth knowledge of each capability must
> be used when analyzing a program to judge which capabilities the program
> will
> exercise."
>
> Should I perhaps cite some of this in the commit?
Yes, but you should also clarify what users are supposed to do with
this. Given ambient capabilities, I suspect that you'll find that
your patch doesn't actually work very well. For example, if you run a
shell script with ambient caps, then you won't notice caps used by
short-lived helper processes.
>
>>
>> What is the intended behavior on fork()? Whatever the intended
>> behavior is, there should IMO be a selftest for it.
>>
>> --Andy
>>
>
> The capabilities could be tracked from three points of daemon
> initialization sequence onwards:
> fork()
> setpcap()
> exec()
>
> fork() case would be logical as the /proc entry is per task. But if you
> consider the tools to set the capabilities (for example systemd unit
> files), there can be between fork() and exec() further preparations
> which need more capabilities than the program itself needs.
>
> setpcap() is probably the real point after which we are interested if
> the capabilities are enough.
>
> The amount of setup between setpcap() and exec() is probably very low.
When I asked "what is the intended behavior on fork()?", I mean "what
should CapUsed be after fork()?". The answer should be about four
words long and should have a test case. There should maybe also be an
explanation of why the intended behavior is useful.
But, as I said above, I think that you may need to rethink this
entirely to make it useful. You might need to do it per process tree
or per cgroup or something.
--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
