linux-kernel - Re: [RFC] capabilities: Ambient capabilities

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Message-ID: <CAGXu5jLj5M4FjhxqWy7Kg7qSXmBZ387f2DdwxRvioKaRJ9opXw@mail.gmail.com>
Date:	Fri, 13 Mar 2015 12:54:12 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"Andrew G. Morgan" <morgan@...nel.org>,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	"Ted Ts'o" <tytso@....edu>, Andrew Lutomirski <luto@...nel.org>,
	Andrew Morton <akpm@...uxfoundation.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Linux API <linux-api@...r.kernel.org>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Aaron Jones <aaronmdjones@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Markku Savela <msa@...h.iki.fi>,
	Jonathan Corbet <corbet@....net>
Subject: Re: [RFC] capabilities: Ambient capabilities

On Fri, Mar 13, 2015 at 12:03 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On Fri, Mar 13, 2015 at 11:52 AM, Kees Cook <keescook@...omium.org> wrote:
>>
>> All this said, almost half of the capabilities, if passed to flawed
>> children with attacker controlled execution, can be elevated to full
>> root privileges pretty easily[1], so I think any documentation around
>> this feature should include some pretty dire warnings about using
>> this.
>
> That's a good point.  I'll make sure to document that.
>
> It's worth noting that, for many applications, that list is
> overstated.  For example, many of the suggested privilege escalations
> don't work if you're in a sufficiently restrictive mount namespace.
>
> For my own use, I plan on adding only CAP_NET_BIND_SERVICE and
> CAP_NET_RAW to pA, and I'll be layering seccomp on top to the extent
> possible.

Right, keeping software authors aware of the fact that their efforts
for attack surface reducing may need additional confinement beyond
just the capability reduction.

-Kees

>
> --Andy
>
>>
>> -Kees
>>
>> [1] https://forums.grsecurity.net/viewtopic.php?f=7&t=2522
>>
>> --
>> Kees Cook
>> Chrome OS Security
>
>
>
> --
> Andy Lutomirski
> AMA Capital Management, LLC



-- 
Kees Cook
Chrome OS Security
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