Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [kernel-hardening] Re: [PATCH resend 2/2] userns: control
 capabilities of some user namespaces
To:     "Serge E. Hallyn" <serge@hallyn.com>,
        Daniel Micay <danielmicay@gmail.com>
Cc:     =?UTF-8?B?TWFoZXNoIEJhbmRld2FyICjgpK7gpLngpYfgpLYg4KSs4KSC4KSh4KWH4KS1?=
         =?UTF-8?B?4KS+4KSwKQ==?= <maheshb@google.com>,
        Mahesh Bandewar <mahesh@bandewar.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
        Kernel-hardening <kernel-hardening@lists.openwall.com>,
        Linux API <linux-api@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Eric Dumazet <edumazet@google.com>,
        David Miller <davem@davemloft.net>
References: <20171103004436.40026-1-mahesh@bandewar.net>
 <20171104235346.GA17170@mail.hallyn.com>
 <CAF2d9jg1tZz-hnVBeXm3geq7jSBt5v5w6+p5B1V-7huS4qbMBA@mail.gmail.com>
 <20171106150302.GA26634@mail.hallyn.com> <1510003994.736.0.camel@gmail.com>
 <20171106221418.GA32543@mail.hallyn.com> <1510020963.736.42.camel@gmail.com>
 <20171107032310.GA6429@mail.hallyn.com>
From:   chris hyser <chris.hyser@oracle.com>
Message-ID: <da764cbf-7522-06a0-6c21-adfa3eaac9c2@oracle.com>
Date:   Thu, 9 Nov 2017 13:01:24 -0500
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.3.0
MIME-Version: 1.0
In-Reply-To: <20171107032310.GA6429@mail.hallyn.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 11/06/2017 10:23 PM, Serge E. Hallyn wrote:
> I think I definately prefer what I mentioned in the email to Boris.
> Basically a "permanent capability bounding set".  The normal bounding
> set gets reset to a full set on every new user_ns creation.  In this
> proposal, it would instead be set to the calling task's permanent
> capability set, which starts (at boot) full, and which privileged
> tasks can pull capabilities out of.

Actually, this may solve a similar problem I've been looking at. The 
idea was basically at strategic points in the kernel (possibly LSM hook 
sites, still evaluating, and probably syscall entry) validate that a 
task has not "magically" acquired capabilities that it or parent 
specifically said it cannot have and then take some action like say 
killing it immediately. Using your terms, basically make the "permanent 
capability set" a write-once privilege escalation defense. To handle the 
0-day threat, perhaps make it writable but only with more "restrictive" 
values.

-chrish

From 1583610253758057579@xxx Thu Nov 09 17:27:06 +0000 2017
X-GM-THRID: 1583003759650790753
X-Gmail-Labels: Inbox,Category Forums,HistoricalUnread