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From: ebiederm@xmission.com (Eric W. Biederman)
To: Kees Cook <keescook@chromium.org>
Cc: "Serge Hallyn" <serge.hallyn@ubuntu.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Richard Weinberger" <richard@nod.at>,
	"Robert Święcki" <robert@swiecki.net>,
	"Dmitry Vyukov" <dvyukov@google.com>,
	"David Howells" <dhowells@redhat.com>,
	"Kostya Serebryany" <kcc@google.com>,
	"Alexander Potapenko" <glider@google.com>,
	"Eric Dumazet" <edumazet@google.com>,
	"Sasha Levin" <sasha.levin@oracle.com>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH 0/2] sysctl: allow CLONE_NEWUSER to be disabled
Date: Wed, 27 Jan 2016 04:27:19 -0600	[thread overview]
Message-ID: <874mdzgvw8.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <CAGXu5j+kkzmnrvfOhcDfsK81bxwrgnywKQKCof+Pqjv-oVB+Kw@mail.gmail.com> (Kees Cook's message of "Tue, 26 Jan 2016 15:13:29 -0800")

Kees Cook <keescook@chromium.org> writes:

> On Tue, Jan 26, 2016 at 9:15 AM, Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
>> Quoting Josh Boyer (jwboyer@fedoraproject.org):
>>> What you're saying is true for the "oh crap" case of a new userns
>>> related CVE being found.  However, there is the case where sysadmins
>>> know for a fact that a set of machines should not allow user
>>> namespaces to be enabled.  Currently they have 2 choices, 1) use their
>>
>> Hi - can you give a specific example of this?  (Where users really should
>> not be able to use them - not where they might not need them)  I think
>> it'll help the discussion tremendously.  Because so far the only good
>> arguments I've seen have been about actual bugs in the user namespaces,
>> which would not warrant a designed-in permanent disable switch.  If
>> there are good use cases where such a disable switch will always be
>> needed (and compiling out can't satisfy) that'd be helpful.
>
> My example is a machine in a colo rack serving web pages. A site gets
> attacked, and www-data uses user namespaces to continue their attack
> to gain root privileges.
>
> The admin of such a machine could have disabled userns months earlier
> and limited the scope of the attack.

Of course for the paranoid there is already a mechanism to do this.
/sbin/chroot.

No new user namespaces are allowed to be created inside of a chroot.

Eric

  reply	other threads:[~2016-01-27 10:40 UTC|newest]

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-22 22:39 [PATCH 0/2] sysctl: allow CLONE_NEWUSER to be disabled Kees Cook
2016-01-22 22:39 ` [kernel-hardening] " Kees Cook
2016-01-22 22:39 ` [PATCH 1/2] sysctl: expand use of proc_dointvec_minmax_sysadmin Kees Cook
2016-01-22 22:39   ` [kernel-hardening] " Kees Cook
2016-01-23  3:10   ` Eric W. Biederman
2016-01-23  3:10     ` [kernel-hardening] " Eric W. Biederman
2016-01-23 22:25     ` Jann Horn
2016-01-24  1:20       ` Eric W. Biederman
2016-01-24  1:43         ` Al Viro
2016-01-24  1:56           ` Jann Horn
2016-01-24  6:02             ` Eric W. Biederman
2016-01-24  6:32               ` Jann Horn
2016-01-24  6:44                 ` Eric W. Biederman
2016-01-22 22:39 ` [PATCH 2/2] sysctl: allow CLONE_NEWUSER to be disabled Kees Cook
2016-01-22 22:39   ` [kernel-hardening] " Kees Cook
2016-01-22 22:47   ` Robert Święcki
2016-01-22 22:47     ` [kernel-hardening] " Robert Święcki
2016-01-22 22:50     ` Kees Cook
2016-01-22 22:50       ` [kernel-hardening] " Kees Cook
2016-01-22 22:55       ` Robert Święcki
2016-01-22 22:55         ` [kernel-hardening] " Robert Święcki
2016-01-22 23:00         ` Kees Cook
2016-01-22 23:00           ` [kernel-hardening] " Kees Cook
2016-01-23  0:44           ` Serge Hallyn
2016-01-23  0:44             ` [kernel-hardening] " Serge Hallyn
2016-01-23  0:44           ` Serge Hallyn
2016-01-23  0:44             ` [kernel-hardening] " Serge Hallyn
2016-01-23  0:59           ` Ben Hutchings
2016-01-24 20:59             ` Kees Cook
2016-01-24 20:59               ` Kees Cook
2016-01-24 22:20               ` Andy Lutomirski
2016-01-25 18:51                 ` Kees Cook
2016-01-22 22:49 ` [PATCH 0/2] " Richard Weinberger
2016-01-22 22:49   ` [kernel-hardening] " Richard Weinberger
2016-01-23  3:02 ` Eric W. Biederman
2016-01-23  3:02   ` [kernel-hardening] " Eric W. Biederman
2016-01-24 20:57   ` Kees Cook
2016-01-24 20:57     ` [kernel-hardening] " Kees Cook
2016-01-26  7:38     ` Serge Hallyn
2016-01-24 22:22   ` Andy Lutomirski
2016-01-24 22:22     ` [kernel-hardening] " Andy Lutomirski
2016-01-25 18:51     ` Kees Cook
2016-01-25 18:51       ` [kernel-hardening] " Kees Cook
2016-01-25 18:53       ` Andy Lutomirski
2016-01-25 18:53         ` [kernel-hardening] " Andy Lutomirski
2016-01-25 18:56         ` Kees Cook
2016-01-25 18:56           ` [kernel-hardening] " Kees Cook
2016-01-25 19:33           ` Eric W. Biederman
2016-01-25 19:33             ` [kernel-hardening] " Eric W. Biederman
2016-01-25 22:34             ` Kees Cook
2016-01-25 22:34               ` [kernel-hardening] " Kees Cook
2016-01-25 23:33               ` Andy Lutomirski
2016-01-25 23:33                 ` [kernel-hardening] " Andy Lutomirski
2016-01-26  2:27               ` Daniel Micay
2016-01-26  4:57               ` Eric W. Biederman
2016-01-26  4:57                 ` [kernel-hardening] " Eric W. Biederman
2016-01-26 14:38                 ` Josh Boyer
2016-01-26 14:38                   ` [kernel-hardening] " Josh Boyer
2016-01-26 14:46                   ` Austin S. Hemmelgarn
2016-01-26 14:46                     ` [kernel-hardening] " Austin S. Hemmelgarn
2016-01-26 14:56                     ` Josh Boyer
2016-01-26 14:56                       ` [kernel-hardening] " Josh Boyer
2016-01-26 17:20                       ` Serge Hallyn
2016-01-26 19:56                         ` Josh Boyer
2016-01-26 20:11                           ` Austin S. Hemmelgarn
2016-01-26 17:15                   ` Serge Hallyn
2016-01-26 18:09                     ` Austin S. Hemmelgarn
2016-01-26 18:27                       ` Andy Lutomirski
2016-01-26 18:45                         ` Austin S. Hemmelgarn
2016-01-26 23:15                         ` Kees Cook
2016-01-26 23:13                     ` Kees Cook
2016-01-27 10:27                       ` Eric W. Biederman [this message]
2016-01-27 12:32                         ` Austin S. Hemmelgarn
2016-01-28 14:41                         ` Robert Święcki
2016-01-28 14:41                           ` Robert Święcki
2016-01-26 23:47                     ` Josh Boyer
2016-01-26 16:37                 ` Kees Cook
2016-01-26 16:37                   ` [kernel-hardening] " Kees Cook
2016-01-28  8:56                 ` Serge E. Hallyn
2016-01-28 12:53                   ` Austin S. Hemmelgarn

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