linux-kernel - Re: [PATCH v2 0/4] PR_SET_NO_NEW

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALCETrWWKpU3RHu25BO9sEWPZbBbemahfF9sjb8c_UfRrLcqVg@mail.gmail.com>
Date:	Sun, 15 Jan 2012 17:04:17 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Casey Schaufler <casey@...aufler-ca.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jamie Lokier <jamie@...reable.org>, Will Drewry <wad@...omium.org>,
	linux-kernel@...r.kernel.org, keescook@...omium.org,
	john.johansen@...onical.com, serge.hallyn@...onical.com,
	coreyb@...ux.vnet.ibm.com, pmoore@...hat.com, eparis@...hat.com,
	djm@...drot.org, segoon@...nwall.com, rostedt@...dmis.org,
	jmorris@...ei.org, scarybeasts@...il.com, avi@...hat.com,
	penberg@...helsinki.fi, viro@...iv.linux.org.uk, mingo@...e.hu,
	akpm@...ux-foundation.org, khilman@...com, borislav.petkov@....com,
	amwang@...hat.com, oleg@...hat.com, ak@...ux.intel.com,
	eric.dumazet@...il.com, gregkh@...e.de, dhowells@...hat.com,
	daniel.lezcano@...e.fr, linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, olofj@...omium.org,
	mhalcrow@...gle.com, dlaor@...hat.com, corbet@....net,
	alan@...rguk.ukuu.org.uk, Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v2 0/4] PR_SET_NO_NEW_PRIVS, unshare, and chroot

On Sun, Jan 15, 2012 at 4:37 PM, Andy Lutomirski <luto@...capital.net> wrote:
> To make the no_new_privs discussion more concrete, here is an updated
> series that is actually useful.  It adds PR_SET_NO_NEW_PRIVS with the
> same semantics as before (plus John Johansen's AppArmor fix and with
> improved bisectability).  It then allows some unshare flags and chroot
> (sometimes) when no_new_privs is set.

Here's another reason to allow setuid/setresuid when no_new_privs is set:

I'd like a pam_no_new_privs module that lets me set no_new_privs for
certain highly untrusted users.  The way to do it is:

PR_SET_NO_NEW_PRIVS
setuid(uid)
execve(the user's shell)

If setuid were disallowed, it would have to be:

setuid(uid)
PR_SET_NO_NEW_PRIVS
execve(the user's shell)

The latter is racy: the user can log in once, then log in a second
time and ptrace the login or sshd process between setuid and
PR_SET_NO_NEW_PRIVS.

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/