From: Djalal Harouni <tixxdz@gmail.com>
To: Ben Hutchings <ben@decadent.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
kernel-hardening@lists.openwall.com,
LSM List <linux-security-module@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Dongsu Park <dpark@posteo.net>,
Casey Schaufler <casey@schaufler-ca.com>,
James Morris <james.l.morris@oracle.com>,
Paul Moore <paul@paul-moore.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jonathan Corbet <corbet@lwn.net>, Jessica Yu <jeyu@redhat.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Mauro Carvalho Chehab <mcheh>
Subject: Re: [kernel-hardening] Re: [PATCH v3 1/2] modules:capabilities: automatic module loading restriction
Date: Thu, 20 Apr 2017 14:44:53 +0200 [thread overview]
Message-ID: <CAEiveUdS=GbyxDVeNFrjTmhvQB-a6UgrJXcGY=BYJLu+3z0x_Q@mail.gmail.com> (raw)
In-Reply-To: <1492654942.31767.21.camel@decadent.org.uk>
On Thu, Apr 20, 2017 at 4:22 AM, Ben Hutchings <ben@decadent.org.uk> wrote:
> On Thu, 2017-04-20 at 00:20 +0200, Djalal Harouni wrote:
> [...]
>> +modules_autoload:
>> +
>> +A sysctl to control if modules auto-load feature is allowed or not.
>> +This sysctl complements "modules_disabled" which is for all module
>> +operations where this flag applies only to automatic module loading.
>> +Automatic module loading happens when programs request a kernel feature
>> +that is implemented by an unloaded module, the kernel automatically
>> +runs the program pointed by "modprobe" sysctl in order to load the
>> +corresponding module.
>> +
>> +When modules_autoload is set to (0), the default, there are no
>> +restrictions.
>> +
>> +When modules_autoload is set to (1), processes must have CAP_SYS_MODULE
>> +to be able to trigger a module auto-load operation, or CAP_NET_ADMIN
>> +for modules with a 'netdev-%s' alias.
>> +
>> +When modules_autoload is set to (2), automatic module loading is
>> +disabled for all. Once set, this value can not be changed.
>
> I would expect a parameter 'modules_autoload' to be a boolean, so this
> behaviour would be surprising.
>
> What is the point of mode 2? Why would someone want to set
> modules_disabled=0 and modules_autoload=2?
modules_disabled is too restrictive and once set it can't be changed,
maybe that's why not all users use it.
With modules_disabled=0 and modules_autoload=2
* The functionality of the system can still be made available.
* You only disable automatic module loading
* Explicit module load/unload can still happen. Administrators or
privileged programs can still explicitly load modules provide a
feature without rebooting.
* You are able to restrict some applications from inserting new
modules at all by also applying a seccomp filter and removing their
CAP_SYS_MODULE, where explicit load/unload is still available to
others.
* You are able to unload an old bad version of the module without
rebooting, and maybe load the new version.
> [...]
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
> [...]
>> +static int modules_autoload_privileged_access(const char *name)
>> +{
>> + if (capable(CAP_SYS_MODULE))
>> + return 0;
>> + else if (name && strstr(name, "netdev-") && capable(CAP_NET_ADMIN))
> [...]
>
> We want a prefix match, so use strncmp() not strstr().
Indeed, will fix it.
Thanks!
> Ben.
>
> --
> Ben Hutchings
> It is easier to change the specification to fit the program than vice
> versa.
>
--
tixxdz
next prev parent reply other threads:[~2017-04-20 12:44 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 22:20 [PATCH v3 0/2] modules:capabilities: automatic module loading restrictions Djalal Harouni
2017-04-19 22:20 ` [PATCH v3 1/2] modules:capabilities: automatic module loading restriction Djalal Harouni
2017-04-19 23:16 ` Andy Lutomirski
2017-04-20 2:22 ` Ben Hutchings
2017-04-20 12:44 ` Djalal Harouni [this message]
2017-04-20 15:02 ` Ben Hutchings
[not found] ` <1492700543.31767.23.camel-/+tVBieCtBitmTQ+vhA3Yw@public.gmane.org>
2017-04-20 20:39 ` [kernel-hardening] " Djalal Harouni
[not found] ` <CAEiveUdFL53XyQpacmN6f8F28M0bLQDcetpRXJjrJ10vDmQi8Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-20 21:28 ` Kees Cook
2017-04-19 22:20 ` [PATCH v3 2/2] modules:capabilities: add a per-task modules autoload restriction Djalal Harouni
2017-04-19 23:15 ` Andy Lutomirski
2017-04-19 23:43 ` Kees Cook
2017-04-20 2:41 ` Andy Lutomirski
[not found] ` <CALCETrUueOx1tqj+Ru93KGpy2HHR-A_GQ6DrAppiomkPTtX7Lw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-21 23:19 ` Kees Cook
2017-04-21 23:28 ` Andy Lutomirski
2017-04-21 23:40 ` Kees Cook
2017-04-21 23:51 ` Andy Lutomirski
2017-04-22 0:12 ` Djalal Harouni
[not found] ` <CAEiveUcx8fwQgXdLPeMNsTjX2KPhQKH__a-XzcHko_1aCmh4sg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-22 1:19 ` Djalal Harouni
2017-04-22 6:51 ` Andy Lutomirski
[not found] ` <CALCETrUT73CcPQx2T=1zWbOUhw9r-c_YqXw5-KTwxgWPgXuTwA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-22 19:29 ` Kees Cook
[not found] ` <CAGXu5jLV+WZyj+xnxVFkFEgEthNt6eXdcSgHT-=85mJ1ECZ1Rw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-24 14:25 ` Djalal Harouni
2017-04-24 18:02 ` Kees Cook
[not found] ` <CAGXu5jL_-cxidy_O4ORaN0iX9o7=hsi3DYTRvQs5w5363Z+MVg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-24 18:35 ` Djalal Harouni
2017-04-21 23:52 ` Casey Schaufler
2017-04-22 0:00 ` Andy Lutomirski
2017-04-22 0:13 ` Casey Schaufler
2017-04-22 6:45 ` Andy Lutomirski
2017-04-22 12:17 ` Djalal Harouni
[not found] ` <CAEiveUdbQcfn1xC5xWMv91vL_uR1MGTvARqw-E4GDTMUZ6t=bA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-04 13:07 ` Djalal Harouni
2017-05-04 14:58 ` Serge E. Hallyn
2017-05-05 13:06 ` Djalal Harouni
2017-05-05 16:18 ` Andy Lutomirski
2017-04-20 1:57 ` kbuild test robot
[not found] ` <1492640420-27345-3-git-send-email-tixxdz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-04-19 22:38 ` Djalal Harouni
2017-04-24 4:29 ` Rusty Russell
2017-04-26 9:06 ` Djalal Harouni
2017-04-27 2:07 ` Rusty Russell
[not found] ` <87k266hacq.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
2017-04-27 13:16 ` Djalal Harouni
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAEiveUdS=GbyxDVeNFrjTmhvQB-a6UgrJXcGY=BYJLu+3z0x_Q@mail.gmail.com' \
--to=tixxdz@gmail.com \
--cc=acme@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=ben@decadent.org.uk \
--cc=casey@schaufler-ca.com \
--cc=corbet@lwn.net \
--cc=dpark@posteo.net \
--cc=gregkh@linuxfoundation.org \
--cc=james.l.morris@oracle.com \
--cc=jeyu@redhat.com \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=luto@kernel.org \
--cc=paul@paul-moore.com \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=rusty@rustcorp.com.au \
--cc=serge@hallyn.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).