From: Vivek Goyal <vgoyal@redhat.com>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Matthew Garrett <mjg@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Khalid Aziz <khalid@gonehiking.org>,
kexec@lists.infradead.org, horms@verge.net.au,
Dave Young <dyoung@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
linux kernel mailing list <linux-kernel@vger.kernel.org>,
Dmitry Kasatkin <dmitry.kasatkin@intel.com>,
Roberto Sassu <roberto.sassu@polito.it>,
Kees Cook <keescook@chromium.org>
Subject: Re: Kdump with signed images
Date: Thu, 1 Nov 2012 09:10:03 -0400 [thread overview]
Message-ID: <20121101131003.GA14573@redhat.com> (raw)
In-Reply-To: <1351276649.18115.217.camel@falcor>
On Fri, Oct 26, 2012 at 02:37:29PM -0400, Mimi Zohar wrote:
> On Fri, 2012-10-26 at 13:06 -0400, Vivek Goyal wrote:
> > On Fri, Oct 26, 2012 at 03:39:16AM +0100, Matthew Garrett wrote:
> > > On Thu, Oct 25, 2012 at 09:15:58PM -0400, Mimi Zohar wrote:
> > >
> > > > On a running system, the package installer, after verifying the package
> > > > integrity, would install each file with the associated 'security.ima'
> > > > extended attribute. The 'security.evm' digital signature would be
> > > > installed with an HMAC, calculated using a system unique key.
> > >
> > > The idea isn't to prevent /sbin/kexec from being modified after
> > > installation - it's to prevent it from being possible to install a
> > > system that has a modified /sbin/kexec. Leaving any part of this up to
> > > the package installer means that it doesn't solve the problem we're
> > > trying to solve here. It must be impossible for the kernel to launch any
> > > /sbin/kexec that hasn't been signed by a trusted key that's been built
> > > into the kernel, and it must be impossible for anything other than
> > > /sbin/kexec to make the kexec system call.
> >
> > I am kind of lost now so just trying to summarize whatever I have
> > learned so far from this thread.
>
> Thanks for summarizing.
>
> > - So say we can sign /sbin/kexec at build time and distros can do that.
> > - Verify the signature at exec time using kernel keyring and if
> > verification happens successfully, say process gains extra capability.
> > - Use this new capability to determine whether kexec_load() will be
> > successful or not.
> >
> > Even if we can do all this, it still has the issue of being able to
> > stop the process in user space and replace the code at run time
> > and be able to launch unsigned kernel.
Thinking more about it. Can we just keep track whether a process was
ptraced or not and disallow kexec_load() syscall if it was ptraced.
(I am assuming that ptrace is the only way to change process code/data).
So binaries can be signed offline. Signature verification can take place
using kernel keyring at exec() time. And we can keep track of ptraced
processes and disallow calling kexec_load() for such processes. If this
is implementable, this should take care of following requirement raised
by matthew.
************************************************************************
It must be impossible for the kernel to launch any /sbin/kexec that hasn't
been signed by a trusted key that's been built into the kernel, and it
must be impossible for anything other than /sbin/kexec to make the kexec
system call.
*************************************************************************
Thoughts?
Thanks
Vivek
next prev parent reply other threads:[~2012-11-01 13:11 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1350588121.30243.7.camel@rhapsody>
[not found] ` <20121018193831.GD18147@redhat.com>
[not found] ` <874nlrv2ni.fsf@xmission.com>
[not found] ` <20121019020630.GA27052@redhat.com>
[not found] ` <877gqnnnf0.fsf@xmission.com>
[not found] ` <20121019143112.GB27052@redhat.com>
[not found] ` <871ugqb4gj.fsf@xmission.com>
[not found] ` <20121023131854.GA16496@redhat.com>
[not found] ` <20121023145920.GD16496@redhat.com>
[not found] ` <87fw552mb4.fsf_-_@xmission.com>
2012-10-24 17:36 ` Kdump with signed images Vivek Goyal
2012-10-25 6:10 ` Mimi Zohar
2012-10-25 14:10 ` Vivek Goyal
2012-10-25 18:40 ` Mimi Zohar
2012-10-25 18:55 ` Vivek Goyal
2012-10-26 1:15 ` Mimi Zohar
2012-10-26 2:39 ` Matthew Garrett
2012-10-26 3:30 ` Eric W. Biederman
2012-10-26 17:06 ` Vivek Goyal
2012-10-26 18:37 ` Mimi Zohar
2012-11-01 13:10 ` Vivek Goyal [this message]
2012-11-01 13:53 ` Vivek Goyal
2012-11-01 14:29 ` Mimi Zohar
2012-11-01 14:43 ` Vivek Goyal
2012-11-01 14:52 ` Matthew Garrett
2012-11-02 13:23 ` Vivek Goyal
2012-11-02 14:29 ` Balbir Singh
2012-11-02 14:36 ` Vivek Goyal
2012-11-03 3:02 ` Balbir Singh
2012-11-02 21:34 ` H. Peter Anvin
2012-11-02 21:32 ` Eric W. Biederman
2012-11-05 18:03 ` Vivek Goyal
2012-11-05 19:44 ` Eric W. Biederman
2012-11-05 20:42 ` Vivek Goyal
2012-11-05 23:01 ` H. Peter Anvin
2012-11-06 19:34 ` Vivek Goyal
2012-11-06 23:51 ` Eric W. Biederman
2012-11-08 19:40 ` Vivek Goyal
2012-11-08 19:45 ` Vivek Goyal
2012-11-08 21:03 ` Eric W. Biederman
2012-11-09 14:39 ` Vivek Goyal
2012-11-15 5:09 ` Eric W. Biederman
2012-11-15 12:56 ` Mimi Zohar
2012-11-08 20:46 ` Mimi Zohar
2012-11-01 14:51 ` Vivek Goyal
2012-11-01 14:57 ` Matthew Garrett
2012-11-01 15:10 ` Khalid Aziz
2012-11-01 16:23 ` Matthew Garrett
2012-11-02 16:57 ` Khalid Aziz
2012-10-26 17:59 ` Mimi Zohar
2012-10-26 18:19 ` Matthew Garrett
2012-10-26 18:25 ` Mimi Zohar
[not found] ` <20121023154123.GA30730@srcf.ucam.org>
[not found] ` <87d309xhmc.fsf_-_@xmission.com>
2012-10-24 17:19 ` [RFC] " Vivek Goyal
2012-10-25 5:43 ` Mimi Zohar
2012-10-25 6:44 ` Kees Cook
2012-10-25 7:01 ` Mimi Zohar
2012-10-25 13:54 ` Vivek Goyal
2012-10-25 19:06 ` Mimi Zohar
2012-10-25 15:39 ` [RFC] Kdump with UEFI secure boot (Re: [PATCH v2] kdump: pass acpi_rsdp= to 2nd kernel for efi booting) Vivek Goyal
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