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 10:43:04 -0400 [thread overview]
Message-ID: <20121101144304.GA15821@redhat.com> (raw)
In-Reply-To: <1351780159.15708.17.camel@falcor>
On Thu, Nov 01, 2012 at 10:29:19AM -0400, Mimi Zohar wrote:
> On Thu, 2012-11-01 at 09:53 -0400, Vivek Goyal wrote:
> > On Thu, Nov 01, 2012 at 09:10:03AM -0400, Vivek Goyal wrote:
> >
> > [..]
> > > >
> > > > > - 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?
> >
> > Eric responded but my mistake he responded to only me. So I will quickly
> > put his idea here.
> >
> > [start quote]
> >
> > You can't ptrace a process that has a capability you don't.
> >
> > That should be enforced in security/commoncap/
> >
> > [end quote]
> >
> > This looks like a good idea. Upon verification signed binaries will be
> > assigned special capability and then no unsigned binary should be able
> > to ptrace signed/verified processes
>
> That's a good generic solution, which I'm all in favor of, but it
> doesn't resolve the latter half of Matthrew's requirement "and it must
> be impossible for anything other than /sbin/kexec to make the kexec
> system call."
Only those executables which have extended capability
(say CAP_SIGNATURES_VERIFIED) will be able to call kexec_load() syscall.
Only signed executables will get this capability upon signature verification
(using keys in kernel keyring only).
so any xyz executable will not be able to call kexec_load() until and
unless it is signed with keys kernel trusts. This is similar to signed
module verification.
So I think this does satisfy the requirement matthew specified. Isn't it?
Matthew, what do you think?
Thanks
Vivek
next prev parent reply other threads:[~2012-11-01 14:44 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
2012-11-01 13:53 ` Vivek Goyal
2012-11-01 14:29 ` Mimi Zohar
2012-11-01 14:43 ` Vivek Goyal [this message]
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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