linux-kernel - Re: [Xen-devel] [PATCH v3 00/11] xen: Initial kexec/kdump implementation

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Message-ID: <20130111210801.GC12019@redhat.com>
Date:	Fri, 11 Jan 2013 16:08:01 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Jan Beulich <JBeulich@...e.com>,
	"maxim.uvarov@...cle.com" <maxim.uvarov@...cle.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	David Howells <dhowells@...hat.com>
Subject: Re: [Xen-devel] [PATCH v3 00/11] xen: Initial kexec/kdump
 implementation

On Fri, Jan 11, 2013 at 01:03:41PM -0800, H. Peter Anvin wrote:
> On 01/11/2013 12:52 PM, Vivek Goyal wrote:
> > 
> > Eric,
> > 
> > In a private conversation, David Howells suggested why not pass kernel
> > signature in a segment to kernel and kernel can do the verification.
> > 
> > /sbin/kexec signature is verified by kernel at exec() time. Then
> > /sbin/kexec just passes one signature segment (after regular segment) for
> > each segment being loaded. The segments which don't have signature,
> > are passed with section size 0. And signature passing behavior can be
> > controlled by one new kexec flag.
> > 
> > That way /sbin/kexec does not have to worry about doing any verification
> > by itself. In fact, I am not sure how it can do the verification when
> > crypto libraries it will need are not signed (assuming they are not
> > statically linked in).
> > 
> > What do you think about this idea?
> > 
> 
> A signed /sbin/kexec would realistically have to be statically linked,
> at least in the short term; otherwise the libraries and ld.so would need
> verification as well.

Yes. That's the expectation. Sign only statically linked exeutables which
don't do any of dlopen() stuff either.

In fact in the patch, I fail the exec() if signed executable has
interpreter.

Thanks
Vivek
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