linux-kernel - Re: Kdump with signed images

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Date:	Fri, 2 Nov 2012 10:36:03 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Balbir Singh <bsingharora@...il.com>
Cc:	Matthew Garrett <mjg@...hat.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Khalid Aziz <khalid@...ehiking.org>, kexec@...ts.infradead.org,
	horms@...ge.net.au, Dave Young <dyoung@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	Roberto Sassu <roberto.sassu@...ito.it>,
	Kees Cook <keescook@...omium.org>,
	Peter Jones <pjones@...hat.com>
Subject: Re: Kdump with signed images

On Fri, Nov 02, 2012 at 07:59:15PM +0530, Balbir Singh wrote:
> On Fri, Nov 2, 2012 at 6:53 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
> > On Thu, Nov 01, 2012 at 02:52:25PM +0000, Matthew Garrett wrote:
> >> On Thu, Nov 01, 2012 at 10:43:04AM -0400, Vivek Goyal wrote:
> >>
> >> > So I think this does satisfy the requirement matthew specified. Isn't it?
> >> > Matthew, what do you think?
> >>
> >> Sure, if you can ensure that. You'll need to figure out how to get the
> >> build system to sign the userspace binaries and you'll need to ensure
> >> that they're statically linked and don't dlopen anything (including the
> >> nsswitch modules), but otherwise that should work.
> >>
> >
> > [ CC peter jones ]
> >
> > Ok, so even if we build kexec-tools statically with glibc, we have the
> > issue of name service switch modules. glibc will still do dlopen on
> > these modules. So what are options now.
> >
> > - Sign glibc and associated shared libraries. Do not allow unsigned
> >   shared library to dynamically link with signed executable.
> >
> > - Peter mentioned that work with uClibc for kexec-tools.
> >
> > I personally think that however hard it is but first option sounds like
> > a long term solution. We might have more user space processes which
> > we might have to trust a generic solution will help with that. For example,
> > we might have to sign and trust qemu at some point of time.
> >
> > Are there other ways of handing glibc issue?
> >
> 
> Have you seen http://sourceware.org/glibc/wiki/FAQ - "Even statically
> linked programs need some shared libraries which is not acceptable for
> me. What can I do?" Probably, worth trying.

Yes I have seen this. IIUC, it says that build libc with -enable-static-nss
and then individual programs need to statically build against the nss
modules program will use.

I think building libc with -enable-static-nss part will be unacceptable
for general server as other programs would like to make use of the
existing nss functionality.

Thanks
Vivek
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