From: Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH 17/18] Hibernate: introduced SNAPSHOT_SIG_HASH config
 for select hash algorithm
Date: Tue, 27 Aug 2013 13:30:44 +0200
Message-ID: <20130827113044.GB20527@amd.pavel.ucw.cz>
References: <1377169317-5959-1-git-send-email-jlee@suse.com>
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 <20130825164329.GL5171@amd.pavel.ucw.cz>
 <1377598937.20140.12.camel@linux-s257.site>
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Cc: linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org, linux-efi@vger.kernel.org,
	linux-pm@vger.kernel.org, linux-crypto@vger.kernel.org,
	opensuse-kernel@opensuse.org, David Howells <dhowells@redhat.com>,
	"Rafael J. Wysocki" <rjw@sisk.pl>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Len Brown <len.brown@intel.com>,
	Josh Boyer <jwboyer@redhat.com>,
	Vojtech Pavlik <vojtech@suse.cz>,
	Matt Fleming <matt.fleming@intel.com>,
	James Bottomley <james.bottomley@hansenpartnership.com>,
	Greg KH <gregkh@linuxfoundation.org>, JKosina@suse.com,
	Rusty Russell <rusty@rustcorp.com.au>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	"H. Peter Anvin" <hpa@zytor.com>, Michal Marek <mmarek@suse.cz>,
	Gary Lin <GLin@suse.com>, Vivek Goyal <vgoyal@redhat.com>
To: joeyli <jlee@suse.com>
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On Tue 2013-08-27 18:22:17, joeyli wrote:
> =E6=96=BC =E6=97=A5=EF=BC=8C2013-08-25 =E6=96=BC 18:43 +0200=EF=BC=8C=
Pavel Machek =E6=8F=90=E5=88=B0=EF=BC=9A
> > On Thu 2013-08-22 19:01:56, Lee, Chun-Yi wrote:
> > > This patch introduced SNAPSHOT_SIG_HASH config for user to select=
 which
> > > hash algorithm will be used during signature generation of snapsh=
ot.
> > >=20
> > > v2:
> > > Add define check of oCONFIG_SNAPSHOT_VERIFICATION in snapshot.c b=
efore
> > > declare pkey_hash().
> > >=20
> > > Reviewed-by: Jiri Kosina <jkosina@suse.cz>
> > > Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
> > > ---
> > >  kernel/power/Kconfig    |   46 +++++++++++++++++++++++++++++++++=
+++++++++++++
> > >  kernel/power/snapshot.c |   27 ++++++++++++++++++++++-----
> > >  2 files changed, 68 insertions(+), 5 deletions(-)
> > >=20
> > > diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> > > index b592d88..79b34fa 100644
> > > --- a/kernel/power/Kconfig
> > > +++ b/kernel/power/Kconfig
> > > @@ -78,6 +78,52 @@ config SNAPSHOT_VERIFICATION
> > >  	  dependent on UEFI environment. EFI bootloader should generate=
 the
> > >  	  key-pair.
> > > =20
> > > +choice
> > > +	prompt "Which hash algorithm should snapshot be signed with?"
> > > +        depends on SNAPSHOT_VERIFICATION
> > > +        help
> > > +          This determines which sort of hashing algorithm will b=
e used during
> > > +          signature generation of snapshot. This algorithm _must=
_ be built into
> > > +	  the kernel directly so that signature verification can take p=
lace.
> > > +	  It is not possible to load a signed snapshot containing the a=
lgorithm
> > > +	  to check the signature on that module.
> >=20
> > Like if 1000 ifdefs you already added to the code are not enough, y=
ou
> > make some new ones?
> > 									Pavel
> >=20
>=20
> This SNAPSHOT_SIG_HASH kernel config is to select which SHA algorithm=
s
> used for generate digest of snapshot. The configuration will captured=
 by
> a const char* in code:
>=20
> +static const char *snapshot_hash =3D CONFIG_SNAPSHOT_SIG_HASH;
> +
> +static int pkey_hash(void)
>=20
> So, there doesn't have any ifdef block derived from this new config.

I'd say select one hash function, and use it. There's no need to make
it configurable.
									Pavel
--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses=
/blog.html