From: joeyli Subject: Re: [PATCH 17/18] Hibernate: introduced SNAPSHOT_SIG_HASH config for select hash algorithm Date: Tue, 27 Aug 2013 20:54:57 +0800 Message-ID: <1377608097.20140.30.camel__21136.1151807525$1377608218$gmane$org@linux-s257.site> References: <1377169317-5959-1-git-send-email-jlee@suse.com> <1377169317-5959-18-git-send-email-jlee@suse.com> <20130825164329.GL5171@amd.pavel.ucw.cz> <1377598937.20140.12.camel@linux-s257.site> <20130827113044.GB20527@amd.pavel.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE 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 , "Rafael J. Wysocki" , Matthew Garrett , Len Brown , Josh Boyer , Vojtech Pavlik , Matt Fleming , James Bottomley , Greg KH , JKosina@suse.com, Rusty Russell , Herbert Xu , "David S. Miller" , "H. Peter Anvin" , Michal Marek , Gary Lin , Vivek Goyal To: Pavel Machek Return-path: Received: from smtp.nue.novell.com ([195.135.221.5]:47885 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752877Ab3H0M4d (ORCPT ); Tue, 27 Aug 2013 08:56:33 -0400 In-Reply-To: <20130827113044.GB20527@amd.pavel.ucw.cz> Sender: linux-crypto-owner@vger.kernel.org List-ID: =E6=96=BC =E4=BA=8C=EF=BC=8C2013-08-27 =E6=96=BC 13:30 +0200=EF=BC=8CPa= vel Machek =E6=8F=90=E5=88=B0=EF=BC=9A > 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 sele= ct which > > > > hash algorithm will be used during signature generation of snap= shot. > > > >=20 > > > > v2: > > > > Add define check of oCONFIG_SNAPSHOT_VERIFICATION in snapshot.c= before > > > > declare pkey_hash(). > > > >=20 > > > > Reviewed-by: Jiri Kosina > > > > Signed-off-by: Lee, Chun-Yi > > > > --- > > > > 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 genera= te 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= be used during > > > > + signature generation of snapshot. This algorithm _mu= st_ be built into > > > > + the kernel directly so that signature verification can take= place. > > > > + It is not possible to load a signed snapshot containing the= algorithm > > > > + to check the signature on that module. > > >=20 > > > Like if 1000 ifdefs you already added to the code are not enough,= you > > > make some new ones? > > > Pavel > > >=20 > >=20 > > This SNAPSHOT_SIG_HASH kernel config is to select which SHA algorit= hms > > used for generate digest of snapshot. The configuration will captur= ed 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= =2E >=20 > I'd say select one hash function, and use it. There's no need to make > it configurable. > Pavel There have better performance when SHA algorithm output shorter hash result. On the other hand, longer hash result provide better security. And, on 64-bits system, the SHA512 has better performance then SHA256. Due to user have different use case and different hardware, why not giv= e them this option to make decision? Thanks a lot! Joey LEe